1 /* inffast.c -- fast decoding 2 * Copyright (C) 1995-2004 Mark Adler 3 * For conditions of distribution and use, see copyright notice in zlib.h 4 */ 5 6 /* U-Boot: we already included these 7 #include "zutil.h" 8 #include "inftrees.h" 9 #include "inflate.h" 10 #include "inffast.h" 11 */ 12 13 #ifndef ASMINF 14 15 /* Allow machine dependent optimization for post-increment or pre-increment. 16 Based on testing to date, 17 Pre-increment preferred for: 18 - PowerPC G3 (Adler) 19 - MIPS R5000 (Randers-Pehrson) 20 Post-increment preferred for: 21 - none 22 No measurable difference: 23 - Pentium III (Anderson) 24 - M68060 (Nikl) 25 */ 26 #ifdef POSTINC 27 # define OFF 0 28 # define PUP(a) *(a)++ 29 #else 30 # define OFF 1 31 # define PUP(a) *++(a) 32 #endif 33 34 /* 35 Decode literal, length, and distance codes and write out the resulting 36 literal and match bytes until either not enough input or output is 37 available, an end-of-block is encountered, or a data error is encountered. 38 When large enough input and output buffers are supplied to inflate(), for 39 example, a 16K input buffer and a 64K output buffer, more than 95% of the 40 inflate execution time is spent in this routine. 41 42 Entry assumptions: 43 44 state->mode == LEN 45 strm->avail_in >= 6 46 strm->avail_out >= 258 47 start >= strm->avail_out 48 state->bits < 8 49 50 On return, state->mode is one of: 51 52 LEN -- ran out of enough output space or enough available input 53 TYPE -- reached end of block code, inflate() to interpret next block 54 BAD -- error in block data 55 56 Notes: 57 58 - The maximum input bits used by a length/distance pair is 15 bits for the 59 length code, 5 bits for the length extra, 15 bits for the distance code, 60 and 13 bits for the distance extra. This totals 48 bits, or six bytes. 61 Therefore if strm->avail_in >= 6, then there is enough input to avoid 62 checking for available input while decoding. 63 64 - The maximum bytes that a single length/distance pair can output is 258 65 bytes, which is the maximum length that can be coded. inflate_fast() 66 requires strm->avail_out >= 258 for each loop to avoid checking for 67 output space. 68 */ 69 void inflate_fast(z_streamp strm, unsigned start) 70 /* start: inflate()'s starting value for strm->avail_out */ 71 { 72 struct inflate_state FAR *state; 73 unsigned char FAR *in; /* local strm->next_in */ 74 unsigned char FAR *last; /* while in < last, enough input available */ 75 unsigned char FAR *out; /* local strm->next_out */ 76 unsigned char FAR *beg; /* inflate()'s initial strm->next_out */ 77 unsigned char FAR *end; /* while out < end, enough space available */ 78 #ifdef INFLATE_STRICT 79 unsigned dmax; /* maximum distance from zlib header */ 80 #endif 81 unsigned wsize; /* window size or zero if not using window */ 82 unsigned whave; /* valid bytes in the window */ 83 unsigned write; /* window write index */ 84 unsigned char FAR *window; /* allocated sliding window, if wsize != 0 */ 85 unsigned long hold; /* local strm->hold */ 86 unsigned bits; /* local strm->bits */ 87 code const FAR *lcode; /* local strm->lencode */ 88 code const FAR *dcode; /* local strm->distcode */ 89 unsigned lmask; /* mask for first level of length codes */ 90 unsigned dmask; /* mask for first level of distance codes */ 91 code this; /* retrieved table entry */ 92 unsigned op; /* code bits, operation, extra bits, or */ 93 /* window position, window bytes to copy */ 94 unsigned len; /* match length, unused bytes */ 95 unsigned dist; /* match distance */ 96 unsigned char FAR *from; /* where to copy match from */ 97 98 /* copy state to local variables */ 99 state = (struct inflate_state FAR *)strm->state; 100 in = strm->next_in - OFF; 101 last = in + (strm->avail_in - 5); 102 if (in > last && strm->avail_in > 5) { 103 /* 104 * overflow detected, limit strm->avail_in to the 105 * max. possible size and recalculate last 106 */ 107 strm->avail_in = 0xffffffff - (uintptr_t)in; 108 last = in + (strm->avail_in - 5); 109 } 110 out = strm->next_out - OFF; 111 beg = out - (start - strm->avail_out); 112 end = out + (strm->avail_out - 257); 113 #ifdef INFLATE_STRICT 114 dmax = state->dmax; 115 #endif 116 wsize = state->wsize; 117 whave = state->whave; 118 write = state->write; 119 window = state->window; 120 hold = state->hold; 121 bits = state->bits; 122 lcode = state->lencode; 123 dcode = state->distcode; 124 lmask = (1U << state->lenbits) - 1; 125 dmask = (1U << state->distbits) - 1; 126 127 /* decode literals and length/distances until end-of-block or not enough 128 input data or output space */ 129 do { 130 if (bits < 15) { 131 hold += (unsigned long)(PUP(in)) << bits; 132 bits += 8; 133 hold += (unsigned long)(PUP(in)) << bits; 134 bits += 8; 135 } 136 this = lcode[hold & lmask]; 137 dolen: 138 op = (unsigned)(this.bits); 139 hold >>= op; 140 bits -= op; 141 op = (unsigned)(this.op); 142 if (op == 0) { /* literal */ 143 Tracevv((stderr, this.val >= 0x20 && this.val < 0x7f ? 144 "inflate: literal '%c'\n" : 145 "inflate: literal 0x%02x\n", this.val)); 146 PUP(out) = (unsigned char)(this.val); 147 } 148 else if (op & 16) { /* length base */ 149 len = (unsigned)(this.val); 150 op &= 15; /* number of extra bits */ 151 if (op) { 152 if (bits < op) { 153 hold += (unsigned long)(PUP(in)) << bits; 154 bits += 8; 155 } 156 len += (unsigned)hold & ((1U << op) - 1); 157 hold >>= op; 158 bits -= op; 159 } 160 Tracevv((stderr, "inflate: length %u\n", len)); 161 if (bits < 15) { 162 hold += (unsigned long)(PUP(in)) << bits; 163 bits += 8; 164 hold += (unsigned long)(PUP(in)) << bits; 165 bits += 8; 166 } 167 this = dcode[hold & dmask]; 168 dodist: 169 op = (unsigned)(this.bits); 170 hold >>= op; 171 bits -= op; 172 op = (unsigned)(this.op); 173 if (op & 16) { /* distance base */ 174 dist = (unsigned)(this.val); 175 op &= 15; /* number of extra bits */ 176 if (bits < op) { 177 hold += (unsigned long)(PUP(in)) << bits; 178 bits += 8; 179 if (bits < op) { 180 hold += (unsigned long)(PUP(in)) << bits; 181 bits += 8; 182 } 183 } 184 dist += (unsigned)hold & ((1U << op) - 1); 185 #ifdef INFLATE_STRICT 186 if (dist > dmax) { 187 strm->msg = (char *)"invalid distance too far back"; 188 state->mode = BAD; 189 break; 190 } 191 #endif 192 hold >>= op; 193 bits -= op; 194 Tracevv((stderr, "inflate: distance %u\n", dist)); 195 op = (unsigned)(out - beg); /* max distance in output */ 196 if (dist > op) { /* see if copy from window */ 197 op = dist - op; /* distance back in window */ 198 if (op > whave) { 199 strm->msg = (char *)"invalid distance too far back"; 200 state->mode = BAD; 201 break; 202 } 203 from = window - OFF; 204 if (write == 0) { /* very common case */ 205 from += wsize - op; 206 if (op < len) { /* some from window */ 207 len -= op; 208 do { 209 PUP(out) = PUP(from); 210 } while (--op); 211 from = out - dist; /* rest from output */ 212 } 213 } 214 else if (write < op) { /* wrap around window */ 215 from += wsize + write - op; 216 op -= write; 217 if (op < len) { /* some from end of window */ 218 len -= op; 219 do { 220 PUP(out) = PUP(from); 221 } while (--op); 222 from = window - OFF; 223 if (write < len) { /* some from start of window */ 224 op = write; 225 len -= op; 226 do { 227 PUP(out) = PUP(from); 228 } while (--op); 229 from = out - dist; /* rest from output */ 230 } 231 } 232 } 233 else { /* contiguous in window */ 234 from += write - op; 235 if (op < len) { /* some from window */ 236 len -= op; 237 do { 238 PUP(out) = PUP(from); 239 } while (--op); 240 from = out - dist; /* rest from output */ 241 } 242 } 243 while (len > 2) { 244 PUP(out) = PUP(from); 245 PUP(out) = PUP(from); 246 PUP(out) = PUP(from); 247 len -= 3; 248 } 249 if (len) { 250 PUP(out) = PUP(from); 251 if (len > 1) 252 PUP(out) = PUP(from); 253 } 254 } 255 else { 256 unsigned short *sout; 257 unsigned long loops; 258 259 from = out - dist; /* copy direct from output */ 260 /* minimum length is three */ 261 /* Align out addr */ 262 if (!((long)(out - 1 + OFF) & 1)) { 263 PUP(out) = PUP(from); 264 len--; 265 } 266 sout = (unsigned short *)(out - OFF); 267 if (dist > 2 ) { 268 unsigned short *sfrom; 269 270 sfrom = (unsigned short *)(from - OFF); 271 loops = len >> 1; 272 do 273 PUP(sout) = get_unaligned(++sfrom); 274 while (--loops); 275 out = (unsigned char *)sout + OFF; 276 from = (unsigned char *)sfrom + OFF; 277 } else { /* dist == 1 or dist == 2 */ 278 unsigned short pat16; 279 280 pat16 = *(sout-2+2*OFF); 281 if (dist == 1) 282 #if defined(__BIG_ENDIAN) 283 pat16 = (pat16 & 0xff) | ((pat16 & 0xff ) << 8); 284 #elif defined(__LITTLE_ENDIAN) 285 pat16 = (pat16 & 0xff00) | ((pat16 & 0xff00 ) >> 8); 286 #else 287 #error __BIG_ENDIAN nor __LITTLE_ENDIAN is defined 288 #endif 289 loops = len >> 1; 290 do 291 PUP(sout) = pat16; 292 while (--loops); 293 out = (unsigned char *)sout + OFF; 294 } 295 if (len & 1) 296 PUP(out) = PUP(from); 297 } 298 } 299 else if ((op & 64) == 0) { /* 2nd level distance code */ 300 this = dcode[this.val + (hold & ((1U << op) - 1))]; 301 goto dodist; 302 } 303 else { 304 strm->msg = (char *)"invalid distance code"; 305 state->mode = BAD; 306 break; 307 } 308 } 309 else if ((op & 64) == 0) { /* 2nd level length code */ 310 this = lcode[this.val + (hold & ((1U << op) - 1))]; 311 goto dolen; 312 } 313 else if (op & 32) { /* end-of-block */ 314 Tracevv((stderr, "inflate: end of block\n")); 315 state->mode = TYPE; 316 break; 317 } 318 else { 319 strm->msg = (char *)"invalid literal/length code"; 320 state->mode = BAD; 321 break; 322 } 323 } while (in < last && out < end); 324 325 /* return unused bytes (on entry, bits < 8, so in won't go too far back) */ 326 len = bits >> 3; 327 in -= len; 328 bits -= len << 3; 329 hold &= (1U << bits) - 1; 330 331 /* update state and return */ 332 strm->next_in = in + OFF; 333 strm->next_out = out + OFF; 334 strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last)); 335 strm->avail_out = (unsigned)(out < end ? 336 257 + (end - out) : 257 - (out - end)); 337 state->hold = hold; 338 state->bits = bits; 339 return; 340 } 341 342 /* 343 inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe): 344 - Using bit fields for code structure 345 - Different op definition to avoid & for extra bits (do & for table bits) 346 - Three separate decoding do-loops for direct, window, and write == 0 347 - Special case for distance > 1 copies to do overlapped load and store copy 348 - Explicit branch predictions (based on measured branch probabilities) 349 - Deferring match copy and interspersed it with decoding subsequent codes 350 - Swapping literal/length else 351 - Swapping window/direct else 352 - Larger unrolled copy loops (three is about right) 353 - Moving len -= 3 statement into middle of loop 354 */ 355 356 #endif /* !ASMINF */ 357
