lib/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
  17 /*
  18    Inflate deflated (PKZIP's method 8 compressed) data.  The compression
  19    method searches for as much of the current string of bytes (up to a
  20    length of 258) in the previous 32 K bytes.  If it doesn't find any
  21    matches (of at least length 3), it codes the next byte.  Otherwise, it
  22    codes the length of the matched string and its distance backwards from
  23    the current position.  There is a single Huffman code that codes both
  24    single bytes (called "literals") and match lengths.  A second Huffman
  25    code codes the distance information, which follows a length code.  Each
  26    length or distance code actually represents a base value and a number
  27    of "extra" (sometimes zero) bits to get to add to the base value.  At
  28    the end of each deflated block is a special end-of-block (EOB) literal/
  29    length code.  The decoding process is basically: get a literal/length
  30    code; if EOB then done; if a literal, emit the decoded byte; if a
  31    length then get the distance and emit the referred-to bytes from the
  32    sliding window of previously emitted data.
  33
  34    There are (currently) three kinds of inflate blocks: stored, fixed, and
  35    dynamic.  The compressor deals with some chunk of data at a time, and
  36    decides which method to use on a chunk-by-chunk basis.  A chunk might
  37    typically be 32 K or 64 K.  If the chunk is incompressible, then the
  38    "stored" method is used.  In this case, the bytes are simply stored as
  39    is, eight bits per byte, with none of the above coding.  The bytes are
  40    preceded by a count, since there is no longer an EOB code.
  41
  42    If the data is compressible, then either the fixed or dynamic methods
  43    are used.  In the dynamic method, the compressed data is preceded by
  44    an encoding of the literal/length and distance Huffman codes that are
  45    to be used to decode this block.  The representation is itself Huffman
  46    coded, and so is preceded by a description of that code.  These code
  47    descriptions take up a little space, and so for small blocks, there is
  48    a predefined set of codes, called the fixed codes.  The fixed method is
  49    used if the block codes up smaller that way (usually for quite small
  50    chunks), otherwise the dynamic method is used.  In the latter case, the
  51    codes are customized to the probabilities in the current block, and so
  52    can code it much better than the pre-determined fixed codes.
  53
  54    The Huffman codes themselves are decoded using a multi-level table
  55    lookup, in order to maximize the speed of decoding plus the speed of
  56    building the decoding tables.  See the comments below that precede the
  57    lbits and dbits tuning parameters.
  58  */
  59
  60
  61 /*
  62    Notes beyond the 1.93a appnote.txt:
  63
  64    1. Distance pointers never point before the beginning of the output
  65       stream.
  66    2. Distance pointers can point back across blocks, up to 32k away.
  67    3. There is an implied maximum of 7 bits for the bit length table and
  68       15 bits for the actual data.
  69    4. If only one code exists, then it is encoded using one bit.  (Zero
  70       would be more efficient, but perhaps a little confusing.)  If two
  71       codes exist, they are coded using one bit each (0 and 1).
  72    5. There is no way of sending zero distance codes--a dummy must be
  73       sent if there are none.  (History: a pre 2.0 version of PKZIP would
  74       store blocks with no distance codes, but this was discovered to be
  75       too harsh a criterion.)  Valid only for 1.93a.  2.04c does allow
  76       zero distance codes, which is sent as one code of zero bits in
  77       length.
  78    6. There are up to 286 literal/length codes.  Code 256 represents the
  79       end-of-block.  Note however that the static length tree defines
  80       288 codes just to fill out the Huffman codes.  Codes 286 and 287
  81       cannot be used though, since there is no length base or extra bits
  82       defined for them.  Similarly, there are up to 30 distance codes.
  83       However, static trees define 32 codes (all 5 bits) to fill out the
  84       Huffman codes, but the last two had better not show up in the data.
  85    7. Unzip can check dynamic Huffman blocks for complete code sets.
  86       The exception is that a single code would not be complete (see #4).
  87    8. The five bits following the block type is really the number of
  88       literal codes sent minus 257.
  89    9. Length codes 8,16,16 are interpreted as 13 length codes of 8 bits
  90       (1+6+6).  Therefore, to output three times the length, you output
  91       three codes (1+1+1), whereas to output four times the same length,
  92       you only need two codes (1+3).  Hmm.
  93   10. In the tree reconstruction algorithm, Code = Code + Increment
  94       only if BitLength(i) is not zero.  (Pretty obvious.)
  95   11. Correction: 4 Bits: # of Bit Length codes - 4     (4 - 19)
  96   12. Note: length code 284 can represent 227-258, but length code 285
  97       really is 258.  The last length deserves its own, short code
  98       since it gets used a lot in very redundant files.  The length
  99       258 is special since 258 - 3 (the min match length) is 255.
 100   13. The literal/length and distance code bit lengths are read as a
 101       single stream of lengths.  It is possible (and advantageous) for
 102       a repeat code (16, 17, or 18) to go across the boundary between
 103       the two sets of lengths.
 104  */
 105 #include <linux/compiler.h>
 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 #ifndef STATIC
 112
 113 #if defined(STDC_HEADERS) || defined(HAVE_STDLIB_H)
 114 #  include <sys/types.h>
 115 #  include <stdlib.h>
 116 #endif
 117
 118 #include "gzip.h"
 119 #define STATIC
 120 #endif /* !STATIC */
 121
 122 #ifndef INIT
 123 #define INIT
 124 #endif
 125
 126 #define slide window
 127
 128 /* Huffman code lookup table entry--this entry is four bytes for machines
 129    that have 16-bit pointers (e.g. PC's in the small or medium model).
 130    Valid extra bits are 0..13.  e == 15 is EOB (end of block), e == 16
 131    means that v is a literal, 16 < e < 32 means that v is a pointer to
 132    the next table, which codes e - 16 bits, and lastly e == 99 indicates
 133    an unused code.  If a code with e == 99 is looked up, this implies an
 134    error in the data. */
 135 struct huft {
 136   uch e;                /* number of extra bits or operation */
 137   uch b;                /* number of bits in this code or subcode */
 138   union {
 139     ush n;              /* literal, length base, or distance base */
 140     struct huft *t;     /* pointer to next level of table */
 141   } v;
 142 };
 143
 144
 145 /* Function prototypes */
 146 STATIC int INIT huft_build OF((unsigned *, unsigned, unsigned,
 147                 const ush *, const ush *, struct huft **, int *));
 148 STATIC int INIT huft_free OF((struct huft *));
 149 STATIC int INIT inflate_codes OF((struct huft *, struct huft *, int, int));
 150 STATIC int INIT inflate_stored OF((void));
 151 STATIC int INIT inflate_fixed OF((void));
 152 STATIC int INIT inflate_dynamic OF((void));
 153 STATIC int INIT inflate_block OF((int *));
 154 STATIC int INIT inflate OF((void));
 155
 156
 157 /* The inflate algorithm uses a sliding 32 K byte window on the uncompressed
 158    stream to find repeated byte strings.  This is implemented here as a
 159    circular buffer.  The index is updated simply by incrementing and then
 160    ANDing with 0x7fff (32K-1). */
 161 /* It is left to other modules to supply the 32 K area.  It is assumed
 162    to be usable as if it were declared "uch slide[32768];" or as just
 163    "uch *slide;" and then malloc'ed in the latter case.  The definition
 164    must be in unzip.h, included above. */
 165 /* unsigned wp;             current position in slide */
 166 #define wp outcnt
 167 #define flush_output(w) (wp=(w),flush_window())
 168
 169 /* Tables for deflate from PKZIP's appnote.txt. */
 170 static const unsigned border[] = {    /* Order of the bit length code lengths */
 171         16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
 172 static const ush cplens[] = {         /* Copy lengths for literal codes 257..285 */
 173         3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
 174         35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
 175         /* note: see note #13 above about the 258 in this list. */
 176 static const ush cplext[] = {         /* Extra bits for literal codes 257..285 */
 177         0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
 178         3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 99, 99}; /* 99==invalid */
 179 static const ush cpdist[] = {         /* Copy offsets for distance codes 0..29 */
 180         1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
 181         257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
 182         8193, 12289, 16385, 24577};
 183 static const ush cpdext[] = {         /* Extra bits for distance codes */
 184         0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
 185         7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
 186         12, 12, 13, 13};
 187
 188
 189
 190 /* Macros for inflate() bit peeking and grabbing.
 191    The usage is:
 192
 193         NEEDBITS(j)
 194         x = b & mask_bits[j];
 195         DUMPBITS(j)
 196
 197    where NEEDBITS makes sure that b has at least j bits in it, and
 198    DUMPBITS removes the bits from b.  The macros use the variable k
 199    for the number of bits in b.  Normally, b and k are register
 200    variables for speed, and are initialized at the beginning of a
 201    routine that uses these macros from a global bit buffer and count.
 202
 203    If we assume that EOB will be the longest code, then we will never
 204    ask for bits with NEEDBITS that are beyond the end of the stream.
 205    So, NEEDBITS should not read any more bytes than are needed to
 206    meet the request.  Then no bytes need to be "returned" to the buffer
 207    at the end of the last block.
 208
 209    However, this assumption is not true for fixed blocks--the EOB code
 210    is 7 bits, but the other literal/length codes can be 8 or 9 bits.
 211    (The EOB code is shorter than other codes because fixed blocks are
 212    generally short.  So, while a block always has an EOB, many other
 213    literal/length codes have a significantly lower probability of
 214    showing up at all.)  However, by making the first table have a
 215    lookup of seven bits, the EOB code will be found in that first
 216    lookup, and so will not require that too many bits be pulled from
 217    the stream.
 218  */
 219
 220 STATIC ulg bb;                         /* bit buffer */
 221 STATIC unsigned bk;                    /* bits in bit buffer */
 222
 223 STATIC const ush mask_bits[] = {
 224     0x0000,
 225     0x0001, 0x0003, 0x0007, 0x000f, 0x001f, 0x003f, 0x007f, 0x00ff,
 226     0x01ff, 0x03ff, 0x07ff, 0x0fff, 0x1fff, 0x3fff, 0x7fff, 0xffff
 227 };
 228
 229 #define NEXTBYTE()  ({ int v = get_byte(); if (v < 0) goto underrun; (uch)v; })
 230 #define NEEDBITS(n) {while(k<(n)){b|=((ulg)NEXTBYTE())<<k;k+=8;}}
 231 #define DUMPBITS(n) {b>>=(n);k-=(n);}
 232
 233
 234 /*
 235    Huffman code decoding is performed using a multi-level table lookup.
 236    The fastest way to decode is to simply build a lookup table whose
 237    size is determined by the longest code.  However, the time it takes
 238    to build this table can also be a factor if the data being decoded
 239    is not very long.  The most common codes are necessarily the
 240    shortest codes, so those codes dominate the decoding time, and hence
 241    the speed.  The idea is you can have a shorter table that decodes the
 242    shorter, more probable codes, and then point to subsidiary tables for
 243    the longer codes.  The time it costs to decode the longer codes is
 244    then traded against the time it takes to make longer tables.
 245
 246    This results of this trade are in the variables lbits and dbits
 247    below.  lbits is the number of bits the first level table for literal/
 248    length codes can decode in one step, and dbits is the same thing for
 249    the distance codes.  Subsequent tables are also less than or equal to
 250    those sizes.  These values may be adjusted either when all of the
 251    codes are shorter than that, in which case the longest code length in
 252    bits is used, or when the shortest code is *longer* than the requested
 253    table size, in which case the length of the shortest code in bits is
 254    used.
 255
 256    There are two different values for the two tables, since they code a
 257    different number of possibilities each.  The literal/length table
 258    codes 286 possible values, or in a flat code, a little over eight
 259    bits.  The distance table codes 30 possible values, or a little less
 260    than five bits, flat.  The optimum values for speed end up being
 261    about one bit more than those, so lbits is 8+1 and dbits is 5+1.
 262    The optimum values may differ though from machine to machine, and
 263    possibly even between compilers.  Your mileage may vary.
 264  */
 265
 266
 267 STATIC const int lbits = 9;          /* bits in base literal/length lookup table */
 268 STATIC const int dbits = 6;          /* bits in base distance lookup table */
 269
 270
 271 /* If BMAX needs to be larger than 16, then h and x[] should be ulg. */
 272 #define BMAX 16         /* maximum bit length of any code (16 for explode) */
 273 #define N_MAX 288       /* maximum number of codes in any set */
 274
 275
 276 STATIC unsigned hufts;         /* track memory usage */
 277
 278
 279 STATIC int INIT huft_build(
 280         unsigned *b,            /* code lengths in bits (all assumed <= BMAX) */
 281         unsigned n,             /* number of codes (assumed <= N_MAX) */
 282         unsigned s,             /* number of simple-valued codes (0..s-1) */
 283         const ush *d,           /* list of base values for non-simple codes */
 284         const ush *e,           /* list of extra bits for non-simple codes */
 285         struct huft **t,        /* result: starting table */
 286         int *m                  /* maximum lookup bits, returns actual */
 287         )
 288 /* Given a list of code lengths and a maximum table size, make a set of
 289    tables to decode that set of codes.  Return zero on success, one if
 290    the given code set is incomplete (the tables are still built in this
 291    case), two if the input is invalid (all zero length codes or an
 292    oversubscribed set of lengths), and three if not enough memory. */
 293 {
 294   unsigned a;                   /* counter for codes of length k */
 295   unsigned c[BMAX+1];           /* bit length count table */
 296   unsigned f;                   /* i repeats in table every f entries */
 297   int g;                        /* maximum code length */
 298   int h;                        /* table level */
 299   register unsigned i;          /* counter, current code */
 300   register unsigned j;          /* counter */
 301   register int k;               /* number of bits in current code */
 302   int l;                        /* bits per table (returned in m) */
 303   register unsigned *p;         /* pointer into c[], b[], or v[] */
 304   register struct huft *q;      /* points to current table */
 305   struct huft r;                /* table entry for structure assignment */
 306   struct huft *u[BMAX];         /* table stack */
 307   unsigned v[N_MAX];            /* values in order of bit length */
 308   register int w;               /* bits before this table == (l * h) */
 309   unsigned x[BMAX+1];           /* bit offsets, then code stack */
 310   unsigned *xp;                 /* pointer into x */
 311   int y;                        /* number of dummy codes added */
 312   unsigned z;                   /* number of entries in current table */
 313
 314 DEBG("huft1 ");
 315
 316   /* Generate counts for each bit length */
 317   memzero(c, sizeof(c));
 318   p = b;  i = n;
 319   do {
 320     Tracecv(*p, (stderr, (n-i >= ' ' && n-i <= '~' ? "%c %d\n" : "0x%x %d\n"),
 321             n-i, *p));
 322     c[*p]++;                    /* assume all entries <= BMAX */
 323     p++;                      /* Can't combine with above line (Solaris bug) */
 324   } while (--i);
 325   if (c[0] == n)                /* null input--all zero length codes */
 326   {
 327     *t = (struct huft *)NULL;
 328     *m = 0;
 329     return 0;
 330   }
 331
 332 DEBG("huft2 ");
 333
 334   /* Find minimum and maximum length, bound *m by those */
 335   l = *m;
 336   for (j = 1; j <= BMAX; j++)
 337     if (c[j])
 338       break;
 339   k = j;                        /* minimum code length */
 340   if ((unsigned)l < j)
 341     l = j;
 342   for (i = BMAX; i; i--)
 343     if (c[i])
 344       break;
 345   g = i;                        /* maximum code length */
 346   if ((unsigned)l > i)
 347     l = i;
 348   *m = l;
 349
 350 DEBG("huft3 ");
 351
 352   /* Adjust last length count to fill out codes, if needed */
 353   for (y = 1 << j; j < i; j++, y <<= 1)
 354     if ((y -= c[j]) < 0)
 355       return 2;                 /* bad input: more codes than bits */
 356   if ((y -= c[i]) < 0)
 357     return 2;
 358   c[i] += y;
 359
 360 DEBG("huft4 ");
 361
 362   /* Generate starting offsets into the value table for each length */
 363   x[1] = j = 0;
 364   p = c + 1;  xp = x + 2;
 365   while (--i) {                 /* note that i == g from above */
 366     *xp++ = (j += *p++);
 367   }
 368
 369 DEBG("huft5 ");
 370
 371   /* Make a table of values in order of bit lengths */
 372   p = b;  i = 0;
 373   do {
 374     if ((j = *p++) != 0)
 375       v[x[j]++] = i;
 376   } while (++i < n);
 377
 378 DEBG("h6 ");
 379
 380   /* Generate the Huffman codes and for each, make the table entries */
 381   x[0] = i = 0;                 /* first Huffman code is zero */
 382   p = v;                        /* grab values in bit order */
 383   h = -1;                       /* no tables yet--level -1 */
 384   w = -l;                       /* bits decoded == (l * h) */
 385   u[0] = (struct huft *)NULL;   /* just to keep compilers happy */
 386   q = (struct huft *)NULL;      /* ditto */
 387   z = 0;                        /* ditto */
 388 DEBG("h6a ");
 389
 390   /* go through the bit lengths (k already is bits in shortest code) */
 391   for (; k <= g; k++)
 392   {
 393 DEBG("h6b ");
 394     a = c[k];
 395     while (a--)
 396     {
 397 DEBG("h6b1 ");
 398       /* here i is the Huffman code of length k bits for value *p */
 399       /* make tables up to required level */
 400       while (k > w + l)
 401       {
 402 DEBG1("1 ");
 403         h++;
 404         w += l;                 /* previous table always l bits */
 405
 406         /* compute minimum size table less than or equal to l bits */
 407         z = (z = g - w) > (unsigned)l ? l : z;  /* upper limit on table size */
 408         if ((f = 1 << (j = k - w)) > a + 1)     /* try a k-w bit table */
 409         {                       /* too few codes for k-w bit table */
 410 DEBG1("2 ");
 411           f -= a + 1;           /* deduct codes from patterns left */
 412           xp = c + k;
 413           while (++j < z)       /* try smaller tables up to z bits */
 414           {
 415             if ((f <<= 1) <= *++xp)
 416               break;            /* enough codes to use up j bits */
 417             f -= *xp;           /* else deduct codes from patterns */
 418           }
 419         }
 420 DEBG1("3 ");
 421         z = 1 << j;             /* table entries for j-bit table */
 422
 423         /* allocate and link in new table */
 424         if ((q = (struct huft *)malloc((z + 1)*sizeof(struct huft))) ==
 425             (struct huft *)NULL)
 426         {
 427           if (h)
 428             huft_free(u[0]);
 429           return 3;             /* not enough memory */
 430         }
 431 DEBG1("4 ");
 432         hufts += z + 1;         /* track memory usage */
 433         *t = q + 1;             /* link to list for huft_free() */
 434         *(t = &(q->v.t)) = (struct huft *)NULL;
 435         u[h] = ++q;             /* table starts after link */
 436
 437 DEBG1("5 ");
 438         /* connect to last table, if there is one */
 439         if (h)
 440         {
 441           x[h] = i;             /* save pattern for backing up */
 442           r.b = (uch)l;         /* bits to dump before this table */
 443           r.e = (uch)(16 + j);  /* bits in this table */
 444           r.v.t = q;            /* pointer to this table */
 445           j = i >> (w - l);     /* (get around Turbo C bug) */
 446           u[h-1][j] = r;        /* connect to last table */
 447         }
 448 DEBG1("6 ");
 449       }
 450 DEBG("h6c ");
 451
 452       /* set up table entry in r */
 453       r.b = (uch)(k - w);
 454       if (p >= v + n)
 455         r.e = 99;               /* out of values--invalid code */
 456       else if (*p < s)
 457       {
 458         r.e = (uch)(*p < 256 ? 16 : 15);    /* 256 is end-of-block code */
 459         r.v.n = (ush)(*p);             /* simple code is just the value */
 460         p++;                           /* one compiler does not like *p++ */
 461       }
 462       else
 463       {
 464         r.e = (uch)e[*p - s];   /* non-simple--look up in lists */
 465         r.v.n = d[*p++ - s];
 466       }
 467 DEBG("h6d ");
 468
 469       /* fill code-like entries with r */
 470       f = 1 << (k - w);
 471       for (j = i >> w; j < z; j += f)
 472         q[j] = r;
 473
 474       /* backwards increment the k-bit code i */
 475       for (j = 1 << (k - 1); i & j; j >>= 1)
 476         i ^= j;
 477       i ^= j;
 478
 479       /* backup over finished tables */
 480       while ((i & ((1 << w) - 1)) != x[h])
 481       {
 482         h--;                    /* don't need to update q */
 483         w -= l;
 484       }
 485 DEBG("h6e ");
 486     }
 487 DEBG("h6f ");
 488   }
 489
 490 DEBG("huft7 ");
 491
 492   /* Return true (1) if we were given an incomplete table */
 493   return y != 0 && g != 1;
 494 }
 495
 496
 497
 498 STATIC int INIT huft_free(
 499         struct huft *t         /* table to free */
 500         )
 501 /* Free the malloc'ed tables built by huft_build(), which makes a linked
 502    list of the tables it made, with the links in a dummy first entry of
 503    each table. */
 504 {
 505   register struct huft *p, *q;
 506
 507
 508   /* Go through linked list, freeing from the malloced (t[-1]) address. */
 509   p = t;
 510   while (p != (struct huft *)NULL)
 511   {
 512     q = (--p)->v.t;
 513     free((char*)p);
 514     p = q;
 515   }
 516   return 0;
 517 }
 518
 519
 520 STATIC int INIT inflate_codes(
 521         struct huft *tl,    /* literal/length decoder tables */
 522         struct huft *td,    /* distance decoder tables */
 523         int bl,             /* number of bits decoded by tl[] */
 524         int bd              /* number of bits decoded by td[] */
 525         )
 526 /* inflate (decompress) the codes in a deflated (compressed) block.
 527    Return an error code or zero if it all goes ok. */
 528 {
 529   register unsigned e;  /* table entry flag/number of extra bits */
 530   unsigned n, d;        /* length and index for copy */
 531   unsigned w;           /* current window position */
 532   struct huft *t;       /* pointer to table entry */
 533   unsigned ml, md;      /* masks for bl and bd bits */
 534   register ulg b;       /* bit buffer */
 535   register unsigned k;  /* number of bits in bit buffer */
 536
 537
 538   /* make local copies of globals */
 539   b = bb;                       /* initialize bit buffer */
 540   k = bk;
 541   w = wp;                       /* initialize window position */
 542
 543   /* inflate the coded data */
 544   ml = mask_bits[bl];           /* precompute masks for speed */
 545   md = mask_bits[bd];
 546   for (;;)                      /* do until end of block */
 547   {
 548     NEEDBITS((unsigned)bl)
 549     if ((e = (t = tl + ((unsigned)b & ml))->e) > 16)
 550       do {
 551         if (e == 99)
 552           return 1;
 553         DUMPBITS(t->b)
 554         e -= 16;
 555         NEEDBITS(e)
 556       } while ((e = (t = t->v.t + ((unsigned)b & mask_bits[e]))->e) > 16);
 557     DUMPBITS(t->b)
 558     if (e == 16)                /* then it's a literal */
 559     {
 560       slide[w++] = (uch)t->v.n;
 561       Tracevv((stderr, "%c", slide[w-1]));
 562       if (w == WSIZE)
 563       {
 564         flush_output(w);
 565         w = 0;
 566       }
 567     }
 568     else                        /* it's an EOB or a length */
 569     {
 570       /* exit if end of block */
 571       if (e == 15)
 572         break;
 573
 574       /* get length of block to copy */
 575       NEEDBITS(e)
 576       n = t->v.n + ((unsigned)b & mask_bits[e]);
 577       DUMPBITS(e);
 578
 579       /* decode distance of block to copy */
 580       NEEDBITS((unsigned)bd)
 581       if ((e = (t = td + ((unsigned)b & md))->e) > 16)
 582         do {
 583           if (e == 99)
 584             return 1;
 585           DUMPBITS(t->b)
 586           e -= 16;
 587           NEEDBITS(e)
 588         } while ((e = (t = t->v.t + ((unsigned)b & mask_bits[e]))->e) > 16);
 589       DUMPBITS(t->b)
 590       NEEDBITS(e)
 591       d = w - t->v.n - ((unsigned)b & mask_bits[e]);
 592       DUMPBITS(e)
 593       Tracevv((stderr,"\\[%d,%d]", w-d, n));
 594
 595       /* do the copy */
 596       do {
 597         n -= (e = (e = WSIZE - ((d &= WSIZE-1) > w ? d : w)) > n ? n : e);
 598 #if !defined(NOMEMCPY) && !defined(DEBUG)
 599         if (w - d >= e)         /* (this test assumes unsigned comparison) */
 600         {
 601           memcpy(slide + w, slide + d, e);
 602           w += e;
 603           d += e;
 604         }
 605         else                      /* do it slow to avoid memcpy() overlap */
 606 #endif /* !NOMEMCPY */
 607           do {
 608             slide[w++] = slide[d++];
 609             Tracevv((stderr, "%c", slide[w-1]));
 610           } while (--e);
 611         if (w == WSIZE)
 612         {
 613           flush_output(w);
 614           w = 0;
 615         }
 616       } while (n);
 617     }
 618   }
 619
 620
 621   /* restore the globals from the locals */
 622   wp = w;                       /* restore global window pointer */
 623   bb = b;                       /* restore global bit buffer */
 624   bk = k;
 625
 626   /* done */
 627   return 0;
 628
 629  underrun:
 630   return 4;                     /* Input underrun */
 631 }
 632
 633
 634
 635 STATIC int INIT inflate_stored(void)
 636 /* "decompress" an inflated type 0 (stored) block. */
 637 {
 638   unsigned n;           /* number of bytes in block */
 639   unsigned w;           /* current window position */
 640   register ulg b;       /* bit buffer */
 641   register unsigned k;  /* number of bits in bit buffer */
 642
 643 DEBG("<stor");
 644
 645   /* make local copies of globals */
 646   b = bb;                       /* initialize bit buffer */
 647   k = bk;
 648   w = wp;                       /* initialize window position */
 649
 650
 651   /* go to byte boundary */
 652   n = k & 7;
 653   DUMPBITS(n);
 654
 655
 656   /* get the length and its complement */
 657   NEEDBITS(16)
 658   n = ((unsigned)b & 0xffff);
 659   DUMPBITS(16)
 660   NEEDBITS(16)
 661   if (n != (unsigned)((~b) & 0xffff))
 662     return 1;                   /* error in compressed data */
 663   DUMPBITS(16)
 664
 665
 666   /* read and output the compressed data */
 667   while (n--)
 668   {
 669     NEEDBITS(8)
 670     slide[w++] = (uch)b;
 671     if (w == WSIZE)
 672     {
 673       flush_output(w);
 674       w = 0;
 675     }
 676     DUMPBITS(8)
 677   }
 678
 679
 680   /* restore the globals from the locals */
 681   wp = w;                       /* restore global window pointer */
 682   bb = b;                       /* restore global bit buffer */
 683   bk = k;
 684
 685   DEBG(">");
 686   return 0;
 687
 688  underrun:
 689   return 4;                     /* Input underrun */
 690 }
 691
 692
 693 /*
 694  * We use `noinline' here to prevent gcc-3.5 from using too much stack space
 695  */
 696 STATIC int noinline INIT inflate_fixed(void)
 697 /* decompress an inflated type 1 (fixed Huffman codes) block.  We should
 698    either replace this with a custom decoder, or at least precompute the
 699    Huffman tables. */
 700 {
 701   int i;                /* temporary variable */
 702   struct huft *tl;      /* literal/length code table */
 703   struct huft *td;      /* distance code table */
 704   int bl;               /* lookup bits for tl */
 705   int bd;               /* lookup bits for td */
 706   unsigned l[288];      /* length list for huft_build */
 707
 708 DEBG("<fix");
 709
 710   /* set up literal table */
 711   for (i = 0; i < 144; i++)
 712     l[i] = 8;
 713   for (; i < 256; i++)
 714     l[i] = 9;
 715   for (; i < 280; i++)
 716     l[i] = 7;
 717   for (; i < 288; i++)          /* make a complete, but wrong code set */
 718     l[i] = 8;
 719   bl = 7;
 720   if ((i = huft_build(l, 288, 257, cplens, cplext, &tl, &bl)) != 0)
 721     return i;
 722
 723
 724   /* set up distance table */
 725   for (i = 0; i < 30; i++)      /* make an incomplete code set */
 726     l[i] = 5;
 727   bd = 5;
 728   if ((i = huft_build(l, 30, 0, cpdist, cpdext, &td, &bd)) > 1)
 729   {
 730     huft_free(tl);
 731
 732     DEBG(">");
 733     return i;
 734   }
 735
 736
 737   /* decompress until an end-of-block code */
 738   if (inflate_codes(tl, td, bl, bd))
 739     return 1;
 740
 741
 742   /* free the decoding tables, return */
 743   huft_free(tl);
 744   huft_free(td);
 745   return 0;
 746 }
 747
 748
 749 /*
 750  * We use `noinline' here to prevent gcc-3.5 from using too much stack space
 751  */
 752 STATIC int noinline INIT inflate_dynamic(void)
 753 /* decompress an inflated type 2 (dynamic Huffman codes) block. */
 754 {
 755   int i;                /* temporary variables */
 756   unsigned j;
 757   unsigned l;           /* last length */
 758   unsigned m;           /* mask for bit lengths table */
 759   unsigned n;           /* number of lengths to get */
 760   struct huft *tl;      /* literal/length code table */
 761   struct huft *td;      /* distance code table */
 762   int bl;               /* lookup bits for tl */
 763   int bd;               /* lookup bits for td */
 764   unsigned nb;          /* number of bit length codes */
 765   unsigned nl;          /* number of literal/length codes */
 766   unsigned nd;          /* number of distance codes */
 767 #ifdef PKZIP_BUG_WORKAROUND
 768   unsigned ll[288+32];  /* literal/length and distance code lengths */
 769 #else
 770   unsigned ll[286+30];  /* literal/length and distance code lengths */
 771 #endif
 772   register ulg b;       /* bit buffer */
 773   register unsigned k;  /* number of bits in bit buffer */
 774
 775 DEBG("<dyn");
 776
 777   /* make local bit buffer */
 778   b = bb;
 779   k = bk;
 780
 781
 782   /* read in table lengths */
 783   NEEDBITS(5)
 784   nl = 257 + ((unsigned)b & 0x1f);      /* number of literal/length codes */
 785   DUMPBITS(5)
 786   NEEDBITS(5)
 787   nd = 1 + ((unsigned)b & 0x1f);        /* number of distance codes */
 788   DUMPBITS(5)
 789   NEEDBITS(4)
 790   nb = 4 + ((unsigned)b & 0xf);         /* number of bit length codes */
 791   DUMPBITS(4)
 792 #ifdef PKZIP_BUG_WORKAROUND
 793   if (nl > 288 || nd > 32)
 794 #else
 795   if (nl > 286 || nd > 30)
 796 #endif
 797     return 1;                   /* bad lengths */
 798
 799 DEBG("dyn1 ");
 800
 801   /* read in bit-length-code lengths */
 802   for (j = 0; j < nb; j++)
 803   {
 804     NEEDBITS(3)
 805     ll[border[j]] = (unsigned)b & 7;
 806     DUMPBITS(3)
 807   }
 808   for (; j < 19; j++)
 809     ll[border[j]] = 0;
 810
 811 DEBG("dyn2 ");
 812
 813   /* build decoding table for trees--single level, 7 bit lookup */
 814   bl = 7;
 815   if ((i = huft_build(ll, 19, 19, NULL, NULL, &tl, &bl)) != 0)
 816   {
 817     if (i == 1)
 818       huft_free(tl);
 819     return i;                   /* incomplete code set */
 820   }
 821
 822 DEBG("dyn3 ");
 823
 824   /* read in literal and distance code lengths */
 825   n = nl + nd;
 826   m = mask_bits[bl];
 827   i = l = 0;
 828   while ((unsigned)i < n)
 829   {
 830     NEEDBITS((unsigned)bl)
 831     j = (td = tl + ((unsigned)b & m))->b;
 832     DUMPBITS(j)
 833     j = td->v.n;
 834     if (j < 16)                 /* length of code in bits (0..15) */
 835       ll[i++] = l = j;          /* save last length in l */
 836     else if (j == 16)           /* repeat last length 3 to 6 times */
 837     {
 838       NEEDBITS(2)
 839       j = 3 + ((unsigned)b & 3);
 840       DUMPBITS(2)
 841       if ((unsigned)i + j > n)
 842         return 1;
 843       while (j--)
 844         ll[i++] = l;
 845     }
 846     else if (j == 17)           /* 3 to 10 zero length codes */
 847     {
 848       NEEDBITS(3)
 849       j = 3 + ((unsigned)b & 7);
 850       DUMPBITS(3)
 851       if ((unsigned)i + j > n)
 852         return 1;
 853       while (j--)
 854         ll[i++] = 0;
 855       l = 0;
 856     }
 857     else                        /* j == 18: 11 to 138 zero length codes */
 858     {
 859       NEEDBITS(7)
 860       j = 11 + ((unsigned)b & 0x7f);
 861       DUMPBITS(7)
 862       if ((unsigned)i + j > n)
 863         return 1;
 864       while (j--)
 865         ll[i++] = 0;
 866       l = 0;
 867     }
 868   }
 869
 870 DEBG("dyn4 ");
 871
 872   /* free decoding table for trees */
 873   huft_free(tl);
 874
 875 DEBG("dyn5 ");
 876
 877   /* restore the global bit buffer */
 878   bb = b;
 879   bk = k;
 880
 881 DEBG("dyn5a ");
 882
 883   /* build the decoding tables for literal/length and distance codes */
 884   bl = lbits;
 885   if ((i = huft_build(ll, nl, 257, cplens, cplext, &tl, &bl)) != 0)
 886   {
 887 DEBG("dyn5b ");
 888     if (i == 1) {
 889       error("incomplete literal tree");
 890       huft_free(tl);
 891     }
 892     return i;                   /* incomplete code set */
 893   }
 894 DEBG("dyn5c ");
 895   bd = dbits;
 896   if ((i = huft_build(ll + nl, nd, 0, cpdist, cpdext, &td, &bd)) != 0)
 897   {
 898 DEBG("dyn5d ");
 899     if (i == 1) {
 900       error("incomplete distance tree");
 901 #ifdef PKZIP_BUG_WORKAROUND
 902       i = 0;
 903     }
 904 #else
 905       huft_free(td);
 906     }
 907     huft_free(tl);
 908     return i;                   /* incomplete code set */
 909 #endif
 910   }
 911
 912 DEBG("dyn6 ");
 913
 914   /* decompress until an end-of-block code */
 915   if (inflate_codes(tl, td, bl, bd))
 916     return 1;
 917
 918 DEBG("dyn7 ");
 919
 920   /* free the decoding tables, return */
 921   huft_free(tl);
 922   huft_free(td);
 923
 924   DEBG(">");
 925   return 0;
 926
 927  underrun:
 928   return 4;                     /* Input underrun */
 929 }
 930
 931
 932
 933 STATIC int INIT inflate_block(
 934         int *e                  /* last block flag */
 935         )
 936 /* decompress an inflated block */
 937 {
 938   unsigned t;           /* block type */
 939   register ulg b;       /* bit buffer */
 940   register unsigned k;  /* number of bits in bit buffer */
 941
 942   DEBG("<blk");
 943
 944   /* make local bit buffer */
 945   b = bb;
 946   k = bk;
 947
 948
 949   /* read in last block bit */
 950   NEEDBITS(1)
 951   *e = (int)b & 1;
 952   DUMPBITS(1)
 953
 954
 955   /* read in block type */
 956   NEEDBITS(2)
 957   t = (unsigned)b & 3;
 958   DUMPBITS(2)
 959
 960
 961   /* restore the global bit buffer */
 962   bb = b;
 963   bk = k;
 964
 965   /* inflate that block type */
 966   if (t == 2)
 967     return inflate_dynamic();
 968   if (t == 0)
 969     return inflate_stored();
 970   if (t == 1)
 971     return inflate_fixed();
 972
 973   DEBG(">");
 974
 975   /* bad block type */
 976   return 2;
 977
 978  underrun:
 979   return 4;                     /* Input underrun */
 980 }
 981
 982
 983
 984 STATIC int INIT inflate(void)
 985 /* decompress an inflated entry */
 986 {
 987   int e;                /* last block flag */
 988   int r;                /* result code */
 989   unsigned h;           /* maximum struct huft's malloc'ed */
 990   void *ptr;
 991
 992   /* initialize window, bit buffer */
 993   wp = 0;
 994   bk = 0;
 995   bb = 0;
 996
 997
 998   /* decompress until the last block */
 999   h = 0;
1000   do {
1001     hufts = 0;
1002     gzip_mark(&ptr);
1003     if ((r = inflate_block(&e)) != 0) {
1004       gzip_release(&ptr);
1005       return r;
1006     }
1007     gzip_release(&ptr);
1008     if (hufts > h)
1009       h = hufts;
1010   } while (!e);
1011
1012   /* Undo too much lookahead. The next read will be byte aligned so we
1013    * can discard unused bits in the last meaningful byte.
1014    */
1015   while (bk >= 8) {
1016     bk -= 8;
1017     inptr--;
1018   }
1019
1020   /* flush out slide */
1021   flush_output(wp);
1022
1023
1024   /* return success */
1025 #ifdef DEBUG
1026   fprintf(stderr, "<%u> ", h);
1027 #endif /* DEBUG */
1028   return 0;
1029 }
1030
1031 /**********************************************************************
1032  *
1033  * The following are support routines for inflate.c
1034  *
1035  **********************************************************************/
1036
1037 static ulg crc_32_tab[256];
1038 static ulg crc;         /* initialized in makecrc() so it'll reside in bss */
1039 #define CRC_VALUE (crc ^ 0xffffffffUL)
1040
1041 /*
1042  * Code to compute the CRC-32 table. Borrowed from
1043  * gzip-1.0.3/makecrc.c.
1044  */
1045
1046 static void INIT
1047 makecrc(void)
1048 {
1049 /* Not copyrighted 1990 Mark Adler      */
1050
1051   unsigned long c;      /* crc shift register */
1052   unsigned long e;      /* polynomial exclusive-or pattern */
1053   int i;                /* counter for all possible eight bit values */
1054   int k;                /* byte being shifted into crc apparatus */
1055
1056   /* terms of polynomial defining this crc (except x^32): */
1057   static const int p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
1058
1059   /* Make exclusive-or pattern from polynomial */
1060   e = 0;
1061   for (i = 0; i < sizeof(p)/sizeof(int); i++)
1062     e |= 1L << (31 - p[i]);
1063
1064   crc_32_tab[0] = 0;
1065
1066   for (i = 1; i < 256; i++)
1067   {
1068     c = 0;
1069     for (k = i | 256; k != 1; k >>= 1)
1070     {
1071       c = c & 1 ? (c >> 1) ^ e : c >> 1;
1072       if (k & 1)
1073         c ^= e;
1074     }
1075     crc_32_tab[i] = c;
1076   }
1077
1078   /* this is initialized here so this code could reside in ROM */
1079   crc = (ulg)0xffffffffUL; /* shift register contents */
1080 }
1081
1082 /* gzip flag byte */
1083 #define ASCII_FLAG   0x01 /* bit 0 set: file probably ASCII text */
1084 #define CONTINUATION 0x02 /* bit 1 set: continuation of multi-part gzip file */
1085 #define EXTRA_FIELD  0x04 /* bit 2 set: extra field present */
1086 #define ORIG_NAME    0x08 /* bit 3 set: original file name present */
1087 #define COMMENT      0x10 /* bit 4 set: file comment present */
1088 #define ENCRYPTED    0x20 /* bit 5 set: file is encrypted */
1089 #define RESERVED     0xC0 /* bit 6,7:   reserved */
1090
1091 /*
1092  * Do the uncompression!
1093  */
1094 static int INIT gunzip(void)
1095 {
1096     uch flags;
1097     unsigned char magic[2]; /* magic header */
1098     char method;
1099     ulg orig_crc = 0;       /* original crc */
1100     ulg orig_len = 0;       /* original uncompressed length */
1101     int res;
1102
1103     magic[0] = NEXTBYTE();
1104     magic[1] = NEXTBYTE();
1105     method   = NEXTBYTE();
1106
1107     if (magic[0] != 037 ||
1108         ((magic[1] != 0213) && (magic[1] != 0236))) {
1109             error("bad gzip magic numbers");
1110             return -1;
1111     }
1112
1113     /* We only support method #8, DEFLATED */
1114     if (method != 8)  {
1115             error("internal error, invalid method");
1116             return -1;
1117     }
1118
1119     flags  = (uch)get_byte();
1120     if ((flags & ENCRYPTED) != 0) {
1121             error("Input is encrypted");
1122             return -1;
1123     }
1124     if ((flags & CONTINUATION) != 0) {
1125             error("Multi part input");
1126             return -1;
1127     }
1128     if ((flags & RESERVED) != 0) {
1129             error("Input has invalid flags");
1130             return -1;
1131     }
1132     NEXTBYTE(); /* Get timestamp */
1133     NEXTBYTE();
1134     NEXTBYTE();
1135     NEXTBYTE();
1136
1137     (void)NEXTBYTE();  /* Ignore extra flags for the moment */
1138     (void)NEXTBYTE();  /* Ignore OS type for the moment */
1139
1140     if ((flags & EXTRA_FIELD) != 0) {
1141             unsigned len = (unsigned)NEXTBYTE();
1142             len |= ((unsigned)NEXTBYTE())<<8;
1143             while (len--) (void)NEXTBYTE();
1144     }
1145
1146     /* Get original file name if it was truncated */
1147     if ((flags & ORIG_NAME) != 0) {
1148             /* Discard the old name */
1149             while (NEXTBYTE() != 0) /* null */ ;
1150     }
1151
1152     /* Discard file comment if any */
1153     if ((flags & COMMENT) != 0) {
1154             while (NEXTBYTE() != 0) /* null */ ;
1155     }
1156
1157     /* Decompress */
1158     if ((res = inflate())) {
1159             switch (res) {
1160             case 0:
1161                     break;
1162             case 1:
1163                     error("invalid compressed format (err=1)");
1164                     break;
1165             case 2:
1166                     error("invalid compressed format (err=2)");
1167                     break;
1168             case 3:
1169                     error("out of memory");
1170                     break;
1171             case 4:
1172                     error("out of input data");
1173                     break;
1174             default:
1175                     error("invalid compressed format (other)");
1176             }
1177             return -1;
1178     }
1179
1180     /* Get the crc and original length */
1181     /* crc32  (see algorithm.doc)
1182      * uncompressed input size modulo 2^32
1183      */
1184     orig_crc = (ulg) NEXTBYTE();
1185     orig_crc |= (ulg) NEXTBYTE() << 8;
1186     orig_crc |= (ulg) NEXTBYTE() << 16;
1187     orig_crc |= (ulg) NEXTBYTE() << 24;
1188
1189     orig_len = (ulg) NEXTBYTE();
1190     orig_len |= (ulg) NEXTBYTE() << 8;
1191     orig_len |= (ulg) NEXTBYTE() << 16;
1192     orig_len |= (ulg) NEXTBYTE() << 24;
1193
1194     /* Validate decompression */
1195     if (orig_crc != CRC_VALUE) {
1196             error("crc error");
1197             return -1;
1198     }
1199     if (orig_len != bytes_out) {
1200             error("length error");
1201             return -1;
1202     }
1203     return 0;
1204
1205  underrun:                      /* NEXTBYTE() goto's here if needed */
1206     error("out of input data");
1207     return -1;
1208 }
1209
1210