1 /* $OpenBSD: inffast.c,v 1.6 2002/03/12 00:26:30 millert Exp $ */ 2 /* inffast.c -- process literals and length/distance pairs fast 3 * Copyright (C) 1995-2002 Mark Adler 4 * For conditions of distribution and use, see copyright notice in zlib.h 5 */ 6 7 #include "zutil.h" 8 #include "inftrees.h" 9 #include "infblock.h" 10 #include "infcodes.h" 11 #include "infutil.h" 12 #include "inffast.h" 13 14 struct inflate_codes_state {int dummy;}; /* for buggy compilers */ 15 16 /* simplify the use of the inflate_huft type with some defines */ 17 #define exop word.what.Exop 18 #define bits word.what.Bits 19 20 /* macros for bit input with no checking and for returning unused bytes */ 21 #define GRABBITS(j) {while(k<(j)){b|=((uLong)NEXTBYTE)<<k;k+=8;}} 22 #define UNGRAB {c=z->avail_in-n;c=(k>>3)<c?k>>3:c;n+=c;p-=c;k-=c<<3;} 23 24 /* Called with number of bytes left to write in window at least 258 25 (the maximum string length) and number of input bytes available 26 at least ten. The ten bytes are six bytes for the longest length/ 27 distance pair plus four bytes for overloading the bit buffer. */ 28 29 int inflate_fast(bl, bd, tl, td, s, z) 30 uInt bl, bd; 31 inflate_huft *tl; 32 inflate_huft *td; /* need separate declaration for Borland C++ */ 33 inflate_blocks_statef *s; 34 z_streamp z; 35 { 36 inflate_huft *t; /* temporary pointer */ 37 uInt e; /* extra bits or operation */ 38 uLong b; /* bit buffer */ 39 uInt k; /* bits in bit buffer */ 40 Bytef *p; /* input data pointer */ 41 uInt n; /* bytes available there */ 42 Bytef *q; /* output window write pointer */ 43 uInt m; /* bytes to end of window or read pointer */ 44 uInt ml; /* mask for literal/length tree */ 45 uInt md; /* mask for distance tree */ 46 uInt c; /* bytes to copy */ 47 uInt d; /* distance back to copy from */ 48 Bytef *r; /* copy source pointer */ 49 50 /* load input, output, bit values */ 51 LOAD 52 53 /* initialize masks */ 54 ml = inflate_mask[bl]; 55 md = inflate_mask[bd]; 56 57 /* do until not enough input or output space for fast loop */ 58 do { /* assume called with m >= 258 && n >= 10 */ 59 /* get literal/length code */ 60 GRABBITS(20) /* max bits for literal/length code */ 61 if ((e = (t = tl + ((uInt)b & ml))->exop) == 0) 62 { 63 DUMPBITS(t->bits) 64 Tracevv((t->base >= 0x20 && t->base < 0x7f ? 65 "inflate: * literal '%c'\n" : 66 "inflate: * literal 0x%02x\n", t->base)); 67 *q++ = (Byte)t->base; 68 m--; 69 continue; 70 } 71 do { 72 DUMPBITS(t->bits) 73 if (e & 16) 74 { 75 /* get extra bits for length */ 76 e &= 15; 77 c = t->base + ((uInt)b & inflate_mask[e]); 78 DUMPBITS(e) 79 Tracevv(("inflate: * length %u\n", c)); 80 81 /* decode distance base of block to copy */ 82 GRABBITS(15); /* max bits for distance code */ 83 e = (t = td + ((uInt)b & md))->exop; 84 do { 85 DUMPBITS(t->bits) 86 if (e & 16) 87 { 88 /* get extra bits to add to distance base */ 89 e &= 15; 90 GRABBITS(e) /* get extra bits (up to 13) */ 91 d = t->base + ((uInt)b & inflate_mask[e]); 92 DUMPBITS(e) 93 Tracevv(("inflate: * distance %u\n", d)); 94 95 /* do the copy */ 96 m -= c; 97 r = q - d; 98 if (r < s->window) /* wrap if needed */ 99 { 100 do { 101 r += s->end - s->window; /* force pointer in window */ 102 } while (r < s->window); /* covers invalid distances */ 103 e = s->end - r; 104 if (c > e) 105 { 106 c -= e; /* wrapped copy */ 107 do { 108 *q++ = *r++; 109 } while (--e); 110 r = s->window; 111 do { 112 *q++ = *r++; 113 } while (--c); 114 } 115 else /* normal copy */ 116 { 117 *q++ = *r++; c--; 118 *q++ = *r++; c--; 119 do { 120 *q++ = *r++; 121 } while (--c); 122 } 123 } 124 else /* normal copy */ 125 { 126 *q++ = *r++; c--; 127 *q++ = *r++; c--; 128 do { 129 *q++ = *r++; 130 } while (--c); 131 } 132 break; 133 } 134 else if ((e & 64) == 0) 135 { 136 t += t->base; 137 e = (t += ((uInt)b & inflate_mask[e]))->exop; 138 } 139 else 140 { 141 z->msg = (char*)"invalid distance code"; 142 UNGRAB 143 UPDATE 144 return Z_DATA_ERROR; 145 } 146 } while (1); 147 break; 148 } 149 if ((e & 64) == 0) 150 { 151 t += t->base; 152 if ((e = (t += ((uInt)b & inflate_mask[e]))->exop) == 0) 153 { 154 DUMPBITS(t->bits) 155 Tracevv((t->base >= 0x20 && t->base < 0x7f ? 156 "inflate: * literal '%c'\n" : 157 "inflate: * literal 0x%02x\n", t->base)); 158 *q++ = (Byte)t->base; 159 m--; 160 break; 161 } 162 } 163 else if (e & 32) 164 { 165 Tracevv(("inflate: * end of block\n")); 166 UNGRAB 167 UPDATE 168 return Z_STREAM_END; 169 } 170 else 171 { 172 z->msg = (char*)"invalid literal/length code"; 173 UNGRAB 174 UPDATE 175 return Z_DATA_ERROR; 176 } 177 } while (1); 178 } while (m >= 258 && n >= 10); 179 180 /* not enough input or output--restore pointers and return */ 181 UNGRAB 182 UPDATE 183 return Z_OK; 184 } 185