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107 pj 1
/* inftrees.c -- generate Huffman trees for efficient decoding
2
 * Copyright (C) 1995-2002 Mark Adler
3
 * For conditions of distribution and use, see copyright notice in zlib.h
4
 */
5
 
6
#include "zutil.h"
7
#include "inftrees.h"
8
 
9
#if !defined(BUILDFIXED) && !defined(STDC)
10
#  define BUILDFIXED   /* non ANSI compilers may not accept inffixed.h */
11
#endif
12
 
13
const char inflate_copyright[] =
14
   " inflate 1.1.4 Copyright 1995-2002 Mark Adler ";
15
/*
16
  If you use the zlib library in a product, an acknowledgment is welcome
17
  in the documentation of your product. If for some reason you cannot
18
  include such an acknowledgment, I would appreciate that you keep this
19
  copyright string in the executable of your product.
20
 */
21
struct internal_state  {int dummy;}; /* for buggy compilers */
22
 
23
/* simplify the use of the inflate_huft type with some defines */
24
#define exop word.what.Exop
25
#define bits word.what.Bits
26
 
27
 
28
local int huft_build OF((
29
    uIntf *,            /* code lengths in bits */
30
    uInt,               /* number of codes */
31
    uInt,               /* number of "simple" codes */
32
    const uIntf *,      /* list of base values for non-simple codes */
33
    const uIntf *,      /* list of extra bits for non-simple codes */
34
    inflate_huft * FAR*,/* result: starting table */
35
    uIntf *,            /* maximum lookup bits (returns actual) */
36
    inflate_huft *,     /* space for trees */
37
    uInt *,             /* hufts used in space */
38
    uIntf * ));         /* space for values */
39
 
40
/* Tables for deflate from PKZIP's appnote.txt. */
41
local const uInt cplens[31] = { /* Copy lengths for literal codes 257..285 */
42
        3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
43
        35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
44
        /* see note #13 above about 258 */
45
local const uInt cplext[31] = { /* Extra bits for literal codes 257..285 */
46
        0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
47
        3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 112, 112}; /* 112==invalid */
48
local const uInt cpdist[30] = { /* Copy offsets for distance codes 0..29 */
49
        1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
50
        257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
51
        8193, 12289, 16385, 24577};
52
local const uInt cpdext[30] = { /* Extra bits for distance codes */
53
        0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
54
        7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
55
        12, 12, 13, 13};
56
 
57
/*
58
   Huffman code decoding is performed using a multi-level table lookup.
59
   The fastest way to decode is to simply build a lookup table whose
60
   size is determined by the longest code.  However, the time it takes
61
   to build this table can also be a factor if the data being decoded
62
   is not very long.  The most common codes are necessarily the
63
   shortest codes, so those codes dominate the decoding time, and hence
64
   the speed.  The idea is you can have a shorter table that decodes the
65
   shorter, more probable codes, and then point to subsidiary tables for
66
   the longer codes.  The time it costs to decode the longer codes is
67
   then traded against the time it takes to make longer tables.
68
 
69
   This results of this trade are in the variables lbits and dbits
70
   below.  lbits is the number of bits the first level table for literal/
71
   length codes can decode in one step, and dbits is the same thing for
72
   the distance codes.  Subsequent tables are also less than or equal to
73
   those sizes.  These values may be adjusted either when all of the
74
   codes are shorter than that, in which case the longest code length in
75
   bits is used, or when the shortest code is *longer* than the requested
76
   table size, in which case the length of the shortest code in bits is
77
   used.
78
 
79
   There are two different values for the two tables, since they code a
80
   different number of possibilities each.  The literal/length table
81
   codes 286 possible values, or in a flat code, a little over eight
82
   bits.  The distance table codes 30 possible values, or a little less
83
   than five bits, flat.  The optimum values for speed end up being
84
   about one bit more than those, so lbits is 8+1 and dbits is 5+1.
85
   The optimum values may differ though from machine to machine, and
86
   possibly even between compilers.  Your mileage may vary.
87
 */
88
 
89
 
90
/* If BMAX needs to be larger than 16, then h and x[] should be uLong. */
91
#define BMAX 15         /* maximum bit length of any code */
92
 
93
local int huft_build(b, n, s, d, e, t, m, hp, hn, v)
94
uIntf *b;               /* code lengths in bits (all assumed <= BMAX) */
95
uInt n;                 /* number of codes (assumed <= 288) */
96
uInt s;                 /* number of simple-valued codes (0..s-1) */
97
const uIntf *d;         /* list of base values for non-simple codes */
98
const uIntf *e;         /* list of extra bits for non-simple codes */
99
inflate_huft * FAR *t;  /* result: starting table */
100
uIntf *m;               /* maximum lookup bits, returns actual */
101
inflate_huft *hp;       /* space for trees */
102
uInt *hn;               /* hufts used in space */
103
uIntf *v;               /* working area: values in order of bit length */
104
/* Given a list of code lengths and a maximum table size, make a set of
105
   tables to decode that set of codes.  Return Z_OK on success, Z_BUF_ERROR
106
   if the given code set is incomplete (the tables are still built in this
107
   case), or Z_DATA_ERROR if the input is invalid. */
108
{
109
 
110
  uInt a;                       /* counter for codes of length k */
111
  uInt c[BMAX+1];               /* bit length count table */
112
  uInt f;                       /* i repeats in table every f entries */
113
  int g;                        /* maximum code length */
114
  int h;                        /* table level */
115
  register uInt i;              /* counter, current code */
116
  register uInt j;              /* counter */
117
  register int k;               /* number of bits in current code */
118
  int l;                        /* bits per table (returned in m) */
119
  uInt mask;                    /* (1 << w) - 1, to avoid cc -O bug on HP */
120
  register uIntf *p;            /* pointer into c[], b[], or v[] */
121
  inflate_huft *q;              /* points to current table */
122
  struct inflate_huft_s r;      /* table entry for structure assignment */
123
  inflate_huft *u[BMAX];        /* table stack */
124
  register int w;               /* bits before this table == (l * h) */
125
  uInt x[BMAX+1];               /* bit offsets, then code stack */
126
  uIntf *xp;                    /* pointer into x */
127
  int y;                        /* number of dummy codes added */
128
  uInt z;                       /* number of entries in current table */
129
 
130
 
131
  /* Generate counts for each bit length */
132
  p = c;
133
#define C0 *p++ = 0;
134
#define C2 C0 C0 C0 C0
135
#define C4 C2 C2 C2 C2
136
  C4                            /* clear c[]--assume BMAX+1 is 16 */
137
  p = b;  i = n;
138
  do {
139
    c[*p++]++;                  /* assume all entries <= BMAX */
140
  } while (--i);
141
  if (c[0] == n)                /* null input--all zero length codes */
142
  {
143
    *t = (inflate_huft *)Z_NULL;
144
    *m = 0;
145
    return Z_OK;
146
  }
147
 
148
 
149
  /* Find minimum and maximum length, bound *m by those */
150
  l = *m;
151
  for (j = 1; j <= BMAX; j++)
152
    if (c[j])
153
      break;
154
  k = j;                        /* minimum code length */
155
  if ((uInt)l < j)
156
    l = j;
157
  for (i = BMAX; i; i--)
158
    if (c[i])
159
      break;
160
  g = i;                        /* maximum code length */
161
  if ((uInt)l > i)
162
    l = i;
163
  *m = l;
164
 
165
 
166
  /* Adjust last length count to fill out codes, if needed */
167
  for (y = 1 << j; j < i; j++, y <<= 1)
168
    if ((y -= c[j]) < 0)
169
      return Z_DATA_ERROR;
170
  if ((y -= c[i]) < 0)
171
    return Z_DATA_ERROR;
172
  c[i] += y;
173
 
174
 
175
  /* Generate starting offsets into the value table for each length */
176
  x[1] = j = 0;
177
  p = c + 1;  xp = x + 2;
178
  while (--i) {                 /* note that i == g from above */
179
    *xp++ = (j += *p++);
180
  }
181
 
182
 
183
  /* Make a table of values in order of bit lengths */
184
  p = b;  i = 0;
185
  do {
186
    if ((j = *p++) != 0)
187
      v[x[j]++] = i;
188
  } while (++i < n);
189
  n = x[g];                     /* set n to length of v */
190
 
191
 
192
  /* Generate the Huffman codes and for each, make the table entries */
193
  x[0] = i = 0;                 /* first Huffman code is zero */
194
  p = v;                        /* grab values in bit order */
195
  h = -1;                       /* no tables yet--level -1 */
196
  w = -l;                       /* bits decoded == (l * h) */
197
  u[0] = (inflate_huft *)Z_NULL;        /* just to keep compilers happy */
198
  q = (inflate_huft *)Z_NULL;   /* ditto */
199
  z = 0;                        /* ditto */
200
 
201
  /* go through the bit lengths (k already is bits in shortest code) */
202
  for (; k <= g; k++)
203
  {
204
    a = c[k];
205
    while (a--)
206
    {
207
      /* here i is the Huffman code of length k bits for value *p */
208
      /* make tables up to required level */
209
      while (k > w + l)
210
      {
211
        h++;
212
        w += l;                 /* previous table always l bits */
213
 
214
        /* compute minimum size table less than or equal to l bits */
215
        z = g - w;
216
        z = z > (uInt)l ? l : z;        /* table size upper limit */
217
        if ((f = 1 << (j = k - w)) > a + 1)     /* try a k-w bit table */
218
        {                       /* too few codes for k-w bit table */
219
          f -= a + 1;           /* deduct codes from patterns left */
220
          xp = c + k;
221
          if (j < z)
222
            while (++j < z)     /* try smaller tables up to z bits */
223
            {
224
              if ((f <<= 1) <= *++xp)
225
                break;          /* enough codes to use up j bits */
226
              f -= *xp;         /* else deduct codes from patterns */
227
            }
228
        }
229
        z = 1 << j;             /* table entries for j-bit table */
230
 
231
        /* allocate new table */
232
        if (*hn + z > MANY)     /* (note: doesn't matter for fixed) */
233
          return Z_DATA_ERROR;  /* overflow of MANY */
234
        u[h] = q = hp + *hn;
235
        *hn += z;
236
 
237
        /* connect to last table, if there is one */
238
        if (h)
239
        {
240
          x[h] = i;             /* save pattern for backing up */
241
          r.bits = (Byte)l;     /* bits to dump before this table */
242
          r.exop = (Byte)j;     /* bits in this table */
243
          j = i >> (w - l);
244
          r.base = (uInt)(q - u[h-1] - j);   /* offset to this table */
245
          u[h-1][j] = r;        /* connect to last table */
246
        }
247
        else
248
          *t = q;               /* first table is returned result */
249
      }
250
 
251
      /* set up table entry in r */
252
      r.bits = (Byte)(k - w);
253
      if (p >= v + n)
254
        r.exop = 128 + 64;      /* out of values--invalid code */
255
      else if (*p < s)
256
      {
257
        r.exop = (Byte)(*p < 256 ? 0 : 32 + 64);     /* 256 is end-of-block */
258
        r.base = *p++;          /* simple code is just the value */
259
      }
260
      else
261
      {
262
        r.exop = (Byte)(e[*p - s] + 16 + 64);/* non-simple--look up in lists */
263
        r.base = d[*p++ - s];
264
      }
265
 
266
      /* fill code-like entries with r */
267
      f = 1 << (k - w);
268
      for (j = i >> w; j < z; j += f)
269
        q[j] = r;
270
 
271
      /* backwards increment the k-bit code i */
272
      for (j = 1 << (k - 1); i & j; j >>= 1)
273
        i ^= j;
274
      i ^= j;
275
 
276
      /* backup over finished tables */
277
      mask = (1 << w) - 1;      /* needed on HP, cc -O bug */
278
      while ((i & mask) != x[h])
279
      {
280
        h--;                    /* don't need to update q */
281
        w -= l;
282
        mask = (1 << w) - 1;
283
      }
284
    }
285
  }
286
 
287
 
288
  /* Return Z_BUF_ERROR if we were given an incomplete table */
289
  return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK;
290
}
291
 
292
 
293
int inflate_trees_bits(c, bb, tb, hp, z)
294
uIntf *c;               /* 19 code lengths */
295
uIntf *bb;              /* bits tree desired/actual depth */
296
inflate_huft * FAR *tb; /* bits tree result */
297
inflate_huft *hp;       /* space for trees */
298
z_streamp z;            /* for messages */
299
{
300
  int r;
301
  uInt hn = 0;          /* hufts used in space */
302
  uIntf *v;             /* work area for huft_build */
303
 
304
  if ((v = (uIntf*)ZALLOC(z, 19, sizeof(uInt))) == Z_NULL)
305
    return Z_MEM_ERROR;
306
  r = huft_build(c, 19, 19, (uIntf*)Z_NULL, (uIntf*)Z_NULL,
307
                 tb, bb, hp, &hn, v);
308
  if (r == Z_DATA_ERROR)
309
    z->msg = (char*)"oversubscribed dynamic bit lengths tree";
310
  else if (r == Z_BUF_ERROR || *bb == 0)
311
  {
312
    z->msg = (char*)"incomplete dynamic bit lengths tree";
313
    r = Z_DATA_ERROR;
314
  }
315
  ZFREE(z, v);
316
  return r;
317
}
318
 
319
 
320
int inflate_trees_dynamic(nl, nd, c, bl, bd, tl, td, hp, z)
321
uInt nl;                /* number of literal/length codes */
322
uInt nd;                /* number of distance codes */
323
uIntf *c;               /* that many (total) code lengths */
324
uIntf *bl;              /* literal desired/actual bit depth */
325
uIntf *bd;              /* distance desired/actual bit depth */
326
inflate_huft * FAR *tl; /* literal/length tree result */
327
inflate_huft * FAR *td; /* distance tree result */
328
inflate_huft *hp;       /* space for trees */
329
z_streamp z;            /* for messages */
330
{
331
  int r;
332
  uInt hn = 0;          /* hufts used in space */
333
  uIntf *v;             /* work area for huft_build */
334
 
335
  /* allocate work area */
336
  if ((v = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL)
337
    return Z_MEM_ERROR;
338
 
339
  /* build literal/length tree */
340
  r = huft_build(c, nl, 257, cplens, cplext, tl, bl, hp, &hn, v);
341
  if (r != Z_OK || *bl == 0)
342
  {
343
    if (r == Z_DATA_ERROR)
344
      z->msg = (char*)"oversubscribed literal/length tree";
345
    else if (r != Z_MEM_ERROR)
346
    {
347
      z->msg = (char*)"incomplete literal/length tree";
348
      r = Z_DATA_ERROR;
349
    }
350
    ZFREE(z, v);
351
    return r;
352
  }
353
 
354
  /* build distance tree */
355
  r = huft_build(c + nl, nd, 0, cpdist, cpdext, td, bd, hp, &hn, v);
356
  if (r != Z_OK || (*bd == 0 && nl > 257))
357
  {
358
    if (r == Z_DATA_ERROR)
359
      z->msg = (char*)"oversubscribed distance tree";
360
    else if (r == Z_BUF_ERROR) {
361
#ifdef PKZIP_BUG_WORKAROUND
362
      r = Z_OK;
363
    }
364
#else
365
      z->msg = (char*)"incomplete distance tree";
366
      r = Z_DATA_ERROR;
367
    }
368
    else if (r != Z_MEM_ERROR)
369
    {
370
      z->msg = (char*)"empty distance tree with lengths";
371
      r = Z_DATA_ERROR;
372
    }
373
    ZFREE(z, v);
374
    return r;
375
#endif
376
  }
377
 
378
  /* done */
379
  ZFREE(z, v);
380
  return Z_OK;
381
}
382
 
383
 
384
/* build fixed tables only once--keep them here */
385
#ifdef BUILDFIXED
386
local int fixed_built = 0;
387
#define FIXEDH 544      /* number of hufts used by fixed tables */
388
local inflate_huft fixed_mem[FIXEDH];
389
local uInt fixed_bl;
390
local uInt fixed_bd;
391
local inflate_huft *fixed_tl;
392
local inflate_huft *fixed_td;
393
#else
394
#include "inffixed.h"
395
#endif
396
 
397
 
398
int inflate_trees_fixed(bl, bd, tl, td, z)
399
uIntf *bl;               /* literal desired/actual bit depth */
400
uIntf *bd;               /* distance desired/actual bit depth */
401
inflate_huft * FAR *tl;  /* literal/length tree result */
402
inflate_huft * FAR *td;  /* distance tree result */
403
z_streamp z;             /* for memory allocation */
404
{
405
#ifdef BUILDFIXED
406
  /* build fixed tables if not already */
407
  if (!fixed_built)
408
  {
409
    int k;              /* temporary variable */
410
    uInt f = 0;         /* number of hufts used in fixed_mem */
411
    uIntf *c;           /* length list for huft_build */
412
    uIntf *v;           /* work area for huft_build */
413
 
414
    /* allocate memory */
415
    if ((c = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL)
416
      return Z_MEM_ERROR;
417
    if ((v = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL)
418
    {
419
      ZFREE(z, c);
420
      return Z_MEM_ERROR;
421
    }
422
 
423
    /* literal table */
424
    for (k = 0; k < 144; k++)
425
      c[k] = 8;
426
    for (; k < 256; k++)
427
      c[k] = 9;
428
    for (; k < 280; k++)
429
      c[k] = 7;
430
    for (; k < 288; k++)
431
      c[k] = 8;
432
    fixed_bl = 9;
433
    huft_build(c, 288, 257, cplens, cplext, &fixed_tl, &fixed_bl,
434
               fixed_mem, &f, v);
435
 
436
    /* distance table */
437
    for (k = 0; k < 30; k++)
438
      c[k] = 5;
439
    fixed_bd = 5;
440
    huft_build(c, 30, 0, cpdist, cpdext, &fixed_td, &fixed_bd,
441
               fixed_mem, &f, v);
442
 
443
    /* done */
444
    ZFREE(z, v);
445
    ZFREE(z, c);
446
    fixed_built = 1;
447
  }
448
#endif
449
  *bl = fixed_bl;
450
  *bd = fixed_bd;
451
  *tl = fixed_tl;
452
  *td = fixed_td;
453
  return Z_OK;
454
}