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comparison: security/nss/lib/zlib/inffast.c
security/nss/lib/zlib/inffast.c
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- TOR_BUG_9701
- changeset 15
- b8a032363ba2
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| -1:000000000000 | 0:d91379e5abf2 |
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| 1 /* inffast.c -- fast decoding | |
| 2 * Copyright (C) 1995-2008, 2010 Mark Adler | |
| 3 * For conditions of distribution and use, see copyright notice in zlib.h | |
| 4 */ | |
| 5 | |
| 6 #include "zutil.h" | |
| 7 #include "inftrees.h" | |
| 8 #include "inflate.h" | |
| 9 #include "inffast.h" | |
| 10 | |
| 11 #ifndef ASMINF | |
| 12 | |
| 13 /* Allow machine dependent optimization for post-increment or pre-increment. | |
| 14 Based on testing to date, | |
| 15 Pre-increment preferred for: | |
| 16 - PowerPC G3 (Adler) | |
| 17 - MIPS R5000 (Randers-Pehrson) | |
| 18 Post-increment preferred for: | |
| 19 - none | |
| 20 No measurable difference: | |
| 21 - Pentium III (Anderson) | |
| 22 - M68060 (Nikl) | |
| 23 */ | |
| 24 #ifdef POSTINC | |
| 25 # define OFF 0 | |
| 26 # define PUP(a) *(a)++ | |
| 27 #else | |
| 28 # define OFF 1 | |
| 29 # define PUP(a) *++(a) | |
| 30 #endif | |
| 31 | |
| 32 /* | |
| 33 Decode literal, length, and distance codes and write out the resulting | |
| 34 literal and match bytes until either not enough input or output is | |
| 35 available, an end-of-block is encountered, or a data error is encountered. | |
| 36 When large enough input and output buffers are supplied to inflate(), for | |
| 37 example, a 16K input buffer and a 64K output buffer, more than 95% of the | |
| 38 inflate execution time is spent in this routine. | |
| 39 | |
| 40 Entry assumptions: | |
| 41 | |
| 42 state->mode == LEN | |
| 43 strm->avail_in >= 6 | |
| 44 strm->avail_out >= 258 | |
| 45 start >= strm->avail_out | |
| 46 state->bits < 8 | |
| 47 | |
| 48 On return, state->mode is one of: | |
| 49 | |
| 50 LEN -- ran out of enough output space or enough available input | |
| 51 TYPE -- reached end of block code, inflate() to interpret next block | |
| 52 BAD -- error in block data | |
| 53 | |
| 54 Notes: | |
| 55 | |
| 56 - The maximum input bits used by a length/distance pair is 15 bits for the | |
| 57 length code, 5 bits for the length extra, 15 bits for the distance code, | |
| 58 and 13 bits for the distance extra. This totals 48 bits, or six bytes. | |
| 59 Therefore if strm->avail_in >= 6, then there is enough input to avoid | |
| 60 checking for available input while decoding. | |
| 61 | |
| 62 - The maximum bytes that a single length/distance pair can output is 258 | |
| 63 bytes, which is the maximum length that can be coded. inflate_fast() | |
| 64 requires strm->avail_out >= 258 for each loop to avoid checking for | |
| 65 output space. | |
| 66 */ | |
| 67 void ZLIB_INTERNAL inflate_fast(strm, start) | |
| 68 z_streamp strm; | |
| 69 unsigned start; /* inflate()'s starting value for strm->avail_out */ | |
| 70 { | |
| 71 struct inflate_state FAR *state; | |
| 72 unsigned char FAR *in; /* local strm->next_in */ | |
| 73 unsigned char FAR *last; /* while in < last, enough input available */ | |
| 74 unsigned char FAR *out; /* local strm->next_out */ | |
| 75 unsigned char FAR *beg; /* inflate()'s initial strm->next_out */ | |
| 76 unsigned char FAR *end; /* while out < end, enough space available */ | |
| 77 #ifdef INFLATE_STRICT | |
| 78 unsigned dmax; /* maximum distance from zlib header */ | |
| 79 #endif | |
| 80 unsigned wsize; /* window size or zero if not using window */ | |
| 81 unsigned whave; /* valid bytes in the window */ | |
| 82 unsigned wnext; /* window write index */ | |
| 83 unsigned char FAR *window; /* allocated sliding window, if wsize != 0 */ | |
| 84 unsigned long hold; /* local strm->hold */ | |
| 85 unsigned bits; /* local strm->bits */ | |
| 86 code const FAR *lcode; /* local strm->lencode */ | |
| 87 code const FAR *dcode; /* local strm->distcode */ | |
| 88 unsigned lmask; /* mask for first level of length codes */ | |
| 89 unsigned dmask; /* mask for first level of distance codes */ | |
| 90 code here; /* retrieved table entry */ | |
| 91 unsigned op; /* code bits, operation, extra bits, or */ | |
| 92 /* window position, window bytes to copy */ | |
| 93 unsigned len; /* match length, unused bytes */ | |
| 94 unsigned dist; /* match distance */ | |
| 95 unsigned char FAR *from; /* where to copy match from */ | |
| 96 | |
| 97 /* copy state to local variables */ | |
| 98 state = (struct inflate_state FAR *)strm->state; | |
| 99 in = strm->next_in - OFF; | |
| 100 last = in + (strm->avail_in - 5); | |
| 101 out = strm->next_out - OFF; | |
| 102 beg = out - (start - strm->avail_out); | |
| 103 end = out + (strm->avail_out - 257); | |
| 104 #ifdef INFLATE_STRICT | |
| 105 dmax = state->dmax; | |
| 106 #endif | |
| 107 wsize = state->wsize; | |
| 108 whave = state->whave; | |
| 109 wnext = state->wnext; | |
| 110 window = state->window; | |
| 111 hold = state->hold; | |
| 112 bits = state->bits; | |
| 113 lcode = state->lencode; | |
| 114 dcode = state->distcode; | |
| 115 lmask = (1U << state->lenbits) - 1; | |
| 116 dmask = (1U << state->distbits) - 1; | |
| 117 | |
| 118 /* decode literals and length/distances until end-of-block or not enough | |
| 119 input data or output space */ | |
| 120 do { | |
| 121 if (bits < 15) { | |
| 122 hold += (unsigned long)(PUP(in)) << bits; | |
| 123 bits += 8; | |
| 124 hold += (unsigned long)(PUP(in)) << bits; | |
| 125 bits += 8; | |
| 126 } | |
| 127 here = lcode[hold & lmask]; | |
| 128 dolen: | |
| 129 op = (unsigned)(here.bits); | |
| 130 hold >>= op; | |
| 131 bits -= op; | |
| 132 op = (unsigned)(here.op); | |
| 133 if (op == 0) { /* literal */ | |
| 134 Tracevv((stderr, here.val >= 0x20 && here.val < 0x7f ? | |
| 135 "inflate: literal '%c'\n" : | |
| 136 "inflate: literal 0x%02x\n", here.val)); | |
| 137 PUP(out) = (unsigned char)(here.val); | |
| 138 } | |
| 139 else if (op & 16) { /* length base */ | |
| 140 len = (unsigned)(here.val); | |
| 141 op &= 15; /* number of extra bits */ | |
| 142 if (op) { | |
| 143 if (bits < op) { | |
| 144 hold += (unsigned long)(PUP(in)) << bits; | |
| 145 bits += 8; | |
| 146 } | |
| 147 len += (unsigned)hold & ((1U << op) - 1); | |
| 148 hold >>= op; | |
| 149 bits -= op; | |
| 150 } | |
| 151 Tracevv((stderr, "inflate: length %u\n", len)); | |
| 152 if (bits < 15) { | |
| 153 hold += (unsigned long)(PUP(in)) << bits; | |
| 154 bits += 8; | |
| 155 hold += (unsigned long)(PUP(in)) << bits; | |
| 156 bits += 8; | |
| 157 } | |
| 158 here = dcode[hold & dmask]; | |
| 159 dodist: | |
| 160 op = (unsigned)(here.bits); | |
| 161 hold >>= op; | |
| 162 bits -= op; | |
| 163 op = (unsigned)(here.op); | |
| 164 if (op & 16) { /* distance base */ | |
| 165 dist = (unsigned)(here.val); | |
| 166 op &= 15; /* number of extra bits */ | |
| 167 if (bits < op) { | |
| 168 hold += (unsigned long)(PUP(in)) << bits; | |
| 169 bits += 8; | |
| 170 if (bits < op) { | |
| 171 hold += (unsigned long)(PUP(in)) << bits; | |
| 172 bits += 8; | |
| 173 } | |
| 174 } | |
| 175 dist += (unsigned)hold & ((1U << op) - 1); | |
| 176 #ifdef INFLATE_STRICT | |
| 177 if (dist > dmax) { | |
| 178 strm->msg = (char *)"invalid distance too far back"; | |
| 179 state->mode = BAD; | |
| 180 break; | |
| 181 } | |
| 182 #endif | |
| 183 hold >>= op; | |
| 184 bits -= op; | |
| 185 Tracevv((stderr, "inflate: distance %u\n", dist)); | |
| 186 op = (unsigned)(out - beg); /* max distance in output */ | |
| 187 if (dist > op) { /* see if copy from window */ | |
| 188 op = dist - op; /* distance back in window */ | |
| 189 if (op > whave) { | |
| 190 if (state->sane) { | |
| 191 strm->msg = | |
| 192 (char *)"invalid distance too far back"; | |
| 193 state->mode = BAD; | |
| 194 break; | |
| 195 } | |
| 196 #ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR | |
| 197 if (len <= op - whave) { | |
| 198 do { | |
| 199 PUP(out) = 0; | |
| 200 } while (--len); | |
| 201 continue; | |
| 202 } | |
| 203 len -= op - whave; | |
| 204 do { | |
| 205 PUP(out) = 0; | |
| 206 } while (--op > whave); | |
| 207 if (op == 0) { | |
| 208 from = out - dist; | |
| 209 do { | |
| 210 PUP(out) = PUP(from); | |
| 211 } while (--len); | |
| 212 continue; | |
| 213 } | |
| 214 #endif | |
| 215 } | |
| 216 from = window - OFF; | |
| 217 if (wnext == 0) { /* very common case */ | |
| 218 from += wsize - op; | |
| 219 if (op < len) { /* some from window */ | |
| 220 len -= op; | |
| 221 do { | |
| 222 PUP(out) = PUP(from); | |
| 223 } while (--op); | |
| 224 from = out - dist; /* rest from output */ | |
| 225 } | |
| 226 } | |
| 227 else if (wnext < op) { /* wrap around window */ | |
| 228 from += wsize + wnext - op; | |
| 229 op -= wnext; | |
| 230 if (op < len) { /* some from end of window */ | |
| 231 len -= op; | |
| 232 do { | |
| 233 PUP(out) = PUP(from); | |
| 234 } while (--op); | |
| 235 from = window - OFF; | |
| 236 if (wnext < len) { /* some from start of window */ | |
| 237 op = wnext; | |
| 238 len -= op; | |
| 239 do { | |
| 240 PUP(out) = PUP(from); | |
| 241 } while (--op); | |
| 242 from = out - dist; /* rest from output */ | |
| 243 } | |
| 244 } | |
| 245 } | |
| 246 else { /* contiguous in window */ | |
| 247 from += wnext - op; | |
| 248 if (op < len) { /* some from window */ | |
| 249 len -= op; | |
| 250 do { | |
| 251 PUP(out) = PUP(from); | |
| 252 } while (--op); | |
| 253 from = out - dist; /* rest from output */ | |
| 254 } | |
| 255 } | |
| 256 while (len > 2) { | |
| 257 PUP(out) = PUP(from); | |
| 258 PUP(out) = PUP(from); | |
| 259 PUP(out) = PUP(from); | |
| 260 len -= 3; | |
| 261 } | |
| 262 if (len) { | |
| 263 PUP(out) = PUP(from); | |
| 264 if (len > 1) | |
| 265 PUP(out) = PUP(from); | |
| 266 } | |
| 267 } | |
| 268 else { | |
| 269 from = out - dist; /* copy direct from output */ | |
| 270 do { /* minimum length is three */ | |
| 271 PUP(out) = PUP(from); | |
| 272 PUP(out) = PUP(from); | |
| 273 PUP(out) = PUP(from); | |
| 274 len -= 3; | |
| 275 } while (len > 2); | |
| 276 if (len) { | |
| 277 PUP(out) = PUP(from); | |
| 278 if (len > 1) | |
| 279 PUP(out) = PUP(from); | |
| 280 } | |
| 281 } | |
| 282 } | |
| 283 else if ((op & 64) == 0) { /* 2nd level distance code */ | |
| 284 here = dcode[here.val + (hold & ((1U << op) - 1))]; | |
| 285 goto dodist; | |
| 286 } | |
| 287 else { | |
| 288 strm->msg = (char *)"invalid distance code"; | |
| 289 state->mode = BAD; | |
| 290 break; | |
| 291 } | |
| 292 } | |
| 293 else if ((op & 64) == 0) { /* 2nd level length code */ | |
| 294 here = lcode[here.val + (hold & ((1U << op) - 1))]; | |
| 295 goto dolen; | |
| 296 } | |
| 297 else if (op & 32) { /* end-of-block */ | |
| 298 Tracevv((stderr, "inflate: end of block\n")); | |
| 299 state->mode = TYPE; | |
| 300 break; | |
| 301 } | |
| 302 else { | |
| 303 strm->msg = (char *)"invalid literal/length code"; | |
| 304 state->mode = BAD; | |
| 305 break; | |
| 306 } | |
| 307 } while (in < last && out < end); | |
| 308 | |
| 309 /* return unused bytes (on entry, bits < 8, so in won't go too far back) */ | |
| 310 len = bits >> 3; | |
| 311 in -= len; | |
| 312 bits -= len << 3; | |
| 313 hold &= (1U << bits) - 1; | |
| 314 | |
| 315 /* update state and return */ | |
| 316 strm->next_in = in + OFF; | |
| 317 strm->next_out = out + OFF; | |
| 318 strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last)); | |
| 319 strm->avail_out = (unsigned)(out < end ? | |
| 320 257 + (end - out) : 257 - (out - end)); | |
| 321 state->hold = hold; | |
| 322 state->bits = bits; | |
| 323 return; | |
| 324 } | |
| 325 | |
| 326 /* | |
| 327 inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe): | |
| 328 - Using bit fields for code structure | |
| 329 - Different op definition to avoid & for extra bits (do & for table bits) | |
| 330 - Three separate decoding do-loops for direct, window, and wnext == 0 | |
| 331 - Special case for distance > 1 copies to do overlapped load and store copy | |
| 332 - Explicit branch predictions (based on measured branch probabilities) | |
| 333 - Deferring match copy and interspersed it with decoding subsequent codes | |
| 334 - Swapping literal/length else | |
| 335 - Swapping window/direct else | |
| 336 - Larger unrolled copy loops (three is about right) | |
| 337 - Moving len -= 3 statement into middle of loop | |
| 338 */ | |
| 339 | |
| 340 #endif /* !ASMINF */ |
