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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 | /* inffast.c -- fast decoding * Copyright (C) 1995-2004 Mark Adler * For conditions of distribution and use, see copyright notice in zlib.h */ #include <linux/zutil.h> #include "inftrees.h" #include "inflate.h" #include "inffast.h" #ifndef ASMINF union uu { unsigned short us; unsigned char b[2]; }; /* Endian independent version */ static inline unsigned short get_unaligned16(const unsigned short *p) { union uu mm; unsigned char *b = (unsigned char *)p; mm.b[0] = b[0]; mm.b[1] = b[1]; return mm.us; } /* Decode literal, length, and distance codes and write out the resulting literal and match bytes until either not enough input or output is available, an end-of-block is encountered, or a data error is encountered. When large enough input and output buffers are supplied to inflate(), for example, a 16K input buffer and a 64K output buffer, more than 95% of the inflate execution time is spent in this routine. Entry assumptions: state->mode == LEN strm->avail_in >= 6 strm->avail_out >= 258 start >= strm->avail_out state->bits < 8 On return, state->mode is one of: LEN -- ran out of enough output space or enough available input TYPE -- reached end of block code, inflate() to interpret next block BAD -- error in block data Notes: - The maximum input bits used by a length/distance pair is 15 bits for the length code, 5 bits for the length extra, 15 bits for the distance code, and 13 bits for the distance extra. This totals 48 bits, or six bytes. Therefore if strm->avail_in >= 6, then there is enough input to avoid checking for available input while decoding. - The maximum bytes that a single length/distance pair can output is 258 bytes, which is the maximum length that can be coded. inflate_fast() requires strm->avail_out >= 258 for each loop to avoid checking for output space. - @start: inflate()'s starting value for strm->avail_out */ void inflate_fast(z_streamp strm, unsigned start) { struct inflate_state *state; const unsigned char *in; /* local strm->next_in */ const unsigned char *last; /* while in < last, enough input available */ unsigned char *out; /* local strm->next_out */ unsigned char *beg; /* inflate()'s initial strm->next_out */ unsigned char *end; /* while out < end, enough space available */ #ifdef INFLATE_STRICT unsigned dmax; /* maximum distance from zlib header */ #endif unsigned wsize; /* window size or zero if not using window */ unsigned whave; /* valid bytes in the window */ unsigned write; /* window write index */ unsigned char *window; /* allocated sliding window, if wsize != 0 */ unsigned long hold; /* local strm->hold */ unsigned bits; /* local strm->bits */ code const *lcode; /* local strm->lencode */ code const *dcode; /* local strm->distcode */ unsigned lmask; /* mask for first level of length codes */ unsigned dmask; /* mask for first level of distance codes */ code this; /* retrieved table entry */ unsigned op; /* code bits, operation, extra bits, or */ /* window position, window bytes to copy */ unsigned len; /* match length, unused bytes */ unsigned dist; /* match distance */ unsigned char *from; /* where to copy match from */ /* copy state to local variables */ state = (struct inflate_state *)strm->state; in = strm->next_in; last = in + (strm->avail_in - 5); out = strm->next_out; beg = out - (start - strm->avail_out); end = out + (strm->avail_out - 257); #ifdef INFLATE_STRICT dmax = state->dmax; #endif wsize = state->wsize; whave = state->whave; write = state->write; window = state->window; hold = state->hold; bits = state->bits; lcode = state->lencode; dcode = state->distcode; lmask = (1U << state->lenbits) - 1; dmask = (1U << state->distbits) - 1; /* decode literals and length/distances until end-of-block or not enough input data or output space */ do { if (bits < 15) { hold += (unsigned long)(*in++) << bits; bits += 8; hold += (unsigned long)(*in++) << bits; bits += 8; } this = lcode[hold & lmask]; dolen: op = (unsigned)(this.bits); hold >>= op; bits -= op; op = (unsigned)(this.op); if (op == 0) { /* literal */ *out++ = (unsigned char)(this.val); } else if (op & 16) { /* length base */ len = (unsigned)(this.val); op &= 15; /* number of extra bits */ if (op) { if (bits < op) { hold += (unsigned long)(*in++) << bits; bits += 8; } len += (unsigned)hold & ((1U << op) - 1); hold >>= op; bits -= op; } if (bits < 15) { hold += (unsigned long)(*in++) << bits; bits += 8; hold += (unsigned long)(*in++) << bits; bits += 8; } this = dcode[hold & dmask]; dodist: op = (unsigned)(this.bits); hold >>= op; bits -= op; op = (unsigned)(this.op); if (op & 16) { /* distance base */ dist = (unsigned)(this.val); op &= 15; /* number of extra bits */ if (bits < op) { hold += (unsigned long)(*in++) << bits; bits += 8; if (bits < op) { hold += (unsigned long)(*in++) << bits; bits += 8; } } dist += (unsigned)hold & ((1U << op) - 1); #ifdef INFLATE_STRICT if (dist > dmax) { strm->msg = (char *)"invalid distance too far back"; state->mode = BAD; break; } #endif hold >>= op; bits -= op; op = (unsigned)(out - beg); /* max distance in output */ if (dist > op) { /* see if copy from window */ op = dist - op; /* distance back in window */ if (op > whave) { strm->msg = (char *)"invalid distance too far back"; state->mode = BAD; break; } from = window; if (write == 0) { /* very common case */ from += wsize - op; if (op < len) { /* some from window */ len -= op; do { *out++ = *from++; } while (--op); from = out - dist; /* rest from output */ } } else if (write < op) { /* wrap around window */ from += wsize + write - op; op -= write; if (op < len) { /* some from end of window */ len -= op; do { *out++ = *from++; } while (--op); from = window; if (write < len) { /* some from start of window */ op = write; len -= op; do { *out++ = *from++; } while (--op); from = out - dist; /* rest from output */ } } } else { /* contiguous in window */ from += write - op; if (op < len) { /* some from window */ len -= op; do { *out++ = *from++; } while (--op); from = out - dist; /* rest from output */ } } while (len > 2) { *out++ = *from++; *out++ = *from++; *out++ = *from++; len -= 3; } if (len) { *out++ = *from++; if (len > 1) *out++ = *from++; } } else { unsigned short *sout; unsigned long loops; from = out - dist; /* copy direct from output */ /* minimum length is three */ /* Align out addr */ if (!((long)(out - 1) & 1)) { *out++ = *from++; len--; } sout = (unsigned short *)(out); if (dist > 2) { unsigned short *sfrom; sfrom = (unsigned short *)(from); loops = len >> 1; do { if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) *sout++ = *sfrom++; else *sout++ = get_unaligned16(sfrom++); } while (--loops); out = (unsigned char *)sout; from = (unsigned char *)sfrom; } else { /* dist == 1 or dist == 2 */ unsigned short pat16; pat16 = *(sout-1); if (dist == 1) { union uu mm; /* copy one char pattern to both bytes */ mm.us = pat16; mm.b[0] = mm.b[1]; pat16 = mm.us; } loops = len >> 1; do *sout++ = pat16; while (--loops); out = (unsigned char *)sout; } if (len & 1) *out++ = *from++; } } else if ((op & 64) == 0) { /* 2nd level distance code */ this = dcode[this.val + (hold & ((1U << op) - 1))]; goto dodist; } else { strm->msg = (char *)"invalid distance code"; state->mode = BAD; break; } } else if ((op & 64) == 0) { /* 2nd level length code */ this = lcode[this.val + (hold & ((1U << op) - 1))]; goto dolen; } else if (op & 32) { /* end-of-block */ state->mode = TYPE; break; } else { strm->msg = (char *)"invalid literal/length code"; state->mode = BAD; break; } } while (in < last && out < end); /* return unused bytes (on entry, bits < 8, so in won't go too far back) */ len = bits >> 3; in -= len; bits -= len << 3; hold &= (1U << bits) - 1; /* update state and return */ strm->next_in = in; strm->next_out = out; strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last)); strm->avail_out = (unsigned)(out < end ? 257 + (end - out) : 257 - (out - end)); state->hold = hold; state->bits = bits; return; } /* inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe): - Using bit fields for code structure - Different op definition to avoid & for extra bits (do & for table bits) - Three separate decoding do-loops for direct, window, and write == 0 - Special case for distance > 1 copies to do overlapped load and store copy - Explicit branch predictions (based on measured branch probabilities) - Deferring match copy and interspersed it with decoding subsequent codes - Swapping literal/length else - Swapping window/direct else - Larger unrolled copy loops (three is about right) - Moving len -= 3 statement into middle of loop */ #endif /* !ASMINF */ |