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author darius
date Sat, 06 Dec 1997 05:41:29 +0000
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2:fba0b6e6cdc7 3:5a977ccbc7a9
1 /* inftrees.c -- generate Huffman trees for efficient decoding
2 * Copyright (C) 1995 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 struct internal_state {int dummy;}; /* for buggy compilers */
10
11 /* simplify the use of the inflate_huft type with some defines */
12 #define base more.Base
13 #define next more.Next
14 #define exop word.what.Exop
15 #define bits word.what.Bits
16
17
18 local int huft_build __P((
19 uInt *, /* code lengths in bits */
20 uInt, /* number of codes */
21 uInt, /* number of "simple" codes */
22 uInt *, /* list of base values for non-simple codes */
23 uInt *, /* list of extra bits for non-simple codes */
24 inflate_huft **, /* result: starting table */
25 uInt *, /* maximum lookup bits (returns actual) */
26 z_stream *)); /* for zalloc function */
27
28 local voidp falloc __P((
29 voidp, /* opaque pointer (not used) */
30 uInt, /* number of items */
31 uInt)); /* size of item */
32
33 local void ffree __P((
34 voidp q, /* opaque pointer (not used) */
35 voidp p)); /* what to free (not used) */
36
37 /* Tables for deflate from PKZIP's appnote.txt. */
38 local uInt cplens[] = { /* Copy lengths for literal codes 257..285 */
39 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
40 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
41 /* actually lengths - 2; also see note #13 above about 258 */
42 local uInt cplext[] = { /* Extra bits for literal codes 257..285 */
43 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
44 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 128, 128}; /* 128==invalid */
45 local uInt cpdist[] = { /* Copy offsets for distance codes 0..29 */
46 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
47 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
48 8193, 12289, 16385, 24577};
49 local uInt cpdext[] = { /* Extra bits for distance codes */
50 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
51 7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
52 12, 12, 13, 13};
53
54 /*
55 Huffman code decoding is performed using a multi-level table lookup.
56 The fastest way to decode is to simply build a lookup table whose
57 size is determined by the longest code. However, the time it takes
58 to build this table can also be a factor if the data being decoded
59 is not very long. The most common codes are necessarily the
60 shortest codes, so those codes dominate the decoding time, and hence
61 the speed. The idea is you can have a shorter table that decodes the
62 shorter, more probable codes, and then point to subsidiary tables for
63 the longer codes. The time it costs to decode the longer codes is
64 then traded against the time it takes to make longer tables.
65
66 This results of this trade are in the variables lbits and dbits
67 below. lbits is the number of bits the first level table for literal/
68 length codes can decode in one step, and dbits is the same thing for
69 the distance codes. Subsequent tables are also less than or equal to
70 those sizes. These values may be adjusted either when all of the
71 codes are shorter than that, in which case the longest code length in
72 bits is used, or when the shortest code is *longer* than the requested
73 table size, in which case the length of the shortest code in bits is
74 used.
75
76 There are two different values for the two tables, since they code a
77 different number of possibilities each. The literal/length table
78 codes 286 possible values, or in a flat code, a little over eight
79 bits. The distance table codes 30 possible values, or a little less
80 than five bits, flat. The optimum values for speed end up being
81 about one bit more than those, so lbits is 8+1 and dbits is 5+1.
82 The optimum values may differ though from machine to machine, and
83 possibly even between compilers. Your mileage may vary.
84 */
85
86
87 /* If BMAX needs to be larger than 16, then h and x[] should be uLong. */
88 #define BMAX 15 /* maximum bit length of any code */
89 #define N_MAX 288 /* maximum number of codes in any set */
90
91 #ifdef DEBUG
92 uInt inflate_hufts;
93 #endif
94
95 local int huft_build(b, n, s, d, e, t, m, zs)
96 uInt *b; /* code lengths in bits (all assumed <= BMAX) */
97 uInt n; /* number of codes (assumed <= N_MAX) */
98 uInt s; /* number of simple-valued codes (0..s-1) */
99 uInt *d; /* list of base values for non-simple codes */
100 uInt *e; /* list of extra bits for non-simple codes */
101 inflate_huft **t; /* result: starting table */
102 uInt *m; /* maximum lookup bits, returns actual */
103 z_stream *zs; /* for zalloc function */
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), Z_DATA_ERROR if the input is invalid (all zero length codes or an
108 over-subscribed set of lengths), or Z_MEM_ERROR if not enough memory. */
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 register uInt *p; /* pointer into c[], b[], or v[] */
120 register inflate_huft *q; /* points to current table */
121 inflate_huft r; /* table entry for structure assignment */
122 inflate_huft *u[BMAX]; /* table stack */
123 uInt v[N_MAX]; /* values in order of bit length */
124 register int w; /* bits before this table == (l * h) */
125 uInt x[BMAX+1]; /* bit offsets, then code stack */
126 uInt *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
190
191 /* Generate the Huffman codes and for each, make the table entries */
192 x[0] = i = 0; /* first Huffman code is zero */
193 p = v; /* grab values in bit order */
194 h = -1; /* no tables yet--level -1 */
195 w = -l; /* bits decoded == (l * h) */
196 u[0] = (inflate_huft *)Z_NULL; /* just to keep compilers happy */
197 q = (inflate_huft *)Z_NULL; /* ditto */
198 z = 0; /* ditto */
199
200 /* go through the bit lengths (k already is bits in shortest code) */
201 for (; k <= g; k++)
202 {
203 a = c[k];
204 while (a--)
205 {
206 /* here i is the Huffman code of length k bits for value *p */
207 /* make tables up to required level */
208 while (k > w + l)
209 {
210 h++;
211 w += l; /* previous table always l bits */
212
213 /* compute minimum size table less than or equal to l bits */
214 z = (z = g - w) > (uInt)l ? l : z; /* table size upper limit */
215 if ((f = 1 << (j = k - w)) > a + 1) /* try a k-w bit table */
216 { /* too few codes for k-w bit table */
217 f -= a + 1; /* deduct codes from patterns left */
218 xp = c + k;
219 if (j < z)
220 while (++j < z) /* try smaller tables up to z bits */
221 {
222 if ((f <<= 1) <= *++xp)
223 break; /* enough codes to use up j bits */
224 f -= *xp; /* else deduct codes from patterns */
225 }
226 }
227 z = 1 << j; /* table entries for j-bit table */
228
229 /* allocate and link in new table */
230 if ((q = (inflate_huft *)ZALLOC
231 (zs,z + 1,sizeof(inflate_huft))) == Z_NULL)
232 {
233 if (h)
234 inflate_trees_free(u[0], zs);
235 return Z_MEM_ERROR; /* not enough memory */
236 }
237 #ifdef DEBUG
238 inflate_hufts += z + 1;
239 #endif
240 *t = q + 1; /* link to list for huft_free() */
241 *(t = &(q->next)) = (inflate_huft *)Z_NULL;
242 u[h] = ++q; /* table starts after link */
243
244 /* connect to last table, if there is one */
245 if (h)
246 {
247 x[h] = i; /* save pattern for backing up */
248 r.bits = (Byte)l; /* bits to dump before this table */
249 r.exop = -(Char)j; /* bits in this table */
250 r.next = q; /* pointer to this table */
251 j = i >> (w - l); /* (get around Turbo C bug) */
252 u[h-1][j] = r; /* connect to last table */
253 }
254 }
255
256 /* set up table entry in r */
257 r.bits = (Byte)(k - w);
258 if (p >= v + n)
259 r.exop = (Char)(-128); /* out of values--invalid code */
260 else if (*p < s)
261 {
262 r.exop = (Char)(*p < 256 ? 16 : -64); /* 256 is end-of-block code */
263 r.base = *p++; /* simple code is just the value */
264 }
265 else
266 {
267 r.exop = (Char)e[*p - s]; /* non-simple--look up in lists */
268 r.base = d[*p++ - s];
269 }
270
271 /* fill code-like entries with r */
272 f = 1 << (k - w);
273 for (j = i >> w; j < z; j += f)
274 q[j] = r;
275
276 /* backwards increment the k-bit code i */
277 for (j = 1 << (k - 1); i & j; j >>= 1)
278 i ^= j;
279 i ^= j;
280
281 /* backup over finished tables */
282 while ((i & ((1 << w) - 1)) != x[h])
283 {
284 h--; /* don't need to update q */
285 w -= l;
286 }
287 }
288 }
289
290
291 /* Return Z_BUF_ERROR if we were given an incomplete table */
292 return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK;
293 }
294
295
296 int inflate_trees_bits(c, bb, tb, z)
297 uInt *c; /* 19 code lengths */
298 uInt *bb; /* bits tree desired/actual depth */
299 inflate_huft **tb; /* bits tree result */
300 z_stream *z; /* for zfree function */
301 {
302 int r;
303
304 r = huft_build(c, 19, 19, (uInt*)Z_NULL, (uInt*)Z_NULL, tb, bb, z);
305 if (r == Z_DATA_ERROR)
306 z->msg = "oversubscribed dynamic bit lengths tree";
307 else if (r == Z_BUF_ERROR)
308 {
309 inflate_trees_free(*tb, z);
310 z->msg = "incomplete dynamic bit lengths tree";
311 r = Z_DATA_ERROR;
312 }
313 return r;
314 }
315
316
317 int inflate_trees_dynamic(nl, nd, c, bl, bd, tl, td, z)
318 uInt nl; /* number of literal/length codes */
319 uInt nd; /* number of distance codes */
320 uInt *c; /* that many (total) code lengths */
321 uInt *bl; /* literal desired/actual bit depth */
322 uInt *bd; /* distance desired/actual bit depth */
323 inflate_huft **tl; /* literal/length tree result */
324 inflate_huft **td; /* distance tree result */
325 z_stream *z; /* for zfree function */
326 {
327 int r;
328
329 /* build literal/length tree */
330 if ((r = huft_build(c, nl, 257, cplens, cplext, tl, bl, z)) != Z_OK)
331 {
332 if (r == Z_DATA_ERROR)
333 z->msg = "oversubscribed literal/length tree";
334 else if (r == Z_BUF_ERROR)
335 {
336 inflate_trees_free(*tl, z);
337 z->msg = "incomplete literal/length tree";
338 r = Z_DATA_ERROR;
339 }
340 return r;
341 }
342
343 /* build distance tree */
344 if ((r = huft_build(c + nl, nd, 0, cpdist, cpdext, td, bd, z)) != Z_OK)
345 {
346 if (r == Z_DATA_ERROR)
347 z->msg = "oversubscribed literal/length tree";
348 else if (r == Z_BUF_ERROR) {
349 #ifdef PKZIP_BUG_WORKAROUND
350 r = Z_OK;
351 }
352 #else
353 inflate_trees_free(*td, z);
354 z->msg = "incomplete literal/length tree";
355 r = Z_DATA_ERROR;
356 }
357 inflate_trees_free(*tl, z);
358 return r;
359 #endif
360 }
361
362 /* done */
363 return Z_OK;
364 }
365
366
367 /* build fixed tables only once--keep them here */
368 local int fixed_lock = 0;
369 local int fixed_built = 0;
370 #define FIXEDH 530 /* number of hufts used by fixed tables */
371 local uInt fixed_left = FIXEDH;
372 local inflate_huft fixed_mem[FIXEDH];
373 local uInt fixed_bl;
374 local uInt fixed_bd;
375 local inflate_huft *fixed_tl;
376 local inflate_huft *fixed_td;
377
378
379 local voidp falloc(q, n, s)
380 voidp q; /* opaque pointer (not used) */
381 uInt n; /* number of items */
382 uInt s; /* size of item */
383 {
384 Assert(s == sizeof(inflate_huft) && n <= fixed_left,
385 "inflate_trees falloc overflow");
386 if (q) s++; /* to make some compilers happy */
387 fixed_left -= n;
388 return (voidp)(fixed_mem + fixed_left);
389 }
390
391
392 local void ffree(q, p)
393 voidp q;
394 voidp p;
395 {
396 Assert(0, "inflate_trees ffree called!");
397 if (q) q = p; /* to make some compilers happy */
398 }
399
400
401 int inflate_trees_fixed(bl, bd, tl, td)
402 uInt *bl; /* literal desired/actual bit depth */
403 uInt *bd; /* distance desired/actual bit depth */
404 inflate_huft **tl; /* literal/length tree result */
405 inflate_huft **td; /* distance tree result */
406 {
407 /* build fixed tables if not built already--lock out other instances */
408 while (++fixed_lock > 1)
409 fixed_lock--;
410 if (!fixed_built)
411 {
412 int k; /* temporary variable */
413 unsigned c[288]; /* length list for huft_build */
414 z_stream z; /* for falloc function */
415
416 /* set up fake z_stream for memory routines */
417 z.zalloc = falloc;
418 z.zfree = ffree;
419 z.opaque = Z_NULL;
420
421 /* literal table */
422 for (k = 0; k < 144; k++)
423 c[k] = 8;
424 for (; k < 256; k++)
425 c[k] = 9;
426 for (; k < 280; k++)
427 c[k] = 7;
428 for (; k < 288; k++)
429 c[k] = 8;
430 fixed_bl = 7;
431 huft_build(c, 288, 257, cplens, cplext, &fixed_tl, &fixed_bl, &z);
432
433 /* distance table */
434 for (k = 0; k < 30; k++)
435 c[k] = 5;
436 fixed_bd = 5;
437 huft_build(c, 30, 0, cpdist, cpdext, &fixed_td, &fixed_bd, &z);
438
439 /* done */
440 fixed_built = 1;
441 }
442 fixed_lock--;
443 *bl = fixed_bl;
444 *bd = fixed_bd;
445 *tl = fixed_tl;
446 *td = fixed_td;
447 return Z_OK;
448 }
449
450
451 int inflate_trees_free(t, z)
452 inflate_huft *t; /* table to free */
453 z_stream *z; /* for zfree function */
454 /* Free the malloc'ed tables built by huft_build(), which makes a linked
455 list of the tables it made, with the links in a dummy first entry of
456 each table. */
457 {
458 register inflate_huft *p, *q;
459
460 /* Don't free fixed trees */
461 if (t >= fixed_mem && t <= fixed_mem + FIXEDH)
462 return Z_OK;
463
464 /* Go through linked list, freeing from the malloced (t[-1]) address. */
465 p = t;
466 while (p != Z_NULL)
467 {
468 q = (--p)->next;
469 ZFREE(z,p);
470 p = q;
471 }
472 return Z_OK;
473 }