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 2;
 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   n = x[g];                   /* set n to length of v */
 378
 379 DEBG("h6 ");
 380
 381   /* Generate the Huffman codes and for each, make the table entries */
 382   x[0] = i = 0;                 /* first Huffman code is zero */
 383   p = v;                        /* grab values in bit order */
 384   h = -1;                       /* no tables yet--level -1 */
 385   w = -l;                       /* bits decoded == (l * h) */
 386   u[0] = (struct huft *)NULL;   /* just to keep compilers happy */
 387   q = (struct huft *)NULL;      /* ditto */
 388   z = 0;                        /* ditto */
 389 DEBG("h6a ");
 390
 391   /* go through the bit lengths (k already is bits in shortest code) */
 392   for (; k <= g; k++)
 393   {
 394 DEBG("h6b ");
 395     a = c[k];
 396     while (a--)
 397     {
 398 DEBG("h6b1 ");
 399       /* here i is the Huffman code of length k bits for value *p */
 400       /* make tables up to required level */
 401       while (k > w + l)
 402       {
 403 DEBG1("1 ");
 404         h++;
 405         w += l;                 /* previous table always l bits */
 406
 407         /* compute minimum size table less than or equal to l bits */
 408         z = (z = g - w) > (unsigned)l ? l : z;  /* upper limit on table size */
 409         if ((f = 1 << (j = k - w)) > a + 1)     /* try a k-w bit table */
 410         {                       /* too few codes for k-w bit table */
 411 DEBG1("2 ");
 412           f -= a + 1;           /* deduct codes from patterns left */
 413           xp = c + k;
 414           if (j < z)
 415             while (++j < z)       /* try smaller tables up to z bits */
 416             {
 417               if ((f <<= 1) <= *++xp)
 418                 break;            /* enough codes to use up j bits */
 419               f -= *xp;           /* else deduct codes from patterns */
 420             }
 421         }
 422 DEBG1("3 ");
 423         z = 1 << j;             /* table entries for j-bit table */
 424
 425         /* allocate and link in new table */
 426         if ((q = (struct huft *)malloc((z + 1)*sizeof(struct huft))) ==
 427             (struct huft *)NULL)
 428         {
 429           if (h)
 430             huft_free(u[0]);
 431           return 3;             /* not enough memory */
 432         }
 433 DEBG1("4 ");
 434         hufts += z + 1;         /* track memory usage */
 435         *t = q + 1;             /* link to list for huft_free() */
 436         *(t = &(q->v.t)) = (struct huft *)NULL;
 437         u[h] = ++q;             /* table starts after link */
 438
 439 DEBG1("5 ");
 440         /* connect to last table, if there is one */
 441         if (h)
 442         {
 443           x[h] = i;             /* save pattern for backing up */
 444           r.b = (uch)l;         /* bits to dump before this table */
 445           r.e = (uch)(16 + j);  /* bits in this table */
 446           r.v.t = q;            /* pointer to this table */
 447           j = i >> (w - l);     /* (get around Turbo C bug) */
 448           u[h-1][j] = r;        /* connect to last table */
 449         }
 450 DEBG1("6 ");
 451       }
 452 DEBG("h6c ");
 453
 454       /* set up table entry in r */
 455       r.b = (uch)(k - w);
 456       if (p >= v + n)
 457         r.e = 99;               /* out of values--invalid code */
 458       else if (*p < s)
 459       {
 460         r.e = (uch)(*p < 256 ? 16 : 15);    /* 256 is end-of-block code */
 461         r.v.n = (ush)(*p);             /* simple code is just the value */
 462         p++;                           /* one compiler does not like *p++ */
 463       }
 464       else
 465       {
 466         r.e = (uch)e[*p - s];   /* non-simple--look up in lists */
 467         r.v.n = d[*p++ - s];
 468       }
 469 DEBG("h6d ");
 470
 471       /* fill code-like entries with r */
 472       f = 1 << (k - w);
 473       for (j = i >> w; j < z; j += f)
 474         q[j] = r;
 475
 476       /* backwards increment the k-bit code i */
 477       for (j = 1 << (k - 1); i & j; j >>= 1)
 478         i ^= j;
 479       i ^= j;
 480
 481       /* backup over finished tables */
 482       while ((i & ((1 << w) - 1)) != x[h])
 483       {
 484         h--;                    /* don't need to update q */
 485         w -= l;
 486       }
 487 DEBG("h6e ");
 488     }
 489 DEBG("h6f ");
 490   }
 491
 492 DEBG("huft7 ");
 493
 494   /* Return true (1) if we were given an incomplete table */
 495   return y != 0 && g != 1;
 496 }
 497
 498
 499
 500 STATIC int INIT huft_free(
 501         struct huft *t         /* table to free */
 502         )
 503 /* Free the malloc'ed tables built by huft_build(), which makes a linked
 504    list of the tables it made, with the links in a dummy first entry of
 505    each table. */
 506 {
 507   register struct huft *p, *q;
 508
 509
 510   /* Go through linked list, freeing from the malloced (t[-1]) address. */
 511   p = t;
 512   while (p != (struct huft *)NULL)
 513   {
 514     q = (--p)->v.t;
 515     free((char*)p);
 516     p = q;
 517   }
 518   return 0;
 519 }
 520
 521
 522 STATIC int INIT inflate_codes(
 523         struct huft *tl,    /* literal/length decoder tables */
 524         struct huft *td,    /* distance decoder tables */
 525         int bl,             /* number of bits decoded by tl[] */
 526         int bd              /* number of bits decoded by td[] */
 527         )
 528 /* inflate (decompress) the codes in a deflated (compressed) block.
 529    Return an error code or zero if it all goes ok. */
 530 {
 531   register unsigned e;  /* table entry flag/number of extra bits */
 532   unsigned n, d;        /* length and index for copy */
 533   unsigned w;           /* current window position */
 534   struct huft *t;       /* pointer to table entry */
 535   unsigned ml, md;      /* masks for bl and bd bits */
 536   register ulg b;       /* bit buffer */
 537   register unsigned k;  /* number of bits in bit buffer */
 538
 539
 540   /* make local copies of globals */
 541   b = bb;                       /* initialize bit buffer */
 542   k = bk;
 543   w = wp;                       /* initialize window position */
 544
 545   /* inflate the coded data */
 546   ml = mask_bits[bl];           /* precompute masks for speed */
 547   md = mask_bits[bd];
 548   for (;;)                      /* do until end of block */
 549   {
 550     NEEDBITS((unsigned)bl)
 551     if ((e = (t = tl + ((unsigned)b & ml))->e) > 16)
 552       do {
 553         if (e == 99)
 554           return 1;
 555         DUMPBITS(t->b)
 556         e -= 16;
 557         NEEDBITS(e)
 558       } while ((e = (t = t->v.t + ((unsigned)b & mask_bits[e]))->e) > 16);
 559     DUMPBITS(t->b)
 560     if (e == 16)                /* then it's a literal */
 561     {
 562       slide[w++] = (uch)t->v.n;
 563       Tracevv((stderr, "%c", slide[w-1]));
 564       if (w == WSIZE)
 565       {
 566         flush_output(w);
 567         w = 0;
 568       }
 569     }
 570     else                        /* it's an EOB or a length */
 571     {
 572       /* exit if end of block */
 573       if (e == 15)
 574         break;
 575
 576       /* get length of block to copy */
 577       NEEDBITS(e)
 578       n = t->v.n + ((unsigned)b & mask_bits[e]);
 579       DUMPBITS(e);
 580
 581       /* decode distance of block to copy */
 582       NEEDBITS((unsigned)bd)
 583       if ((e = (t = td + ((unsigned)b & md))->e) > 16)
 584         do {
 585           if (e == 99)
 586             return 1;
 587           DUMPBITS(t->b)
 588           e -= 16;
 589           NEEDBITS(e)
 590         } while ((e = (t = t->v.t + ((unsigned)b & mask_bits[e]))->e) > 16);
 591       DUMPBITS(t->b)
 592       NEEDBITS(e)
 593       d = w - t->v.n - ((unsigned)b & mask_bits[e]);
 594       DUMPBITS(e)
 595       Tracevv((stderr,"\\[%d,%d]", w-d, n));
 596
 597       /* do the copy */
 598       do {
 599         n -= (e = (e = WSIZE - ((d &= WSIZE-1) > w ? d : w)) > n ? n : e);
 600 #if !defined(NOMEMCPY) && !defined(DEBUG)
 601         if (w - d >= e)         /* (this test assumes unsigned comparison) */
 602         {
 603           memcpy(slide + w, slide + d, e);
 604           w += e;
 605           d += e;
 606         }
 607         else                      /* do it slow to avoid memcpy() overlap */
 608 #endif /* !NOMEMCPY */
 609           do {
 610             slide[w++] = slide[d++];
 611             Tracevv((stderr, "%c", slide[w-1]));
 612           } while (--e);
 613         if (w == WSIZE)
 614         {
 615           flush_output(w);
 616           w = 0;
 617         }
 618       } while (n);
 619     }
 620   }
 621
 622
 623   /* restore the globals from the locals */
 624   wp = w;                       /* restore global window pointer */
 625   bb = b;                       /* restore global bit buffer */
 626   bk = k;
 627
 628   /* done */
 629   return 0;
 630
 631  underrun:
 632   return 4;                     /* Input underrun */
 633 }
 634
 635
 636
 637 STATIC int INIT inflate_stored(void)
 638 /* "decompress" an inflated type 0 (stored) block. */
 639 {
 640   unsigned n;           /* number of bytes in block */
 641   unsigned w;           /* current window position */
 642   register ulg b;       /* bit buffer */
 643   register unsigned k;  /* number of bits in bit buffer */
 644
 645 DEBG("<stor");
 646
 647   /* make local copies of globals */
 648   b = bb;                       /* initialize bit buffer */
 649   k = bk;
 650   w = wp;                       /* initialize window position */
 651
 652
 653   /* go to byte boundary */
 654   n = k & 7;
 655   DUMPBITS(n);
 656
 657
 658   /* get the length and its complement */
 659   NEEDBITS(16)
 660   n = ((unsigned)b & 0xffff);
 661   DUMPBITS(16)
 662   NEEDBITS(16)
 663   if (n != (unsigned)((~b) & 0xffff))
 664     return 1;                   /* error in compressed data */
 665   DUMPBITS(16)
 666
 667
 668   /* read and output the compressed data */
 669   while (n--)
 670   {
 671     NEEDBITS(8)
 672     slide[w++] = (uch)b;
 673     if (w == WSIZE)
 674     {
 675       flush_output(w);
 676       w = 0;
 677     }
 678     DUMPBITS(8)
 679   }
 680
 681
 682   /* restore the globals from the locals */
 683   wp = w;                       /* restore global window pointer */
 684   bb = b;                       /* restore global bit buffer */
 685   bk = k;
 686
 687   DEBG(">");
 688   return 0;
 689
 690  underrun:
 691   return 4;                     /* Input underrun */
 692 }
 693
 694
 695 /*
 696  * We use `noinline' here to prevent gcc-3.5 from using too much stack space
 697  */
 698 STATIC int noinline INIT inflate_fixed(void)
 699 /* decompress an inflated type 1 (fixed Huffman codes) block.  We should
 700    either replace this with a custom decoder, or at least precompute the
 701    Huffman tables. */
 702 {
 703   int i;                /* temporary variable */
 704   struct huft *tl;      /* literal/length code table */
 705   struct huft *td;      /* distance code table */
 706   int bl;               /* lookup bits for tl */
 707   int bd;               /* lookup bits for td */
 708   unsigned l[288];      /* length list for huft_build */
 709
 710 DEBG("<fix");
 711
 712   /* set up literal table */
 713   for (i = 0; i < 144; i++)
 714     l[i] = 8;
 715   for (; i < 256; i++)
 716     l[i] = 9;
 717   for (; i < 280; i++)
 718     l[i] = 7;
 719   for (; i < 288; i++)          /* make a complete, but wrong code set */
 720     l[i] = 8;
 721   bl = 7;
 722   if ((i = huft_build(l, 288, 257, cplens, cplext, &tl, &bl)) != 0)
 723     return i;
 724
 725
 726   /* set up distance table */
 727   for (i = 0; i < 30; i++)      /* make an incomplete code set */
 728     l[i] = 5;
 729   bd = 5;
 730   if ((i = huft_build(l, 30, 0, cpdist, cpdext, &td, &bd)) > 1)
 731   {
 732     huft_free(tl);
 733
 734     DEBG(">");
 735     return i;
 736   }
 737
 738
 739   /* decompress until an end-of-block code */
 740   if (inflate_codes(tl, td, bl, bd))
 741     return 1;
 742
 743
 744   /* free the decoding tables, return */
 745   huft_free(tl);
 746   huft_free(td);
 747   return 0;
 748 }
 749
 750
 751 /*
 752  * We use `noinline' here to prevent gcc-3.5 from using too much stack space
 753  */
 754 STATIC int noinline INIT inflate_dynamic(void)
 755 /* decompress an inflated type 2 (dynamic Huffman codes) block. */
 756 {
 757   int i;                /* temporary variables */
 758   unsigned j;
 759   unsigned l;           /* last length */
 760   unsigned m;           /* mask for bit lengths table */
 761   unsigned n;           /* number of lengths to get */
 762   struct huft *tl;      /* literal/length code table */
 763   struct huft *td;      /* distance code table */
 764   int bl;               /* lookup bits for tl */
 765   int bd;               /* lookup bits for td */
 766   unsigned nb;          /* number of bit length codes */
 767   unsigned nl;          /* number of literal/length codes */
 768   unsigned nd;          /* number of distance codes */
 769 #ifdef PKZIP_BUG_WORKAROUND
 770   unsigned ll[288+32];  /* literal/length and distance code lengths */
 771 #else
 772   unsigned ll[286+30];  /* literal/length and distance code lengths */
 773 #endif
 774   register ulg b;       /* bit buffer */
 775   register unsigned k;  /* number of bits in bit buffer */
 776
 777 DEBG("<dyn");
 778
 779   /* make local bit buffer */
 780   b = bb;
 781   k = bk;
 782
 783
 784   /* read in table lengths */
 785   NEEDBITS(5)
 786   nl = 257 + ((unsigned)b & 0x1f);      /* number of literal/length codes */
 787   DUMPBITS(5)
 788   NEEDBITS(5)
 789   nd = 1 + ((unsigned)b & 0x1f);        /* number of distance codes */
 790   DUMPBITS(5)
 791   NEEDBITS(4)
 792   nb = 4 + ((unsigned)b & 0xf);         /* number of bit length codes */
 793   DUMPBITS(4)
 794 #ifdef PKZIP_BUG_WORKAROUND
 795   if (nl > 288 || nd > 32)
 796 #else
 797   if (nl > 286 || nd > 30)
 798 #endif
 799     return 1;                   /* bad lengths */
 800
 801 DEBG("dyn1 ");
 802
 803   /* read in bit-length-code lengths */
 804   for (j = 0; j < nb; j++)
 805   {
 806     NEEDBITS(3)
 807     ll[border[j]] = (unsigned)b & 7;
 808     DUMPBITS(3)
 809   }
 810   for (; j < 19; j++)
 811     ll[border[j]] = 0;
 812
 813 DEBG("dyn2 ");
 814
 815   /* build decoding table for trees--single level, 7 bit lookup */
 816   bl = 7;
 817   if ((i = huft_build(ll, 19, 19, NULL, NULL, &tl, &bl)) != 0)
 818   {
 819     if (i == 1)
 820       huft_free(tl);
 821     return i;                   /* incomplete code set */
 822   }
 823
 824 DEBG("dyn3 ");
 825
 826   /* read in literal and distance code lengths */
 827   n = nl + nd;
 828   m = mask_bits[bl];
 829   i = l = 0;
 830   while ((unsigned)i < n)
 831   {
 832     NEEDBITS((unsigned)bl)
 833     j = (td = tl + ((unsigned)b & m))->b;
 834     DUMPBITS(j)
 835     j = td->v.n;
 836     if (j < 16)                 /* length of code in bits (0..15) */
 837       ll[i++] = l = j;          /* save last length in l */
 838     else if (j == 16)           /* repeat last length 3 to 6 times */
 839     {
 840       NEEDBITS(2)
 841       j = 3 + ((unsigned)b & 3);
 842       DUMPBITS(2)
 843       if ((unsigned)i + j > n)
 844         return 1;
 845       while (j--)
 846         ll[i++] = l;
 847     }
 848     else if (j == 17)           /* 3 to 10 zero length codes */
 849     {
 850       NEEDBITS(3)
 851       j = 3 + ((unsigned)b & 7);
 852       DUMPBITS(3)
 853       if ((unsigned)i + j > n)
 854         return 1;
 855       while (j--)
 856         ll[i++] = 0;
 857       l = 0;
 858     }
 859     else                        /* j == 18: 11 to 138 zero length codes */
 860     {
 861       NEEDBITS(7)
 862       j = 11 + ((unsigned)b & 0x7f);
 863       DUMPBITS(7)
 864       if ((unsigned)i + j > n)
 865         return 1;
 866       while (j--)
 867         ll[i++] = 0;
 868       l = 0;
 869     }
 870   }
 871
 872 DEBG("dyn4 ");
 873
 874   /* free decoding table for trees */
 875   huft_free(tl);
 876
 877 DEBG("dyn5 ");
 878
 879   /* restore the global bit buffer */
 880   bb = b;
 881   bk = k;
 882
 883 DEBG("dyn5a ");
 884
 885   /* build the decoding tables for literal/length and distance codes */
 886   bl = lbits;
 887   if ((i = huft_build(ll, nl, 257, cplens, cplext, &tl, &bl)) != 0)
 888   {
 889 DEBG("dyn5b ");
 890     if (i == 1) {
 891       error("incomplete literal tree");
 892       huft_free(tl);
 893     }
 894     return i;                   /* incomplete code set */
 895   }
 896 DEBG("dyn5c ");
 897   bd = dbits;
 898   if ((i = huft_build(ll + nl, nd, 0, cpdist, cpdext, &td, &bd)) != 0)
 899   {
 900 DEBG("dyn5d ");
 901     if (i == 1) {
 902       error("incomplete distance tree");
 903 #ifdef PKZIP_BUG_WORKAROUND
 904       i = 0;
 905     }
 906 #else
 907       huft_free(td);
 908     }
 909     huft_free(tl);
 910     return i;                   /* incomplete code set */
 911 #endif
 912   }
 913
 914 DEBG("dyn6 ");
 915
 916   /* decompress until an end-of-block code */
 917   if (inflate_codes(tl, td, bl, bd))
 918     return 1;
 919
 920 DEBG("dyn7 ");
 921
 922   /* free the decoding tables, return */
 923   huft_free(tl);
 924   huft_free(td);
 925
 926   DEBG(">");
 927   return 0;
 928
 929  underrun:
 930   return 4;                     /* Input underrun */
 931 }
 932
 933
 934
 935 STATIC int INIT inflate_block(
 936         int *e                  /* last block flag */
 937         )
 938 /* decompress an inflated block */
 939 {
 940   unsigned t;           /* block type */
 941   register ulg b;       /* bit buffer */
 942   register unsigned k;  /* number of bits in bit buffer */
 943
 944   DEBG("<blk");
 945
 946   /* make local bit buffer */
 947   b = bb;
 948   k = bk;
 949
 950
 951   /* read in last block bit */
 952   NEEDBITS(1)
 953   *e = (int)b & 1;
 954   DUMPBITS(1)
 955
 956
 957   /* read in block type */
 958   NEEDBITS(2)
 959   t = (unsigned)b & 3;
 960   DUMPBITS(2)
 961
 962
 963   /* restore the global bit buffer */
 964   bb = b;
 965   bk = k;
 966
 967   /* inflate that block type */
 968   if (t == 2)
 969     return inflate_dynamic();
 970   if (t == 0)
 971     return inflate_stored();
 972   if (t == 1)
 973     return inflate_fixed();
 974
 975   DEBG(">");
 976
 977   /* bad block type */
 978   return 2;
 979
 980  underrun:
 981   return 4;                     /* Input underrun */
 982 }
 983
 984
 985
 986 STATIC int INIT inflate(void)
 987 /* decompress an inflated entry */
 988 {
 989   int e;                /* last block flag */
 990   int r;                /* result code */
 991   unsigned h;           /* maximum struct huft's malloc'ed */
 992   void *ptr;
 993
 994   /* initialize window, bit buffer */
 995   wp = 0;
 996   bk = 0;
 997   bb = 0;
 998
 999
1000   /* decompress until the last block */
1001   h = 0;
1002   do {
1003     hufts = 0;
1004     gzip_mark(&ptr);
1005     if ((r = inflate_block(&e)) != 0) {
1006       gzip_release(&ptr);
1007       return r;
1008     }
1009     gzip_release(&ptr);
1010     if (hufts > h)
1011       h = hufts;
1012   } while (!e);
1013
1014   /* Undo too much lookahead. The next read will be byte aligned so we
1015    * can discard unused bits in the last meaningful byte.
1016    */
1017   while (bk >= 8) {
1018     bk -= 8;
1019     inptr--;
1020   }
1021
1022   /* flush out slide */
1023   flush_output(wp);
1024
1025
1026   /* return success */
1027 #ifdef DEBUG
1028   fprintf(stderr, "<%u> ", h);
1029 #endif /* DEBUG */
1030   return 0;
1031 }
1032
1033 /**********************************************************************
1034  *
1035  * The following are support routines for inflate.c
1036  *
1037  **********************************************************************/
1038
1039 static ulg crc_32_tab[256];
1040 static ulg crc;         /* initialized in makecrc() so it'll reside in bss */
1041 #define CRC_VALUE (crc ^ 0xffffffffUL)
1042
1043 /*
1044  * Code to compute the CRC-32 table. Borrowed from
1045  * gzip-1.0.3/makecrc.c.
1046  */
1047
1048 static void INIT
1049 makecrc(void)
1050 {
1051 /* Not copyrighted 1990 Mark Adler      */
1052
1053   unsigned long c;      /* crc shift register */
1054   unsigned long e;      /* polynomial exclusive-or pattern */
1055   int i;                /* counter for all possible eight bit values */
1056   int k;                /* byte being shifted into crc apparatus */
1057
1058   /* terms of polynomial defining this crc (except x^32): */
1059   static const int p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
1060
1061   /* Make exclusive-or pattern from polynomial */
1062   e = 0;
1063   for (i = 0; i < sizeof(p)/sizeof(int); i++)
1064     e |= 1L << (31 - p[i]);
1065
1066   crc_32_tab[0] = 0;
1067
1068   for (i = 1; i < 256; i++)
1069   {
1070     c = 0;
1071     for (k = i | 256; k != 1; k >>= 1)
1072     {
1073       c = c & 1 ? (c >> 1) ^ e : c >> 1;
1074       if (k & 1)
1075         c ^= e;
1076     }
1077     crc_32_tab[i] = c;
1078   }
1079
1080   /* this is initialized here so this code could reside in ROM */
1081   crc = (ulg)0xffffffffUL; /* shift register contents */
1082 }
1083
1084 /* gzip flag byte */
1085 #define ASCII_FLAG   0x01 /* bit 0 set: file probably ASCII text */
1086 #define CONTINUATION 0x02 /* bit 1 set: continuation of multi-part gzip file */
1087 #define EXTRA_FIELD  0x04 /* bit 2 set: extra field present */
1088 #define ORIG_NAME    0x08 /* bit 3 set: original file name present */
1089 #define COMMENT      0x10 /* bit 4 set: file comment present */
1090 #define ENCRYPTED    0x20 /* bit 5 set: file is encrypted */
1091 #define RESERVED     0xC0 /* bit 6,7:   reserved */
1092
1093 /*
1094  * Do the uncompression!
1095  */
1096 static int INIT gunzip(void)
1097 {
1098     uch flags;
1099     unsigned char magic[2]; /* magic header */
1100     char method;
1101     ulg orig_crc = 0;       /* original crc */
1102     ulg orig_len = 0;       /* original uncompressed length */
1103     int res;
1104
1105     magic[0] = NEXTBYTE();
1106     magic[1] = NEXTBYTE();
1107     method   = NEXTBYTE();
1108
1109     if (magic[0] != 037 ||
1110         ((magic[1] != 0213) && (magic[1] != 0236))) {
1111             error("bad gzip magic numbers");
1112             return -1;
1113     }
1114
1115     /* We only support method #8, DEFLATED */
1116     if (method != 8)  {
1117             error("internal error, invalid method");
1118             return -1;
1119     }
1120
1121     flags  = (uch)get_byte();
1122     if ((flags & ENCRYPTED) != 0) {
1123             error("Input is encrypted");
1124             return -1;
1125     }
1126     if ((flags & CONTINUATION) != 0) {
1127             error("Multi part input");
1128             return -1;
1129     }
1130     if ((flags & RESERVED) != 0) {
1131             error("Input has invalid flags");
1132             return -1;
1133     }
1134     NEXTBYTE(); /* Get timestamp */
1135     NEXTBYTE();
1136     NEXTBYTE();
1137     NEXTBYTE();
1138
1139     (void)NEXTBYTE();  /* Ignore extra flags for the moment */
1140     (void)NEXTBYTE();  /* Ignore OS type for the moment */
1141
1142     if ((flags & EXTRA_FIELD) != 0) {
1143             unsigned len = (unsigned)NEXTBYTE();
1144             len |= ((unsigned)NEXTBYTE())<<8;
1145             while (len--) (void)NEXTBYTE();
1146     }
1147
1148     /* Get original file name if it was truncated */
1149     if ((flags & ORIG_NAME) != 0) {
1150             /* Discard the old name */
1151             while (NEXTBYTE() != 0) /* null */ ;
1152     }
1153
1154     /* Discard file comment if any */
1155     if ((flags & COMMENT) != 0) {
1156             while (NEXTBYTE() != 0) /* null */ ;
1157     }
1158
1159     /* Decompress */
1160     if ((res = inflate())) {
1161             switch (res) {
1162             case 0:
1163                     break;
1164             case 1:
1165                     error("invalid compressed format (err=1)");
1166                     break;
1167             case 2:
1168                     error("invalid compressed format (err=2)");
1169                     break;
1170             case 3:
1171                     error("out of memory");
1172                     break;
1173             case 4:
1174                     error("out of input data");
1175                     break;
1176             default:
1177                     error("invalid compressed format (other)");
1178             }
1179             return -1;
1180     }
1181
1182     /* Get the crc and original length */
1183     /* crc32  (see algorithm.doc)
1184      * uncompressed input size modulo 2^32
1185      */
1186     orig_crc = (ulg) NEXTBYTE();
1187     orig_crc |= (ulg) NEXTBYTE() << 8;
1188     orig_crc |= (ulg) NEXTBYTE() << 16;
1189     orig_crc |= (ulg) NEXTBYTE() << 24;
1190
1191     orig_len = (ulg) NEXTBYTE();
1192     orig_len |= (ulg) NEXTBYTE() << 8;
1193     orig_len |= (ulg) NEXTBYTE() << 16;
1194     orig_len |= (ulg) NEXTBYTE() << 24;
1195
1196     /* Validate decompression */
1197     if (orig_crc != CRC_VALUE) {
1198             error("crc error");
1199             return -1;
1200     }
1201     if (orig_len != bytes_out) {
1202             error("length error");
1203             return -1;
1204     }
1205     return 0;
1206
1207  underrun:                      /* NEXTBYTE() goto's here if needed */
1208     error("out of input data");
1209     return -1;
1210 }
1211
1212