lib/zlib/inffast.c

   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(strm, start)
  70 z_streamp strm;
  71 unsigned start;         /* inflate()'s starting value for strm->avail_out */
  72 {
  73     struct inflate_state FAR *state;
  74     unsigned char FAR *in;      /* local strm->next_in */
  75     unsigned char FAR *last;    /* while in < last, enough input available */
  76     unsigned char FAR *out;     /* local strm->next_out */
  77     unsigned char FAR *beg;     /* inflate()'s initial strm->next_out */
  78     unsigned char FAR *end;     /* while out < end, enough space available */
  79 #ifdef INFLATE_STRICT
  80     unsigned dmax;              /* maximum distance from zlib header */
  81 #endif
  82     unsigned wsize;             /* window size or zero if not using window */
  83     unsigned whave;             /* valid bytes in the window */
  84     unsigned write;             /* window write index */
  85     unsigned char FAR *window;  /* allocated sliding window, if wsize != 0 */
  86     unsigned long hold;         /* local strm->hold */
  87     unsigned bits;              /* local strm->bits */
  88     code const FAR *lcode;      /* local strm->lencode */
  89     code const FAR *dcode;      /* local strm->distcode */
  90     unsigned lmask;             /* mask for first level of length codes */
  91     unsigned dmask;             /* mask for first level of distance codes */
  92     code this;                  /* retrieved table entry */
  93     unsigned op;                /* code bits, operation, extra bits, or */
  94                                 /*  window position, window bytes to copy */
  95     unsigned len;               /* match length, unused bytes */
  96     unsigned dist;              /* match distance */
  97     unsigned char FAR *from;    /* where to copy match from */
  98
  99     /* copy state to local variables */
 100     state = (struct inflate_state FAR *)strm->state;
 101     in = strm->next_in - OFF;
 102     last = in + (strm->avail_in - 5);
 103     if (in > last && strm->avail_in > 5) {
 104         /*
 105          * overflow detected, limit strm->avail_in to the
 106          * max. possible size and recalculate last
 107          */
 108         strm->avail_in = 0xffffffff - (unsigned int)in;
 109         last = in + (strm->avail_in - 5);
 110     }
 111     out = strm->next_out - OFF;
 112     beg = out - (start - strm->avail_out);
 113     end = out + (strm->avail_out - 257);
 114 #ifdef INFLATE_STRICT
 115     dmax = state->dmax;
 116 #endif
 117     wsize = state->wsize;
 118     whave = state->whave;
 119     write = state->write;
 120     window = state->window;
 121     hold = state->hold;
 122     bits = state->bits;
 123     lcode = state->lencode;
 124     dcode = state->distcode;
 125     lmask = (1U << state->lenbits) - 1;
 126     dmask = (1U << state->distbits) - 1;
 127
 128     /* decode literals and length/distances until end-of-block or not enough
 129        input data or output space */
 130     do {
 131         if (bits < 15) {
 132             hold += (unsigned long)(PUP(in)) << bits;
 133             bits += 8;
 134             hold += (unsigned long)(PUP(in)) << bits;
 135             bits += 8;
 136         }
 137         this = lcode[hold & lmask];
 138       dolen:
 139         op = (unsigned)(this.bits);
 140         hold >>= op;
 141         bits -= op;
 142         op = (unsigned)(this.op);
 143         if (op == 0) {                          /* literal */
 144             Tracevv((stderr, this.val >= 0x20 && this.val < 0x7f ?
 145                     "inflate:         literal '%c'\n" :
 146                     "inflate:         literal 0x%02x\n", this.val));
 147             PUP(out) = (unsigned char)(this.val);
 148         }
 149         else if (op & 16) {                     /* length base */
 150             len = (unsigned)(this.val);
 151             op &= 15;                           /* number of extra bits */
 152             if (op) {
 153                 if (bits < op) {
 154                     hold += (unsigned long)(PUP(in)) << bits;
 155                     bits += 8;
 156                 }
 157                 len += (unsigned)hold & ((1U << op) - 1);
 158                 hold >>= op;
 159                 bits -= op;
 160             }
 161             Tracevv((stderr, "inflate:         length %u\n", len));
 162             if (bits < 15) {
 163                 hold += (unsigned long)(PUP(in)) << bits;
 164                 bits += 8;
 165                 hold += (unsigned long)(PUP(in)) << bits;
 166                 bits += 8;
 167             }
 168             this = dcode[hold & dmask];
 169           dodist:
 170             op = (unsigned)(this.bits);
 171             hold >>= op;
 172             bits -= op;
 173             op = (unsigned)(this.op);
 174             if (op & 16) {                      /* distance base */
 175                 dist = (unsigned)(this.val);
 176                 op &= 15;                       /* number of extra bits */
 177                 if (bits < op) {
 178                     hold += (unsigned long)(PUP(in)) << bits;
 179                     bits += 8;
 180                     if (bits < op) {
 181                         hold += (unsigned long)(PUP(in)) << bits;
 182                         bits += 8;
 183                     }
 184                 }
 185                 dist += (unsigned)hold & ((1U << op) - 1);
 186 #ifdef INFLATE_STRICT
 187                 if (dist > dmax) {
 188                     strm->msg = (char *)"invalid distance too far back";
 189                     state->mode = BAD;
 190                     break;
 191                 }
 192 #endif
 193                 hold >>= op;
 194                 bits -= op;
 195                 Tracevv((stderr, "inflate:         distance %u\n", dist));
 196                 op = (unsigned)(out - beg);     /* max distance in output */
 197                 if (dist > op) {                /* see if copy from window */
 198                     op = dist - op;             /* distance back in window */
 199                     if (op > whave) {
 200                         strm->msg = (char *)"invalid distance too far back";
 201                         state->mode = BAD;
 202                         break;
 203                     }
 204                     from = window - OFF;
 205                     if (write == 0) {           /* very common case */
 206                         from += wsize - op;
 207                         if (op < len) {         /* some from window */
 208                             len -= op;
 209                             do {
 210                                 PUP(out) = PUP(from);
 211                             } while (--op);
 212                             from = out - dist;  /* rest from output */
 213                         }
 214                     }
 215                     else if (write < op) {      /* wrap around window */
 216                         from += wsize + write - op;
 217                         op -= write;
 218                         if (op < len) {         /* some from end of window */
 219                             len -= op;
 220                             do {
 221                                 PUP(out) = PUP(from);
 222                             } while (--op);
 223                             from = window - OFF;
 224                             if (write < len) {  /* some from start of window */
 225                                 op = write;
 226                                 len -= op;
 227                                 do {
 228                                     PUP(out) = PUP(from);
 229                                 } while (--op);
 230                                 from = out - dist;      /* rest from output */
 231                             }
 232                         }
 233                     }
 234                     else {                      /* contiguous in window */
 235                         from += write - op;
 236                         if (op < len) {         /* some from window */
 237                             len -= op;
 238                             do {
 239                                 PUP(out) = PUP(from);
 240                             } while (--op);
 241                             from = out - dist;  /* rest from output */
 242                         }
 243                     }
 244                     while (len > 2) {
 245                         PUP(out) = PUP(from);
 246                         PUP(out) = PUP(from);
 247                         PUP(out) = PUP(from);
 248                         len -= 3;
 249                     }
 250                     if (len) {
 251                         PUP(out) = PUP(from);
 252                         if (len > 1)
 253                             PUP(out) = PUP(from);
 254                     }
 255                 }
 256                 else {
 257                     unsigned short *sout;
 258                     unsigned long loops;
 259
 260                     from = out - dist;          /* copy direct from output */
 261                     /* minimum length is three */
 262                     /* Align out addr */
 263                     if (!((long)(out - 1 + OFF) & 1)) {
 264                         PUP(out) = PUP(from);
 265                         len--;
 266                     }
 267                     sout = (unsigned short *)(out - OFF);
 268                     if (dist > 2 ) {
 269                         unsigned short *sfrom;
 270
 271                         sfrom = (unsigned short *)(from - OFF);
 272                         loops = len >> 1;
 273                         do
 274                             PUP(sout) = get_unaligned(++sfrom);
 275                         while (--loops);
 276                         out = (unsigned char *)sout + OFF;
 277                         from = (unsigned char *)sfrom + OFF;
 278                     } else { /* dist == 1 or dist == 2 */
 279                         unsigned short pat16;
 280
 281                         pat16 = *(sout-2+2*OFF);
 282                         if (dist == 1)
 283 #if defined(__BIG_ENDIAN)
 284                             pat16 = (pat16 & 0xff) | ((pat16 & 0xff ) << 8);
 285 #elif defined(__LITTLE_ENDIAN)
 286                             pat16 = (pat16 & 0xff00) | ((pat16 & 0xff00 ) >> 8);
 287 #else
 288 #error __BIG_ENDIAN nor __LITTLE_ENDIAN is defined
 289 #endif
 290                         loops = len >> 1;
 291                         do
 292                             PUP(sout) = pat16;
 293                         while (--loops);
 294                         out = (unsigned char *)sout + OFF;
 295                     }
 296                     if (len & 1)
 297                         PUP(out) = PUP(from);
 298                 }
 299             }
 300             else if ((op & 64) == 0) {          /* 2nd level distance code */
 301                 this = dcode[this.val + (hold & ((1U << op) - 1))];
 302                 goto dodist;
 303             }
 304             else {
 305                 strm->msg = (char *)"invalid distance code";
 306                 state->mode = BAD;
 307                 break;
 308             }
 309         }
 310         else if ((op & 64) == 0) {              /* 2nd level length code */
 311             this = lcode[this.val + (hold & ((1U << op) - 1))];
 312             goto dolen;
 313         }
 314         else if (op & 32) {                     /* end-of-block */
 315             Tracevv((stderr, "inflate:         end of block\n"));
 316             state->mode = TYPE;
 317             break;
 318         }
 319         else {
 320             strm->msg = (char *)"invalid literal/length code";
 321             state->mode = BAD;
 322             break;
 323         }
 324     } while (in < last && out < end);
 325
 326     /* return unused bytes (on entry, bits < 8, so in won't go too far back) */
 327     len = bits >> 3;
 328     in -= len;
 329     bits -= len << 3;
 330     hold &= (1U << bits) - 1;
 331
 332     /* update state and return */
 333     strm->next_in = in + OFF;
 334     strm->next_out = out + OFF;
 335     strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
 336     strm->avail_out = (unsigned)(out < end ?
 337                                  257 + (end - out) : 257 - (out - end));
 338     state->hold = hold;
 339     state->bits = bits;
 340     return;
 341 }
 342
 343 /*
 344    inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
 345    - Using bit fields for code structure
 346    - Different op definition to avoid & for extra bits (do & for table bits)
 347    - Three separate decoding do-loops for direct, window, and write == 0
 348    - Special case for distance > 1 copies to do overlapped load and store copy
 349    - Explicit branch predictions (based on measured branch probabilities)
 350    - Deferring match copy and interspersed it with decoding subsequent codes
 351    - Swapping literal/length else
 352    - Swapping window/direct else
 353    - Larger unrolled copy loops (three is about right)
 354    - Moving len -= 3 statement into middle of loop
 355  */
 356
 357 #endif /* !ASMINF */