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
9
#if !defined(BUILDFIXED) && !defined(STDC)
10
# define BUILDFIXED /* non ANSI compilers may not accept inffixed.h */
13
const char inflate_copyright[] =
14
" inflate 1.1.4 Copyright 1995-2002 Mark Adler ";
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.
21
struct internal_state {int dummy;}; /* for buggy compilers */
23
/* simplify the use of the inflate_huft type with some defines */
24
#define exop word.what.Exop
25
#define bits word.what.Bits
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 */
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,
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.
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
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.
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 */
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. */
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 */
131
/* Generate counts for each bit length */
134
#define C2 C0 C0 C0 C0
135
#define C4 C2 C2 C2 C2
136
C4 /* clear c[]--assume BMAX+1 is 16 */
139
c[*p++]++; /* assume all entries <= BMAX */
141
if (c[0] == n) /* null input--all zero length codes */
143
*t = (inflate_huft *)Z_NULL;
149
/* Find minimum and maximum length, bound *m by those */
151
for (j = 1; j <= BMAX; j++)
154
k = j; /* minimum code length */
157
for (i = BMAX; i; i--)
160
g = i; /* maximum code length */
166
/* Adjust last length count to fill out codes, if needed */
167
for (y = 1 << j; j < i; j++, y <<= 1)
175
/* Generate starting offsets into the value table for each length */
177
p = c + 1; xp = x + 2;
178
while (--i) { /* note that i == g from above */
183
/* Make a table of values in order of bit lengths */
189
n = x[g]; /* set n to length of v */
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 */
201
/* go through the bit lengths (k already is bits in shortest code) */
207
/* here i is the Huffman code of length k bits for value *p */
208
/* make tables up to required level */
212
w += l; /* previous table always l bits */
214
/* compute minimum size table less than or equal to l bits */
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 */
222
while (++j < z) /* try smaller tables up to z bits */
224
if ((f <<= 1) <= *++xp)
225
break; /* enough codes to use up j bits */
226
f -= *xp; /* else deduct codes from patterns */
229
z = 1 << j; /* table entries for j-bit table */
231
/* allocate new table */
232
if (*hn + z > MANY) /* (note: doesn't matter for fixed) */
233
return Z_DATA_ERROR; /* overflow of MANY */
237
/* connect to last table, if there is one */
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 */
244
r.base = (uInt)(q - u[h-1] - j); /* offset to this table */
245
u[h-1][j] = r; /* connect to last table */
248
*t = q; /* first table is returned result */
251
/* set up table entry in r */
252
r.bits = (Byte)(k - w);
254
r.exop = 128 + 64; /* out of values--invalid code */
257
r.exop = (Byte)(*p < 256 ? 0 : 32 + 64); /* 256 is end-of-block */
258
r.base = *p++; /* simple code is just the value */
262
r.exop = (Byte)(e[*p - s] + 16 + 64);/* non-simple--look up in lists */
263
r.base = d[*p++ - s];
266
/* fill code-like entries with r */
268
for (j = i >> w; j < z; j += f)
271
/* backwards increment the k-bit code i */
272
for (j = 1 << (k - 1); i & j; j >>= 1)
276
/* backup over finished tables */
277
mask = (1 << w) - 1; /* needed on HP, cc -O bug */
278
while ((i & mask) != x[h])
280
h--; /* don't need to update q */
288
/* Return Z_BUF_ERROR if we were given an incomplete table */
289
return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK;
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 */
301
uInt hn = 0; /* hufts used in space */
302
uIntf *v; /* work area for huft_build */
304
if ((v = (uIntf*)ZALLOC(z, 19, sizeof(uInt))) == Z_NULL)
306
r = huft_build(c, 19, 19, (uIntf*)Z_NULL, (uIntf*)Z_NULL,
308
if (r == Z_DATA_ERROR)
309
z->msg = (char*)"oversubscribed dynamic bit lengths tree";
310
else if (r == Z_BUF_ERROR || *bb == 0)
312
z->msg = (char*)"incomplete dynamic bit lengths tree";
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 */
332
uInt hn = 0; /* hufts used in space */
333
uIntf *v; /* work area for huft_build */
335
/* allocate work area */
336
if ((v = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL)
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)
343
if (r == Z_DATA_ERROR)
344
z->msg = (char*)"oversubscribed literal/length tree";
345
else if (r != Z_MEM_ERROR)
347
z->msg = (char*)"incomplete literal/length tree";
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))
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
365
z->msg = (char*)"incomplete distance tree";
368
else if (r != Z_MEM_ERROR)
370
z->msg = (char*)"empty distance tree with lengths";
384
/* build fixed tables only once--keep them here */
386
local int fixed_built = 0;
387
#define FIXEDH 544 /* number of hufts used by fixed tables */
388
local inflate_huft fixed_mem[FIXEDH];
391
local inflate_huft *fixed_tl;
392
local inflate_huft *fixed_td;
394
#include "inffixed.h"
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 */
406
/* build fixed tables if not already */
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 */
414
/* allocate memory */
415
if ((c = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL)
417
if ((v = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL)
424
for (k = 0; k < 144; k++)
433
huft_build(c, 288, 257, cplens, cplext, &fixed_tl, &fixed_bl,
437
for (k = 0; k < 30; k++)
440
huft_build(c, 30, 0, cpdist, cpdext, &fixed_td, &fixed_bd,