1 ///////////////////////////////////////////////////////////////////////////////
2 //
3 /// \file lz_decoder.c
4 /// \brief LZ out window
5 ///
6 // Authors: Igor Pavlov
7 // Lasse Collin
8 //
9 // This file has been put into the public domain.
10 // You can do whatever you want with this file.
11 //
12 ///////////////////////////////////////////////////////////////////////////////
13
14 // liblzma supports multiple LZ77-based filters. The LZ part is shared
15 // between these filters. The LZ code takes care of dictionary handling
16 // and passing the data between filters in the chain. The filter-specific
17 // part decodes from the input buffer to the dictionary.
18
19
20 #include "lz_decoder.h"
21
22
23 typedef struct {
24 /// Dictionary (history buffer)
25 lzma_dict dict;
26
27 /// The actual LZ-based decoder e.g. LZMA
28 lzma_lz_decoder lz;
29
30 /// Next filter in the chain, if any. Note that LZMA and LZMA2 are
31 /// only allowed as the last filter, but the long-range filter in
32 /// future can be in the middle of the chain.
33 lzma_next_coder next;
34
35 /// True if the next filter in the chain has returned LZMA_STREAM_END.
36 bool next_finished;
37
38 /// True if the LZ decoder (e.g. LZMA) has detected end of payload
39 /// marker. This may become true before next_finished becomes true.
40 bool this_finished;
41
42 /// Temporary buffer needed when the LZ-based filter is not the last
43 /// filter in the chain. The output of the next filter is first
44 /// decoded into buffer[], which is then used as input for the actual
45 /// LZ-based decoder.
46 struct {
47 size_t pos;
48 size_t size;
49 uint8_t buffer[LZMA_BUFFER_SIZE];
50 } temp;
51 } lzma_coder;
52
53
54 static void
lz_decoder_reset(lzma_coder * coder)55 lz_decoder_reset(lzma_coder *coder)
56 {
57 coder->dict.pos = 0;
58 coder->dict.full = 0;
59 coder->dict.buf[coder->dict.size - 1] = '\0';
60 coder->dict.need_reset = false;
61 return;
62 }
63
64
65 static lzma_ret
decode_buffer(lzma_coder * coder,const uint8_t * restrict in,size_t * restrict in_pos,size_t in_size,uint8_t * restrict out,size_t * restrict out_pos,size_t out_size)66 decode_buffer(lzma_coder *coder,
67 const uint8_t *restrict in, size_t *restrict in_pos,
68 size_t in_size, uint8_t *restrict out,
69 size_t *restrict out_pos, size_t out_size)
70 {
71 while (true) {
72 // Wrap the dictionary if needed.
73 if (coder->dict.pos == coder->dict.size)
74 coder->dict.pos = 0;
75
76 // Store the current dictionary position. It is needed to know
77 // where to start copying to the out[] buffer.
78 const size_t dict_start = coder->dict.pos;
79
80 // Calculate how much we allow coder->lz.code() to decode.
81 // It must not decode past the end of the dictionary
82 // buffer, and we don't want it to decode more than is
83 // actually needed to fill the out[] buffer.
84 coder->dict.limit = coder->dict.pos
85 + my_min(out_size - *out_pos,
86 coder->dict.size - coder->dict.pos);
87
88 // Call the coder->lz.code() to do the actual decoding.
89 const lzma_ret ret = coder->lz.code(
90 coder->lz.coder, &coder->dict,
91 in, in_pos, in_size);
92
93 // Copy the decoded data from the dictionary to the out[]
94 // buffer.
95 const size_t copy_size = coder->dict.pos - dict_start;
96 assert(copy_size <= out_size - *out_pos);
97 memcpy(out + *out_pos, coder->dict.buf + dict_start,
98 copy_size);
99 *out_pos += copy_size;
100
101 // Reset the dictionary if so requested by coder->lz.code().
102 if (coder->dict.need_reset) {
103 lz_decoder_reset(coder);
104
105 // Since we reset dictionary, we don't check if
106 // dictionary became full.
107 if (ret != LZMA_OK || *out_pos == out_size)
108 return ret;
109 } else {
110 // Return if everything got decoded or an error
111 // occurred, or if there's no more data to decode.
112 //
113 // Note that detecting if there's something to decode
114 // is done by looking if dictionary become full
115 // instead of looking if *in_pos == in_size. This
116 // is because it is possible that all the input was
117 // consumed already but some data is pending to be
118 // written to the dictionary.
119 if (ret != LZMA_OK || *out_pos == out_size
120 || coder->dict.pos < coder->dict.size)
121 return ret;
122 }
123 }
124 }
125
126
127 static lzma_ret
lz_decode(void * coder_ptr,const lzma_allocator * allocator lzma_attribute ((__unused__)),const uint8_t * restrict in,size_t * restrict in_pos,size_t in_size,uint8_t * restrict out,size_t * restrict out_pos,size_t out_size,lzma_action action)128 lz_decode(void *coder_ptr,
129 const lzma_allocator *allocator lzma_attribute((__unused__)),
130 const uint8_t *restrict in, size_t *restrict in_pos,
131 size_t in_size, uint8_t *restrict out,
132 size_t *restrict out_pos, size_t out_size,
133 lzma_action action)
134 {
135 lzma_coder *coder = coder_ptr;
136
137 if (coder->next.code == NULL)
138 return decode_buffer(coder, in, in_pos, in_size,
139 out, out_pos, out_size);
140
141 // We aren't the last coder in the chain, we need to decode
142 // our input to a temporary buffer.
143 while (*out_pos < out_size) {
144 // Fill the temporary buffer if it is empty.
145 if (!coder->next_finished
146 && coder->temp.pos == coder->temp.size) {
147 coder->temp.pos = 0;
148 coder->temp.size = 0;
149
150 const lzma_ret ret = coder->next.code(
151 coder->next.coder,
152 allocator, in, in_pos, in_size,
153 coder->temp.buffer, &coder->temp.size,
154 LZMA_BUFFER_SIZE, action);
155
156 if (ret == LZMA_STREAM_END)
157 coder->next_finished = true;
158 else if (ret != LZMA_OK || coder->temp.size == 0)
159 return ret;
160 }
161
162 if (coder->this_finished) {
163 if (coder->temp.size != 0)
164 return LZMA_DATA_ERROR;
165
166 if (coder->next_finished)
167 return LZMA_STREAM_END;
168
169 return LZMA_OK;
170 }
171
172 const lzma_ret ret = decode_buffer(coder, coder->temp.buffer,
173 &coder->temp.pos, coder->temp.size,
174 out, out_pos, out_size);
175
176 if (ret == LZMA_STREAM_END)
177 coder->this_finished = true;
178 else if (ret != LZMA_OK)
179 return ret;
180 else if (coder->next_finished && *out_pos < out_size)
181 return LZMA_DATA_ERROR;
182 }
183
184 return LZMA_OK;
185 }
186
187
188 static void
lz_decoder_end(void * coder_ptr,const lzma_allocator * allocator)189 lz_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
190 {
191 lzma_coder *coder = coder_ptr;
192
193 lzma_next_end(&coder->next, allocator);
194 lzma_free(coder->dict.buf, allocator);
195
196 if (coder->lz.end != NULL)
197 coder->lz.end(coder->lz.coder, allocator);
198 else
199 lzma_free(coder->lz.coder, allocator);
200
201 lzma_free(coder, allocator);
202 return;
203 }
204
205
206 extern lzma_ret
lzma_lz_decoder_init(lzma_next_coder * next,const lzma_allocator * allocator,const lzma_filter_info * filters,lzma_ret (* lz_init)(lzma_lz_decoder * lz,const lzma_allocator * allocator,const void * options,lzma_lz_options * lz_options))207 lzma_lz_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
208 const lzma_filter_info *filters,
209 lzma_ret (*lz_init)(lzma_lz_decoder *lz,
210 const lzma_allocator *allocator, const void *options,
211 lzma_lz_options *lz_options))
212 {
213 // Allocate the base structure if it isn't already allocated.
214 lzma_coder *coder = next->coder;
215 if (coder == NULL) {
216 coder = lzma_alloc(sizeof(lzma_coder), allocator);
217 if (coder == NULL)
218 return LZMA_MEM_ERROR;
219
220 next->coder = coder;
221 next->code = &lz_decode;
222 next->end = &lz_decoder_end;
223
224 coder->dict.buf = NULL;
225 coder->dict.size = 0;
226 coder->lz = LZMA_LZ_DECODER_INIT;
227 coder->next = LZMA_NEXT_CODER_INIT;
228 }
229
230 // Allocate and initialize the LZ-based decoder. It will also give
231 // us the dictionary size.
232 lzma_lz_options lz_options;
233 return_if_error(lz_init(&coder->lz, allocator,
234 filters[0].options, &lz_options));
235
236 // If the dictionary size is very small, increase it to 4096 bytes.
237 // This is to prevent constant wrapping of the dictionary, which
238 // would slow things down. The downside is that since we don't check
239 // separately for the real dictionary size, we may happily accept
240 // corrupt files.
241 if (lz_options.dict_size < 4096)
242 lz_options.dict_size = 4096;
243
244 // Make dictionary size a multipe of 16. Some LZ-based decoders like
245 // LZMA use the lowest bits lzma_dict.pos to know the alignment of the
246 // data. Aligned buffer is also good when memcpying from the
247 // dictionary to the output buffer, since applications are
248 // recommended to give aligned buffers to liblzma.
249 //
250 // Avoid integer overflow.
251 if (lz_options.dict_size > SIZE_MAX - 15)
252 return LZMA_MEM_ERROR;
253
254 lz_options.dict_size = (lz_options.dict_size + 15) & ~((size_t)(15));
255
256 // Allocate and initialize the dictionary.
257 if (coder->dict.size != lz_options.dict_size) {
258 lzma_free(coder->dict.buf, allocator);
259 coder->dict.buf
260 = lzma_alloc(lz_options.dict_size, allocator);
261 if (coder->dict.buf == NULL)
262 return LZMA_MEM_ERROR;
263
264 coder->dict.size = lz_options.dict_size;
265 }
266
267 lz_decoder_reset(next->coder);
268
269 // Use the preset dictionary if it was given to us.
270 if (lz_options.preset_dict != NULL
271 && lz_options.preset_dict_size > 0) {
272 // If the preset dictionary is bigger than the actual
273 // dictionary, copy only the tail.
274 const size_t copy_size = my_min(lz_options.preset_dict_size,
275 lz_options.dict_size);
276 const size_t offset = lz_options.preset_dict_size - copy_size;
277 memcpy(coder->dict.buf, lz_options.preset_dict + offset,
278 copy_size);
279 coder->dict.pos = copy_size;
280 coder->dict.full = copy_size;
281 }
282
283 // Miscellaneous initializations
284 coder->next_finished = false;
285 coder->this_finished = false;
286 coder->temp.pos = 0;
287 coder->temp.size = 0;
288
289 // Initialize the next filter in the chain, if any.
290 return lzma_next_filter_init(&coder->next, allocator, filters + 1);
291 }
292
293
294 extern uint64_t
lzma_lz_decoder_memusage(size_t dictionary_size)295 lzma_lz_decoder_memusage(size_t dictionary_size)
296 {
297 return sizeof(lzma_coder) + (uint64_t)(dictionary_size);
298 }
299
300
301 extern void
lzma_lz_decoder_uncompressed(void * coder_ptr,lzma_vli uncompressed_size)302 lzma_lz_decoder_uncompressed(void *coder_ptr, lzma_vli uncompressed_size)
303 {
304 lzma_coder *coder = coder_ptr;
305 coder->lz.set_uncompressed(coder->lz.coder, uncompressed_size);
306 }
307