1*3117ece4Schristos<html> 2*3117ece4Schristos<head> 3*3117ece4Schristos<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> 4*3117ece4Schristos<title>zstd 1.5.6 Manual</title> 5*3117ece4Schristos</head> 6*3117ece4Schristos<body> 7*3117ece4Schristos<h1>zstd 1.5.6 Manual</h1> 8*3117ece4Schristos<hr> 9*3117ece4Schristos<a name="Contents"></a><h2>Contents</h2> 10*3117ece4Schristos<ol> 11*3117ece4Schristos<li><a href="#Chapter1">Introduction</a></li> 12*3117ece4Schristos<li><a href="#Chapter2">Version</a></li> 13*3117ece4Schristos<li><a href="#Chapter3">Simple API</a></li> 14*3117ece4Schristos<li><a href="#Chapter4">Explicit context</a></li> 15*3117ece4Schristos<li><a href="#Chapter5">Advanced compression API (Requires v1.4.0+)</a></li> 16*3117ece4Schristos<li><a href="#Chapter6">Advanced decompression API (Requires v1.4.0+)</a></li> 17*3117ece4Schristos<li><a href="#Chapter7">Streaming</a></li> 18*3117ece4Schristos<li><a href="#Chapter8">Streaming compression - HowTo</a></li> 19*3117ece4Schristos<li><a href="#Chapter9">Streaming decompression - HowTo</a></li> 20*3117ece4Schristos<li><a href="#Chapter10">Simple dictionary API</a></li> 21*3117ece4Schristos<li><a href="#Chapter11">Bulk processing dictionary API</a></li> 22*3117ece4Schristos<li><a href="#Chapter12">Dictionary helper functions</a></li> 23*3117ece4Schristos<li><a href="#Chapter13">Advanced dictionary and prefix API (Requires v1.4.0+)</a></li> 24*3117ece4Schristos<li><a href="#Chapter14">experimental API (static linking only)</a></li> 25*3117ece4Schristos<li><a href="#Chapter15">Frame header and size functions</a></li> 26*3117ece4Schristos<li><a href="#Chapter16">Memory management</a></li> 27*3117ece4Schristos<li><a href="#Chapter17">Advanced compression functions</a></li> 28*3117ece4Schristos<li><a href="#Chapter18">Advanced decompression functions</a></li> 29*3117ece4Schristos<li><a href="#Chapter19">Advanced streaming functions</a></li> 30*3117ece4Schristos<li><a href="#Chapter20">Buffer-less and synchronous inner streaming functions (DEPRECATED)</a></li> 31*3117ece4Schristos<li><a href="#Chapter21">Buffer-less streaming compression (synchronous mode)</a></li> 32*3117ece4Schristos<li><a href="#Chapter22">Buffer-less streaming decompression (synchronous mode)</a></li> 33*3117ece4Schristos<li><a href="#Chapter23">Block level API (DEPRECATED)</a></li> 34*3117ece4Schristos</ol> 35*3117ece4Schristos<hr> 36*3117ece4Schristos<a name="Chapter1"></a><h2>Introduction</h2><pre> 37*3117ece4Schristos zstd, short for Zstandard, is a fast lossless compression algorithm, targeting 38*3117ece4Schristos real-time compression scenarios at zlib-level and better compression ratios. 39*3117ece4Schristos The zstd compression library provides in-memory compression and decompression 40*3117ece4Schristos functions. 41*3117ece4Schristos 42*3117ece4Schristos The library supports regular compression levels from 1 up to ZSTD_maxCLevel(), 43*3117ece4Schristos which is currently 22. Levels >= 20, labeled `--ultra`, should be used with 44*3117ece4Schristos caution, as they require more memory. The library also offers negative 45*3117ece4Schristos compression levels, which extend the range of speed vs. ratio preferences. 46*3117ece4Schristos The lower the level, the faster the speed (at the cost of compression). 47*3117ece4Schristos 48*3117ece4Schristos Compression can be done in: 49*3117ece4Schristos - a single step (described as Simple API) 50*3117ece4Schristos - a single step, reusing a context (described as Explicit context) 51*3117ece4Schristos - unbounded multiple steps (described as Streaming compression) 52*3117ece4Schristos 53*3117ece4Schristos The compression ratio achievable on small data can be highly improved using 54*3117ece4Schristos a dictionary. Dictionary compression can be performed in: 55*3117ece4Schristos - a single step (described as Simple dictionary API) 56*3117ece4Schristos - a single step, reusing a dictionary (described as Bulk-processing 57*3117ece4Schristos dictionary API) 58*3117ece4Schristos 59*3117ece4Schristos Advanced experimental functions can be accessed using 60*3117ece4Schristos `#define ZSTD_STATIC_LINKING_ONLY` before including zstd.h. 61*3117ece4Schristos 62*3117ece4Schristos Advanced experimental APIs should never be used with a dynamically-linked 63*3117ece4Schristos library. They are not "stable"; their definitions or signatures may change in 64*3117ece4Schristos the future. Only static linking is allowed. 65*3117ece4Schristos<BR></pre> 66*3117ece4Schristos 67*3117ece4Schristos<a name="Chapter2"></a><h2>Version</h2><pre></pre> 68*3117ece4Schristos 69*3117ece4Schristos<pre><b>unsigned ZSTD_versionNumber(void); 70*3117ece4Schristos</b><p> Return runtime library version, the value is (MAJOR*100*100 + MINOR*100 + RELEASE). 71*3117ece4Schristos</p></pre><BR> 72*3117ece4Schristos 73*3117ece4Schristos<pre><b>const char* ZSTD_versionString(void); 74*3117ece4Schristos</b><p> Return runtime library version, like "1.4.5". Requires v1.3.0+. 75*3117ece4Schristos</p></pre><BR> 76*3117ece4Schristos 77*3117ece4Schristos<a name="Chapter3"></a><h2>Simple API</h2><pre></pre> 78*3117ece4Schristos 79*3117ece4Schristos<pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity, 80*3117ece4Schristos const void* src, size_t srcSize, 81*3117ece4Schristos int compressionLevel); 82*3117ece4Schristos</b><p> Compresses `src` content as a single zstd compressed frame into already allocated `dst`. 83*3117ece4Schristos NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have 84*3117ece4Schristos enough space to successfully compress the data. 85*3117ece4Schristos @return : compressed size written into `dst` (<= `dstCapacity), 86*3117ece4Schristos or an error code if it fails (which can be tested using ZSTD_isError()). 87*3117ece4Schristos</p></pre><BR> 88*3117ece4Schristos 89*3117ece4Schristos<pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity, 90*3117ece4Schristos const void* src, size_t compressedSize); 91*3117ece4Schristos</b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames. 92*3117ece4Schristos `dstCapacity` is an upper bound of originalSize to regenerate. 93*3117ece4Schristos If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data. 94*3117ece4Schristos @return : the number of bytes decompressed into `dst` (<= `dstCapacity`), 95*3117ece4Schristos or an errorCode if it fails (which can be tested using ZSTD_isError()). 96*3117ece4Schristos</p></pre><BR> 97*3117ece4Schristos 98*3117ece4Schristos<pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1) 99*3117ece4Schristos#define ZSTD_CONTENTSIZE_ERROR (0ULL - 2) 100*3117ece4Schristosunsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize); 101*3117ece4Schristos</b><p> `src` should point to the start of a ZSTD encoded frame. 102*3117ece4Schristos `srcSize` must be at least as large as the frame header. 103*3117ece4Schristos hint : any size >= `ZSTD_frameHeaderSize_max` is large enough. 104*3117ece4Schristos @return : - decompressed size of `src` frame content, if known 105*3117ece4Schristos - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined 106*3117ece4Schristos - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small) 107*3117ece4Schristos note 1 : a 0 return value means the frame is valid but "empty". 108*3117ece4Schristos note 2 : decompressed size is an optional field, it may not be present, typically in streaming mode. 109*3117ece4Schristos When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size. 110*3117ece4Schristos In which case, it's necessary to use streaming mode to decompress data. 111*3117ece4Schristos Optionally, application can rely on some implicit limit, 112*3117ece4Schristos as ZSTD_decompress() only needs an upper bound of decompressed size. 113*3117ece4Schristos (For example, data could be necessarily cut into blocks <= 16 KB). 114*3117ece4Schristos note 3 : decompressed size is always present when compression is completed using single-pass functions, 115*3117ece4Schristos such as ZSTD_compress(), ZSTD_compressCCtx() ZSTD_compress_usingDict() or ZSTD_compress_usingCDict(). 116*3117ece4Schristos note 4 : decompressed size can be very large (64-bits value), 117*3117ece4Schristos potentially larger than what local system can handle as a single memory segment. 118*3117ece4Schristos In which case, it's necessary to use streaming mode to decompress data. 119*3117ece4Schristos note 5 : If source is untrusted, decompressed size could be wrong or intentionally modified. 120*3117ece4Schristos Always ensure return value fits within application's authorized limits. 121*3117ece4Schristos Each application can set its own limits. 122*3117ece4Schristos note 6 : This function replaces ZSTD_getDecompressedSize() 123*3117ece4Schristos</p></pre><BR> 124*3117ece4Schristos 125*3117ece4Schristos<pre><b>ZSTD_DEPRECATED("Replaced by ZSTD_getFrameContentSize") 126*3117ece4SchristosZSTDLIB_API 127*3117ece4Schristosunsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize); 128*3117ece4Schristos</b><p> NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize(). 129*3117ece4Schristos Both functions work the same way, but ZSTD_getDecompressedSize() blends 130*3117ece4Schristos "empty", "unknown" and "error" results to the same return value (0), 131*3117ece4Schristos while ZSTD_getFrameContentSize() gives them separate return values. 132*3117ece4Schristos @return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise. 133*3117ece4Schristos</p></pre><BR> 134*3117ece4Schristos 135*3117ece4Schristos<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize); 136*3117ece4Schristos</b><p> `src` should point to the start of a ZSTD frame or skippable frame. 137*3117ece4Schristos `srcSize` must be >= first frame size 138*3117ece4Schristos @return : the compressed size of the first frame starting at `src`, 139*3117ece4Schristos suitable to pass as `srcSize` to `ZSTD_decompress` or similar, 140*3117ece4Schristos or an error code if input is invalid 141*3117ece4Schristos</p></pre><BR> 142*3117ece4Schristos 143*3117ece4Schristos<h3>Helper functions</h3><pre></pre><b><pre></b>/* ZSTD_compressBound() :<b> 144*3117ece4Schristos * maximum compressed size in worst case single-pass scenario. 145*3117ece4Schristos * When invoking `ZSTD_compress()` or any other one-pass compression function, 146*3117ece4Schristos * it's recommended to provide @dstCapacity >= ZSTD_compressBound(srcSize) 147*3117ece4Schristos * as it eliminates one potential failure scenario, 148*3117ece4Schristos * aka not enough room in dst buffer to write the compressed frame. 149*3117ece4Schristos * Note : ZSTD_compressBound() itself can fail, if @srcSize > ZSTD_MAX_INPUT_SIZE . 150*3117ece4Schristos * In which case, ZSTD_compressBound() will return an error code 151*3117ece4Schristos * which can be tested using ZSTD_isError(). 152*3117ece4Schristos * 153*3117ece4Schristos * ZSTD_COMPRESSBOUND() : 154*3117ece4Schristos * same as ZSTD_compressBound(), but as a macro. 155*3117ece4Schristos * It can be used to produce constants, which can be useful for static allocation, 156*3117ece4Schristos * for example to size a static array on stack. 157*3117ece4Schristos * Will produce constant value 0 if srcSize too large. 158*3117ece4Schristos */ 159*3117ece4Schristos#define ZSTD_MAX_INPUT_SIZE ((sizeof(size_t)==8) ? 0xFF00FF00FF00FF00ULL : 0xFF00FF00U) 160*3117ece4Schristos#define ZSTD_COMPRESSBOUND(srcSize) (((size_t)(srcSize) >= ZSTD_MAX_INPUT_SIZE) ? 0 : (srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) </b>/* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */<b> 161*3117ece4Schristossize_t ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case single-pass scenario */<b> 162*3117ece4Schristos</b>/* ZSTD_isError() :<b> 163*3117ece4Schristos * Most ZSTD_* functions returning a size_t value can be tested for error, 164*3117ece4Schristos * using ZSTD_isError(). 165*3117ece4Schristos * @return 1 if error, 0 otherwise 166*3117ece4Schristos */ 167*3117ece4Schristosunsigned ZSTD_isError(size_t code); </b>/*!< tells if a `size_t` function result is an error code */<b> 168*3117ece4Schristosconst char* ZSTD_getErrorName(size_t code); </b>/*!< provides readable string from an error code */<b> 169*3117ece4Schristosint ZSTD_minCLevel(void); </b>/*!< minimum negative compression level allowed, requires v1.4.0+ */<b> 170*3117ece4Schristosint ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b> 171*3117ece4Schristosint ZSTD_defaultCLevel(void); </b>/*!< default compression level, specified by ZSTD_CLEVEL_DEFAULT, requires v1.5.0+ */<b> 172*3117ece4Schristos</pre></b><BR> 173*3117ece4Schristos<a name="Chapter4"></a><h2>Explicit context</h2><pre></pre> 174*3117ece4Schristos 175*3117ece4Schristos<h3>Compression context</h3><pre> When compressing many times, 176*3117ece4Schristos it is recommended to allocate a context just once, 177*3117ece4Schristos and reuse it for each successive compression operation. 178*3117ece4Schristos This will make workload friendlier for system's memory. 179*3117ece4Schristos Note : re-using context is just a speed / resource optimization. 180*3117ece4Schristos It doesn't change the compression ratio, which remains identical. 181*3117ece4Schristos Note 2 : In multi-threaded environments, 182*3117ece4Schristos use one different context per thread for parallel execution. 183*3117ece4Schristos 184*3117ece4Schristos</pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx; 185*3117ece4SchristosZSTD_CCtx* ZSTD_createCCtx(void); 186*3117ece4Schristossize_t ZSTD_freeCCtx(ZSTD_CCtx* cctx); </b>/* accept NULL pointer */<b> 187*3117ece4Schristos</pre></b><BR> 188*3117ece4Schristos<pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx, 189*3117ece4Schristos void* dst, size_t dstCapacity, 190*3117ece4Schristos const void* src, size_t srcSize, 191*3117ece4Schristos int compressionLevel); 192*3117ece4Schristos</b><p> Same as ZSTD_compress(), using an explicit ZSTD_CCtx. 193*3117ece4Schristos Important : in order to mirror `ZSTD_compress()` behavior, 194*3117ece4Schristos this function compresses at the requested compression level, 195*3117ece4Schristos __ignoring any other advanced parameter__ . 196*3117ece4Schristos If any advanced parameter was set using the advanced API, 197*3117ece4Schristos they will all be reset. Only `compressionLevel` remains. 198*3117ece4Schristos 199*3117ece4Schristos</p></pre><BR> 200*3117ece4Schristos 201*3117ece4Schristos<h3>Decompression context</h3><pre> When decompressing many times, 202*3117ece4Schristos it is recommended to allocate a context only once, 203*3117ece4Schristos and reuse it for each successive compression operation. 204*3117ece4Schristos This will make workload friendlier for system's memory. 205*3117ece4Schristos Use one context per thread for parallel execution. 206*3117ece4Schristos</pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx; 207*3117ece4SchristosZSTD_DCtx* ZSTD_createDCtx(void); 208*3117ece4Schristossize_t ZSTD_freeDCtx(ZSTD_DCtx* dctx); </b>/* accept NULL pointer */<b> 209*3117ece4Schristos</pre></b><BR> 210*3117ece4Schristos<pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx, 211*3117ece4Schristos void* dst, size_t dstCapacity, 212*3117ece4Schristos const void* src, size_t srcSize); 213*3117ece4Schristos</b><p> Same as ZSTD_decompress(), 214*3117ece4Schristos requires an allocated ZSTD_DCtx. 215*3117ece4Schristos Compatible with sticky parameters (see below). 216*3117ece4Schristos 217*3117ece4Schristos</p></pre><BR> 218*3117ece4Schristos 219*3117ece4Schristos<a name="Chapter5"></a><h2>Advanced compression API (Requires v1.4.0+)</h2><pre></pre> 220*3117ece4Schristos 221*3117ece4Schristos<pre><b>typedef enum { ZSTD_fast=1, 222*3117ece4Schristos ZSTD_dfast=2, 223*3117ece4Schristos ZSTD_greedy=3, 224*3117ece4Schristos ZSTD_lazy=4, 225*3117ece4Schristos ZSTD_lazy2=5, 226*3117ece4Schristos ZSTD_btlazy2=6, 227*3117ece4Schristos ZSTD_btopt=7, 228*3117ece4Schristos ZSTD_btultra=8, 229*3117ece4Schristos ZSTD_btultra2=9 230*3117ece4Schristos </b>/* note : new strategies _might_ be added in the future.<b> 231*3117ece4Schristos Only the order (from fast to strong) is guaranteed */ 232*3117ece4Schristos} ZSTD_strategy; 233*3117ece4Schristos</b></pre><BR> 234*3117ece4Schristos<pre><b>typedef enum { 235*3117ece4Schristos 236*3117ece4Schristos </b>/* compression parameters<b> 237*3117ece4Schristos * Note: When compressing with a ZSTD_CDict these parameters are superseded 238*3117ece4Schristos * by the parameters used to construct the ZSTD_CDict. 239*3117ece4Schristos * See ZSTD_CCtx_refCDict() for more info (superseded-by-cdict). */ 240*3117ece4Schristos ZSTD_c_compressionLevel=100, </b>/* Set compression parameters according to pre-defined cLevel table.<b> 241*3117ece4Schristos * Note that exact compression parameters are dynamically determined, 242*3117ece4Schristos * depending on both compression level and srcSize (when known). 243*3117ece4Schristos * Default level is ZSTD_CLEVEL_DEFAULT==3. 244*3117ece4Schristos * Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT. 245*3117ece4Schristos * Note 1 : it's possible to pass a negative compression level. 246*3117ece4Schristos * Note 2 : setting a level does not automatically set all other compression parameters 247*3117ece4Schristos * to default. Setting this will however eventually dynamically impact the compression 248*3117ece4Schristos * parameters which have not been manually set. The manually set 249*3117ece4Schristos * ones will 'stick'. */ 250*3117ece4Schristos </b>/* Advanced compression parameters :<b> 251*3117ece4Schristos * It's possible to pin down compression parameters to some specific values. 252*3117ece4Schristos * In which case, these values are no longer dynamically selected by the compressor */ 253*3117ece4Schristos ZSTD_c_windowLog=101, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b> 254*3117ece4Schristos * This will set a memory budget for streaming decompression, 255*3117ece4Schristos * with larger values requiring more memory 256*3117ece4Schristos * and typically compressing more. 257*3117ece4Schristos * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX. 258*3117ece4Schristos * Special: value 0 means "use default windowLog". 259*3117ece4Schristos * Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT 260*3117ece4Schristos * requires explicitly allowing such size at streaming decompression stage. */ 261*3117ece4Schristos ZSTD_c_hashLog=102, </b>/* Size of the initial probe table, as a power of 2.<b> 262*3117ece4Schristos * Resulting memory usage is (1 << (hashLog+2)). 263*3117ece4Schristos * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX. 264*3117ece4Schristos * Larger tables improve compression ratio of strategies <= dFast, 265*3117ece4Schristos * and improve speed of strategies > dFast. 266*3117ece4Schristos * Special: value 0 means "use default hashLog". */ 267*3117ece4Schristos ZSTD_c_chainLog=103, </b>/* Size of the multi-probe search table, as a power of 2.<b> 268*3117ece4Schristos * Resulting memory usage is (1 << (chainLog+2)). 269*3117ece4Schristos * Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX. 270*3117ece4Schristos * Larger tables result in better and slower compression. 271*3117ece4Schristos * This parameter is useless for "fast" strategy. 272*3117ece4Schristos * It's still useful when using "dfast" strategy, 273*3117ece4Schristos * in which case it defines a secondary probe table. 274*3117ece4Schristos * Special: value 0 means "use default chainLog". */ 275*3117ece4Schristos ZSTD_c_searchLog=104, </b>/* Number of search attempts, as a power of 2.<b> 276*3117ece4Schristos * More attempts result in better and slower compression. 277*3117ece4Schristos * This parameter is useless for "fast" and "dFast" strategies. 278*3117ece4Schristos * Special: value 0 means "use default searchLog". */ 279*3117ece4Schristos ZSTD_c_minMatch=105, </b>/* Minimum size of searched matches.<b> 280*3117ece4Schristos * Note that Zstandard can still find matches of smaller size, 281*3117ece4Schristos * it just tweaks its search algorithm to look for this size and larger. 282*3117ece4Schristos * Larger values increase compression and decompression speed, but decrease ratio. 283*3117ece4Schristos * Must be clamped between ZSTD_MINMATCH_MIN and ZSTD_MINMATCH_MAX. 284*3117ece4Schristos * Note that currently, for all strategies < btopt, effective minimum is 4. 285*3117ece4Schristos * , for all strategies > fast, effective maximum is 6. 286*3117ece4Schristos * Special: value 0 means "use default minMatchLength". */ 287*3117ece4Schristos ZSTD_c_targetLength=106, </b>/* Impact of this field depends on strategy.<b> 288*3117ece4Schristos * For strategies btopt, btultra & btultra2: 289*3117ece4Schristos * Length of Match considered "good enough" to stop search. 290*3117ece4Schristos * Larger values make compression stronger, and slower. 291*3117ece4Schristos * For strategy fast: 292*3117ece4Schristos * Distance between match sampling. 293*3117ece4Schristos * Larger values make compression faster, and weaker. 294*3117ece4Schristos * Special: value 0 means "use default targetLength". */ 295*3117ece4Schristos ZSTD_c_strategy=107, </b>/* See ZSTD_strategy enum definition.<b> 296*3117ece4Schristos * The higher the value of selected strategy, the more complex it is, 297*3117ece4Schristos * resulting in stronger and slower compression. 298*3117ece4Schristos * Special: value 0 means "use default strategy". */ 299*3117ece4Schristos 300*3117ece4Schristos ZSTD_c_targetCBlockSize=130, </b>/* v1.5.6+<b> 301*3117ece4Schristos * Attempts to fit compressed block size into approximatively targetCBlockSize. 302*3117ece4Schristos * Bound by ZSTD_TARGETCBLOCKSIZE_MIN and ZSTD_TARGETCBLOCKSIZE_MAX. 303*3117ece4Schristos * Note that it's not a guarantee, just a convergence target (default:0). 304*3117ece4Schristos * No target when targetCBlockSize == 0. 305*3117ece4Schristos * This is helpful in low bandwidth streaming environments to improve end-to-end latency, 306*3117ece4Schristos * when a client can make use of partial documents (a prominent example being Chrome). 307*3117ece4Schristos * Note: this parameter is stable since v1.5.6. 308*3117ece4Schristos * It was present as an experimental parameter in earlier versions, 309*3117ece4Schristos * but it's not recommended using it with earlier library versions 310*3117ece4Schristos * due to massive performance regressions. 311*3117ece4Schristos */ 312*3117ece4Schristos </b>/* LDM mode parameters */<b> 313*3117ece4Schristos ZSTD_c_enableLongDistanceMatching=160, </b>/* Enable long distance matching.<b> 314*3117ece4Schristos * This parameter is designed to improve compression ratio 315*3117ece4Schristos * for large inputs, by finding large matches at long distance. 316*3117ece4Schristos * It increases memory usage and window size. 317*3117ece4Schristos * Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB 318*3117ece4Schristos * except when expressly set to a different value. 319*3117ece4Schristos * Note: will be enabled by default if ZSTD_c_windowLog >= 128 MB and 320*3117ece4Schristos * compression strategy >= ZSTD_btopt (== compression level 16+) */ 321*3117ece4Schristos ZSTD_c_ldmHashLog=161, </b>/* Size of the table for long distance matching, as a power of 2.<b> 322*3117ece4Schristos * Larger values increase memory usage and compression ratio, 323*3117ece4Schristos * but decrease compression speed. 324*3117ece4Schristos * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX 325*3117ece4Schristos * default: windowlog - 7. 326*3117ece4Schristos * Special: value 0 means "automatically determine hashlog". */ 327*3117ece4Schristos ZSTD_c_ldmMinMatch=162, </b>/* Minimum match size for long distance matcher.<b> 328*3117ece4Schristos * Larger/too small values usually decrease compression ratio. 329*3117ece4Schristos * Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX. 330*3117ece4Schristos * Special: value 0 means "use default value" (default: 64). */ 331*3117ece4Schristos ZSTD_c_ldmBucketSizeLog=163, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b> 332*3117ece4Schristos * Larger values improve collision resolution but decrease compression speed. 333*3117ece4Schristos * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX. 334*3117ece4Schristos * Special: value 0 means "use default value" (default: 3). */ 335*3117ece4Schristos ZSTD_c_ldmHashRateLog=164, </b>/* Frequency of inserting/looking up entries into the LDM hash table.<b> 336*3117ece4Schristos * Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN). 337*3117ece4Schristos * Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage. 338*3117ece4Schristos * Larger values improve compression speed. 339*3117ece4Schristos * Deviating far from default value will likely result in a compression ratio decrease. 340*3117ece4Schristos * Special: value 0 means "automatically determine hashRateLog". */ 341*3117ece4Schristos 342*3117ece4Schristos </b>/* frame parameters */<b> 343*3117ece4Schristos ZSTD_c_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b> 344*3117ece4Schristos * Content size must be known at the beginning of compression. 345*3117ece4Schristos * This is automatically the case when using ZSTD_compress2(), 346*3117ece4Schristos * For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */ 347*3117ece4Schristos ZSTD_c_checksumFlag=201, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b> 348*3117ece4Schristos ZSTD_c_dictIDFlag=202, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b> 349*3117ece4Schristos 350*3117ece4Schristos </b>/* multi-threading parameters */<b> 351*3117ece4Schristos </b>/* These parameters are only active if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b> 352*3117ece4Schristos * Otherwise, trying to set any other value than default (0) will be a no-op and return an error. 353*3117ece4Schristos * In a situation where it's unknown if the linked library supports multi-threading or not, 354*3117ece4Schristos * setting ZSTD_c_nbWorkers to any value >= 1 and consulting the return value provides a quick way to check this property. 355*3117ece4Schristos */ 356*3117ece4Schristos ZSTD_c_nbWorkers=400, </b>/* Select how many threads will be spawned to compress in parallel.<b> 357*3117ece4Schristos * When nbWorkers >= 1, triggers asynchronous mode when invoking ZSTD_compressStream*() : 358*3117ece4Schristos * ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller, 359*3117ece4Schristos * while compression is performed in parallel, within worker thread(s). 360*3117ece4Schristos * (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end : 361*3117ece4Schristos * in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call). 362*3117ece4Schristos * More workers improve speed, but also increase memory usage. 363*3117ece4Schristos * Default value is `0`, aka "single-threaded mode" : no worker is spawned, 364*3117ece4Schristos * compression is performed inside Caller's thread, and all invocations are blocking */ 365*3117ece4Schristos ZSTD_c_jobSize=401, </b>/* Size of a compression job. This value is enforced only when nbWorkers >= 1.<b> 366*3117ece4Schristos * Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads. 367*3117ece4Schristos * 0 means default, which is dynamically determined based on compression parameters. 368*3117ece4Schristos * Job size must be a minimum of overlap size, or ZSTDMT_JOBSIZE_MIN (= 512 KB), whichever is largest. 369*3117ece4Schristos * The minimum size is automatically and transparently enforced. */ 370*3117ece4Schristos ZSTD_c_overlapLog=402, </b>/* Control the overlap size, as a fraction of window size.<b> 371*3117ece4Schristos * The overlap size is an amount of data reloaded from previous job at the beginning of a new job. 372*3117ece4Schristos * It helps preserve compression ratio, while each job is compressed in parallel. 373*3117ece4Schristos * This value is enforced only when nbWorkers >= 1. 374*3117ece4Schristos * Larger values increase compression ratio, but decrease speed. 375*3117ece4Schristos * Possible values range from 0 to 9 : 376*3117ece4Schristos * - 0 means "default" : value will be determined by the library, depending on strategy 377*3117ece4Schristos * - 1 means "no overlap" 378*3117ece4Schristos * - 9 means "full overlap", using a full window size. 379*3117ece4Schristos * Each intermediate rank increases/decreases load size by a factor 2 : 380*3117ece4Schristos * 9: full window; 8: w/2; 7: w/4; 6: w/8; 5:w/16; 4: w/32; 3:w/64; 2:w/128; 1:no overlap; 0:default 381*3117ece4Schristos * default value varies between 6 and 9, depending on strategy */ 382*3117ece4Schristos 383*3117ece4Schristos </b>/* note : additional experimental parameters are also available<b> 384*3117ece4Schristos * within the experimental section of the API. 385*3117ece4Schristos * At the time of this writing, they include : 386*3117ece4Schristos * ZSTD_c_rsyncable 387*3117ece4Schristos * ZSTD_c_format 388*3117ece4Schristos * ZSTD_c_forceMaxWindow 389*3117ece4Schristos * ZSTD_c_forceAttachDict 390*3117ece4Schristos * ZSTD_c_literalCompressionMode 391*3117ece4Schristos * ZSTD_c_srcSizeHint 392*3117ece4Schristos * ZSTD_c_enableDedicatedDictSearch 393*3117ece4Schristos * ZSTD_c_stableInBuffer 394*3117ece4Schristos * ZSTD_c_stableOutBuffer 395*3117ece4Schristos * ZSTD_c_blockDelimiters 396*3117ece4Schristos * ZSTD_c_validateSequences 397*3117ece4Schristos * ZSTD_c_useBlockSplitter 398*3117ece4Schristos * ZSTD_c_useRowMatchFinder 399*3117ece4Schristos * ZSTD_c_prefetchCDictTables 400*3117ece4Schristos * ZSTD_c_enableSeqProducerFallback 401*3117ece4Schristos * ZSTD_c_maxBlockSize 402*3117ece4Schristos * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them. 403*3117ece4Schristos * note : never ever use experimentalParam? names directly; 404*3117ece4Schristos * also, the enums values themselves are unstable and can still change. 405*3117ece4Schristos */ 406*3117ece4Schristos ZSTD_c_experimentalParam1=500, 407*3117ece4Schristos ZSTD_c_experimentalParam2=10, 408*3117ece4Schristos ZSTD_c_experimentalParam3=1000, 409*3117ece4Schristos ZSTD_c_experimentalParam4=1001, 410*3117ece4Schristos ZSTD_c_experimentalParam5=1002, 411*3117ece4Schristos </b>/* was ZSTD_c_experimentalParam6=1003; is now ZSTD_c_targetCBlockSize */<b> 412*3117ece4Schristos ZSTD_c_experimentalParam7=1004, 413*3117ece4Schristos ZSTD_c_experimentalParam8=1005, 414*3117ece4Schristos ZSTD_c_experimentalParam9=1006, 415*3117ece4Schristos ZSTD_c_experimentalParam10=1007, 416*3117ece4Schristos ZSTD_c_experimentalParam11=1008, 417*3117ece4Schristos ZSTD_c_experimentalParam12=1009, 418*3117ece4Schristos ZSTD_c_experimentalParam13=1010, 419*3117ece4Schristos ZSTD_c_experimentalParam14=1011, 420*3117ece4Schristos ZSTD_c_experimentalParam15=1012, 421*3117ece4Schristos ZSTD_c_experimentalParam16=1013, 422*3117ece4Schristos ZSTD_c_experimentalParam17=1014, 423*3117ece4Schristos ZSTD_c_experimentalParam18=1015, 424*3117ece4Schristos ZSTD_c_experimentalParam19=1016 425*3117ece4Schristos} ZSTD_cParameter; 426*3117ece4Schristos</b></pre><BR> 427*3117ece4Schristos<pre><b>typedef struct { 428*3117ece4Schristos size_t error; 429*3117ece4Schristos int lowerBound; 430*3117ece4Schristos int upperBound; 431*3117ece4Schristos} ZSTD_bounds; 432*3117ece4Schristos</b></pre><BR> 433*3117ece4Schristos<pre><b>ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam); 434*3117ece4Schristos</b><p> All parameters must belong to an interval with lower and upper bounds, 435*3117ece4Schristos otherwise they will either trigger an error or be automatically clamped. 436*3117ece4Schristos @return : a structure, ZSTD_bounds, which contains 437*3117ece4Schristos - an error status field, which must be tested using ZSTD_isError() 438*3117ece4Schristos - lower and upper bounds, both inclusive 439*3117ece4Schristos 440*3117ece4Schristos</p></pre><BR> 441*3117ece4Schristos 442*3117ece4Schristos<pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value); 443*3117ece4Schristos</b><p> Set one compression parameter, selected by enum ZSTD_cParameter. 444*3117ece4Schristos All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds(). 445*3117ece4Schristos Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter). 446*3117ece4Schristos Setting a parameter is generally only possible during frame initialization (before starting compression). 447*3117ece4Schristos Exception : when using multi-threading mode (nbWorkers >= 1), 448*3117ece4Schristos the following parameters can be updated _during_ compression (within same frame): 449*3117ece4Schristos => compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy. 450*3117ece4Schristos new parameters will be active for next job only (after a flush()). 451*3117ece4Schristos @return : an error code (which can be tested using ZSTD_isError()). 452*3117ece4Schristos 453*3117ece4Schristos</p></pre><BR> 454*3117ece4Schristos 455*3117ece4Schristos<pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize); 456*3117ece4Schristos</b><p> Total input data size to be compressed as a single frame. 457*3117ece4Schristos Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag. 458*3117ece4Schristos This value will also be controlled at end of frame, and trigger an error if not respected. 459*3117ece4Schristos @result : 0, or an error code (which can be tested with ZSTD_isError()). 460*3117ece4Schristos Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame. 461*3117ece4Schristos In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN. 462*3117ece4Schristos ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame. 463*3117ece4Schristos Note 2 : pledgedSrcSize is only valid once, for the next frame. 464*3117ece4Schristos It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN. 465*3117ece4Schristos Note 3 : Whenever all input data is provided and consumed in a single round, 466*3117ece4Schristos for example with ZSTD_compress2(), 467*3117ece4Schristos or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end), 468*3117ece4Schristos this value is automatically overridden by srcSize instead. 469*3117ece4Schristos 470*3117ece4Schristos</p></pre><BR> 471*3117ece4Schristos 472*3117ece4Schristos<pre><b>typedef enum { 473*3117ece4Schristos ZSTD_reset_session_only = 1, 474*3117ece4Schristos ZSTD_reset_parameters = 2, 475*3117ece4Schristos ZSTD_reset_session_and_parameters = 3 476*3117ece4Schristos} ZSTD_ResetDirective; 477*3117ece4Schristos</b></pre><BR> 478*3117ece4Schristos<pre><b>size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset); 479*3117ece4Schristos</b><p> There are 2 different things that can be reset, independently or jointly : 480*3117ece4Schristos - The session : will stop compressing current frame, and make CCtx ready to start a new one. 481*3117ece4Schristos Useful after an error, or to interrupt any ongoing compression. 482*3117ece4Schristos Any internal data not yet flushed is cancelled. 483*3117ece4Schristos Compression parameters and dictionary remain unchanged. 484*3117ece4Schristos They will be used to compress next frame. 485*3117ece4Schristos Resetting session never fails. 486*3117ece4Schristos - The parameters : changes all parameters back to "default". 487*3117ece4Schristos This also removes any reference to any dictionary or external sequence producer. 488*3117ece4Schristos Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing) 489*3117ece4Schristos otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError()) 490*3117ece4Schristos - Both : similar to resetting the session, followed by resetting parameters. 491*3117ece4Schristos 492*3117ece4Schristos</p></pre><BR> 493*3117ece4Schristos 494*3117ece4Schristos<pre><b>size_t ZSTD_compress2( ZSTD_CCtx* cctx, 495*3117ece4Schristos void* dst, size_t dstCapacity, 496*3117ece4Schristos const void* src, size_t srcSize); 497*3117ece4Schristos</b><p> Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API. 498*3117ece4Schristos (note that this entry point doesn't even expose a compression level parameter). 499*3117ece4Schristos ZSTD_compress2() always starts a new frame. 500*3117ece4Schristos Should cctx hold data from a previously unfinished frame, everything about it is forgotten. 501*3117ece4Schristos - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*() 502*3117ece4Schristos - The function is always blocking, returns when compression is completed. 503*3117ece4Schristos NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have 504*3117ece4Schristos enough space to successfully compress the data, though it is possible it fails for other reasons. 505*3117ece4Schristos @return : compressed size written into `dst` (<= `dstCapacity), 506*3117ece4Schristos or an error code if it fails (which can be tested using ZSTD_isError()). 507*3117ece4Schristos 508*3117ece4Schristos</p></pre><BR> 509*3117ece4Schristos 510*3117ece4Schristos<a name="Chapter6"></a><h2>Advanced decompression API (Requires v1.4.0+)</h2><pre></pre> 511*3117ece4Schristos 512*3117ece4Schristos<pre><b>typedef enum { 513*3117ece4Schristos 514*3117ece4Schristos ZSTD_d_windowLogMax=100, </b>/* Select a size limit (in power of 2) beyond which<b> 515*3117ece4Schristos * the streaming API will refuse to allocate memory buffer 516*3117ece4Schristos * in order to protect the host from unreasonable memory requirements. 517*3117ece4Schristos * This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode. 518*3117ece4Schristos * By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT). 519*3117ece4Schristos * Special: value 0 means "use default maximum windowLog". */ 520*3117ece4Schristos 521*3117ece4Schristos </b>/* note : additional experimental parameters are also available<b> 522*3117ece4Schristos * within the experimental section of the API. 523*3117ece4Schristos * At the time of this writing, they include : 524*3117ece4Schristos * ZSTD_d_format 525*3117ece4Schristos * ZSTD_d_stableOutBuffer 526*3117ece4Schristos * ZSTD_d_forceIgnoreChecksum 527*3117ece4Schristos * ZSTD_d_refMultipleDDicts 528*3117ece4Schristos * ZSTD_d_disableHuffmanAssembly 529*3117ece4Schristos * ZSTD_d_maxBlockSize 530*3117ece4Schristos * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them. 531*3117ece4Schristos * note : never ever use experimentalParam? names directly 532*3117ece4Schristos */ 533*3117ece4Schristos ZSTD_d_experimentalParam1=1000, 534*3117ece4Schristos ZSTD_d_experimentalParam2=1001, 535*3117ece4Schristos ZSTD_d_experimentalParam3=1002, 536*3117ece4Schristos ZSTD_d_experimentalParam4=1003, 537*3117ece4Schristos ZSTD_d_experimentalParam5=1004, 538*3117ece4Schristos ZSTD_d_experimentalParam6=1005 539*3117ece4Schristos 540*3117ece4Schristos} ZSTD_dParameter; 541*3117ece4Schristos</b></pre><BR> 542*3117ece4Schristos<pre><b>ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam); 543*3117ece4Schristos</b><p> All parameters must belong to an interval with lower and upper bounds, 544*3117ece4Schristos otherwise they will either trigger an error or be automatically clamped. 545*3117ece4Schristos @return : a structure, ZSTD_bounds, which contains 546*3117ece4Schristos - an error status field, which must be tested using ZSTD_isError() 547*3117ece4Schristos - both lower and upper bounds, inclusive 548*3117ece4Schristos 549*3117ece4Schristos</p></pre><BR> 550*3117ece4Schristos 551*3117ece4Schristos<pre><b>size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value); 552*3117ece4Schristos</b><p> Set one compression parameter, selected by enum ZSTD_dParameter. 553*3117ece4Schristos All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds(). 554*3117ece4Schristos Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter). 555*3117ece4Schristos Setting a parameter is only possible during frame initialization (before starting decompression). 556*3117ece4Schristos @return : 0, or an error code (which can be tested using ZSTD_isError()). 557*3117ece4Schristos 558*3117ece4Schristos</p></pre><BR> 559*3117ece4Schristos 560*3117ece4Schristos<pre><b>size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset); 561*3117ece4Schristos</b><p> Return a DCtx to clean state. 562*3117ece4Schristos Session and parameters can be reset jointly or separately. 563*3117ece4Schristos Parameters can only be reset when no active frame is being decompressed. 564*3117ece4Schristos @return : 0, or an error code, which can be tested with ZSTD_isError() 565*3117ece4Schristos 566*3117ece4Schristos</p></pre><BR> 567*3117ece4Schristos 568*3117ece4Schristos<a name="Chapter7"></a><h2>Streaming</h2><pre></pre> 569*3117ece4Schristos 570*3117ece4Schristos<pre><b>typedef struct ZSTD_inBuffer_s { 571*3117ece4Schristos const void* src; </b>/**< start of input buffer */<b> 572*3117ece4Schristos size_t size; </b>/**< size of input buffer */<b> 573*3117ece4Schristos size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b> 574*3117ece4Schristos} ZSTD_inBuffer; 575*3117ece4Schristos</b></pre><BR> 576*3117ece4Schristos<pre><b>typedef struct ZSTD_outBuffer_s { 577*3117ece4Schristos void* dst; </b>/**< start of output buffer */<b> 578*3117ece4Schristos size_t size; </b>/**< size of output buffer */<b> 579*3117ece4Schristos size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b> 580*3117ece4Schristos} ZSTD_outBuffer; 581*3117ece4Schristos</b></pre><BR> 582*3117ece4Schristos<a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre> 583*3117ece4Schristos A ZSTD_CStream object is required to track streaming operation. 584*3117ece4Schristos Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources. 585*3117ece4Schristos ZSTD_CStream objects can be reused multiple times on consecutive compression operations. 586*3117ece4Schristos It is recommended to reuse ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory. 587*3117ece4Schristos 588*3117ece4Schristos For parallel execution, use one separate ZSTD_CStream per thread. 589*3117ece4Schristos 590*3117ece4Schristos note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing. 591*3117ece4Schristos 592*3117ece4Schristos Parameters are sticky : when starting a new compression on the same context, 593*3117ece4Schristos it will reuse the same sticky parameters as previous compression session. 594*3117ece4Schristos When in doubt, it's recommended to fully initialize the context before usage. 595*3117ece4Schristos Use ZSTD_CCtx_reset() to reset the context and ZSTD_CCtx_setParameter(), 596*3117ece4Schristos ZSTD_CCtx_setPledgedSrcSize(), or ZSTD_CCtx_loadDictionary() and friends to 597*3117ece4Schristos set more specific parameters, the pledged source size, or load a dictionary. 598*3117ece4Schristos 599*3117ece4Schristos Use ZSTD_compressStream2() with ZSTD_e_continue as many times as necessary to 600*3117ece4Schristos consume input stream. The function will automatically update both `pos` 601*3117ece4Schristos fields within `input` and `output`. 602*3117ece4Schristos Note that the function may not consume the entire input, for example, because 603*3117ece4Schristos the output buffer is already full, in which case `input.pos < input.size`. 604*3117ece4Schristos The caller must check if input has been entirely consumed. 605*3117ece4Schristos If not, the caller must make some room to receive more compressed data, 606*3117ece4Schristos and then present again remaining input data. 607*3117ece4Schristos note: ZSTD_e_continue is guaranteed to make some forward progress when called, 608*3117ece4Schristos but doesn't guarantee maximal forward progress. This is especially relevant 609*3117ece4Schristos when compressing with multiple threads. The call won't block if it can 610*3117ece4Schristos consume some input, but if it can't it will wait for some, but not all, 611*3117ece4Schristos output to be flushed. 612*3117ece4Schristos @return : provides a minimum amount of data remaining to be flushed from internal buffers 613*3117ece4Schristos or an error code, which can be tested using ZSTD_isError(). 614*3117ece4Schristos 615*3117ece4Schristos At any moment, it's possible to flush whatever data might remain stuck within internal buffer, 616*3117ece4Schristos using ZSTD_compressStream2() with ZSTD_e_flush. `output->pos` will be updated. 617*3117ece4Schristos Note that, if `output->size` is too small, a single invocation with ZSTD_e_flush might not be enough (return code > 0). 618*3117ece4Schristos In which case, make some room to receive more compressed data, and call again ZSTD_compressStream2() with ZSTD_e_flush. 619*3117ece4Schristos You must continue calling ZSTD_compressStream2() with ZSTD_e_flush until it returns 0, at which point you can change the 620*3117ece4Schristos operation. 621*3117ece4Schristos note: ZSTD_e_flush will flush as much output as possible, meaning when compressing with multiple threads, it will 622*3117ece4Schristos block until the flush is complete or the output buffer is full. 623*3117ece4Schristos @return : 0 if internal buffers are entirely flushed, 624*3117ece4Schristos >0 if some data still present within internal buffer (the value is minimal estimation of remaining size), 625*3117ece4Schristos or an error code, which can be tested using ZSTD_isError(). 626*3117ece4Schristos 627*3117ece4Schristos Calling ZSTD_compressStream2() with ZSTD_e_end instructs to finish a frame. 628*3117ece4Schristos It will perform a flush and write frame epilogue. 629*3117ece4Schristos The epilogue is required for decoders to consider a frame completed. 630*3117ece4Schristos flush operation is the same, and follows same rules as calling ZSTD_compressStream2() with ZSTD_e_flush. 631*3117ece4Schristos You must continue calling ZSTD_compressStream2() with ZSTD_e_end until it returns 0, at which point you are free to 632*3117ece4Schristos start a new frame. 633*3117ece4Schristos note: ZSTD_e_end will flush as much output as possible, meaning when compressing with multiple threads, it will 634*3117ece4Schristos block until the flush is complete or the output buffer is full. 635*3117ece4Schristos @return : 0 if frame fully completed and fully flushed, 636*3117ece4Schristos >0 if some data still present within internal buffer (the value is minimal estimation of remaining size), 637*3117ece4Schristos or an error code, which can be tested using ZSTD_isError(). 638*3117ece4Schristos 639*3117ece4Schristos 640*3117ece4Schristos<BR></pre> 641*3117ece4Schristos 642*3117ece4Schristos<pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b> 643*3117ece4Schristos</b></pre><BR> 644*3117ece4Schristos<h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void); 645*3117ece4Schristossize_t ZSTD_freeCStream(ZSTD_CStream* zcs); </b>/* accept NULL pointer */<b> 646*3117ece4Schristos</pre></b><BR> 647*3117ece4Schristos<h3>Streaming compression functions</h3><pre></pre><b><pre>typedef enum { 648*3117ece4Schristos ZSTD_e_continue=0, </b>/* collect more data, encoder decides when to output compressed result, for optimal compression ratio */<b> 649*3117ece4Schristos ZSTD_e_flush=1, </b>/* flush any data provided so far,<b> 650*3117ece4Schristos * it creates (at least) one new block, that can be decoded immediately on reception; 651*3117ece4Schristos * frame will continue: any future data can still reference previously compressed data, improving compression. 652*3117ece4Schristos * note : multithreaded compression will block to flush as much output as possible. */ 653*3117ece4Schristos ZSTD_e_end=2 </b>/* flush any remaining data _and_ close current frame.<b> 654*3117ece4Schristos * note that frame is only closed after compressed data is fully flushed (return value == 0). 655*3117ece4Schristos * After that point, any additional data starts a new frame. 656*3117ece4Schristos * note : each frame is independent (does not reference any content from previous frame). 657*3117ece4Schristos : note : multithreaded compression will block to flush as much output as possible. */ 658*3117ece4Schristos} ZSTD_EndDirective; 659*3117ece4Schristos</pre></b><BR> 660*3117ece4Schristos<pre><b>size_t ZSTD_compressStream2( ZSTD_CCtx* cctx, 661*3117ece4Schristos ZSTD_outBuffer* output, 662*3117ece4Schristos ZSTD_inBuffer* input, 663*3117ece4Schristos ZSTD_EndDirective endOp); 664*3117ece4Schristos</b><p> Behaves about the same as ZSTD_compressStream, with additional control on end directive. 665*3117ece4Schristos - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*() 666*3117ece4Schristos - Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode) 667*3117ece4Schristos - output->pos must be <= dstCapacity, input->pos must be <= srcSize 668*3117ece4Schristos - output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit. 669*3117ece4Schristos - endOp must be a valid directive 670*3117ece4Schristos - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller. 671*3117ece4Schristos - When nbWorkers>=1, function is non-blocking : it copies a portion of input, distributes jobs to internal worker threads, flush to output whatever is available, 672*3117ece4Schristos and then immediately returns, just indicating that there is some data remaining to be flushed. 673*3117ece4Schristos The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte. 674*3117ece4Schristos - Exception : if the first call requests a ZSTD_e_end directive and provides enough dstCapacity, the function delegates to ZSTD_compress2() which is always blocking. 675*3117ece4Schristos - @return provides a minimum amount of data remaining to be flushed from internal buffers 676*3117ece4Schristos or an error code, which can be tested using ZSTD_isError(). 677*3117ece4Schristos if @return != 0, flush is not fully completed, there is still some data left within internal buffers. 678*3117ece4Schristos This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers. 679*3117ece4Schristos For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed. 680*3117ece4Schristos - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0), 681*3117ece4Schristos only ZSTD_e_end or ZSTD_e_flush operations are allowed. 682*3117ece4Schristos Before starting a new compression job, or changing compression parameters, 683*3117ece4Schristos it is required to fully flush internal buffers. 684*3117ece4Schristos - note: if an operation ends with an error, it may leave @cctx in an undefined state. 685*3117ece4Schristos Therefore, it's UB to invoke ZSTD_compressStream2() of ZSTD_compressStream() on such a state. 686*3117ece4Schristos In order to be re-employed after an error, a state must be reset, 687*3117ece4Schristos which can be done explicitly (ZSTD_CCtx_reset()), 688*3117ece4Schristos or is sometimes implied by methods starting a new compression job (ZSTD_initCStream(), ZSTD_compressCCtx()) 689*3117ece4Schristos 690*3117ece4Schristos</p></pre><BR> 691*3117ece4Schristos 692*3117ece4Schristos<pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b> 693*3117ece4Schristos</b></pre><BR> 694*3117ece4Schristos<pre><b>size_t ZSTD_CStreamOutSize(void); </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block. */<b> 695*3117ece4Schristos</b></pre><BR> 696*3117ece4Schristos<pre><b>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel); 697*3117ece4Schristos</b>/*!<b> 698*3117ece4Schristos * Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue). 699*3117ece4Schristos * NOTE: The return value is different. ZSTD_compressStream() returns a hint for 700*3117ece4Schristos * the next read size (if non-zero and not an error). ZSTD_compressStream2() 701*3117ece4Schristos * returns the minimum nb of bytes left to flush (if non-zero and not an error). 702*3117ece4Schristos */ 703*3117ece4Schristossize_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input); 704*3117ece4Schristos</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush). */<b> 705*3117ece4Schristossize_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); 706*3117ece4Schristos</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end). */<b> 707*3117ece4Schristossize_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); 708*3117ece4Schristos</b><p> 709*3117ece4Schristos ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); 710*3117ece4Schristos ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any) 711*3117ece4Schristos ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); 712*3117ece4Schristos 713*3117ece4Schristos Note that ZSTD_initCStream() clears any previously set dictionary. Use the new API 714*3117ece4Schristos to compress with a dictionary. 715*3117ece4Schristos 716*3117ece4Schristos</p></pre><BR> 717*3117ece4Schristos 718*3117ece4Schristos<a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre> 719*3117ece4Schristos A ZSTD_DStream object is required to track streaming operations. 720*3117ece4Schristos Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources. 721*3117ece4Schristos ZSTD_DStream objects can be reused multiple times. 722*3117ece4Schristos 723*3117ece4Schristos Use ZSTD_initDStream() to start a new decompression operation. 724*3117ece4Schristos @return : recommended first input size 725*3117ece4Schristos Alternatively, use advanced API to set specific properties. 726*3117ece4Schristos 727*3117ece4Schristos Use ZSTD_decompressStream() repetitively to consume your input. 728*3117ece4Schristos The function will update both `pos` fields. 729*3117ece4Schristos If `input.pos < input.size`, some input has not been consumed. 730*3117ece4Schristos It's up to the caller to present again remaining data. 731*3117ece4Schristos The function tries to flush all data decoded immediately, respecting output buffer size. 732*3117ece4Schristos If `output.pos < output.size`, decoder has flushed everything it could. 733*3117ece4Schristos But if `output.pos == output.size`, there might be some data left within internal buffers., 734*3117ece4Schristos In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer. 735*3117ece4Schristos Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX. 736*3117ece4Schristos @return : 0 when a frame is completely decoded and fully flushed, 737*3117ece4Schristos or an error code, which can be tested using ZSTD_isError(), 738*3117ece4Schristos or any other value > 0, which means there is still some decoding or flushing to do to complete current frame : 739*3117ece4Schristos the return value is a suggested next input size (just a hint for better latency) 740*3117ece4Schristos that will never request more than the remaining frame size. 741*3117ece4Schristos 742*3117ece4Schristos<BR></pre> 743*3117ece4Schristos 744*3117ece4Schristos<pre><b>typedef ZSTD_DCtx ZSTD_DStream; </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b> 745*3117ece4Schristos</b></pre><BR> 746*3117ece4Schristos<h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void); 747*3117ece4Schristossize_t ZSTD_freeDStream(ZSTD_DStream* zds); </b>/* accept NULL pointer */<b> 748*3117ece4Schristos</pre></b><BR> 749*3117ece4Schristos<h3>Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR> 750*3117ece4Schristos<pre><b>size_t ZSTD_initDStream(ZSTD_DStream* zds); 751*3117ece4Schristos</b><p> Initialize/reset DStream state for new decompression operation. 752*3117ece4Schristos Call before new decompression operation using same DStream. 753*3117ece4Schristos 754*3117ece4Schristos Note : This function is redundant with the advanced API and equivalent to: 755*3117ece4Schristos ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); 756*3117ece4Schristos ZSTD_DCtx_refDDict(zds, NULL); 757*3117ece4Schristos 758*3117ece4Schristos</p></pre><BR> 759*3117ece4Schristos 760*3117ece4Schristos<pre><b>size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input); 761*3117ece4Schristos</b><p> Streaming decompression function. 762*3117ece4Schristos Call repetitively to consume full input updating it as necessary. 763*3117ece4Schristos Function will update both input and output `pos` fields exposing current state via these fields: 764*3117ece4Schristos - `input.pos < input.size`, some input remaining and caller should provide remaining input 765*3117ece4Schristos on the next call. 766*3117ece4Schristos - `output.pos < output.size`, decoder finished and flushed all remaining buffers. 767*3117ece4Schristos - `output.pos == output.size`, potentially uncflushed data present in the internal buffers, 768*3117ece4Schristos call ZSTD_decompressStream() again to flush remaining data to output. 769*3117ece4Schristos Note : with no additional input, amount of data flushed <= ZSTD_BLOCKSIZE_MAX. 770*3117ece4Schristos 771*3117ece4Schristos @return : 0 when a frame is completely decoded and fully flushed, 772*3117ece4Schristos or an error code, which can be tested using ZSTD_isError(), 773*3117ece4Schristos or any other value > 0, which means there is some decoding or flushing to do to complete current frame. 774*3117ece4Schristos 775*3117ece4Schristos Note: when an operation returns with an error code, the @zds state may be left in undefined state. 776*3117ece4Schristos It's UB to invoke `ZSTD_decompressStream()` on such a state. 777*3117ece4Schristos In order to re-use such a state, it must be first reset, 778*3117ece4Schristos which can be done explicitly (`ZSTD_DCtx_reset()`), 779*3117ece4Schristos or is implied for operations starting some new decompression job (`ZSTD_initDStream`, `ZSTD_decompressDCtx()`, `ZSTD_decompress_usingDict()`) 780*3117ece4Schristos 781*3117ece4Schristos</p></pre><BR> 782*3117ece4Schristos 783*3117ece4Schristos<pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b> 784*3117ece4Schristos</b></pre><BR> 785*3117ece4Schristos<pre><b>size_t ZSTD_DStreamOutSize(void); </b>/*!< recommended size for output buffer. Guarantee to successfully flush at least one complete block in all circumstances. */<b> 786*3117ece4Schristos</b></pre><BR> 787*3117ece4Schristos<a name="Chapter10"></a><h2>Simple dictionary API</h2><pre></pre> 788*3117ece4Schristos 789*3117ece4Schristos<pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx, 790*3117ece4Schristos void* dst, size_t dstCapacity, 791*3117ece4Schristos const void* src, size_t srcSize, 792*3117ece4Schristos const void* dict,size_t dictSize, 793*3117ece4Schristos int compressionLevel); 794*3117ece4Schristos</b><p> Compression at an explicit compression level using a Dictionary. 795*3117ece4Schristos A dictionary can be any arbitrary data segment (also called a prefix), 796*3117ece4Schristos or a buffer with specified information (see zdict.h). 797*3117ece4Schristos Note : This function loads the dictionary, resulting in significant startup delay. 798*3117ece4Schristos It's intended for a dictionary used only once. 799*3117ece4Schristos Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used. 800*3117ece4Schristos</p></pre><BR> 801*3117ece4Schristos 802*3117ece4Schristos<pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx, 803*3117ece4Schristos void* dst, size_t dstCapacity, 804*3117ece4Schristos const void* src, size_t srcSize, 805*3117ece4Schristos const void* dict,size_t dictSize); 806*3117ece4Schristos</b><p> Decompression using a known Dictionary. 807*3117ece4Schristos Dictionary must be identical to the one used during compression. 808*3117ece4Schristos Note : This function loads the dictionary, resulting in significant startup delay. 809*3117ece4Schristos It's intended for a dictionary used only once. 810*3117ece4Schristos Note : When `dict == NULL || dictSize < 8` no dictionary is used. 811*3117ece4Schristos</p></pre><BR> 812*3117ece4Schristos 813*3117ece4Schristos<a name="Chapter11"></a><h2>Bulk processing dictionary API</h2><pre></pre> 814*3117ece4Schristos 815*3117ece4Schristos<pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize, 816*3117ece4Schristos int compressionLevel); 817*3117ece4Schristos</b><p> When compressing multiple messages or blocks using the same dictionary, 818*3117ece4Schristos it's recommended to digest the dictionary only once, since it's a costly operation. 819*3117ece4Schristos ZSTD_createCDict() will create a state from digesting a dictionary. 820*3117ece4Schristos The resulting state can be used for future compression operations with very limited startup cost. 821*3117ece4Schristos ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only. 822*3117ece4Schristos @dictBuffer can be released after ZSTD_CDict creation, because its content is copied within CDict. 823*3117ece4Schristos Note 1 : Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate @dictBuffer content. 824*3117ece4Schristos Note 2 : A ZSTD_CDict can be created from an empty @dictBuffer, 825*3117ece4Schristos in which case the only thing that it transports is the @compressionLevel. 826*3117ece4Schristos This can be useful in a pipeline featuring ZSTD_compress_usingCDict() exclusively, 827*3117ece4Schristos expecting a ZSTD_CDict parameter with any data, including those without a known dictionary. 828*3117ece4Schristos</p></pre><BR> 829*3117ece4Schristos 830*3117ece4Schristos<pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict); 831*3117ece4Schristos</b><p> Function frees memory allocated by ZSTD_createCDict(). 832*3117ece4Schristos If a NULL pointer is passed, no operation is performed. 833*3117ece4Schristos</p></pre><BR> 834*3117ece4Schristos 835*3117ece4Schristos<pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx, 836*3117ece4Schristos void* dst, size_t dstCapacity, 837*3117ece4Schristos const void* src, size_t srcSize, 838*3117ece4Schristos const ZSTD_CDict* cdict); 839*3117ece4Schristos</b><p> Compression using a digested Dictionary. 840*3117ece4Schristos Recommended when same dictionary is used multiple times. 841*3117ece4Schristos Note : compression level is _decided at dictionary creation time_, 842*3117ece4Schristos and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no) 843*3117ece4Schristos</p></pre><BR> 844*3117ece4Schristos 845*3117ece4Schristos<pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize); 846*3117ece4Schristos</b><p> Create a digested dictionary, ready to start decompression operation without startup delay. 847*3117ece4Schristos dictBuffer can be released after DDict creation, as its content is copied inside DDict. 848*3117ece4Schristos</p></pre><BR> 849*3117ece4Schristos 850*3117ece4Schristos<pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict); 851*3117ece4Schristos</b><p> Function frees memory allocated with ZSTD_createDDict() 852*3117ece4Schristos If a NULL pointer is passed, no operation is performed. 853*3117ece4Schristos</p></pre><BR> 854*3117ece4Schristos 855*3117ece4Schristos<pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx, 856*3117ece4Schristos void* dst, size_t dstCapacity, 857*3117ece4Schristos const void* src, size_t srcSize, 858*3117ece4Schristos const ZSTD_DDict* ddict); 859*3117ece4Schristos</b><p> Decompression using a digested Dictionary. 860*3117ece4Schristos Recommended when same dictionary is used multiple times. 861*3117ece4Schristos</p></pre><BR> 862*3117ece4Schristos 863*3117ece4Schristos<a name="Chapter12"></a><h2>Dictionary helper functions</h2><pre></pre> 864*3117ece4Schristos 865*3117ece4Schristos<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize); 866*3117ece4Schristos</b><p> Provides the dictID stored within dictionary. 867*3117ece4Schristos if @return == 0, the dictionary is not conformant with Zstandard specification. 868*3117ece4Schristos It can still be loaded, but as a content-only dictionary. 869*3117ece4Schristos</p></pre><BR> 870*3117ece4Schristos 871*3117ece4Schristos<pre><b>unsigned ZSTD_getDictID_fromCDict(const ZSTD_CDict* cdict); 872*3117ece4Schristos</b><p> Provides the dictID of the dictionary loaded into `cdict`. 873*3117ece4Schristos If @return == 0, the dictionary is not conformant to Zstandard specification, or empty. 874*3117ece4Schristos Non-conformant dictionaries can still be loaded, but as content-only dictionaries. 875*3117ece4Schristos</p></pre><BR> 876*3117ece4Schristos 877*3117ece4Schristos<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict); 878*3117ece4Schristos</b><p> Provides the dictID of the dictionary loaded into `ddict`. 879*3117ece4Schristos If @return == 0, the dictionary is not conformant to Zstandard specification, or empty. 880*3117ece4Schristos Non-conformant dictionaries can still be loaded, but as content-only dictionaries. 881*3117ece4Schristos</p></pre><BR> 882*3117ece4Schristos 883*3117ece4Schristos<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize); 884*3117ece4Schristos</b><p> Provides the dictID required to decompressed the frame stored within `src`. 885*3117ece4Schristos If @return == 0, the dictID could not be decoded. 886*3117ece4Schristos This could for one of the following reasons : 887*3117ece4Schristos - The frame does not require a dictionary to be decoded (most common case). 888*3117ece4Schristos - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden piece of information. 889*3117ece4Schristos Note : this use case also happens when using a non-conformant dictionary. 890*3117ece4Schristos - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`). 891*3117ece4Schristos - This is not a Zstandard frame. 892*3117ece4Schristos When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code. 893*3117ece4Schristos</p></pre><BR> 894*3117ece4Schristos 895*3117ece4Schristos<a name="Chapter13"></a><h2>Advanced dictionary and prefix API (Requires v1.4.0+)</h2><pre> 896*3117ece4Schristos This API allows dictionaries to be used with ZSTD_compress2(), 897*3117ece4Schristos ZSTD_compressStream2(), and ZSTD_decompressDCtx(). 898*3117ece4Schristos Dictionaries are sticky, they remain valid when same context is reused, 899*3117ece4Schristos they only reset when the context is reset 900*3117ece4Schristos with ZSTD_reset_parameters or ZSTD_reset_session_and_parameters. 901*3117ece4Schristos In contrast, Prefixes are single-use. 902*3117ece4Schristos<BR></pre> 903*3117ece4Schristos 904*3117ece4Schristos<pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); 905*3117ece4Schristos</b><p> Create an internal CDict from `dict` buffer. 906*3117ece4Schristos Decompression will have to use same dictionary. 907*3117ece4Schristos @result : 0, or an error code (which can be tested with ZSTD_isError()). 908*3117ece4Schristos Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary, 909*3117ece4Schristos meaning "return to no-dictionary mode". 910*3117ece4Schristos Note 1 : Dictionary is sticky, it will be used for all future compressed frames, 911*3117ece4Schristos until parameters are reset, a new dictionary is loaded, or the dictionary 912*3117ece4Schristos is explicitly invalidated by loading a NULL dictionary. 913*3117ece4Schristos Note 2 : Loading a dictionary involves building tables. 914*3117ece4Schristos It's also a CPU consuming operation, with non-negligible impact on latency. 915*3117ece4Schristos Tables are dependent on compression parameters, and for this reason, 916*3117ece4Schristos compression parameters can no longer be changed after loading a dictionary. 917*3117ece4Schristos Note 3 :`dict` content will be copied internally. 918*3117ece4Schristos Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead. 919*3117ece4Schristos In such a case, dictionary buffer must outlive its users. 920*3117ece4Schristos Note 4 : Use ZSTD_CCtx_loadDictionary_advanced() 921*3117ece4Schristos to precisely select how dictionary content must be interpreted. 922*3117ece4Schristos Note 5 : This method does not benefit from LDM (long distance mode). 923*3117ece4Schristos If you want to employ LDM on some large dictionary content, 924*3117ece4Schristos prefer employing ZSTD_CCtx_refPrefix() described below. 925*3117ece4Schristos 926*3117ece4Schristos</p></pre><BR> 927*3117ece4Schristos 928*3117ece4Schristos<pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); 929*3117ece4Schristos</b><p> Reference a prepared dictionary, to be used for all future compressed frames. 930*3117ece4Schristos Note that compression parameters are enforced from within CDict, 931*3117ece4Schristos and supersede any compression parameter previously set within CCtx. 932*3117ece4Schristos The parameters ignored are labelled as "superseded-by-cdict" in the ZSTD_cParameter enum docs. 933*3117ece4Schristos The ignored parameters will be used again if the CCtx is returned to no-dictionary mode. 934*3117ece4Schristos The dictionary will remain valid for future compressed frames using same CCtx. 935*3117ece4Schristos @result : 0, or an error code (which can be tested with ZSTD_isError()). 936*3117ece4Schristos Special : Referencing a NULL CDict means "return to no-dictionary mode". 937*3117ece4Schristos Note 1 : Currently, only one dictionary can be managed. 938*3117ece4Schristos Referencing a new dictionary effectively "discards" any previous one. 939*3117ece4Schristos Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx. 940*3117ece4Schristos</p></pre><BR> 941*3117ece4Schristos 942*3117ece4Schristos<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, 943*3117ece4Schristos const void* prefix, size_t prefixSize); 944*3117ece4Schristos</b><p> Reference a prefix (single-usage dictionary) for next compressed frame. 945*3117ece4Schristos A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end). 946*3117ece4Schristos Decompression will need same prefix to properly regenerate data. 947*3117ece4Schristos Compressing with a prefix is similar in outcome as performing a diff and compressing it, 948*3117ece4Schristos but performs much faster, especially during decompression (compression speed is tunable with compression level). 949*3117ece4Schristos This method is compatible with LDM (long distance mode). 950*3117ece4Schristos @result : 0, or an error code (which can be tested with ZSTD_isError()). 951*3117ece4Schristos Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary 952*3117ece4Schristos Note 1 : Prefix buffer is referenced. It **must** outlive compression. 953*3117ece4Schristos Its content must remain unmodified during compression. 954*3117ece4Schristos Note 2 : If the intention is to diff some large src data blob with some prior version of itself, 955*3117ece4Schristos ensure that the window size is large enough to contain the entire source. 956*3117ece4Schristos See ZSTD_c_windowLog. 957*3117ece4Schristos Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters. 958*3117ece4Schristos It's a CPU consuming operation, with non-negligible impact on latency. 959*3117ece4Schristos If there is a need to use the same prefix multiple times, consider loadDictionary instead. 960*3117ece4Schristos Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dct_rawContent). 961*3117ece4Schristos Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation. 962*3117ece4Schristos</p></pre><BR> 963*3117ece4Schristos 964*3117ece4Schristos<pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); 965*3117ece4Schristos</b><p> Create an internal DDict from dict buffer, to be used to decompress all future frames. 966*3117ece4Schristos The dictionary remains valid for all future frames, until explicitly invalidated, or 967*3117ece4Schristos a new dictionary is loaded. 968*3117ece4Schristos @result : 0, or an error code (which can be tested with ZSTD_isError()). 969*3117ece4Schristos Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary, 970*3117ece4Schristos meaning "return to no-dictionary mode". 971*3117ece4Schristos Note 1 : Loading a dictionary involves building tables, 972*3117ece4Schristos which has a non-negligible impact on CPU usage and latency. 973*3117ece4Schristos It's recommended to "load once, use many times", to amortize the cost 974*3117ece4Schristos Note 2 :`dict` content will be copied internally, so `dict` can be released after loading. 975*3117ece4Schristos Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead. 976*3117ece4Schristos Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of 977*3117ece4Schristos how dictionary content is loaded and interpreted. 978*3117ece4Schristos 979*3117ece4Schristos</p></pre><BR> 980*3117ece4Schristos 981*3117ece4Schristos<pre><b>size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict); 982*3117ece4Schristos</b><p> Reference a prepared dictionary, to be used to decompress next frames. 983*3117ece4Schristos The dictionary remains active for decompression of future frames using same DCtx. 984*3117ece4Schristos 985*3117ece4Schristos If called with ZSTD_d_refMultipleDDicts enabled, repeated calls of this function 986*3117ece4Schristos will store the DDict references in a table, and the DDict used for decompression 987*3117ece4Schristos will be determined at decompression time, as per the dict ID in the frame. 988*3117ece4Schristos The memory for the table is allocated on the first call to refDDict, and can be 989*3117ece4Schristos freed with ZSTD_freeDCtx(). 990*3117ece4Schristos 991*3117ece4Schristos If called with ZSTD_d_refMultipleDDicts disabled (the default), only one dictionary 992*3117ece4Schristos will be managed, and referencing a dictionary effectively "discards" any previous one. 993*3117ece4Schristos 994*3117ece4Schristos @result : 0, or an error code (which can be tested with ZSTD_isError()). 995*3117ece4Schristos Special: referencing a NULL DDict means "return to no-dictionary mode". 996*3117ece4Schristos Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx. 997*3117ece4Schristos 998*3117ece4Schristos</p></pre><BR> 999*3117ece4Schristos 1000*3117ece4Schristos<pre><b>size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx, 1001*3117ece4Schristos const void* prefix, size_t prefixSize); 1002*3117ece4Schristos</b><p> Reference a prefix (single-usage dictionary) to decompress next frame. 1003*3117ece4Schristos This is the reverse operation of ZSTD_CCtx_refPrefix(), 1004*3117ece4Schristos and must use the same prefix as the one used during compression. 1005*3117ece4Schristos Prefix is **only used once**. Reference is discarded at end of frame. 1006*3117ece4Schristos End of frame is reached when ZSTD_decompressStream() returns 0. 1007*3117ece4Schristos @result : 0, or an error code (which can be tested with ZSTD_isError()). 1008*3117ece4Schristos Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary 1009*3117ece4Schristos Note 2 : Prefix buffer is referenced. It **must** outlive decompression. 1010*3117ece4Schristos Prefix buffer must remain unmodified up to the end of frame, 1011*3117ece4Schristos reached when ZSTD_decompressStream() returns 0. 1012*3117ece4Schristos Note 3 : By default, the prefix is treated as raw content (ZSTD_dct_rawContent). 1013*3117ece4Schristos Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section) 1014*3117ece4Schristos Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost. 1015*3117ece4Schristos A full dictionary is more costly, as it requires building tables. 1016*3117ece4Schristos 1017*3117ece4Schristos</p></pre><BR> 1018*3117ece4Schristos 1019*3117ece4Schristos<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx); 1020*3117ece4Schristossize_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx); 1021*3117ece4Schristossize_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs); 1022*3117ece4Schristossize_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds); 1023*3117ece4Schristossize_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict); 1024*3117ece4Schristossize_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict); 1025*3117ece4Schristos</b><p> These functions give the _current_ memory usage of selected object. 1026*3117ece4Schristos Note that object memory usage can evolve (increase or decrease) over time. 1027*3117ece4Schristos</p></pre><BR> 1028*3117ece4Schristos 1029*3117ece4Schristos<a name="Chapter14"></a><h2>experimental API (static linking only)</h2><pre> 1030*3117ece4Schristos The following symbols and constants 1031*3117ece4Schristos are not planned to join "stable API" status in the near future. 1032*3117ece4Schristos They can still change in future versions. 1033*3117ece4Schristos Some of them are planned to remain in the static_only section indefinitely. 1034*3117ece4Schristos Some of them might be removed in the future (especially when redundant with existing stable functions) 1035*3117ece4Schristos 1036*3117ece4Schristos<BR></pre> 1037*3117ece4Schristos 1038*3117ece4Schristos<pre><b>typedef struct { 1039*3117ece4Schristos unsigned int offset; </b>/* The offset of the match. (NOT the same as the offset code)<b> 1040*3117ece4Schristos * If offset == 0 and matchLength == 0, this sequence represents the last 1041*3117ece4Schristos * literals in the block of litLength size. 1042*3117ece4Schristos */ 1043*3117ece4Schristos 1044*3117ece4Schristos unsigned int litLength; </b>/* Literal length of the sequence. */<b> 1045*3117ece4Schristos unsigned int matchLength; </b>/* Match length of the sequence. */<b> 1046*3117ece4Schristos 1047*3117ece4Schristos </b>/* Note: Users of this API may provide a sequence with matchLength == litLength == offset == 0.<b> 1048*3117ece4Schristos * In this case, we will treat the sequence as a marker for a block boundary. 1049*3117ece4Schristos */ 1050*3117ece4Schristos 1051*3117ece4Schristos unsigned int rep; </b>/* Represents which repeat offset is represented by the field 'offset'.<b> 1052*3117ece4Schristos * Ranges from [0, 3]. 1053*3117ece4Schristos * 1054*3117ece4Schristos * Repeat offsets are essentially previous offsets from previous sequences sorted in 1055*3117ece4Schristos * recency order. For more detail, see doc/zstd_compression_format.md 1056*3117ece4Schristos * 1057*3117ece4Schristos * If rep == 0, then 'offset' does not contain a repeat offset. 1058*3117ece4Schristos * If rep > 0: 1059*3117ece4Schristos * If litLength != 0: 1060*3117ece4Schristos * rep == 1 --> offset == repeat_offset_1 1061*3117ece4Schristos * rep == 2 --> offset == repeat_offset_2 1062*3117ece4Schristos * rep == 3 --> offset == repeat_offset_3 1063*3117ece4Schristos * If litLength == 0: 1064*3117ece4Schristos * rep == 1 --> offset == repeat_offset_2 1065*3117ece4Schristos * rep == 2 --> offset == repeat_offset_3 1066*3117ece4Schristos * rep == 3 --> offset == repeat_offset_1 - 1 1067*3117ece4Schristos * 1068*3117ece4Schristos * Note: This field is optional. ZSTD_generateSequences() will calculate the value of 1069*3117ece4Schristos * 'rep', but repeat offsets do not necessarily need to be calculated from an external 1070*3117ece4Schristos * sequence provider's perspective. For example, ZSTD_compressSequences() does not 1071*3117ece4Schristos * use this 'rep' field at all (as of now). 1072*3117ece4Schristos */ 1073*3117ece4Schristos} ZSTD_Sequence; 1074*3117ece4Schristos</b></pre><BR> 1075*3117ece4Schristos<pre><b>typedef struct { 1076*3117ece4Schristos unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b> 1077*3117ece4Schristos unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b> 1078*3117ece4Schristos unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b> 1079*3117ece4Schristos unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b> 1080*3117ece4Schristos unsigned minMatch; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b> 1081*3117ece4Schristos unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b> 1082*3117ece4Schristos ZSTD_strategy strategy; </b>/**< see ZSTD_strategy definition above */<b> 1083*3117ece4Schristos} ZSTD_compressionParameters; 1084*3117ece4Schristos</b></pre><BR> 1085*3117ece4Schristos<pre><b>typedef struct { 1086*3117ece4Schristos int contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b> 1087*3117ece4Schristos int checksumFlag; </b>/**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */<b> 1088*3117ece4Schristos int noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */<b> 1089*3117ece4Schristos} ZSTD_frameParameters; 1090*3117ece4Schristos</b></pre><BR> 1091*3117ece4Schristos<pre><b>typedef struct { 1092*3117ece4Schristos ZSTD_compressionParameters cParams; 1093*3117ece4Schristos ZSTD_frameParameters fParams; 1094*3117ece4Schristos} ZSTD_parameters; 1095*3117ece4Schristos</b></pre><BR> 1096*3117ece4Schristos<pre><b>typedef enum { 1097*3117ece4Schristos ZSTD_dct_auto = 0, </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b> 1098*3117ece4Schristos ZSTD_dct_rawContent = 1, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b> 1099*3117ece4Schristos ZSTD_dct_fullDict = 2 </b>/* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */<b> 1100*3117ece4Schristos} ZSTD_dictContentType_e; 1101*3117ece4Schristos</b></pre><BR> 1102*3117ece4Schristos<pre><b>typedef enum { 1103*3117ece4Schristos ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b> 1104*3117ece4Schristos ZSTD_dlm_byRef = 1 </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b> 1105*3117ece4Schristos} ZSTD_dictLoadMethod_e; 1106*3117ece4Schristos</b></pre><BR> 1107*3117ece4Schristos<pre><b>typedef enum { 1108*3117ece4Schristos ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b> 1109*3117ece4Schristos ZSTD_f_zstd1_magicless = 1 </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b> 1110*3117ece4Schristos * Useful to save 4 bytes per generated frame. 1111*3117ece4Schristos * Decoder cannot recognise automatically this format, requiring this instruction. */ 1112*3117ece4Schristos} ZSTD_format_e; 1113*3117ece4Schristos</b></pre><BR> 1114*3117ece4Schristos<pre><b>typedef enum { 1115*3117ece4Schristos </b>/* Note: this enum controls ZSTD_d_forceIgnoreChecksum */<b> 1116*3117ece4Schristos ZSTD_d_validateChecksum = 0, 1117*3117ece4Schristos ZSTD_d_ignoreChecksum = 1 1118*3117ece4Schristos} ZSTD_forceIgnoreChecksum_e; 1119*3117ece4Schristos</b></pre><BR> 1120*3117ece4Schristos<pre><b>typedef enum { 1121*3117ece4Schristos </b>/* Note: this enum controls ZSTD_d_refMultipleDDicts */<b> 1122*3117ece4Schristos ZSTD_rmd_refSingleDDict = 0, 1123*3117ece4Schristos ZSTD_rmd_refMultipleDDicts = 1 1124*3117ece4Schristos} ZSTD_refMultipleDDicts_e; 1125*3117ece4Schristos</b></pre><BR> 1126*3117ece4Schristos<pre><b>typedef enum { 1127*3117ece4Schristos </b>/* Note: this enum and the behavior it controls are effectively internal<b> 1128*3117ece4Schristos * implementation details of the compressor. They are expected to continue 1129*3117ece4Schristos * to evolve and should be considered only in the context of extremely 1130*3117ece4Schristos * advanced performance tuning. 1131*3117ece4Schristos * 1132*3117ece4Schristos * Zstd currently supports the use of a CDict in three ways: 1133*3117ece4Schristos * 1134*3117ece4Schristos * - The contents of the CDict can be copied into the working context. This 1135*3117ece4Schristos * means that the compression can search both the dictionary and input 1136*3117ece4Schristos * while operating on a single set of internal tables. This makes 1137*3117ece4Schristos * the compression faster per-byte of input. However, the initial copy of 1138*3117ece4Schristos * the CDict's tables incurs a fixed cost at the beginning of the 1139*3117ece4Schristos * compression. For small compressions (< 8 KB), that copy can dominate 1140*3117ece4Schristos * the cost of the compression. 1141*3117ece4Schristos * 1142*3117ece4Schristos * - The CDict's tables can be used in-place. In this model, compression is 1143*3117ece4Schristos * slower per input byte, because the compressor has to search two sets of 1144*3117ece4Schristos * tables. However, this model incurs no start-up cost (as long as the 1145*3117ece4Schristos * working context's tables can be reused). For small inputs, this can be 1146*3117ece4Schristos * faster than copying the CDict's tables. 1147*3117ece4Schristos * 1148*3117ece4Schristos * - The CDict's tables are not used at all, and instead we use the working 1149*3117ece4Schristos * context alone to reload the dictionary and use params based on the source 1150*3117ece4Schristos * size. See ZSTD_compress_insertDictionary() and ZSTD_compress_usingDict(). 1151*3117ece4Schristos * This method is effective when the dictionary sizes are very small relative 1152*3117ece4Schristos * to the input size, and the input size is fairly large to begin with. 1153*3117ece4Schristos * 1154*3117ece4Schristos * Zstd has a simple internal heuristic that selects which strategy to use 1155*3117ece4Schristos * at the beginning of a compression. However, if experimentation shows that 1156*3117ece4Schristos * Zstd is making poor choices, it is possible to override that choice with 1157*3117ece4Schristos * this enum. 1158*3117ece4Schristos */ 1159*3117ece4Schristos ZSTD_dictDefaultAttach = 0, </b>/* Use the default heuristic. */<b> 1160*3117ece4Schristos ZSTD_dictForceAttach = 1, </b>/* Never copy the dictionary. */<b> 1161*3117ece4Schristos ZSTD_dictForceCopy = 2, </b>/* Always copy the dictionary. */<b> 1162*3117ece4Schristos ZSTD_dictForceLoad = 3 </b>/* Always reload the dictionary */<b> 1163*3117ece4Schristos} ZSTD_dictAttachPref_e; 1164*3117ece4Schristos</b></pre><BR> 1165*3117ece4Schristos<pre><b>typedef enum { 1166*3117ece4Schristos ZSTD_lcm_auto = 0, </b>/**< Automatically determine the compression mode based on the compression level.<b> 1167*3117ece4Schristos * Negative compression levels will be uncompressed, and positive compression 1168*3117ece4Schristos * levels will be compressed. */ 1169*3117ece4Schristos ZSTD_lcm_huffman = 1, </b>/**< Always attempt Huffman compression. Uncompressed literals will still be<b> 1170*3117ece4Schristos * emitted if Huffman compression is not profitable. */ 1171*3117ece4Schristos ZSTD_lcm_uncompressed = 2 </b>/**< Always emit uncompressed literals. */<b> 1172*3117ece4Schristos} ZSTD_literalCompressionMode_e; 1173*3117ece4Schristos</b></pre><BR> 1174*3117ece4Schristos<pre><b>typedef enum { 1175*3117ece4Schristos </b>/* Note: This enum controls features which are conditionally beneficial. Zstd typically will make a final<b> 1176*3117ece4Schristos * decision on whether or not to enable the feature (ZSTD_ps_auto), but setting the switch to ZSTD_ps_enable 1177*3117ece4Schristos * or ZSTD_ps_disable allow for a force enable/disable the feature. 1178*3117ece4Schristos */ 1179*3117ece4Schristos ZSTD_ps_auto = 0, </b>/* Let the library automatically determine whether the feature shall be enabled */<b> 1180*3117ece4Schristos ZSTD_ps_enable = 1, </b>/* Force-enable the feature */<b> 1181*3117ece4Schristos ZSTD_ps_disable = 2 </b>/* Do not use the feature */<b> 1182*3117ece4Schristos} ZSTD_paramSwitch_e; 1183*3117ece4Schristos</b></pre><BR> 1184*3117ece4Schristos<a name="Chapter15"></a><h2>Frame header and size functions</h2><pre></pre> 1185*3117ece4Schristos 1186*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize); 1187*3117ece4Schristos</b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames 1188*3117ece4Schristos `srcSize` must be the _exact_ size of this series 1189*3117ece4Schristos (i.e. there should be a frame boundary at `src + srcSize`) 1190*3117ece4Schristos @return : - decompressed size of all data in all successive frames 1191*3117ece4Schristos - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN 1192*3117ece4Schristos - if an error occurred: ZSTD_CONTENTSIZE_ERROR 1193*3117ece4Schristos 1194*3117ece4Schristos note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode. 1195*3117ece4Schristos When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size. 1196*3117ece4Schristos In which case, it's necessary to use streaming mode to decompress data. 1197*3117ece4Schristos note 2 : decompressed size is always present when compression is done with ZSTD_compress() 1198*3117ece4Schristos note 3 : decompressed size can be very large (64-bits value), 1199*3117ece4Schristos potentially larger than what local system can handle as a single memory segment. 1200*3117ece4Schristos In which case, it's necessary to use streaming mode to decompress data. 1201*3117ece4Schristos note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified. 1202*3117ece4Schristos Always ensure result fits within application's authorized limits. 1203*3117ece4Schristos Each application can set its own limits. 1204*3117ece4Schristos note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to 1205*3117ece4Schristos read each contained frame header. This is fast as most of the data is skipped, 1206*3117ece4Schristos however it does mean that all frame data must be present and valid. 1207*3117ece4Schristos</p></pre><BR> 1208*3117ece4Schristos 1209*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize); 1210*3117ece4Schristos</b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames 1211*3117ece4Schristos `srcSize` must be the _exact_ size of this series 1212*3117ece4Schristos (i.e. there should be a frame boundary at `src + srcSize`) 1213*3117ece4Schristos @return : - upper-bound for the decompressed size of all data in all successive frames 1214*3117ece4Schristos - if an error occurred: ZSTD_CONTENTSIZE_ERROR 1215*3117ece4Schristos 1216*3117ece4Schristos note 1 : an error can occur if `src` contains an invalid or incorrectly formatted frame. 1217*3117ece4Schristos note 2 : the upper-bound is exact when the decompressed size field is available in every ZSTD encoded frame of `src`. 1218*3117ece4Schristos in this case, `ZSTD_findDecompressedSize` and `ZSTD_decompressBound` return the same value. 1219*3117ece4Schristos note 3 : when the decompressed size field isn't available, the upper-bound for that frame is calculated by: 1220*3117ece4Schristos upper-bound = # blocks * min(128 KB, Window_Size) 1221*3117ece4Schristos 1222*3117ece4Schristos</p></pre><BR> 1223*3117ece4Schristos 1224*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize); 1225*3117ece4Schristos</b><p> srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX. 1226*3117ece4Schristos @return : size of the Frame Header, 1227*3117ece4Schristos or an error code (if srcSize is too small) 1228*3117ece4Schristos</p></pre><BR> 1229*3117ece4Schristos 1230*3117ece4Schristos<pre><b>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e; 1231*3117ece4Schristos</b></pre><BR> 1232*3117ece4Schristos<pre><b>typedef struct { 1233*3117ece4Schristos unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b> 1234*3117ece4Schristos unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b> 1235*3117ece4Schristos unsigned blockSizeMax; 1236*3117ece4Schristos ZSTD_frameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b> 1237*3117ece4Schristos unsigned headerSize; 1238*3117ece4Schristos unsigned dictID; 1239*3117ece4Schristos unsigned checksumFlag; 1240*3117ece4Schristos unsigned _reserved1; 1241*3117ece4Schristos unsigned _reserved2; 1242*3117ece4Schristos} ZSTD_frameHeader; 1243*3117ece4Schristos</b></pre><BR> 1244*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b> 1245*3117ece4Schristos</b>/*! ZSTD_getFrameHeader_advanced() :<b> 1246*3117ece4Schristos * same as ZSTD_getFrameHeader(), 1247*3117ece4Schristos * with added capability to select a format (like ZSTD_f_zstd1_magicless) */ 1248*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format); 1249*3117ece4Schristos</b><p> decode Frame Header, or requires larger `srcSize`. 1250*3117ece4Schristos @return : 0, `zfhPtr` is correctly filled, 1251*3117ece4Schristos >0, `srcSize` is too small, value is wanted `srcSize` amount, 1252*3117ece4Schristos or an error code, which can be tested using ZSTD_isError() 1253*3117ece4Schristos</p></pre><BR> 1254*3117ece4Schristos 1255*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decompressionMargin(const void* src, size_t srcSize); 1256*3117ece4Schristos</b><p> Zstd supports in-place decompression, where the input and output buffers overlap. 1257*3117ece4Schristos In this case, the output buffer must be at least (Margin + Output_Size) bytes large, 1258*3117ece4Schristos and the input buffer must be at the end of the output buffer. 1259*3117ece4Schristos 1260*3117ece4Schristos _______________________ Output Buffer ________________________ 1261*3117ece4Schristos | | 1262*3117ece4Schristos | ____ Input Buffer ____| 1263*3117ece4Schristos | | | 1264*3117ece4Schristos v v v 1265*3117ece4Schristos |---------------------------------------|-----------|----------| 1266*3117ece4Schristos ^ ^ ^ 1267*3117ece4Schristos |___________________ Output_Size ___________________|_ Margin _| 1268*3117ece4Schristos 1269*3117ece4Schristos NOTE: See also ZSTD_DECOMPRESSION_MARGIN(). 1270*3117ece4Schristos NOTE: This applies only to single-pass decompression through ZSTD_decompress() or 1271*3117ece4Schristos ZSTD_decompressDCtx(). 1272*3117ece4Schristos NOTE: This function supports multi-frame input. 1273*3117ece4Schristos 1274*3117ece4Schristos @param src The compressed frame(s) 1275*3117ece4Schristos @param srcSize The size of the compressed frame(s) 1276*3117ece4Schristos @returns The decompression margin or an error that can be checked with ZSTD_isError(). 1277*3117ece4Schristos 1278*3117ece4Schristos</p></pre><BR> 1279*3117ece4Schristos 1280*3117ece4Schristos<pre><b>#define ZSTD_DECOMPRESSION_MARGIN(originalSize, blockSize) ((size_t)( \ 1281*3117ece4Schristos ZSTD_FRAMEHEADERSIZE_MAX </b>/* Frame header */ + \<b> 1282*3117ece4Schristos 4 </b>/* checksum */ + \<b> 1283*3117ece4Schristos ((originalSize) == 0 ? 0 : 3 * (((originalSize) + (blockSize) - 1) / blockSize)) </b>/* 3 bytes per block */ + \<b> 1284*3117ece4Schristos (blockSize) </b>/* One block of margin */ \<b> 1285*3117ece4Schristos )) 1286*3117ece4Schristos</b><p> Similar to ZSTD_decompressionMargin(), but instead of computing the margin from 1287*3117ece4Schristos the compressed frame, compute it from the original size and the blockSizeLog. 1288*3117ece4Schristos See ZSTD_decompressionMargin() for details. 1289*3117ece4Schristos 1290*3117ece4Schristos WARNING: This macro does not support multi-frame input, the input must be a single 1291*3117ece4Schristos zstd frame. If you need that support use the function, or implement it yourself. 1292*3117ece4Schristos 1293*3117ece4Schristos @param originalSize The original uncompressed size of the data. 1294*3117ece4Schristos @param blockSize The block size == MIN(windowSize, ZSTD_BLOCKSIZE_MAX). 1295*3117ece4Schristos Unless you explicitly set the windowLog smaller than 1296*3117ece4Schristos ZSTD_BLOCKSIZELOG_MAX you can just use ZSTD_BLOCKSIZE_MAX. 1297*3117ece4Schristos 1298*3117ece4Schristos</p></pre><BR> 1299*3117ece4Schristos 1300*3117ece4Schristos<pre><b>typedef enum { 1301*3117ece4Schristos ZSTD_sf_noBlockDelimiters = 0, </b>/* Representation of ZSTD_Sequence has no block delimiters, sequences only */<b> 1302*3117ece4Schristos ZSTD_sf_explicitBlockDelimiters = 1 </b>/* Representation of ZSTD_Sequence contains explicit block delimiters */<b> 1303*3117ece4Schristos} ZSTD_sequenceFormat_e; 1304*3117ece4Schristos</b></pre><BR> 1305*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_sequenceBound(size_t srcSize); 1306*3117ece4Schristos</b><p> `srcSize` : size of the input buffer 1307*3117ece4Schristos @return : upper-bound for the number of sequences that can be generated 1308*3117ece4Schristos from a buffer of srcSize bytes 1309*3117ece4Schristos 1310*3117ece4Schristos note : returns number of sequences - to get bytes, multiply by sizeof(ZSTD_Sequence). 1311*3117ece4Schristos 1312*3117ece4Schristos</p></pre><BR> 1313*3117ece4Schristos 1314*3117ece4Schristos<pre><b></b><p> Generate sequences using ZSTD_compress2(), given a source buffer. 1315*3117ece4Schristos 1316*3117ece4Schristos Each block will end with a dummy sequence 1317*3117ece4Schristos with offset == 0, matchLength == 0, and litLength == length of last literals. 1318*3117ece4Schristos litLength may be == 0, and if so, then the sequence of (of: 0 ml: 0 ll: 0) 1319*3117ece4Schristos simply acts as a block delimiter. 1320*3117ece4Schristos 1321*3117ece4Schristos @zc can be used to insert custom compression params. 1322*3117ece4Schristos This function invokes ZSTD_compress2(). 1323*3117ece4Schristos 1324*3117ece4Schristos The output of this function can be fed into ZSTD_compressSequences() with CCtx 1325*3117ece4Schristos setting of ZSTD_c_blockDelimiters as ZSTD_sf_explicitBlockDelimiters 1326*3117ece4Schristos @return : number of sequences generated 1327*3117ece4Schristos 1328*3117ece4Schristos</p></pre><BR> 1329*3117ece4Schristos 1330*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_mergeBlockDelimiters(ZSTD_Sequence* sequences, size_t seqsSize); 1331*3117ece4Schristos</b><p> Given an array of ZSTD_Sequence, remove all sequences that represent block delimiters/last literals 1332*3117ece4Schristos by merging them into the literals of the next sequence. 1333*3117ece4Schristos 1334*3117ece4Schristos As such, the final generated result has no explicit representation of block boundaries, 1335*3117ece4Schristos and the final last literals segment is not represented in the sequences. 1336*3117ece4Schristos 1337*3117ece4Schristos The output of this function can be fed into ZSTD_compressSequences() with CCtx 1338*3117ece4Schristos setting of ZSTD_c_blockDelimiters as ZSTD_sf_noBlockDelimiters 1339*3117ece4Schristos @return : number of sequences left after merging 1340*3117ece4Schristos 1341*3117ece4Schristos</p></pre><BR> 1342*3117ece4Schristos 1343*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t 1344*3117ece4SchristosZSTD_compressSequences( ZSTD_CCtx* cctx, void* dst, size_t dstSize, 1345*3117ece4Schristos const ZSTD_Sequence* inSeqs, size_t inSeqsSize, 1346*3117ece4Schristos const void* src, size_t srcSize); 1347*3117ece4Schristos</b><p> Compress an array of ZSTD_Sequence, associated with @src buffer, into dst. 1348*3117ece4Schristos @src contains the entire input (not just the literals). 1349*3117ece4Schristos If @srcSize > sum(sequence.length), the remaining bytes are considered all literals 1350*3117ece4Schristos If a dictionary is included, then the cctx should reference the dict. (see: ZSTD_CCtx_refCDict(), ZSTD_CCtx_loadDictionary(), etc.) 1351*3117ece4Schristos The entire source is compressed into a single frame. 1352*3117ece4Schristos 1353*3117ece4Schristos The compression behavior changes based on cctx params. In particular: 1354*3117ece4Schristos If ZSTD_c_blockDelimiters == ZSTD_sf_noBlockDelimiters, the array of ZSTD_Sequence is expected to contain 1355*3117ece4Schristos no block delimiters (defined in ZSTD_Sequence). Block boundaries are roughly determined based on 1356*3117ece4Schristos the block size derived from the cctx, and sequences may be split. This is the default setting. 1357*3117ece4Schristos 1358*3117ece4Schristos If ZSTD_c_blockDelimiters == ZSTD_sf_explicitBlockDelimiters, the array of ZSTD_Sequence is expected to contain 1359*3117ece4Schristos block delimiters (defined in ZSTD_Sequence). Behavior is undefined if no block delimiters are provided. 1360*3117ece4Schristos 1361*3117ece4Schristos If ZSTD_c_validateSequences == 0, this function will blindly accept the sequences provided. Invalid sequences cause undefined 1362*3117ece4Schristos behavior. If ZSTD_c_validateSequences == 1, then if sequence is invalid (see doc/zstd_compression_format.md for 1363*3117ece4Schristos specifics regarding offset/matchlength requirements) then the function will bail out and return an error. 1364*3117ece4Schristos 1365*3117ece4Schristos In addition to the two adjustable experimental params, there are other important cctx params. 1366*3117ece4Schristos - ZSTD_c_minMatch MUST be set as less than or equal to the smallest match generated by the match finder. It has a minimum value of ZSTD_MINMATCH_MIN. 1367*3117ece4Schristos - ZSTD_c_compressionLevel accordingly adjusts the strength of the entropy coder, as it would in typical compression. 1368*3117ece4Schristos - ZSTD_c_windowLog affects offset validation: this function will return an error at higher debug levels if a provided offset 1369*3117ece4Schristos is larger than what the spec allows for a given window log and dictionary (if present). See: doc/zstd_compression_format.md 1370*3117ece4Schristos 1371*3117ece4Schristos Note: Repcodes are, as of now, always re-calculated within this function, so ZSTD_Sequence::rep is unused. 1372*3117ece4Schristos Note 2: Once we integrate ability to ingest repcodes, the explicit block delims mode must respect those repcodes exactly, 1373*3117ece4Schristos and cannot emit an RLE block that disagrees with the repcode history 1374*3117ece4Schristos @return : final compressed size, or a ZSTD error code. 1375*3117ece4Schristos 1376*3117ece4Schristos</p></pre><BR> 1377*3117ece4Schristos 1378*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_writeSkippableFrame(void* dst, size_t dstCapacity, 1379*3117ece4Schristos const void* src, size_t srcSize, unsigned magicVariant); 1380*3117ece4Schristos</b><p> Generates a zstd skippable frame containing data given by src, and writes it to dst buffer. 1381*3117ece4Schristos 1382*3117ece4Schristos Skippable frames begin with a 4-byte magic number. There are 16 possible choices of magic number, 1383*3117ece4Schristos ranging from ZSTD_MAGIC_SKIPPABLE_START to ZSTD_MAGIC_SKIPPABLE_START+15. 1384*3117ece4Schristos As such, the parameter magicVariant controls the exact skippable frame magic number variant used, so 1385*3117ece4Schristos the magic number used will be ZSTD_MAGIC_SKIPPABLE_START + magicVariant. 1386*3117ece4Schristos 1387*3117ece4Schristos Returns an error if destination buffer is not large enough, if the source size is not representable 1388*3117ece4Schristos with a 4-byte unsigned int, or if the parameter magicVariant is greater than 15 (and therefore invalid). 1389*3117ece4Schristos 1390*3117ece4Schristos @return : number of bytes written or a ZSTD error. 1391*3117ece4Schristos 1392*3117ece4Schristos</p></pre><BR> 1393*3117ece4Schristos 1394*3117ece4Schristos<pre><b>size_t ZSTD_readSkippableFrame(void* dst, size_t dstCapacity, unsigned* magicVariant, 1395*3117ece4Schristos const void* src, size_t srcSize); 1396*3117ece4Schristos</b><p> Retrieves a zstd skippable frame containing data given by src, and writes it to dst buffer. 1397*3117ece4Schristos 1398*3117ece4Schristos The parameter magicVariant will receive the magicVariant that was supplied when the frame was written, 1399*3117ece4Schristos i.e. magicNumber - ZSTD_MAGIC_SKIPPABLE_START. This can be NULL if the caller is not interested 1400*3117ece4Schristos in the magicVariant. 1401*3117ece4Schristos 1402*3117ece4Schristos Returns an error if destination buffer is not large enough, or if the frame is not skippable. 1403*3117ece4Schristos 1404*3117ece4Schristos @return : number of bytes written or a ZSTD error. 1405*3117ece4Schristos 1406*3117ece4Schristos</p></pre><BR> 1407*3117ece4Schristos 1408*3117ece4Schristos<pre><b>unsigned ZSTD_isSkippableFrame(const void* buffer, size_t size); 1409*3117ece4Schristos</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier for a skippable frame. 1410*3117ece4Schristos 1411*3117ece4Schristos</p></pre><BR> 1412*3117ece4Schristos 1413*3117ece4Schristos<a name="Chapter16"></a><h2>Memory management</h2><pre></pre> 1414*3117ece4Schristos 1415*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize(int maxCompressionLevel); 1416*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams); 1417*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params); 1418*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_estimateDCtxSize(void); 1419*3117ece4Schristos</b><p> These functions make it possible to estimate memory usage 1420*3117ece4Schristos of a future {D,C}Ctx, before its creation. 1421*3117ece4Schristos This is useful in combination with ZSTD_initStatic(), 1422*3117ece4Schristos which makes it possible to employ a static buffer for ZSTD_CCtx* state. 1423*3117ece4Schristos 1424*3117ece4Schristos ZSTD_estimateCCtxSize() will provide a memory budget large enough 1425*3117ece4Schristos to compress data of any size using one-shot compression ZSTD_compressCCtx() or ZSTD_compress2() 1426*3117ece4Schristos associated with any compression level up to max specified one. 1427*3117ece4Schristos The estimate will assume the input may be arbitrarily large, 1428*3117ece4Schristos which is the worst case. 1429*3117ece4Schristos 1430*3117ece4Schristos Note that the size estimation is specific for one-shot compression, 1431*3117ece4Schristos it is not valid for streaming (see ZSTD_estimateCStreamSize*()) 1432*3117ece4Schristos nor other potential ways of using a ZSTD_CCtx* state. 1433*3117ece4Schristos 1434*3117ece4Schristos When srcSize can be bound by a known and rather "small" value, 1435*3117ece4Schristos this knowledge can be used to provide a tighter budget estimation 1436*3117ece4Schristos because the ZSTD_CCtx* state will need less memory for small inputs. 1437*3117ece4Schristos This tighter estimation can be provided by employing more advanced functions 1438*3117ece4Schristos ZSTD_estimateCCtxSize_usingCParams(), which can be used in tandem with ZSTD_getCParams(), 1439*3117ece4Schristos and ZSTD_estimateCCtxSize_usingCCtxParams(), which can be used in tandem with ZSTD_CCtxParams_setParameter(). 1440*3117ece4Schristos Both can be used to estimate memory using custom compression parameters and arbitrary srcSize limits. 1441*3117ece4Schristos 1442*3117ece4Schristos Note : only single-threaded compression is supported. 1443*3117ece4Schristos ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1. 1444*3117ece4Schristos 1445*3117ece4Schristos</p></pre><BR> 1446*3117ece4Schristos 1447*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize(int maxCompressionLevel); 1448*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams); 1449*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params); 1450*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize(size_t maxWindowSize); 1451*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize); 1452*3117ece4Schristos</b><p> ZSTD_estimateCStreamSize() will provide a memory budget large enough for streaming compression 1453*3117ece4Schristos using any compression level up to the max specified one. 1454*3117ece4Schristos It will also consider src size to be arbitrarily "large", which is a worst case scenario. 1455*3117ece4Schristos If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation. 1456*3117ece4Schristos ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel. 1457*3117ece4Schristos ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParams_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_c_nbWorkers is >= 1. 1458*3117ece4Schristos Note : CStream size estimation is only correct for single-threaded compression. 1459*3117ece4Schristos ZSTD_estimateCStreamSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1. 1460*3117ece4Schristos Note 2 : ZSTD_estimateCStreamSize* functions are not compatible with the Block-Level Sequence Producer API at this time. 1461*3117ece4Schristos Size estimates assume that no external sequence producer is registered. 1462*3117ece4Schristos 1463*3117ece4Schristos ZSTD_DStream memory budget depends on frame's window Size. 1464*3117ece4Schristos This information can be passed manually, using ZSTD_estimateDStreamSize, 1465*3117ece4Schristos or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame(); 1466*3117ece4Schristos Any frame requesting a window size larger than max specified one will be rejected. 1467*3117ece4Schristos Note : if streaming is init with function ZSTD_init?Stream_usingDict(), 1468*3117ece4Schristos an internal ?Dict will be created, which additional size is not estimated here. 1469*3117ece4Schristos In this case, get total size by adding ZSTD_estimate?DictSize 1470*3117ece4Schristos 1471*3117ece4Schristos</p></pre><BR> 1472*3117ece4Schristos 1473*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel); 1474*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod); 1475*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod); 1476*3117ece4Schristos</b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict(). 1477*3117ece4Schristos ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced(). 1478*3117ece4Schristos Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller. 1479*3117ece4Schristos 1480*3117ece4Schristos</p></pre><BR> 1481*3117ece4Schristos 1482*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize); 1483*3117ece4SchristosZSTDLIB_STATIC_API ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b> 1484*3117ece4Schristos</b><p> Initialize an object using a pre-allocated fixed-size buffer. 1485*3117ece4Schristos workspace: The memory area to emplace the object into. 1486*3117ece4Schristos Provided pointer *must be 8-bytes aligned*. 1487*3117ece4Schristos Buffer must outlive object. 1488*3117ece4Schristos workspaceSize: Use ZSTD_estimate*Size() to determine 1489*3117ece4Schristos how large workspace must be to support target scenario. 1490*3117ece4Schristos @return : pointer to object (same address as workspace, just different type), 1491*3117ece4Schristos or NULL if error (size too small, incorrect alignment, etc.) 1492*3117ece4Schristos Note : zstd will never resize nor malloc() when using a static buffer. 1493*3117ece4Schristos If the object requires more memory than available, 1494*3117ece4Schristos zstd will just error out (typically ZSTD_error_memory_allocation). 1495*3117ece4Schristos Note 2 : there is no corresponding "free" function. 1496*3117ece4Schristos Since workspace is allocated externally, it must be freed externally too. 1497*3117ece4Schristos Note 3 : cParams : use ZSTD_getCParams() to convert a compression level 1498*3117ece4Schristos into its associated cParams. 1499*3117ece4Schristos Limitation 1 : currently not compatible with internal dictionary creation, triggered by 1500*3117ece4Schristos ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict(). 1501*3117ece4Schristos Limitation 2 : static cctx currently not compatible with multi-threading. 1502*3117ece4Schristos Limitation 3 : static dctx is incompatible with legacy support. 1503*3117ece4Schristos 1504*3117ece4Schristos</p></pre><BR> 1505*3117ece4Schristos 1506*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b> 1507*3117ece4Schristos</b></pre><BR> 1508*3117ece4Schristos<pre><b>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size); 1509*3117ece4Schristostypedef void (*ZSTD_freeFunction) (void* opaque, void* address); 1510*3117ece4Schristostypedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem; 1511*3117ece4Schristosstatic 1512*3117ece4Schristos#ifdef __GNUC__ 1513*3117ece4Schristos__attribute__((__unused__)) 1514*3117ece4Schristos#endif 1515*3117ece4SchristosZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; </b>/**< this constant defers to stdlib's functions */<b> 1516*3117ece4Schristos</b><p> These prototypes make it possible to pass your own allocation/free functions. 1517*3117ece4Schristos ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below. 1518*3117ece4Schristos All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones. 1519*3117ece4Schristos 1520*3117ece4Schristos</p></pre><BR> 1521*3117ece4Schristos 1522*3117ece4Schristos<pre><b>typedef struct POOL_ctx_s ZSTD_threadPool; 1523*3117ece4SchristosZSTDLIB_STATIC_API ZSTD_threadPool* ZSTD_createThreadPool(size_t numThreads); 1524*3117ece4SchristosZSTDLIB_STATIC_API void ZSTD_freeThreadPool (ZSTD_threadPool* pool); </b>/* accept NULL pointer */<b> 1525*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_CCtx_refThreadPool(ZSTD_CCtx* cctx, ZSTD_threadPool* pool); 1526*3117ece4Schristos</b><p> These prototypes make it possible to share a thread pool among multiple compression contexts. 1527*3117ece4Schristos This can limit resources for applications with multiple threads where each one uses 1528*3117ece4Schristos a threaded compression mode (via ZSTD_c_nbWorkers parameter). 1529*3117ece4Schristos ZSTD_createThreadPool creates a new thread pool with a given number of threads. 1530*3117ece4Schristos Note that the lifetime of such pool must exist while being used. 1531*3117ece4Schristos ZSTD_CCtx_refThreadPool assigns a thread pool to a context (use NULL argument value 1532*3117ece4Schristos to use an internal thread pool). 1533*3117ece4Schristos ZSTD_freeThreadPool frees a thread pool, accepts NULL pointer. 1534*3117ece4Schristos 1535*3117ece4Schristos</p></pre><BR> 1536*3117ece4Schristos 1537*3117ece4Schristos<a name="Chapter17"></a><h2>Advanced compression functions</h2><pre></pre> 1538*3117ece4Schristos 1539*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel); 1540*3117ece4Schristos</b><p> Create a digested dictionary for compression 1541*3117ece4Schristos Dictionary content is just referenced, not duplicated. 1542*3117ece4Schristos As a consequence, `dictBuffer` **must** outlive CDict, 1543*3117ece4Schristos and its content must remain unmodified throughout the lifetime of CDict. 1544*3117ece4Schristos note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef 1545*3117ece4Schristos</p></pre><BR> 1546*3117ece4Schristos 1547*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); 1548*3117ece4Schristos</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize. 1549*3117ece4Schristos `estimatedSrcSize` value is optional, select 0 if not known 1550*3117ece4Schristos</p></pre><BR> 1551*3117ece4Schristos 1552*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); 1553*3117ece4Schristos</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`. 1554*3117ece4Schristos All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0 1555*3117ece4Schristos</p></pre><BR> 1556*3117ece4Schristos 1557*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_checkCParams(ZSTD_compressionParameters params); 1558*3117ece4Schristos</b><p> Ensure param values remain within authorized range. 1559*3117ece4Schristos @return 0 on success, or an error code (can be checked with ZSTD_isError()) 1560*3117ece4Schristos</p></pre><BR> 1561*3117ece4Schristos 1562*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize); 1563*3117ece4Schristos</b><p> optimize params for a given `srcSize` and `dictSize`. 1564*3117ece4Schristos `srcSize` can be unknown, in which case use ZSTD_CONTENTSIZE_UNKNOWN. 1565*3117ece4Schristos `dictSize` must be `0` when there is no dictionary. 1566*3117ece4Schristos cPar can be invalid : all parameters will be clamped within valid range in the @return struct. 1567*3117ece4Schristos This function never fails (wide contract) 1568*3117ece4Schristos</p></pre><BR> 1569*3117ece4Schristos 1570*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setCParams(ZSTD_CCtx* cctx, ZSTD_compressionParameters cparams); 1571*3117ece4Schristos</b><p> Set all parameters provided within @p cparams into the working @p cctx. 1572*3117ece4Schristos Note : if modifying parameters during compression (MT mode only), 1573*3117ece4Schristos note that changes to the .windowLog parameter will be ignored. 1574*3117ece4Schristos @return 0 on success, or an error code (can be checked with ZSTD_isError()). 1575*3117ece4Schristos On failure, no parameters are updated. 1576*3117ece4Schristos 1577*3117ece4Schristos</p></pre><BR> 1578*3117ece4Schristos 1579*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setFParams(ZSTD_CCtx* cctx, ZSTD_frameParameters fparams); 1580*3117ece4Schristos</b><p> Set all parameters provided within @p fparams into the working @p cctx. 1581*3117ece4Schristos @return 0 on success, or an error code (can be checked with ZSTD_isError()). 1582*3117ece4Schristos 1583*3117ece4Schristos</p></pre><BR> 1584*3117ece4Schristos 1585*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParams(ZSTD_CCtx* cctx, ZSTD_parameters params); 1586*3117ece4Schristos</b><p> Set all parameters provided within @p params into the working @p cctx. 1587*3117ece4Schristos @return 0 on success, or an error code (can be checked with ZSTD_isError()). 1588*3117ece4Schristos 1589*3117ece4Schristos</p></pre><BR> 1590*3117ece4Schristos 1591*3117ece4Schristos<pre><b>ZSTD_DEPRECATED("use ZSTD_compress2") 1592*3117ece4SchristosZSTDLIB_STATIC_API 1593*3117ece4Schristossize_t ZSTD_compress_advanced(ZSTD_CCtx* cctx, 1594*3117ece4Schristos void* dst, size_t dstCapacity, 1595*3117ece4Schristos const void* src, size_t srcSize, 1596*3117ece4Schristos const void* dict,size_t dictSize, 1597*3117ece4Schristos ZSTD_parameters params); 1598*3117ece4Schristos</b><p> Note : this function is now DEPRECATED. 1599*3117ece4Schristos It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters. 1600*3117ece4Schristos This prototype will generate compilation warnings. 1601*3117ece4Schristos</p></pre><BR> 1602*3117ece4Schristos 1603*3117ece4Schristos<pre><b>ZSTD_DEPRECATED("use ZSTD_compress2 with ZSTD_CCtx_loadDictionary") 1604*3117ece4SchristosZSTDLIB_STATIC_API 1605*3117ece4Schristossize_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx, 1606*3117ece4Schristos void* dst, size_t dstCapacity, 1607*3117ece4Schristos const void* src, size_t srcSize, 1608*3117ece4Schristos const ZSTD_CDict* cdict, 1609*3117ece4Schristos ZSTD_frameParameters fParams); 1610*3117ece4Schristos</b><p> Note : this function is now DEPRECATED. 1611*3117ece4Schristos It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters. 1612*3117ece4Schristos This prototype will generate compilation warnings. 1613*3117ece4Schristos</p></pre><BR> 1614*3117ece4Schristos 1615*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); 1616*3117ece4Schristos</b><p> Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx. 1617*3117ece4Schristos It saves some memory, but also requires that `dict` outlives its usage within `cctx` 1618*3117ece4Schristos</p></pre><BR> 1619*3117ece4Schristos 1620*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType); 1621*3117ece4Schristos</b><p> Same as ZSTD_CCtx_loadDictionary(), but gives finer control over 1622*3117ece4Schristos how to load the dictionary (by copy ? by reference ?) 1623*3117ece4Schristos and how to interpret it (automatic ? force raw mode ? full mode only ?) 1624*3117ece4Schristos</p></pre><BR> 1625*3117ece4Schristos 1626*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType); 1627*3117ece4Schristos</b><p> Same as ZSTD_CCtx_refPrefix(), but gives finer control over 1628*3117ece4Schristos how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) 1629*3117ece4Schristos</p></pre><BR> 1630*3117ece4Schristos 1631*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_getParameter(const ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value); 1632*3117ece4Schristos</b><p> Get the requested compression parameter value, selected by enum ZSTD_cParameter, 1633*3117ece4Schristos and store it into int* value. 1634*3117ece4Schristos @return : 0, or an error code (which can be tested with ZSTD_isError()). 1635*3117ece4Schristos 1636*3117ece4Schristos</p></pre><BR> 1637*3117ece4Schristos 1638*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API ZSTD_CCtx_params* ZSTD_createCCtxParams(void); 1639*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params); </b>/* accept NULL pointer */<b> 1640*3117ece4Schristos</b><p> Quick howto : 1641*3117ece4Schristos - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure 1642*3117ece4Schristos - ZSTD_CCtxParams_setParameter() : Push parameters one by one into 1643*3117ece4Schristos an existing ZSTD_CCtx_params structure. 1644*3117ece4Schristos This is similar to 1645*3117ece4Schristos ZSTD_CCtx_setParameter(). 1646*3117ece4Schristos - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to 1647*3117ece4Schristos an existing CCtx. 1648*3117ece4Schristos These parameters will be applied to 1649*3117ece4Schristos all subsequent frames. 1650*3117ece4Schristos - ZSTD_compressStream2() : Do compression using the CCtx. 1651*3117ece4Schristos - ZSTD_freeCCtxParams() : Free the memory, accept NULL pointer. 1652*3117ece4Schristos 1653*3117ece4Schristos This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams() 1654*3117ece4Schristos for static allocation of CCtx for single-threaded compression. 1655*3117ece4Schristos 1656*3117ece4Schristos</p></pre><BR> 1657*3117ece4Schristos 1658*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params); 1659*3117ece4Schristos</b><p> Reset params to default values. 1660*3117ece4Schristos 1661*3117ece4Schristos</p></pre><BR> 1662*3117ece4Schristos 1663*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel); 1664*3117ece4Schristos</b><p> Initializes the compression parameters of cctxParams according to 1665*3117ece4Schristos compression level. All other parameters are reset to their default values. 1666*3117ece4Schristos 1667*3117ece4Schristos</p></pre><BR> 1668*3117ece4Schristos 1669*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params); 1670*3117ece4Schristos</b><p> Initializes the compression and frame parameters of cctxParams according to 1671*3117ece4Schristos params. All other parameters are reset to their default values. 1672*3117ece4Schristos 1673*3117ece4Schristos</p></pre><BR> 1674*3117ece4Schristos 1675*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value); 1676*3117ece4Schristos</b><p> Similar to ZSTD_CCtx_setParameter. 1677*3117ece4Schristos Set one compression parameter, selected by enum ZSTD_cParameter. 1678*3117ece4Schristos Parameters must be applied to a ZSTD_CCtx using 1679*3117ece4Schristos ZSTD_CCtx_setParametersUsingCCtxParams(). 1680*3117ece4Schristos @result : a code representing success or failure (which can be tested with 1681*3117ece4Schristos ZSTD_isError()). 1682*3117ece4Schristos 1683*3117ece4Schristos</p></pre><BR> 1684*3117ece4Schristos 1685*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_getParameter(const ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value); 1686*3117ece4Schristos</b><p> Similar to ZSTD_CCtx_getParameter. 1687*3117ece4Schristos Get the requested value of one compression parameter, selected by enum ZSTD_cParameter. 1688*3117ece4Schristos @result : 0, or an error code (which can be tested with ZSTD_isError()). 1689*3117ece4Schristos 1690*3117ece4Schristos</p></pre><BR> 1691*3117ece4Schristos 1692*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParametersUsingCCtxParams( 1693*3117ece4Schristos ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params); 1694*3117ece4Schristos</b><p> Apply a set of ZSTD_CCtx_params to the compression context. 1695*3117ece4Schristos This can be done even after compression is started, 1696*3117ece4Schristos if nbWorkers==0, this will have no impact until a new compression is started. 1697*3117ece4Schristos if nbWorkers>=1, new parameters will be picked up at next job, 1698*3117ece4Schristos with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated). 1699*3117ece4Schristos 1700*3117ece4Schristos</p></pre><BR> 1701*3117ece4Schristos 1702*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_compressStream2_simpleArgs ( 1703*3117ece4Schristos ZSTD_CCtx* cctx, 1704*3117ece4Schristos void* dst, size_t dstCapacity, size_t* dstPos, 1705*3117ece4Schristos const void* src, size_t srcSize, size_t* srcPos, 1706*3117ece4Schristos ZSTD_EndDirective endOp); 1707*3117ece4Schristos</b><p> Same as ZSTD_compressStream2(), 1708*3117ece4Schristos but using only integral types as arguments. 1709*3117ece4Schristos This variant might be helpful for binders from dynamic languages 1710*3117ece4Schristos which have troubles handling structures containing memory pointers. 1711*3117ece4Schristos 1712*3117ece4Schristos</p></pre><BR> 1713*3117ece4Schristos 1714*3117ece4Schristos<a name="Chapter18"></a><h2>Advanced decompression functions</h2><pre></pre> 1715*3117ece4Schristos 1716*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API unsigned ZSTD_isFrame(const void* buffer, size_t size); 1717*3117ece4Schristos</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier. 1718*3117ece4Schristos Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0. 1719*3117ece4Schristos Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled. 1720*3117ece4Schristos Note 3 : Skippable Frame Identifiers are considered valid. 1721*3117ece4Schristos</p></pre><BR> 1722*3117ece4Schristos 1723*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize); 1724*3117ece4Schristos</b><p> Create a digested dictionary, ready to start decompression operation without startup delay. 1725*3117ece4Schristos Dictionary content is referenced, and therefore stays in dictBuffer. 1726*3117ece4Schristos It is important that dictBuffer outlives DDict, 1727*3117ece4Schristos it must remain read accessible throughout the lifetime of DDict 1728*3117ece4Schristos</p></pre><BR> 1729*3117ece4Schristos 1730*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); 1731*3117ece4Schristos</b><p> Same as ZSTD_DCtx_loadDictionary(), 1732*3117ece4Schristos but references `dict` content instead of copying it into `dctx`. 1733*3117ece4Schristos This saves memory if `dict` remains around., 1734*3117ece4Schristos However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression. 1735*3117ece4Schristos</p></pre><BR> 1736*3117ece4Schristos 1737*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType); 1738*3117ece4Schristos</b><p> Same as ZSTD_DCtx_loadDictionary(), 1739*3117ece4Schristos but gives direct control over 1740*3117ece4Schristos how to load the dictionary (by copy ? by reference ?) 1741*3117ece4Schristos and how to interpret it (automatic ? force raw mode ? full mode only ?). 1742*3117ece4Schristos</p></pre><BR> 1743*3117ece4Schristos 1744*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType); 1745*3117ece4Schristos</b><p> Same as ZSTD_DCtx_refPrefix(), but gives finer control over 1746*3117ece4Schristos how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) 1747*3117ece4Schristos</p></pre><BR> 1748*3117ece4Schristos 1749*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize); 1750*3117ece4Schristos</b><p> Refuses allocating internal buffers for frames requiring a window size larger than provided limit. 1751*3117ece4Schristos This protects a decoder context from reserving too much memory for itself (potential attack scenario). 1752*3117ece4Schristos This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode. 1753*3117ece4Schristos By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT) 1754*3117ece4Schristos @return : 0, or an error code (which can be tested using ZSTD_isError()). 1755*3117ece4Schristos 1756*3117ece4Schristos</p></pre><BR> 1757*3117ece4Schristos 1758*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_getParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int* value); 1759*3117ece4Schristos</b><p> Get the requested decompression parameter value, selected by enum ZSTD_dParameter, 1760*3117ece4Schristos and store it into int* value. 1761*3117ece4Schristos @return : 0, or an error code (which can be tested with ZSTD_isError()). 1762*3117ece4Schristos 1763*3117ece4Schristos</p></pre><BR> 1764*3117ece4Schristos 1765*3117ece4Schristos<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_setParameter() instead") 1766*3117ece4SchristosZSTDLIB_STATIC_API 1767*3117ece4Schristossize_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format); 1768*3117ece4Schristos</b><p> This function is REDUNDANT. Prefer ZSTD_DCtx_setParameter(). 1769*3117ece4Schristos Instruct the decoder context about what kind of data to decode next. 1770*3117ece4Schristos This instruction is mandatory to decode data without a fully-formed header, 1771*3117ece4Schristos such ZSTD_f_zstd1_magicless for example. 1772*3117ece4Schristos @return : 0, or an error code (which can be tested using ZSTD_isError()). 1773*3117ece4Schristos</p></pre><BR> 1774*3117ece4Schristos 1775*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decompressStream_simpleArgs ( 1776*3117ece4Schristos ZSTD_DCtx* dctx, 1777*3117ece4Schristos void* dst, size_t dstCapacity, size_t* dstPos, 1778*3117ece4Schristos const void* src, size_t srcSize, size_t* srcPos); 1779*3117ece4Schristos</b><p> Same as ZSTD_decompressStream(), 1780*3117ece4Schristos but using only integral types as arguments. 1781*3117ece4Schristos This can be helpful for binders from dynamic languages 1782*3117ece4Schristos which have troubles handling structures containing memory pointers. 1783*3117ece4Schristos 1784*3117ece4Schristos</p></pre><BR> 1785*3117ece4Schristos 1786*3117ece4Schristos<a name="Chapter19"></a><h2>Advanced streaming functions</h2><pre> Warning : most of these functions are now redundant with the Advanced API. 1787*3117ece4Schristos Once Advanced API reaches "stable" status, 1788*3117ece4Schristos redundant functions will be deprecated, and then at some point removed. 1789*3117ece4Schristos<BR></pre> 1790*3117ece4Schristos 1791*3117ece4Schristos<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre></pre></b><BR> 1792*3117ece4Schristos<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") 1793*3117ece4SchristosZSTDLIB_STATIC_API 1794*3117ece4Schristossize_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, 1795*3117ece4Schristos int compressionLevel, 1796*3117ece4Schristos unsigned long long pledgedSrcSize); 1797*3117ece4Schristos</b><p> This function is DEPRECATED, and equivalent to: 1798*3117ece4Schristos ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); 1799*3117ece4Schristos ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any) 1800*3117ece4Schristos ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); 1801*3117ece4Schristos ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); 1802*3117ece4Schristos 1803*3117ece4Schristos pledgedSrcSize must be correct. If it is not known at init time, use 1804*3117ece4Schristos ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs, 1805*3117ece4Schristos "0" also disables frame content size field. It may be enabled in the future. 1806*3117ece4Schristos This prototype will generate compilation warnings. 1807*3117ece4Schristos 1808*3117ece4Schristos</p></pre><BR> 1809*3117ece4Schristos 1810*3117ece4Schristos<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") 1811*3117ece4SchristosZSTDLIB_STATIC_API 1812*3117ece4Schristossize_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, 1813*3117ece4Schristos const void* dict, size_t dictSize, 1814*3117ece4Schristos int compressionLevel); 1815*3117ece4Schristos</b><p> This function is DEPRECATED, and is equivalent to: 1816*3117ece4Schristos ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); 1817*3117ece4Schristos ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); 1818*3117ece4Schristos ZSTD_CCtx_loadDictionary(zcs, dict, dictSize); 1819*3117ece4Schristos 1820*3117ece4Schristos Creates of an internal CDict (incompatible with static CCtx), except if 1821*3117ece4Schristos dict == NULL or dictSize < 8, in which case no dict is used. 1822*3117ece4Schristos Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if 1823*3117ece4Schristos it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy. 1824*3117ece4Schristos This prototype will generate compilation warnings. 1825*3117ece4Schristos 1826*3117ece4Schristos</p></pre><BR> 1827*3117ece4Schristos 1828*3117ece4Schristos<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") 1829*3117ece4SchristosZSTDLIB_STATIC_API 1830*3117ece4Schristossize_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, 1831*3117ece4Schristos const void* dict, size_t dictSize, 1832*3117ece4Schristos ZSTD_parameters params, 1833*3117ece4Schristos unsigned long long pledgedSrcSize); 1834*3117ece4Schristos</b><p> This function is DEPRECATED, and is equivalent to: 1835*3117ece4Schristos ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); 1836*3117ece4Schristos ZSTD_CCtx_setParams(zcs, params); 1837*3117ece4Schristos ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); 1838*3117ece4Schristos ZSTD_CCtx_loadDictionary(zcs, dict, dictSize); 1839*3117ece4Schristos 1840*3117ece4Schristos dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy. 1841*3117ece4Schristos pledgedSrcSize must be correct. 1842*3117ece4Schristos If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN. 1843*3117ece4Schristos This prototype will generate compilation warnings. 1844*3117ece4Schristos 1845*3117ece4Schristos</p></pre><BR> 1846*3117ece4Schristos 1847*3117ece4Schristos<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions") 1848*3117ece4SchristosZSTDLIB_STATIC_API 1849*3117ece4Schristossize_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict); 1850*3117ece4Schristos</b><p> This function is DEPRECATED, and equivalent to: 1851*3117ece4Schristos ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); 1852*3117ece4Schristos ZSTD_CCtx_refCDict(zcs, cdict); 1853*3117ece4Schristos 1854*3117ece4Schristos note : cdict will just be referenced, and must outlive compression session 1855*3117ece4Schristos This prototype will generate compilation warnings. 1856*3117ece4Schristos 1857*3117ece4Schristos</p></pre><BR> 1858*3117ece4Schristos 1859*3117ece4Schristos<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions") 1860*3117ece4SchristosZSTDLIB_STATIC_API 1861*3117ece4Schristossize_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, 1862*3117ece4Schristos const ZSTD_CDict* cdict, 1863*3117ece4Schristos ZSTD_frameParameters fParams, 1864*3117ece4Schristos unsigned long long pledgedSrcSize); 1865*3117ece4Schristos</b><p> This function is DEPRECATED, and is equivalent to: 1866*3117ece4Schristos ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); 1867*3117ece4Schristos ZSTD_CCtx_setFParams(zcs, fParams); 1868*3117ece4Schristos ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); 1869*3117ece4Schristos ZSTD_CCtx_refCDict(zcs, cdict); 1870*3117ece4Schristos 1871*3117ece4Schristos same as ZSTD_initCStream_usingCDict(), with control over frame parameters. 1872*3117ece4Schristos pledgedSrcSize must be correct. If srcSize is not known at init time, use 1873*3117ece4Schristos value ZSTD_CONTENTSIZE_UNKNOWN. 1874*3117ece4Schristos This prototype will generate compilation warnings. 1875*3117ece4Schristos 1876*3117ece4Schristos</p></pre><BR> 1877*3117ece4Schristos 1878*3117ece4Schristos<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") 1879*3117ece4SchristosZSTDLIB_STATIC_API 1880*3117ece4Schristossize_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize); 1881*3117ece4Schristos</b><p> This function is DEPRECATED, and is equivalent to: 1882*3117ece4Schristos ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); 1883*3117ece4Schristos ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); 1884*3117ece4Schristos Note: ZSTD_resetCStream() interprets pledgedSrcSize == 0 as ZSTD_CONTENTSIZE_UNKNOWN, but 1885*3117ece4Schristos ZSTD_CCtx_setPledgedSrcSize() does not do the same, so ZSTD_CONTENTSIZE_UNKNOWN must be 1886*3117ece4Schristos explicitly specified. 1887*3117ece4Schristos 1888*3117ece4Schristos start a new frame, using same parameters from previous frame. 1889*3117ece4Schristos This is typically useful to skip dictionary loading stage, since it will reuse it in-place. 1890*3117ece4Schristos Note that zcs must be init at least once before using ZSTD_resetCStream(). 1891*3117ece4Schristos If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN. 1892*3117ece4Schristos If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end. 1893*3117ece4Schristos For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs, 1894*3117ece4Schristos but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead. 1895*3117ece4Schristos @return : 0, or an error code (which can be tested using ZSTD_isError()) 1896*3117ece4Schristos This prototype will generate compilation warnings. 1897*3117ece4Schristos 1898*3117ece4Schristos</p></pre><BR> 1899*3117ece4Schristos 1900*3117ece4Schristos<pre><b>typedef struct { 1901*3117ece4Schristos unsigned long long ingested; </b>/* nb input bytes read and buffered */<b> 1902*3117ece4Schristos unsigned long long consumed; </b>/* nb input bytes actually compressed */<b> 1903*3117ece4Schristos unsigned long long produced; </b>/* nb of compressed bytes generated and buffered */<b> 1904*3117ece4Schristos unsigned long long flushed; </b>/* nb of compressed bytes flushed : not provided; can be tracked from caller side */<b> 1905*3117ece4Schristos unsigned currentJobID; </b>/* MT only : latest started job nb */<b> 1906*3117ece4Schristos unsigned nbActiveWorkers; </b>/* MT only : nb of workers actively compressing at probe time */<b> 1907*3117ece4Schristos} ZSTD_frameProgression; 1908*3117ece4Schristos</b></pre><BR> 1909*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx); 1910*3117ece4Schristos</b><p> Tell how many bytes are ready to be flushed immediately. 1911*3117ece4Schristos Useful for multithreading scenarios (nbWorkers >= 1). 1912*3117ece4Schristos Probe the oldest active job, defined as oldest job not yet entirely flushed, 1913*3117ece4Schristos and check its output buffer. 1914*3117ece4Schristos @return : amount of data stored in oldest job and ready to be flushed immediately. 1915*3117ece4Schristos if @return == 0, it means either : 1916*3117ece4Schristos + there is no active job (could be checked with ZSTD_frameProgression()), or 1917*3117ece4Schristos + oldest job is still actively compressing data, 1918*3117ece4Schristos but everything it has produced has also been flushed so far, 1919*3117ece4Schristos therefore flush speed is limited by production speed of oldest job 1920*3117ece4Schristos irrespective of the speed of concurrent (and newer) jobs. 1921*3117ece4Schristos 1922*3117ece4Schristos</p></pre><BR> 1923*3117ece4Schristos 1924*3117ece4Schristos<h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR> 1925*3117ece4Schristos<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_loadDictionary, see zstd.h for detailed instructions") 1926*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); 1927*3117ece4Schristos</b><p> 1928*3117ece4Schristos ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); 1929*3117ece4Schristos ZSTD_DCtx_loadDictionary(zds, dict, dictSize); 1930*3117ece4Schristos 1931*3117ece4Schristos note: no dictionary will be used if dict == NULL or dictSize < 8 1932*3117ece4Schristos 1933*3117ece4Schristos</p></pre><BR> 1934*3117ece4Schristos 1935*3117ece4Schristos<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_refDDict, see zstd.h for detailed instructions") 1936*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict); 1937*3117ece4Schristos</b><p> 1938*3117ece4Schristos ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); 1939*3117ece4Schristos ZSTD_DCtx_refDDict(zds, ddict); 1940*3117ece4Schristos 1941*3117ece4Schristos note : ddict is referenced, it must outlive decompression session 1942*3117ece4Schristos 1943*3117ece4Schristos</p></pre><BR> 1944*3117ece4Schristos 1945*3117ece4Schristos<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset, see zstd.h for detailed instructions") 1946*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_resetDStream(ZSTD_DStream* zds); 1947*3117ece4Schristos</b><p> 1948*3117ece4Schristos ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); 1949*3117ece4Schristos 1950*3117ece4Schristos reuse decompression parameters from previous init; saves dictionary loading 1951*3117ece4Schristos 1952*3117ece4Schristos</p></pre><BR> 1953*3117ece4Schristos 1954*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API void 1955*3117ece4SchristosZSTD_registerSequenceProducer( 1956*3117ece4Schristos ZSTD_CCtx* cctx, 1957*3117ece4Schristos void* sequenceProducerState, 1958*3117ece4Schristos ZSTD_sequenceProducer_F sequenceProducer 1959*3117ece4Schristos); 1960*3117ece4Schristos</b><p> Instruct zstd to use a block-level external sequence producer function. 1961*3117ece4Schristos 1962*3117ece4Schristos The sequenceProducerState must be initialized by the caller, and the caller is 1963*3117ece4Schristos responsible for managing its lifetime. This parameter is sticky across 1964*3117ece4Schristos compressions. It will remain set until the user explicitly resets compression 1965*3117ece4Schristos parameters. 1966*3117ece4Schristos 1967*3117ece4Schristos Sequence producer registration is considered to be an "advanced parameter", 1968*3117ece4Schristos part of the "advanced API". This means it will only have an effect on compression 1969*3117ece4Schristos APIs which respect advanced parameters, such as compress2() and compressStream2(). 1970*3117ece4Schristos Older compression APIs such as compressCCtx(), which predate the introduction of 1971*3117ece4Schristos "advanced parameters", will ignore any external sequence producer setting. 1972*3117ece4Schristos 1973*3117ece4Schristos The sequence producer can be "cleared" by registering a NULL function pointer. This 1974*3117ece4Schristos removes all limitations described above in the "LIMITATIONS" section of the API docs. 1975*3117ece4Schristos 1976*3117ece4Schristos The user is strongly encouraged to read the full API documentation (above) before 1977*3117ece4Schristos calling this function. 1978*3117ece4Schristos</p></pre><BR> 1979*3117ece4Schristos 1980*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API void 1981*3117ece4SchristosZSTD_CCtxParams_registerSequenceProducer( 1982*3117ece4Schristos ZSTD_CCtx_params* params, 1983*3117ece4Schristos void* sequenceProducerState, 1984*3117ece4Schristos ZSTD_sequenceProducer_F sequenceProducer 1985*3117ece4Schristos); 1986*3117ece4Schristos</b><p> Same as ZSTD_registerSequenceProducer(), but operates on ZSTD_CCtx_params. 1987*3117ece4Schristos This is used for accurate size estimation with ZSTD_estimateCCtxSize_usingCCtxParams(), 1988*3117ece4Schristos which is needed when creating a ZSTD_CCtx with ZSTD_initStaticCCtx(). 1989*3117ece4Schristos 1990*3117ece4Schristos If you are using the external sequence producer API in a scenario where ZSTD_initStaticCCtx() 1991*3117ece4Schristos is required, then this function is for you. Otherwise, you probably don't need it. 1992*3117ece4Schristos 1993*3117ece4Schristos See tests/zstreamtest.c for example usage. 1994*3117ece4Schristos</p></pre><BR> 1995*3117ece4Schristos 1996*3117ece4Schristos<a name="Chapter20"></a><h2>Buffer-less and synchronous inner streaming functions (DEPRECATED)</h2><pre> 1997*3117ece4Schristos This API is deprecated, and will be removed in a future version. 1998*3117ece4Schristos It allows streaming (de)compression with user allocated buffers. 1999*3117ece4Schristos However, it is hard to use, and not as well tested as the rest of 2000*3117ece4Schristos our API. 2001*3117ece4Schristos 2002*3117ece4Schristos Please use the normal streaming API instead: ZSTD_compressStream2, 2003*3117ece4Schristos and ZSTD_decompressStream. 2004*3117ece4Schristos If there is functionality that you need, but it doesn't provide, 2005*3117ece4Schristos please open an issue on our GitHub. 2006*3117ece4Schristos 2007*3117ece4Schristos<BR></pre> 2008*3117ece4Schristos 2009*3117ece4Schristos<a name="Chapter21"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre> 2010*3117ece4Schristos A ZSTD_CCtx object is required to track streaming operations. 2011*3117ece4Schristos Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource. 2012*3117ece4Schristos ZSTD_CCtx object can be reused multiple times within successive compression operations. 2013*3117ece4Schristos 2014*3117ece4Schristos Start by initializing a context. 2015*3117ece4Schristos Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression. 2016*3117ece4Schristos 2017*3117ece4Schristos Then, consume your input using ZSTD_compressContinue(). 2018*3117ece4Schristos There are some important considerations to keep in mind when using this advanced function : 2019*3117ece4Schristos - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only. 2020*3117ece4Schristos - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks. 2021*3117ece4Schristos - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario. 2022*3117ece4Schristos Worst case evaluation is provided by ZSTD_compressBound(). 2023*3117ece4Schristos ZSTD_compressContinue() doesn't guarantee recover after a failed compression. 2024*3117ece4Schristos - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog). 2025*3117ece4Schristos It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks) 2026*3117ece4Schristos - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps. 2027*3117ece4Schristos In which case, it will "discard" the relevant memory section from its history. 2028*3117ece4Schristos 2029*3117ece4Schristos Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum. 2030*3117ece4Schristos It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame. 2031*3117ece4Schristos Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders. 2032*3117ece4Schristos 2033*3117ece4Schristos `ZSTD_CCtx` object can be reused (ZSTD_compressBegin()) to compress again. 2034*3117ece4Schristos<BR></pre> 2035*3117ece4Schristos 2036*3117ece4Schristos<h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.") 2037*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel); 2038*3117ece4SchristosZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.") 2039*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel); 2040*3117ece4SchristosZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.") 2041*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b> 2042*3117ece4Schristos</pre></b><BR> 2043*3117ece4Schristos<pre><b>size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); </b>/**< note: if pledgedSrcSize is not known, use ZSTD_CONTENTSIZE_UNKNOWN */<b> 2044*3117ece4Schristos</b></pre><BR> 2045*3117ece4Schristos<pre><b>size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize : If srcSize is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN */<b> 2046*3117ece4Schristos</b></pre><BR> 2047*3117ece4Schristos<a name="Chapter22"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre> 2048*3117ece4Schristos A ZSTD_DCtx object is required to track streaming operations. 2049*3117ece4Schristos Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it. 2050*3117ece4Schristos A ZSTD_DCtx object can be reused multiple times. 2051*3117ece4Schristos 2052*3117ece4Schristos First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader(). 2053*3117ece4Schristos Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough. 2054*3117ece4Schristos Data fragment must be large enough to ensure successful decoding. 2055*3117ece4Schristos `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough. 2056*3117ece4Schristos result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled. 2057*3117ece4Schristos >0 : `srcSize` is too small, please provide at least result bytes on next attempt. 2058*3117ece4Schristos errorCode, which can be tested using ZSTD_isError(). 2059*3117ece4Schristos 2060*3117ece4Schristos It fills a ZSTD_frameHeader structure with important information to correctly decode the frame, 2061*3117ece4Schristos such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`). 2062*3117ece4Schristos Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information. 2063*3117ece4Schristos As a consequence, check that values remain within valid application range. 2064*3117ece4Schristos For example, do not allocate memory blindly, check that `windowSize` is within expectation. 2065*3117ece4Schristos Each application can set its own limits, depending on local restrictions. 2066*3117ece4Schristos For extended interoperability, it is recommended to support `windowSize` of at least 8 MB. 2067*3117ece4Schristos 2068*3117ece4Schristos ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes. 2069*3117ece4Schristos ZSTD_decompressContinue() is very sensitive to contiguity, 2070*3117ece4Schristos if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place, 2071*3117ece4Schristos or that previous contiguous segment is large enough to properly handle maximum back-reference distance. 2072*3117ece4Schristos There are multiple ways to guarantee this condition. 2073*3117ece4Schristos 2074*3117ece4Schristos The most memory efficient way is to use a round buffer of sufficient size. 2075*3117ece4Schristos Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(), 2076*3117ece4Schristos which can return an error code if required value is too large for current system (in 32-bits mode). 2077*3117ece4Schristos In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one, 2078*3117ece4Schristos up to the moment there is not enough room left in the buffer to guarantee decoding another full block, 2079*3117ece4Schristos which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`. 2080*3117ece4Schristos At which point, decoding can resume from the beginning of the buffer. 2081*3117ece4Schristos Note that already decoded data stored in the buffer should be flushed before being overwritten. 2082*3117ece4Schristos 2083*3117ece4Schristos There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory. 2084*3117ece4Schristos 2085*3117ece4Schristos Finally, if you control the compression process, you can also ignore all buffer size rules, 2086*3117ece4Schristos as long as the encoder and decoder progress in "lock-step", 2087*3117ece4Schristos aka use exactly the same buffer sizes, break contiguity at the same place, etc. 2088*3117ece4Schristos 2089*3117ece4Schristos Once buffers are setup, start decompression, with ZSTD_decompressBegin(). 2090*3117ece4Schristos If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict(). 2091*3117ece4Schristos 2092*3117ece4Schristos Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively. 2093*3117ece4Schristos ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue(). 2094*3117ece4Schristos ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail. 2095*3117ece4Schristos 2096*3117ece4Schristos result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity). 2097*3117ece4Schristos It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item. 2098*3117ece4Schristos It can also be an error code, which can be tested with ZSTD_isError(). 2099*3117ece4Schristos 2100*3117ece4Schristos A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero. 2101*3117ece4Schristos Context can then be reset to start a new decompression. 2102*3117ece4Schristos 2103*3117ece4Schristos Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType(). 2104*3117ece4Schristos This information is not required to properly decode a frame. 2105*3117ece4Schristos 2106*3117ece4Schristos == Special case : skippable frames 2107*3117ece4Schristos 2108*3117ece4Schristos Skippable frames allow integration of user-defined data into a flow of concatenated frames. 2109*3117ece4Schristos Skippable frames will be ignored (skipped) by decompressor. 2110*3117ece4Schristos The format of skippable frames is as follows : 2111*3117ece4Schristos a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F 2112*3117ece4Schristos b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits 2113*3117ece4Schristos c) Frame Content - any content (User Data) of length equal to Frame Size 2114*3117ece4Schristos For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame. 2115*3117ece4Schristos For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content. 2116*3117ece4Schristos<BR></pre> 2117*3117ece4Schristos 2118*3117ece4Schristos<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR> 2119*3117ece4Schristos<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize); </b>/**< when frame content size is not known, pass in frameContentSize == ZSTD_CONTENTSIZE_UNKNOWN */<b> 2120*3117ece4Schristos</b></pre><BR> 2121*3117ece4Schristos<pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e; 2122*3117ece4Schristos</b></pre><BR> 2123*3117ece4Schristos<a name="Chapter23"></a><h2>Block level API (DEPRECATED)</h2><pre></pre> 2124*3117ece4Schristos 2125*3117ece4Schristos<pre><b></b><p> You can get the frame header down to 2 bytes by setting: 2126*3117ece4Schristos - ZSTD_c_format = ZSTD_f_zstd1_magicless 2127*3117ece4Schristos - ZSTD_c_contentSizeFlag = 0 2128*3117ece4Schristos - ZSTD_c_checksumFlag = 0 2129*3117ece4Schristos - ZSTD_c_dictIDFlag = 0 2130*3117ece4Schristos 2131*3117ece4Schristos This API is not as well tested as our normal API, so we recommend not using it. 2132*3117ece4Schristos We will be removing it in a future version. If the normal API doesn't provide 2133*3117ece4Schristos the functionality you need, please open a GitHub issue. 2134*3117ece4Schristos 2135*3117ece4Schristos Block functions produce and decode raw zstd blocks, without frame metadata. 2136*3117ece4Schristos Frame metadata cost is typically ~12 bytes, which can be non-negligible for very small blocks (< 100 bytes). 2137*3117ece4Schristos But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes. 2138*3117ece4Schristos 2139*3117ece4Schristos A few rules to respect : 2140*3117ece4Schristos - Compressing and decompressing require a context structure 2141*3117ece4Schristos + Use ZSTD_createCCtx() and ZSTD_createDCtx() 2142*3117ece4Schristos - It is necessary to init context before starting 2143*3117ece4Schristos + compression : any ZSTD_compressBegin*() variant, including with dictionary 2144*3117ece4Schristos + decompression : any ZSTD_decompressBegin*() variant, including with dictionary 2145*3117ece4Schristos - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB 2146*3117ece4Schristos + If input is larger than a block size, it's necessary to split input data into multiple blocks 2147*3117ece4Schristos + For inputs larger than a single block, consider using regular ZSTD_compress() instead. 2148*3117ece4Schristos Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block. 2149*3117ece4Schristos - When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) ! 2150*3117ece4Schristos ===> In which case, nothing is produced into `dst` ! 2151*3117ece4Schristos + User __must__ test for such outcome and deal directly with uncompressed data 2152*3117ece4Schristos + A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0. 2153*3117ece4Schristos Doing so would mess up with statistics history, leading to potential data corruption. 2154*3117ece4Schristos + ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !! 2155*3117ece4Schristos + In case of multiple successive blocks, should some of them be uncompressed, 2156*3117ece4Schristos decoder must be informed of their existence in order to follow proper history. 2157*3117ece4Schristos Use ZSTD_insertBlock() for such a case. 2158*3117ece4Schristos</p></pre><BR> 2159*3117ece4Schristos 2160*3117ece4Schristos<h3>Raw zstd block functions</h3><pre></pre><b><pre>ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") 2161*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx); 2162*3117ece4SchristosZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") 2163*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); 2164*3117ece4SchristosZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") 2165*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); 2166*3117ece4SchristosZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") 2167*3117ece4SchristosZSTDLIB_STATIC_API size_t ZSTD_insertBlock (ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize); </b>/**< insert uncompressed block into `dctx` history. Useful for multi-blocks decompression. */<b> 2168*3117ece4Schristos</pre></b><BR> 2169*3117ece4Schristos</html> 2170*3117ece4Schristos</body> 2171