memdisk/inflate.c

   1 #define DEBG(x)
   2 #define DEBG1(x)
   3 /* inflate.c -- Not copyrighted 1992 by Mark Adler
   4    version c10p1, 10 January 1993 */
   5
   6 /*
   7  * Adapted for booting Linux by Hannu Savolainen 1993
   8  * based on gzip-1.0.3
   9  *
  10  * Nicolas Pitre <nico@cam.org>, 1999/04/14 :
  11  *   Little mods for all variable to reside either into rodata or bss segments
  12  *   by marking constant variables with 'const' and initializing all the others
  13  *   at run-time only.  This allows for the kernel uncompressor to run
  14  *   directly from Flash or ROM memory on embedded systems.
  15  *
  16  * Adapted for MEMDISK by H. Peter Anvin, April 2003
  17  */
  18
  19 /*
  20    Inflate deflated (PKZIP's method 8 compressed) data.  The compression
  21    method searches for as much of the current string of bytes (up to a
  22    length of 258) in the previous 32 K bytes.  If it doesn't find any
  23    matches (of at least length 3), it codes the next byte.  Otherwise, it
  24    codes the length of the matched string and its distance backwards from
  25    the current position.  There is a single Huffman code that codes both
  26    single bytes (called "literals") and match lengths.  A second Huffman
  27    code codes the distance information, which follows a length code.  Each
  28    length or distance code actually represents a base value and a number
  29    of "extra" (sometimes zero) bits to get to add to the base value.  At
  30    the end of each deflated block is a special end-of-block (EOB) literal/
  31    length code.  The decoding process is basically: get a literal/length
  32    code; if EOB then done; if a literal, emit the decoded byte; if a
  33    length then get the distance and emit the referred-to bytes from the
  34    sliding window of previously emitted data.
  35
  36    There are (currently) three kinds of inflate blocks: stored, fixed, and
  37    dynamic.  The compressor deals with some chunk of data at a time, and
  38    decides which method to use on a chunk-by-chunk basis.  A chunk might
  39    typically be 32 K or 64 K.  If the chunk is incompressible, then the
  40    "stored" method is used.  In this case, the bytes are simply stored as
  41    is, eight bits per byte, with none of the above coding.  The bytes are
  42    preceded by a count, since there is no longer an EOB code.
  43
  44    If the data is compressible, then either the fixed or dynamic methods
  45    are used.  In the dynamic method, the compressed data is preceded by
  46    an encoding of the literal/length and distance Huffman codes that are
  47    to be used to decode this block.  The representation is itself Huffman
  48    coded, and so is preceded by a description of that code.  These code
  49    descriptions take up a little space, and so for small blocks, there is
  50    a predefined set of codes, called the fixed codes.  The fixed method is
  51    used if the block codes up smaller that way (usually for quite small
  52    chunks), otherwise the dynamic method is used.  In the latter case, the
  53    codes are customized to the probabilities in the current block, and so
  54    can code it much better than the pre-determined fixed codes.
  55
  56    The Huffman codes themselves are decoded using a multi-level table
  57    lookup, in order to maximize the speed of decoding plus the speed of
  58    building the decoding tables.  See the comments below that precede the
  59    lbits and dbits tuning parameters.
  60  */
  61
  62 /*
  63    Notes beyond the 1.93a appnote.txt:
  64
  65    1. Distance pointers never point before the beginning of the output
  66       stream.
  67    2. Distance pointers can point back across blocks, up to 32k away.
  68    3. There is an implied maximum of 7 bits for the bit length table and
  69       15 bits for the actual data.
  70    4. If only one code exists, then it is encoded using one bit.  (Zero
  71       would be more efficient, but perhaps a little confusing.)  If two
  72       codes exist, they are coded using one bit each (0 and 1).
  73    5. There is no way of sending zero distance codes--a dummy must be
  74       sent if there are none.  (History: a pre 2.0 version of PKZIP would
  75       store blocks with no distance codes, but this was discovered to be
  76       too harsh a criterion.)  Valid only for 1.93a.  2.04c does allow
  77       zero distance codes, which is sent as one code of zero bits in
  78       length.
  79    6. There are up to 286 literal/length codes.  Code 256 represents the
  80       end-of-block.  Note however that the static length tree defines
  81       288 codes just to fill out the Huffman codes.  Codes 286 and 287
  82       cannot be used though, since there is no length base or extra bits
  83       defined for them.  Similarly, there are up to 30 distance codes.
  84       However, static trees define 32 codes (all 5 bits) to fill out the
  85       Huffman codes, but the last two had better not show up in the data.
  86    7. Unzip can check dynamic Huffman blocks for complete code sets.
  87       The exception is that a single code would not be complete (see #4).
  88    8. The five bits following the block type is really the number of
  89       literal codes sent minus 257.
  90    9. Length codes 8,16,16 are interpreted as 13 length codes of 8 bits
  91       (1+6+6).  Therefore, to output three times the length, you output
  92       three codes (1+1+1), whereas to output four times the same length,
  93       you only need two codes (1+3).  Hmm.
  94   10. In the tree reconstruction algorithm, Code = Code + Increment
  95       only if BitLength(i) is not zero.  (Pretty obvious.)
  96   11. Correction: 4 Bits: # of Bit Length codes - 4     (4 - 19)
  97   12. Note: length code 284 can represent 227-258, but length code 285
  98       really is 258.  The last length deserves its own, short code
  99       since it gets used a lot in very redundant files.  The length
 100       258 is special since 258 - 3 (the min match length) is 255.
 101   13. The literal/length and distance code bit lengths are read as a
 102       single stream of lengths.  It is possible (and advantageous) for
 103       a repeat code (16, 17, or 18) to go across the boundary between
 104       the two sets of lengths.
 105  */
 106
 107 #ifdef RCSID
 108 static char rcsid[] = "#Id: inflate.c,v 0.14 1993/06/10 13:27:04 jloup Exp #";
 109 #endif
 110
 111 #define slide window
 112
 113 /* Huffman code lookup table entry--this entry is four bytes for machines
 114    that have 16-bit pointers (e.g. PC's in the small or medium model).
 115    Valid extra bits are 0..13.  e == 15 is EOB (end of block), e == 16
 116    means that v is a literal, 16 < e < 32 means that v is a pointer to
 117    the next table, which codes e - 16 bits, and lastly e == 99 indicates
 118    an unused code.  If a code with e == 99 is looked up, this implies an
 119    error in the data. */
 120 struct huft {
 121     uch e;                      /* number of extra bits or operation */
 122     uch b;                      /* number of bits in this code or subcode */
 123     union {
 124         ush n;                  /* literal, length base, or distance base */
 125         struct huft *t;         /* pointer to next level of table */
 126     } v;
 127 };
 128
 129 /* Function prototypes */
 130 STATIC int huft_build OF((unsigned *, unsigned, unsigned,
 131                           const ush *, const ush *, struct huft **, int *));
 132 STATIC int huft_free OF((struct huft *));
 133 STATIC int inflate_codes OF((struct huft *, struct huft *, int, int));
 134 STATIC int inflate_stored OF((void));
 135 STATIC int inflate_fixed OF((void));
 136 STATIC int inflate_dynamic OF((void));
 137 STATIC int inflate_block OF((int *));
 138 STATIC int inflate OF((void));
 139
 140 /* The inflate algorithm uses a sliding 32 K byte window on the uncompressed
 141    stream to find repeated byte strings.  This is implemented here as a
 142    circular buffer.  The index is updated simply by incrementing and then
 143    ANDing with 0x7fff (32K-1). */
 144 /* It is left to other modules to supply the 32 K area.  It is assumed
 145    to be usable as if it were declared "uch slide[32768];" or as just
 146    "uch *slide;" and then malloc'ed in the latter case.  The definition
 147    must be in unzip.h, included above. */
 148 /* unsigned wp;             current position in slide */
 149 #define wp outcnt
 150 #define flush_output(w) (wp=(w),flush_window())
 151
 152 /* Tables for deflate from PKZIP's appnote.txt. */
 153 static const unsigned border[] = {      /* Order of the bit length code lengths */
 154     16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15
 155 };
 156
 157 static const ush cplens[] = {   /* Copy lengths for literal codes 257..285 */
 158     3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
 159     35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0
 160 };
 161
 162         /* note: see note #13 above about the 258 in this list. */
 163 static const ush cplext[] = {   /* Extra bits for literal codes 257..285 */
 164     0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
 165     3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 99, 99
 166 };                              /* 99==invalid */
 167
 168 static const ush cpdist[] = {   /* Copy offsets for distance codes 0..29 */
 169     1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
 170     257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
 171     8193, 12289, 16385, 24577
 172 };
 173
 174 static const ush cpdext[] = {   /* Extra bits for distance codes */
 175     0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
 176     7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
 177     12, 12, 13, 13
 178 };
 179
 180 /* Macros for inflate() bit peeking and grabbing.
 181    The usage is:
 182
 183         NEEDBITS(j)
 184         x = b & mask_bits[j];
 185         DUMPBITS(j)
 186
 187    where NEEDBITS makes sure that b has at least j bits in it, and
 188    DUMPBITS removes the bits from b.  The macros use the variable k
 189    for the number of bits in b.  Normally, b and k are register
 190    variables for speed, and are initialized at the beginning of a
 191    routine that uses these macros from a global bit buffer and count.
 192
 193    If we assume that EOB will be the longest code, then we will never
 194    ask for bits with NEEDBITS that are beyond the end of the stream.
 195    So, NEEDBITS should not read any more bytes than are needed to
 196    meet the request.  Then no bytes need to be "returned" to the buffer
 197    at the end of the last block.
 198
 199    However, this assumption is not true for fixed blocks--the EOB code
 200    is 7 bits, but the other literal/length codes can be 8 or 9 bits.
 201    (The EOB code is shorter than other codes because fixed blocks are
 202    generally short.  So, while a block always has an EOB, many other
 203    literal/length codes have a significantly lower probability of
 204    showing up at all.)  However, by making the first table have a
 205    lookup of seven bits, the EOB code will be found in that first
 206    lookup, and so will not require that too many bits be pulled from
 207    the stream.
 208  */
 209
 210 STATIC ulg bb;                  /* bit buffer */
 211 STATIC unsigned bk;             /* bits in bit buffer */
 212
 213 STATIC const ush mask_bits[] = {
 214     0x0000,
 215     0x0001, 0x0003, 0x0007, 0x000f, 0x001f, 0x003f, 0x007f, 0x00ff,
 216     0x01ff, 0x03ff, 0x07ff, 0x0fff, 0x1fff, 0x3fff, 0x7fff, 0xffff
 217 };
 218
 219 #define NEXTBYTE()  (uch)get_byte()
 220 #define NEEDBITS(n) {while(k<(n)){b|=((ulg)NEXTBYTE())<<k;k+=8;}}
 221 #define DUMPBITS(n) {b>>=(n);k-=(n);}
 222
 223 /*
 224    Huffman code decoding is performed using a multi-level table lookup.
 225    The fastest way to decode is to simply build a lookup table whose
 226    size is determined by the longest code.  However, the time it takes
 227    to build this table can also be a factor if the data being decoded
 228    is not very long.  The most common codes are necessarily the
 229    shortest codes, so those codes dominate the decoding time, and hence
 230    the speed.  The idea is you can have a shorter table that decodes the
 231    shorter, more probable codes, and then point to subsidiary tables for
 232    the longer codes.  The time it costs to decode the longer codes is
 233    then traded against the time it takes to make longer tables.
 234
 235    This results of this trade are in the variables lbits and dbits
 236    below.  lbits is the number of bits the first level table for literal/
 237    length codes can decode in one step, and dbits is the same thing for
 238    the distance codes.  Subsequent tables are also less than or equal to
 239    those sizes.  These values may be adjusted either when all of the
 240    codes are shorter than that, in which case the longest code length in
 241    bits is used, or when the shortest code is *longer* than the requested
 242    table size, in which case the length of the shortest code in bits is
 243    used.
 244
 245    There are two different values for the two tables, since they code a
 246    different number of possibilities each.  The literal/length table
 247    codes 286 possible values, or in a flat code, a little over eight
 248    bits.  The distance table codes 30 possible values, or a little less
 249    than five bits, flat.  The optimum values for speed end up being
 250    about one bit more than those, so lbits is 8+1 and dbits is 5+1.
 251    The optimum values may differ though from machine to machine, and
 252    possibly even between compilers.  Your mileage may vary.
 253  */
 254
 255 STATIC const int lbits = 9;     /* bits in base literal/length lookup table */
 256 STATIC const int dbits = 6;     /* bits in base distance lookup table */
 257
 258 /* If BMAX needs to be larger than 16, then h and x[] should be ulg. */
 259 #define BMAX 16                 /* maximum bit length of any code (16 for explode) */
 260 #define N_MAX 288               /* maximum number of codes in any set */
 261
 262 STATIC unsigned hufts;          /* track memory usage */
 263
 264 STATIC int huft_build(b, n, s, d, e, t, m)
 265 unsigned *b;                    /* code lengths in bits (all assumed <= BMAX) */
 266 unsigned n;                     /* number of codes (assumed <= N_MAX) */
 267 unsigned s;                     /* number of simple-valued codes (0..s-1) */
 268 const ush *d;                   /* list of base values for non-simple codes */
 269 const ush *e;                   /* list of extra bits for non-simple codes */
 270 struct huft **t;                /* result: starting table */
 271 int *m;                         /* maximum lookup bits, returns actual */
 272 /* Given a list of code lengths and a maximum table size, make a set of
 273    tables to decode that set of codes.  Return zero on success, one if
 274    the given code set is incomplete (the tables are still built in this
 275    case), two if the input is invalid (all zero length codes or an
 276    oversubscribed set of lengths), and three if not enough memory. */
 277 {
 278     unsigned a;                 /* counter for codes of length k */
 279     unsigned c[BMAX + 1];       /* bit length count table */
 280     unsigned f;                 /* i repeats in table every f entries */
 281     int g;                      /* maximum code length */
 282     int h;                      /* table level */
 283     register unsigned i;        /* counter, current code */
 284     register unsigned j;        /* counter */
 285     register int k;             /* number of bits in current code */
 286     int l;                      /* bits per table (returned in m) */
 287     register unsigned *p;       /* pointer into c[], b[], or v[] */
 288     register struct huft *q;    /* points to current table */
 289     struct huft r;              /* table entry for structure assignment */
 290     struct huft *u[BMAX];       /* table stack */
 291     unsigned v[N_MAX];          /* values in order of bit length */
 292     register int w;             /* bits before this table == (l * h) */
 293     unsigned x[BMAX + 1];       /* bit offsets, then code stack */
 294     unsigned *xp;               /* pointer into x */
 295     int y;                      /* number of dummy codes added */
 296     unsigned z;                 /* number of entries in current table */
 297
 298     DEBG("huft1 ");
 299
 300     /* Generate counts for each bit length */
 301     memzero(c, sizeof(c));
 302     p = b;
 303     i = n;
 304     do {
 305         Tracecv(*p,
 306                 (stderr,
 307                  (n - i >= ' '
 308                   && n - i <= '~' ? "%c %d\n" : "0x%x %d\n"), n - i, *p));
 309         c[*p]++;                /* assume all entries <= BMAX */
 310         p++;                    /* Can't combine with above line (Solaris bug) */
 311     } while (--i);
 312     if (c[0] == n) {            /* null input--all zero length codes */
 313         *t = (struct huft *)NULL;
 314         *m = 0;
 315         return 0;
 316     }
 317
 318     DEBG("huft2 ");
 319
 320     /* Find minimum and maximum length, bound *m by those */
 321     l = *m;
 322     for (j = 1; j <= BMAX; j++)
 323         if (c[j])
 324             break;
 325     k = j;                      /* minimum code length */
 326     if ((unsigned)l < j)
 327         l = j;
 328     for (i = BMAX; i; i--)
 329         if (c[i])
 330             break;
 331     g = i;                      /* maximum code length */
 332     if ((unsigned)l > i)
 333         l = i;
 334     *m = l;
 335
 336     DEBG("huft3 ");
 337
 338     /* Adjust last length count to fill out codes, if needed */
 339     for (y = 1 << j; j < i; j++, y <<= 1)
 340         if ((y -= c[j]) < 0)
 341             return 2;           /* bad input: more codes than bits */
 342     if ((y -= c[i]) < 0)
 343         return 2;
 344     c[i] += y;
 345
 346     DEBG("huft4 ");
 347
 348     /* Generate starting offsets into the value table for each length */
 349     x[1] = j = 0;
 350     p = c + 1;
 351     xp = x + 2;
 352     while (--i) {               /* note that i == g from above */
 353         *xp++ = (j += *p++);
 354     }
 355
 356     DEBG("huft5 ");
 357
 358     /* Make a table of values in order of bit lengths */
 359     p = b;
 360     i = 0;
 361     do {
 362         if ((j = *p++) != 0)
 363             v[x[j]++] = i;
 364     } while (++i < n);
 365
 366     DEBG("h6 ");
 367
 368     /* Generate the Huffman codes and for each, make the table entries */
 369     x[0] = i = 0;               /* first Huffman code is zero */
 370     p = v;                      /* grab values in bit order */
 371     h = -1;                     /* no tables yet--level -1 */
 372     w = -l;                     /* bits decoded == (l * h) */
 373     u[0] = (struct huft *)NULL; /* just to keep compilers happy */
 374     q = (struct huft *)NULL;    /* ditto */
 375     z = 0;                      /* ditto */
 376     DEBG("h6a ");
 377
 378     /* go through the bit lengths (k already is bits in shortest code) */
 379     for (; k <= g; k++) {
 380         DEBG("h6b ");
 381         a = c[k];
 382         while (a--) {
 383             DEBG("h6b1 ");
 384             /* here i is the Huffman code of length k bits for value *p */
 385             /* make tables up to required level */
 386             while (k > w + l) {
 387                 DEBG1("1 ");
 388                 h++;
 389                 w += l;         /* previous table always l bits */
 390
 391                 /* compute minimum size table less than or equal to l bits */
 392                 z = (z = g - w) > (unsigned)l ? l : z;  /* upper limit on table size */
 393                 if ((f = 1 << (j = k - w)) > a + 1) {   /* try a k-w bit table *//* too few codes for k-w bit table */
 394                     DEBG1("2 ");
 395                     f -= a + 1; /* deduct codes from patterns left */
 396                     xp = c + k;
 397                     while (++j < z) {   /* try smaller tables up to z bits */
 398                         if ((f <<= 1) <= *++xp)
 399                             break;      /* enough codes to use up j bits */
 400                         f -= *xp;       /* else deduct codes from patterns */
 401                     }
 402                 }
 403                 DEBG1("3 ");
 404                 z = 1 << j;     /* table entries for j-bit table */
 405
 406                 /* allocate and link in new table */
 407                 if ((q =
 408                      (struct huft *)malloc((z + 1) * sizeof(struct huft))) ==
 409                     (struct huft *)NULL) {
 410                     if (h)
 411                         huft_free(u[0]);
 412                     return 3;   /* not enough memory */
 413                 }
 414                 DEBG1("4 ");
 415                 hufts += z + 1; /* track memory usage */
 416                 *t = q + 1;     /* link to list for huft_free() */
 417                 *(t = &(q->v.t)) = (struct huft *)NULL;
 418                 u[h] = ++q;     /* table starts after link */
 419
 420                 DEBG1("5 ");
 421                 /* connect to last table, if there is one */
 422                 if (h) {
 423                     x[h] = i;   /* save pattern for backing up */
 424                     r.b = (uch) l;      /* bits to dump before this table */
 425                     r.e = (uch) (16 + j);       /* bits in this table */
 426                     r.v.t = q;  /* pointer to this table */
 427                     j = i >> (w - l);   /* (get around Turbo C bug) */
 428                     u[h - 1][j] = r;    /* connect to last table */
 429                 }
 430                 DEBG1("6 ");
 431             }
 432             DEBG("h6c ");
 433
 434             /* set up table entry in r */
 435             r.b = (uch) (k - w);
 436             if (p >= v + n)
 437                 r.e = 99;       /* out of values--invalid code */
 438             else if (*p < s) {
 439                 r.e = (uch) (*p < 256 ? 16 : 15);       /* 256 is end-of-block code */
 440                 r.v.n = (ush) (*p);     /* simple code is just the value */
 441                 p++;            /* one compiler does not like *p++ */
 442             } else {
 443                 r.e = (uch) e[*p - s];  /* non-simple--look up in lists */
 444                 r.v.n = d[*p++ - s];
 445             }
 446             DEBG("h6d ");
 447
 448             /* fill code-like entries with r */
 449             f = 1 << (k - w);
 450             for (j = i >> w; j < z; j += f)
 451                 q[j] = r;
 452
 453             /* backwards increment the k-bit code i */
 454             for (j = 1 << (k - 1); i & j; j >>= 1)
 455                 i ^= j;
 456             i ^= j;
 457
 458             /* backup over finished tables */
 459             while ((i & ((1 << w) - 1)) != x[h]) {
 460                 h--;            /* don't need to update q */
 461                 w -= l;
 462             }
 463             DEBG("h6e ");
 464         }
 465         DEBG("h6f ");
 466     }
 467
 468     DEBG("huft7 ");
 469
 470     /* Return true (1) if we were given an incomplete table */
 471     return y != 0 && g != 1;
 472 }
 473
 474 STATIC int huft_free(t)
 475 struct huft *t;                 /* table to free */
 476 /* Free the malloc'ed tables built by huft_build(), which makes a linked
 477    list of the tables it made, with the links in a dummy first entry of
 478    each table. */
 479 {
 480     register struct huft *p, *q;
 481
 482     /* Go through linked list, freeing from the malloced (t[-1]) address. */
 483     p = t;
 484     while (p != (struct huft *)NULL) {
 485         q = (--p)->v.t;
 486         free((char *)p);
 487         p = q;
 488     }
 489     return 0;
 490 }
 491
 492 STATIC int inflate_codes(tl, td, bl, bd)
 493 struct huft *tl, *td;           /* literal/length and distance decoder tables */
 494 int bl, bd;                     /* number of bits decoded by tl[] and td[] */
 495 /* inflate (decompress) the codes in a deflated (compressed) block.
 496    Return an error code or zero if it all goes ok. */
 497 {
 498     register unsigned e;        /* table entry flag/number of extra bits */
 499     unsigned n, d;              /* length and index for copy */
 500     unsigned w;                 /* current window position */
 501     struct huft *t;             /* pointer to table entry */
 502     unsigned ml, md;            /* masks for bl and bd bits */
 503     register ulg b;             /* bit buffer */
 504     register unsigned k;        /* number of bits in bit buffer */
 505
 506     /* make local copies of globals */
 507     b = bb;                     /* initialize bit buffer */
 508     k = bk;
 509     w = wp;                     /* initialize window position */
 510
 511     /* inflate the coded data */
 512     ml = mask_bits[bl];         /* precompute masks for speed */
 513     md = mask_bits[bd];
 514     for (;;) {                  /* do until end of block */
 515         NEEDBITS((unsigned)bl)
 516             if ((e = (t = tl + ((unsigned)b & ml))->e) > 16)
 517             do {
 518                 if (e == 99)
 519                     return 1;
 520                 DUMPBITS(t->b)
 521                     e -= 16;
 522                 NEEDBITS(e)
 523             } while ((e = (t = t->v.t + ((unsigned)b & mask_bits[e]))->e) > 16);
 524         DUMPBITS(t->b)
 525             if (e == 16) {      /* then it's a literal */
 526             slide[w++] = (uch) t->v.n;
 527             Tracevv((stderr, "%c", slide[w - 1]));
 528             if (w == WSIZE) {
 529                 flush_output(w);
 530                 w = 0;
 531             }
 532         } else {                /* it's an EOB or a length */
 533
 534             /* exit if end of block */
 535             if (e == 15)
 536                 break;
 537
 538             /* get length of block to copy */
 539             NEEDBITS(e)
 540                 n = t->v.n + ((unsigned)b & mask_bits[e]);
 541             DUMPBITS(e);
 542
 543             /* decode distance of block to copy */
 544             NEEDBITS((unsigned)bd)
 545                 if ((e = (t = td + ((unsigned)b & md))->e) > 16)
 546                 do {
 547                     if (e == 99)
 548                         return 1;
 549                     DUMPBITS(t->b)
 550                         e -= 16;
 551                     NEEDBITS(e)
 552                 } while ((e =
 553                           (t = t->v.t + ((unsigned)b & mask_bits[e]))->e) > 16);
 554             DUMPBITS(t->b)
 555                 NEEDBITS(e)
 556                 d = w - t->v.n - ((unsigned)b & mask_bits[e]);
 557             DUMPBITS(e)
 558                 Tracevv((stderr, "\\[%d,%d]", w - d, n));
 559
 560             /* do the copy */
 561             do {
 562                 n -= (e =
 563                       (e = WSIZE - ((d &= WSIZE - 1) > w ? d : w)) > n ? n : e);
 564 #if !defined(NOMEMCPY) && !defined(DEBUG)
 565                 if (w - d >= e) {       /* (this test assumes unsigned comparison) */
 566                     memcpy(slide + w, slide + d, e);
 567                     w += e;
 568                     d += e;
 569                 } else          /* do it slow to avoid memcpy() overlap */
 570 #endif /* !NOMEMCPY */
 571                     do {
 572                         slide[w++] = slide[d++];
 573                         Tracevv((stderr, "%c", slide[w - 1]));
 574                     } while (--e);
 575                 if (w == WSIZE) {
 576                     flush_output(w);
 577                     w = 0;
 578                 }
 579             } while (n);
 580         }
 581     }
 582
 583     /* restore the globals from the locals */
 584     wp = w;                     /* restore global window pointer */
 585     bb = b;                     /* restore global bit buffer */
 586     bk = k;
 587
 588     /* done */
 589     return 0;
 590 }
 591
 592 STATIC int inflate_stored()
 593 /* "decompress" an inflated type 0 (stored) block. */
 594 {
 595     unsigned n;                 /* number of bytes in block */
 596     unsigned w;                 /* current window position */
 597     register ulg b;             /* bit buffer */
 598     register unsigned k;        /* number of bits in bit buffer */
 599
 600     DEBG("<stor");
 601
 602     /* make local copies of globals */
 603     b = bb;                     /* initialize bit buffer */
 604     k = bk;
 605     w = wp;                     /* initialize window position */
 606
 607     /* go to byte boundary */
 608     n = k & 7;
 609     DUMPBITS(n);
 610
 611     /* get the length and its complement */
 612     NEEDBITS(16)
 613         n = ((unsigned)b & 0xffff);
 614     DUMPBITS(16)
 615         NEEDBITS(16)
 616         if (n != (unsigned)((~b) & 0xffff))
 617         return 1;               /* error in compressed data */
 618     DUMPBITS(16)
 619
 620         /* read and output the compressed data */
 621         while (n--) {
 622         NEEDBITS(8)
 623             slide[w++] = (uch) b;
 624         if (w == WSIZE) {
 625             flush_output(w);
 626             w = 0;
 627         }
 628         DUMPBITS(8)
 629     }
 630
 631     /* restore the globals from the locals */
 632     wp = w;                     /* restore global window pointer */
 633     bb = b;                     /* restore global bit buffer */
 634     bk = k;
 635
 636     DEBG(">");
 637     return 0;
 638 }
 639
 640 STATIC int inflate_fixed()
 641 /* decompress an inflated type 1 (fixed Huffman codes) block.  We should
 642    either replace this with a custom decoder, or at least precompute the
 643    Huffman tables. */
 644 {
 645     int i;                      /* temporary variable */
 646     struct huft *tl;            /* literal/length code table */
 647     struct huft *td;            /* distance code table */
 648     int bl;                     /* lookup bits for tl */
 649     int bd;                     /* lookup bits for td */
 650     unsigned l[288];            /* length list for huft_build */
 651
 652     DEBG("<fix");
 653
 654     /* set up literal table */
 655     for (i = 0; i < 144; i++)
 656         l[i] = 8;
 657     for (; i < 256; i++)
 658         l[i] = 9;
 659     for (; i < 280; i++)
 660         l[i] = 7;
 661     for (; i < 288; i++)        /* make a complete, but wrong code set */
 662         l[i] = 8;
 663     bl = 7;
 664     if ((i = huft_build(l, 288, 257, cplens, cplext, &tl, &bl)) != 0)
 665         return i;
 666
 667     /* set up distance table */
 668     for (i = 0; i < 30; i++)    /* make an incomplete code set */
 669         l[i] = 5;
 670     bd = 5;
 671     if ((i = huft_build(l, 30, 0, cpdist, cpdext, &td, &bd)) > 1) {
 672         huft_free(tl);
 673
 674         DEBG(">");
 675         return i;
 676     }
 677
 678     /* decompress until an end-of-block code */
 679     if (inflate_codes(tl, td, bl, bd))
 680         return 1;
 681
 682     /* free the decoding tables, return */
 683     huft_free(tl);
 684     huft_free(td);
 685     return 0;
 686 }
 687
 688 STATIC int inflate_dynamic()
 689 /* decompress an inflated type 2 (dynamic Huffman codes) block. */
 690 {
 691     int i;                      /* temporary variables */
 692     unsigned j;
 693     unsigned l;                 /* last length */
 694     unsigned m;                 /* mask for bit lengths table */
 695     unsigned n;                 /* number of lengths to get */
 696     struct huft *tl;            /* literal/length code table */
 697     struct huft *td;            /* distance code table */
 698     int bl;                     /* lookup bits for tl */
 699     int bd;                     /* lookup bits for td */
 700     unsigned nb;                /* number of bit length codes */
 701     unsigned nl;                /* number of literal/length codes */
 702     unsigned nd;                /* number of distance codes */
 703 #ifdef PKZIP_BUG_WORKAROUND
 704     unsigned ll[288 + 32];      /* literal/length and distance code lengths */
 705 #else
 706     unsigned ll[286 + 30];      /* literal/length and distance code lengths */
 707 #endif
 708     register ulg b;             /* bit buffer */
 709     register unsigned k;        /* number of bits in bit buffer */
 710
 711     DEBG("<dyn");
 712
 713     /* make local bit buffer */
 714     b = bb;
 715     k = bk;
 716
 717     /* read in table lengths */
 718     NEEDBITS(5)
 719         nl = 257 + ((unsigned)b & 0x1f);        /* number of literal/length codes */
 720     DUMPBITS(5)
 721         NEEDBITS(5)
 722         nd = 1 + ((unsigned)b & 0x1f);  /* number of distance codes */
 723     DUMPBITS(5)
 724         NEEDBITS(4)
 725         nb = 4 + ((unsigned)b & 0xf);   /* number of bit length codes */
 726     DUMPBITS(4)
 727 #ifdef PKZIP_BUG_WORKAROUND
 728         if (nl > 288 || nd > 32)
 729 #else
 730         if (nl > 286 || nd > 30)
 731 #endif
 732         return 1;               /* bad lengths */
 733
 734     DEBG("dyn1 ");
 735
 736     /* read in bit-length-code lengths */
 737     for (j = 0; j < nb; j++) {
 738         NEEDBITS(3)
 739             ll[border[j]] = (unsigned)b & 7;
 740         DUMPBITS(3)
 741     }
 742     for (; j < 19; j++)
 743         ll[border[j]] = 0;
 744
 745     DEBG("dyn2 ");
 746
 747     /* build decoding table for trees--single level, 7 bit lookup */
 748     bl = 7;
 749     if ((i = huft_build(ll, 19, 19, NULL, NULL, &tl, &bl)) != 0) {
 750         if (i == 1)
 751             huft_free(tl);
 752         return i;               /* incomplete code set */
 753     }
 754
 755     DEBG("dyn3 ");
 756
 757     /* read in literal and distance code lengths */
 758     n = nl + nd;
 759     m = mask_bits[bl];
 760     i = l = 0;
 761     while ((unsigned)i < n) {
 762         NEEDBITS((unsigned)bl)
 763             j = (td = tl + ((unsigned)b & m))->b;
 764         DUMPBITS(j)
 765             j = td->v.n;
 766         if (j < 16)             /* length of code in bits (0..15) */
 767             ll[i++] = l = j;    /* save last length in l */
 768         else if (j == 16) {     /* repeat last length 3 to 6 times */
 769             NEEDBITS(2)
 770                 j = 3 + ((unsigned)b & 3);
 771             DUMPBITS(2)
 772                 if ((unsigned)i + j > n)
 773                 return 1;
 774             while (j--)
 775                 ll[i++] = l;
 776         } else if (j == 17) {   /* 3 to 10 zero length codes */
 777             NEEDBITS(3)
 778                 j = 3 + ((unsigned)b & 7);
 779             DUMPBITS(3)
 780                 if ((unsigned)i + j > n)
 781                 return 1;
 782             while (j--)
 783                 ll[i++] = 0;
 784             l = 0;
 785         } else {                /* j == 18: 11 to 138 zero length codes */
 786
 787             NEEDBITS(7)
 788                 j = 11 + ((unsigned)b & 0x7f);
 789             DUMPBITS(7)
 790                 if ((unsigned)i + j > n)
 791                 return 1;
 792             while (j--)
 793                 ll[i++] = 0;
 794             l = 0;
 795         }
 796     }
 797
 798     DEBG("dyn4 ");
 799
 800     /* free decoding table for trees */
 801     huft_free(tl);
 802
 803     DEBG("dyn5 ");
 804
 805     /* restore the global bit buffer */
 806     bb = b;
 807     bk = k;
 808
 809     DEBG("dyn5a ");
 810
 811     /* build the decoding tables for literal/length and distance codes */
 812     bl = lbits;
 813     if ((i = huft_build(ll, nl, 257, cplens, cplext, &tl, &bl)) != 0) {
 814         DEBG("dyn5b ");
 815         if (i == 1) {
 816             error(" incomplete literal tree");
 817             huft_free(tl);
 818         }
 819         return i;               /* incomplete code set */
 820     }
 821     DEBG("dyn5c ");
 822     bd = dbits;
 823     if ((i = huft_build(ll + nl, nd, 0, cpdist, cpdext, &td, &bd)) != 0) {
 824         DEBG("dyn5d ");
 825         if (i == 1) {
 826             error(" incomplete distance tree");
 827 #ifdef PKZIP_BUG_WORKAROUND
 828             i = 0;
 829         }
 830 #else
 831             huft_free(td);
 832         }
 833         huft_free(tl);
 834         return i;               /* incomplete code set */
 835 #endif
 836     }
 837
 838     DEBG("dyn6 ");
 839
 840     /* decompress until an end-of-block code */
 841     if (inflate_codes(tl, td, bl, bd))
 842         return 1;
 843
 844     DEBG("dyn7 ");
 845
 846     /* free the decoding tables, return */
 847     huft_free(tl);
 848     huft_free(td);
 849
 850     DEBG(">");
 851     return 0;
 852 }
 853
 854 STATIC int inflate_block(e)
 855 int *e;                         /* last block flag */
 856 /* decompress an inflated block */
 857 {
 858     unsigned t;                 /* block type */
 859     register ulg b;             /* bit buffer */
 860     register unsigned k;        /* number of bits in bit buffer */
 861
 862     DEBG("<blk");
 863
 864     /* make local bit buffer */
 865     b = bb;
 866     k = bk;
 867
 868     /* read in last block bit */
 869     NEEDBITS(1)
 870         * e = (int)b & 1;
 871     DUMPBITS(1)
 872
 873         /* read in block type */
 874         NEEDBITS(2)
 875         t = (unsigned)b & 3;
 876     DUMPBITS(2)
 877
 878         /* restore the global bit buffer */
 879         bb = b;
 880     bk = k;
 881
 882     /* inflate that block type */
 883     if (t == 2)
 884         return inflate_dynamic();
 885     if (t == 0)
 886         return inflate_stored();
 887     if (t == 1)
 888         return inflate_fixed();
 889
 890     DEBG(">");
 891
 892     /* bad block type */
 893     return 2;
 894 }
 895
 896 STATIC int inflate()
 897 /* decompress an inflated entry */
 898 {
 899     int e;                      /* last block flag */
 900     int r;                      /* result code */
 901     unsigned h;                 /* maximum struct huft's malloc'ed */
 902     void *ptr;
 903
 904     /* initialize window, bit buffer */
 905     wp = 0;
 906     bk = 0;
 907     bb = 0;
 908
 909     /* decompress until the last block */
 910     h = 0;
 911     do {
 912         hufts = 0;
 913         gzip_mark(&ptr);
 914         if ((r = inflate_block(&e)) != 0) {
 915             gzip_release(&ptr);
 916             return r;
 917         }
 918         gzip_release(&ptr);
 919         if (hufts > h)
 920             h = hufts;
 921     } while (!e);
 922
 923     /* Undo too much lookahead. The next read will be byte aligned so we
 924      * can discard unused bits in the last meaningful byte.
 925      */
 926     while (bk >= 8) {
 927         bk -= 8;
 928         unget_byte();
 929     }
 930
 931     /* flush out slide */
 932     flush_output(wp);
 933
 934     /* return success */
 935 #ifdef DEBUG
 936     fprintf(stderr, "<%u> ", h);
 937 #endif /* DEBUG */
 938     return 0;
 939 }
 940
 941 /**********************************************************************
 942  *
 943  * The following are support routines for inflate.c
 944  *
 945  **********************************************************************/
 946
 947 static ulg crc_32_tab[256];
 948 static ulg crc;                 /* initialized in makecrc() so it'll reside in bss */
 949 #define CRC_VALUE (crc ^ 0xffffffffL)
 950
 951 /*
 952  * Code to compute the CRC-32 table. Borrowed from
 953  * gzip-1.0.3/makecrc.c.
 954  */
 955
 956 static void makecrc(void)
 957 {
 958 /* Not copyrighted 1990 Mark Adler      */
 959
 960     unsigned long c;            /* crc shift register */
 961     unsigned long e;            /* polynomial exclusive-or pattern */
 962     int i;                      /* counter for all possible eight bit values */
 963     int k;                      /* byte being shifted into crc apparatus */
 964
 965     /* terms of polynomial defining this crc (except x^32): */
 966     static const int p[] = { 0, 1, 2, 4, 5, 7, 8, 10, 11, 12, 16, 22, 23, 26 };
 967
 968     /* Make exclusive-or pattern from polynomial */
 969     e = 0;
 970     for (i = 0; i < sizeof(p) / sizeof(int); i++)
 971         e |= 1L << (31 - p[i]);
 972
 973     crc_32_tab[0] = 0;
 974
 975     for (i = 1; i < 256; i++) {
 976         c = 0;
 977         for (k = i | 256; k != 1; k >>= 1) {
 978             c = c & 1 ? (c >> 1) ^ e : c >> 1;
 979             if (k & 1)
 980                 c ^= e;
 981         }
 982         crc_32_tab[i] = c;
 983     }
 984
 985     /* this is initialized here so this code could reside in ROM */
 986     crc = (ulg) 0xffffffffL;    /* shift register contents */
 987 }
 988
 989 /* gzip flag byte */
 990 #define ASCII_FLAG   0x01       /* bit 0 set: file probably ASCII text */
 991 #define CONTINUATION 0x02       /* bit 1 set: continuation of multi-part gzip file */
 992 #define EXTRA_FIELD  0x04       /* bit 2 set: extra field present */
 993 #define ORIG_NAME    0x08       /* bit 3 set: original file name present */
 994 #define COMMENT      0x10       /* bit 4 set: file comment present */
 995 #define ENCRYPTED    0x20       /* bit 5 set: file is encrypted */
 996 #define RESERVED     0xC0       /* bit 6,7:   reserved */
 997
 998 /*
 999  * Do the uncompression!
1000  */
1001 int gunzip(void)
1002 {
1003     int res;
1004
1005     /* Decompress */
1006     if ((res = inflate())) {
1007         switch (res) {
1008         case 0:
1009             break;
1010         case 1:
1011             error("invalid compressed format (err=1)");
1012             break;
1013         case 2:
1014             error("invalid compressed format (err=2)");
1015             break;
1016         case 3:
1017             error("out of memory");
1018             break;
1019         default:
1020             error("invalid compressed format (other)");
1021         }
1022         return -1;
1023     }
1024
1025     return 0;
1026 }