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
14#if 0
15local const char inflate_copyright[] =
16 " inflate 1.1.4 Copyright 1995-2002 Mark Adler ";
17#endif
18/*
19 If you use the zlib library in a product, an acknowledgment is welcome
20 in the documentation of your product. If for some reason you cannot
21 include such an acknowledgment, I would appreciate that you keep this
22 copyright string in the executable of your product.
23 */
24
25/* simplify the use of the inflate_huft type with some defines */
26#define exop word.what.Exop
27#define bits word.what.Bits
28
29
30local int huft_build OF((
31 uIntf *, /* code lengths in bits */
32 uInt, /* number of codes */
33 uInt, /* number of "simple" codes */
34 const uIntf *, /* list of base values for non-simple codes */
35 const uIntf *, /* list of extra bits for non-simple codes */
36 inflate_huft * FAR*,/* result: starting table */
37 uIntf *, /* maximum lookup bits (returns actual) */
38 inflate_huft *, /* space for trees */
39 uInt *, /* hufts used in space */
40 uIntf * )); /* space for values */
41
42/* Tables for deflate from PKZIP's appnote.txt. */
43local const uInt cplens[31] = { /* Copy lengths for literal codes 257..285 */
44 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
45 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
46 /* see note #13 above about 258 */
47local const uInt cplext[31] = { /* Extra bits for literal codes 257..285 */
48 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
49 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 112, 112}; /* 112==invalid */
50local const uInt cpdist[30] = { /* Copy offsets for distance codes 0..29 */
51 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
52 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
53 8193, 12289, 16385, 24577};
54local const uInt cpdext[30] = { /* Extra bits for distance codes */
55 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
56 7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
57 12, 12, 13, 13};
58
59/*
60 Huffman code decoding is performed using a multi-level table lookup.
61 The fastest way to decode is to simply build a lookup table whose
62 size is determined by the longest code. However, the time it takes
63 to build this table can also be a factor if the data being decoded
64 is not very long. The most common codes are necessarily the
65 shortest codes, so those codes dominate the decoding time, and hence
66 the speed. The idea is you can have a shorter table that decodes the
67 shorter, more probable codes, and then point to subsidiary tables for
68 the longer codes. The time it costs to decode the longer codes is
69 then traded against the time it takes to make longer tables.
70
71 This results of this trade are in the variables lbits and dbits
72 below. lbits is the number of bits the first level table for literal/
73 length codes can decode in one step, and dbits is the same thing for
74 the distance codes. Subsequent tables are also less than or equal to
75 those sizes. These values may be adjusted either when all of the
76 codes are shorter than that, in which case the longest code length in
77 bits is used, or when the shortest code is *longer* than the requested
78 table size, in which case the length of the shortest code in bits is
79 used.
80
81 There are two different values for the two tables, since they code a
82 different number of possibilities each. The literal/length table
83 codes 286 possible values, or in a flat code, a little over eight
84 bits. The distance table codes 30 possible values, or a little less
85 than five bits, flat. The optimum values for speed end up being
86 about one bit more than those, so lbits is 8+1 and dbits is 5+1.
87 The optimum values may differ though from machine to machine, and
88 possibly even between compilers. Your mileage may vary.
89 */
90
91
92/* If BMAX needs to be larger than 16, then h and x[] should be uLong. */
93#define BMAX 15 /* maximum bit length of any code */
94
95local int huft_build( /* b, n, s, d, e, t, m, hp, hn, v) */
96uIntf *b, /* code lengths in bits (all assumed <= BMAX) */
97uInt n, /* number of codes (assumed <= 288) */
98uInt s, /* number of simple-valued codes (0..s-1) */
99const uIntf *d, /* list of base values for non-simple codes */
100const uIntf *e, /* list of extra bits for non-simple codes */
101inflate_huft * FAR *t, /* result: starting table */
102uIntf *m, /* maximum lookup bits, returns actual */
103inflate_huft *hp, /* space for trees */
104uInt *hn, /* hufts used in space */
105uIntf *v /* working area: values in order of bit length */
106/* Given a list of code lengths and a maximum table size, make a set of
107 tables to decode that set of codes. Return Z_OK on success, Z_BUF_ERROR
108 if the given code set is incomplete (the tables are still built in this
109 case), or Z_DATA_ERROR if the input is invalid. */
110)
111{
112
113 uInt a; /* counter for codes of length k */
114 uInt c[BMAX+1]; /* bit length count table */
115 uInt f; /* i repeats in table every f entries */
116 int g; /* maximum code length */
117 int h; /* table level */
118 uInt i; /* counter, current code */
119 uInt j; /* counter */
120 int k; /* number of bits in current code */
121 int l; /* bits per table (returned in m) */
122 uInt mask; /* (1 << w) - 1, to avoid cc -O bug on HP */
123 uIntf *p; /* pointer into c[], b[], or v[] */
124 inflate_huft *q; /* points to current table */
125 struct inflate_huft_s r; /* table entry for structure assignment */
126 inflate_huft *u[BMAX]; /* table stack */
127 int w; /* bits before this table == (l * h) */
128 uInt x[BMAX+1]; /* bit offsets, then code stack */
129 uIntf *xp; /* pointer into x */
130 int y; /* number of dummy codes added */
131 uInt z; /* number of entries in current table */
132
133
134 /* Make compiler happy */
135 r.base = 0;
136
137 /* Generate counts for each bit length */
138 p = c;
139#define C0 *p++ = 0;
140#define C2 C0 C0 C0 C0
141#define C4 C2 C2 C2 C2
142 C4 /* clear c[]--assume BMAX+1 is 16 */
143 p = b; i = n;
144 do {
145 c[*p++]++; /* assume all entries <= BMAX */
146 } while (--i);
147 if (c[0] == n) /* null input--all zero length codes */
148 {
149 *t = (inflate_huft *)Z_NULL;
150 *m = 0;
151 return Z_OK;
152 }
153
154
155 /* Find minimum and maximum length, bound *m by those */
156 l = *m;
157 for (j = 1; j <= BMAX; j++)
158 if (c[j])
159 break;
160 k = j; /* minimum code length */
161 if ((uInt)l < j)
162 l = j;
163 for (i = BMAX; i; i--)
164 if (c[i])
165 break;
166 g = i; /* maximum code length */
167 if ((uInt)l > i)
168 l = i;
169 *m = l;
170
171
172 /* Adjust last length count to fill out codes, if needed */
173 for (y = 1 << j; j < i; j++, y <<= 1)
174 if ((y -= c[j]) < 0)
175 return Z_DATA_ERROR;
176 if ((y -= c[i]) < 0)
177 return Z_DATA_ERROR;
178 c[i] += y;
179
180
181 /* Generate starting offsets into the value table for each length */
182 x[1] = j = 0;
183 p = c + 1; xp = x + 2;
184 while (--i) { /* note that i == g from above */
185 *xp++ = (j += *p++);
186 }
187
188
189 /* Make a table of values in order of bit lengths */
190 p = b; i = 0;
191 do {
192 if ((j = *p++) != 0)
193 v[x[j]++] = i;
194 } while (++i < n);
195 n = x[g]; /* set n to length of v */
196
197
198 /* Generate the Huffman codes and for each, make the table entries */
199 x[0] = i = 0; /* first Huffman code is zero */
200 p = v; /* grab values in bit order */
201 h = -1; /* no tables yet--level -1 */
202 w = -l; /* bits decoded == (l * h) */
203 u[0] = (inflate_huft *)Z_NULL; /* just to keep compilers happy */
204 q = (inflate_huft *)Z_NULL; /* ditto */
205 z = 0; /* ditto */
206
207 /* go through the bit lengths (k already is bits in shortest code) */
208 for (; k <= g; k++)
209 {
210 a = c[k];
211 while (a--)
212 {
213 /* here i is the Huffman code of length k bits for value *p */
214 /* make tables up to required level */
215 while (k > w + l)
216 {
217 h++;
218 w += l; /* previous table always l bits */
219
220 /* compute minimum size table less than or equal to l bits */
221 z = g - w;
222 z = z > (uInt)l ? (uInt)l : z; /* table size upper limit */
223 if ((f = 1 << (j = k - w)) > a + 1) /* try a k-w bit table */
224 { /* too few codes for k-w bit table */
225 f -= a + 1; /* deduct codes from patterns left */
226 xp = c + k;
227 if (j < z)
228 while (++j < z) /* try smaller tables up to z bits */
229 {
230 if ((f <<= 1) <= *++xp)
231 break; /* enough codes to use up j bits */
232 f -= *xp; /* else deduct codes from patterns */
233 }
234 }
235 z = 1 << j; /* table entries for j-bit table */
236
237 /* allocate new table */
238 if (*hn + z > MANY) /* (note: doesn't matter for fixed) */
239 return Z_DATA_ERROR; /* overflow of MANY */
240 u[h] = q = hp + *hn;
241 *hn += z;
242
243 /* connect to last table, if there is one */
244 if (h)
245 {
246 x[h] = i; /* save pattern for backing up */
247 r.bits = (Byte)l; /* bits to dump before this table */
248 r.exop = (Byte)j; /* bits in this table */
249 j = i >> (w - l);
250 r.base = (uInt)(q - u[h-1] - j); /* offset to this table */
251 u[h-1][j] = r; /* connect to last table */
252 }
253 else
254 *t = q; /* first table is returned result */
255 }
256
257 /* set up table entry in r */
258 r.bits = (Byte)(k - w);
259 if (p >= v + n)
260 r.exop = 128 + 64; /* out of values--invalid code */
261 else if (*p < s)
262 {
263 r.exop = (Byte)(*p < 256 ? 0 : 32 + 64); /* 256 is end-of-block */
264 r.base = *p++; /* simple code is just the value */
265 }
266 else
267 {
268 r.exop = (Byte)(e[*p - s] + 16 + 64);/* non-simple--look up in lists */
269 r.base = d[*p++ - s];
270 }
271
272 /* fill code-like entries with r */
273 f = 1 << (k - w);
274 for (j = i >> w; j < z; j += f)
275 q[j] = r;
276
277 /* backwards increment the k-bit code i */
278 for (j = 1 << (k - 1); i & j; j >>= 1)
279 i ^= j;
280 i ^= j;
281
282 /* backup over finished tables */
283 mask = (1 << w) - 1; /* needed on HP, cc -O bug */
284 while ((i & mask) != x[h])
285 {
286 h--; /* don't need to update q */
287 w -= l;
288 mask = (1 << w) - 1;
289 }
290 }
291 }
292
293
294 /* Return Z_BUF_ERROR if we were given an incomplete table */
295 return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK;
296}
297
298
299local int inflate_trees_bits( /* c, bb, tb, hp, z) */
300uIntf *c, /* 19 code lengths */
301uIntf *bb, /* bits tree desired/actual depth */
302inflate_huft * FAR *tb, /* bits tree result */
303inflate_huft *hp, /* space for trees */
304z_streamp z /* for messages */
305)
306{
307 int r;
308 uInt hn = 0; /* hufts used in space */
309 uIntf *v; /* work area for huft_build */
310
311 if ((v = (uIntf*)ZALLOC(z, 19, sizeof(uInt))) == Z_NULL)
312 return Z_MEM_ERROR;
313 r = huft_build(c, 19, 19, (uIntf*)Z_NULL, (uIntf*)Z_NULL,
314 tb, bb, hp, &hn, v);
315 if (r == Z_DATA_ERROR)
316 z->msg = (char*)"oversubscribed dynamic bit lengths tree";
317 else if (r == Z_BUF_ERROR || *bb == 0)
318 {
319 z->msg = (char*)"incomplete dynamic bit lengths tree";
320 r = Z_DATA_ERROR;
321 }
322 ZFREE(z, v);
323 return r;
324}
325
326
327local int inflate_trees_dynamic( /* nl, nd, c, bl, bd, tl, td, hp, z) */
328uInt nl, /* number of literal/length codes */
329uInt nd, /* number of distance codes */
330uIntf *c, /* that many (total) code lengths */
331uIntf *bl, /* literal desired/actual bit depth */
332uIntf *bd, /* distance desired/actual bit depth */
333inflate_huft * FAR *tl, /* literal/length tree result */
334inflate_huft * FAR *td, /* distance tree result */
335inflate_huft *hp, /* space for trees */
336z_streamp z /* for messages */
337)
338{
339 int r;
340 uInt hn = 0; /* hufts used in space */
341 uIntf *v; /* work area for huft_build */
342
343 /* allocate work area */
344 if ((v = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL)
345 return Z_MEM_ERROR;
346
347 /* build literal/length tree */
348 r = huft_build(c, nl, 257, cplens, cplext, tl, bl, hp, &hn, v);
349 if (r != Z_OK || *bl == 0)
350 {
351 if (r == Z_DATA_ERROR)
352 z->msg = (char*)"oversubscribed literal/length tree";
353 else if (r != Z_MEM_ERROR)
354 {
355 z->msg = (char*)"incomplete literal/length tree";
356 r = Z_DATA_ERROR;
357 }
358 ZFREE(z, v);
359 return r;
360 }
361
362 /* build distance tree */
363 r = huft_build(c + nl, nd, 0, cpdist, cpdext, td, bd, hp, &hn, v);
364 if (r != Z_OK || (*bd == 0 && nl > 257))
365 {
366 if (r == Z_DATA_ERROR)
367 z->msg = (char*)"oversubscribed distance tree";
368 else if (r == Z_BUF_ERROR) {
369#if 0
370 {
371#endif
372#ifdef PKZIP_BUG_WORKAROUND
373 r = Z_OK;
374 }
375#else
376 z->msg = (char*)"incomplete distance tree";
377 r = Z_DATA_ERROR;
378 }
379 else if (r != Z_MEM_ERROR)
380 {
381 z->msg = (char*)"empty distance tree with lengths";
382 r = Z_DATA_ERROR;
383 }
384 ZFREE(z, v);
385 return r;
386#endif
387 }
388
389 /* done */
390 ZFREE(z, v);
391 return Z_OK;
392}
393
394
395/* build fixed tables only once--keep them here */
396#ifdef BUILDFIXED
397local int fixed_built = 0;
398#define FIXEDH 544 /* number of hufts used by fixed tables */
399local inflate_huft fixed_mem[FIXEDH];
400local uInt fixed_bl;
401local uInt fixed_bd;
402local inflate_huft *fixed_tl;
403local inflate_huft *fixed_td;
404#else
405#include "inffixed.h"
406#endif
407
408
409local int inflate_trees_fixed( /* bl, bd, tl, td, z) */
410uIntf *bl, /* literal desired/actual bit depth */
411uIntf *bd, /* distance desired/actual bit depth */
412const inflate_huft * FAR *tl, /* literal/length tree result */
413const inflate_huft * FAR *td, /* distance tree result */
414z_streamp z /* for memory allocation */
415)
416{
417#ifdef BUILDFIXED
418 /* build fixed tables if not already */
419 if (!fixed_built)
420 {
421 int k; /* temporary variable */
422 uInt f = 0; /* number of hufts used in fixed_mem */
423 uIntf *c; /* length list for huft_build */
424 uIntf *v; /* work area for huft_build */
425
426 /* allocate memory */
427 if ((c = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL)
428 return Z_MEM_ERROR;
429 if ((v = (uIntf*)ZALLOC(z, 288, sizeof(uInt))) == Z_NULL)
430 {
431 ZFREE(z, c);
432 return Z_MEM_ERROR;
433 }
434
435 /* literal table */
436 for (k = 0; k < 144; k++)
437 c[k] = 8;
438 for (; k < 256; k++)
439 c[k] = 9;
440 for (; k < 280; k++)
441 c[k] = 7;
442 for (; k < 288; k++)
443 c[k] = 8;
444 fixed_bl = 9;
445 huft_build(c, 288, 257, cplens, cplext, &fixed_tl, &fixed_bl,
446 fixed_mem, &f, v);
447
448 /* distance table */
449 for (k = 0; k < 30; k++)
450 c[k] = 5;
451 fixed_bd = 5;
452 huft_build(c, 30, 0, cpdist, cpdext, &fixed_td, &fixed_bd,
453 fixed_mem, &f, v);
454
455 /* done */
456 ZFREE(z, v);
457 ZFREE(z, c);
458 fixed_built = 1;
459 }
460#else
461 FT_UNUSED(z);
462#endif
463 *bl = fixed_bl;
464 *bd = fixed_bd;
465 *tl = fixed_tl;
466 *td = fixed_td;
467 return Z_OK;
468}
469