1 /* inftrees.c -- generate Huffman trees for efficient decoding
2 * Copyright (C) 1995-1996 Mark Adler
3 * For conditions of distribution and use, see copyright notice in zlib.h
9 char inflate_copyright[] = " inflate 1.0.2 Copyright 1995-1996 Mark Adler ";
11 If you use the zlib library in a product, an acknowledgment is welcome
12 in the documentation of your product. If for some reason you cannot
13 include such an acknowledgment, I would appreciate that you keep this
14 copyright string in the executable of your product.
16 struct internal_state {int dummy;}; /* for buggy compilers */
18 /* simplify the use of the inflate_huft type with some defines */
19 #define base more.Base
20 #define next more.Next
21 #define exop word.what.Exop
22 #define bits word.what.Bits
25 local int huft_build OF((
26 uIntf *, /* code lengths in bits */
27 uInt, /* number of codes */
28 uInt, /* number of "simple" codes */
29 uIntf *, /* list of base values for non-simple codes */
30 uIntf *, /* list of extra bits for non-simple codes */
31 inflate_huft * FAR*,/* result: starting table */
32 uIntf *, /* maximum lookup bits (returns actual) */
33 z_stream *)); /* for zalloc function */
35 local voidpf falloc OF((
36 voidpf, /* opaque pointer (not used) */
37 uInt, /* number of items */
38 uInt)); /* size of item */
40 /* Tables for deflate from PKZIP's appnote.txt. */
41 local 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 /* actually lengths - 2; also see note #13 above about 258 */
45 local 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, 192, 192}; /* 192==invalid */
48 local 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 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 */
92 #define N_MAX 288 /* maximum number of codes in any set */
98 local int huft_build(b, n, s, d, e, t, m, zs)
99 uIntf *b; /* code lengths in bits (all assumed <= BMAX) */
100 uInt n; /* number of codes (assumed <= N_MAX) */
101 uInt s; /* number of simple-valued codes (0..s-1) */
102 uIntf *d; /* list of base values for non-simple codes */
103 uIntf *e; /* list of extra bits for non-simple codes */
104 inflate_huft * FAR *t; /* result: starting table */
105 uIntf *m; /* maximum lookup bits, returns actual */
106 z_stream *zs; /* for zalloc function */
107 /* Given a list of code lengths and a maximum table size, make a set of
108 tables to decode that set of codes. Return Z_OK on success, Z_BUF_ERROR
109 if the given code set is incomplete (the tables are still built in this
110 case), Z_DATA_ERROR if the input is invalid (all zero length codes or an
111 over-subscribed set of lengths), or Z_MEM_ERROR if not enough memory. */
114 uInt a; /* counter for codes of length k */
115 uInt c[BMAX+1]; /* bit length count table */
116 uInt f; /* i repeats in table every f entries */
117 int g; /* maximum code length */
118 int h; /* table level */
119 register uInt i; /* counter, current code */
120 register uInt j; /* counter */
121 register int k; /* number of bits in current code */
122 int l; /* bits per table (returned in m) */
123 register 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 uInt v[N_MAX]; /* values in order of bit length */
128 register int w; /* bits before this table == (l * h) */
129 uInt x[BMAX+1]; /* bit offsets, then code stack */
130 uIntf *xp; /* pointer into x */
131 int y; /* number of dummy codes added */
132 uInt z; /* number of entries in current table */
135 /* Generate counts for each bit length */
138 #define C2 C0 C0 C0 C0
139 #define C4 C2 C2 C2 C2
140 C4 /* clear c[]--assume BMAX+1 is 16 */
143 c[*p++]++; /* assume all entries <= BMAX */
145 if (c[0] == n) /* null input--all zero length codes */
147 *t = (inflate_huft *)Z_NULL;
153 /* Find minimum and maximum length, bound *m by those */
155 for (j = 1; j <= BMAX; j++)
158 k = j; /* minimum code length */
161 for (i = BMAX; i; i--)
164 g = i; /* maximum code length */
170 /* Adjust last length count to fill out codes, if needed */
171 for (y = 1 << j; j < i; j++, y <<= 1)
179 /* Generate starting offsets into the value table for each length */
181 p = c + 1; xp = x + 2;
182 while (--i) { /* note that i == g from above */
187 /* Make a table of values in order of bit lengths */
195 /* Generate the Huffman codes and for each, make the table entries */
196 x[0] = i = 0; /* first Huffman code is zero */
197 p = v; /* grab values in bit order */
198 h = -1; /* no tables yet--level -1 */
199 w = -l; /* bits decoded == (l * h) */
200 u[0] = (inflate_huft *)Z_NULL; /* just to keep compilers happy */
201 q = (inflate_huft *)Z_NULL; /* ditto */
204 /* go through the bit lengths (k already is bits in shortest code) */
210 /* here i is the Huffman code of length k bits for value *p */
211 /* make tables up to required level */
215 w += l; /* previous table always l bits */
217 /* compute minimum size table less than or equal to l bits */
219 z = z > (uInt)l ? l : z; /* table size upper limit */
220 if ((f = 1 << (j = k - w)) > a + 1) /* try a k-w bit table */
221 { /* too few codes for k-w bit table */
222 f -= a + 1; /* deduct codes from patterns left */
225 while (++j < z) /* try smaller tables up to z bits */
227 if ((f <<= 1) <= *++xp)
228 break; /* enough codes to use up j bits */
229 f -= *xp; /* else deduct codes from patterns */
232 z = 1 << j; /* table entries for j-bit table */
234 /* allocate and link in new table */
235 if ((q = (inflate_huft *)ZALLOC
236 (zs,z + 1,sizeof(inflate_huft))) == Z_NULL)
239 inflate_trees_free(u[0], zs);
240 return Z_MEM_ERROR; /* not enough memory */
243 inflate_hufts += z + 1;
245 *t = q + 1; /* link to list for huft_free() */
246 *(t = &(q->next)) = Z_NULL;
247 u[h] = ++q; /* table starts after link */
249 /* connect to last table, if there is one */
252 x[h] = i; /* save pattern for backing up */
253 r.bits = (Byte)l; /* bits to dump before this table */
254 r.exop = (Byte)j; /* bits in this table */
255 r.next = q; /* pointer to this table */
256 j = i >> (w - l); /* (get around Turbo C bug) */
257 u[h-1][j] = r; /* connect to last table */
261 /* set up table entry in r */
262 r.bits = (Byte)(k - w);
264 r.exop = 128 + 64; /* out of values--invalid code */
267 r.exop = (Byte)(*p < 256 ? 0 : 32 + 64); /* 256 is end-of-block */
268 r.base = *p++; /* simple code is just the value */
272 r.exop = (Byte)(e[*p - s] + 16 + 64);/* non-simple--look up in lists */
273 r.base = d[*p++ - s];
276 /* fill code-like entries with r */
278 for (j = i >> w; j < z; j += f)
281 /* backwards increment the k-bit code i */
282 for (j = 1 << (k - 1); i & j; j >>= 1)
286 /* backup over finished tables */
287 while ((i & ((1 << w) - 1)) != x[h])
289 h--; /* don't need to update q */
296 /* Return Z_BUF_ERROR if we were given an incomplete table */
297 return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK;
301 int inflate_trees_bits(c, bb, tb, z)
302 uIntf *c; /* 19 code lengths */
303 uIntf *bb; /* bits tree desired/actual depth */
304 inflate_huft * FAR *tb; /* bits tree result */
305 z_stream *z; /* for zfree function */
309 r = huft_build(c, 19, 19, (uIntf*)Z_NULL, (uIntf*)Z_NULL, tb, bb, z);
310 if (r == Z_DATA_ERROR)
311 z->msg = (char*)"oversubscribed dynamic bit lengths tree";
312 else if (r == Z_BUF_ERROR)
314 inflate_trees_free(*tb, z);
315 z->msg = (char*)"incomplete dynamic bit lengths tree";
322 int inflate_trees_dynamic(nl, nd, c, bl, bd, tl, td, z)
323 uInt nl; /* number of literal/length codes */
324 uInt nd; /* number of distance codes */
325 uIntf *c; /* that many (total) code lengths */
326 uIntf *bl; /* literal desired/actual bit depth */
327 uIntf *bd; /* distance desired/actual bit depth */
328 inflate_huft * FAR *tl; /* literal/length tree result */
329 inflate_huft * FAR *td; /* distance tree result */
330 z_stream *z; /* for zfree function */
334 /* build literal/length tree */
335 if ((r = huft_build(c, nl, 257, cplens, cplext, tl, bl, z)) != Z_OK)
337 if (r == Z_DATA_ERROR)
338 z->msg = (char*)"oversubscribed literal/length tree";
339 else if (r == Z_BUF_ERROR)
341 inflate_trees_free(*tl, z);
342 z->msg = (char*)"incomplete literal/length tree";
348 /* build distance tree */
349 if ((r = huft_build(c + nl, nd, 0, cpdist, cpdext, td, bd, z)) != Z_OK)
351 if (r == Z_DATA_ERROR)
352 z->msg = (char*)"oversubscribed literal/length tree";
353 else if (r == Z_BUF_ERROR) {
354 #ifdef PKZIP_BUG_WORKAROUND
358 inflate_trees_free(*td, z);
359 z->msg = (char*)"incomplete literal/length tree";
362 inflate_trees_free(*tl, z);
372 /* build fixed tables only once--keep them here */
373 local int fixed_built = 0;
374 #define FIXEDH 530 /* number of hufts used by fixed tables */
375 local inflate_huft fixed_mem[FIXEDH];
378 local inflate_huft *fixed_tl;
379 local inflate_huft *fixed_td;
382 local voidpf falloc(q, n, s)
383 voidpf q; /* opaque pointer */
384 uInt n; /* number of items */
385 uInt s; /* size of item */
387 Assert(s == sizeof(inflate_huft) && n <= *(intf *)q,
388 "inflate_trees falloc overflow");
389 *(intf *)q -= n+s-s; /* s-s to avoid warning */
390 return (voidpf)(fixed_mem + *(intf *)q);
394 int inflate_trees_fixed(bl, bd, tl, td)
395 uIntf *bl; /* literal desired/actual bit depth */
396 uIntf *bd; /* distance desired/actual bit depth */
397 inflate_huft * FAR *tl; /* literal/length tree result */
398 inflate_huft * FAR *td; /* distance tree result */
400 /* build fixed tables if not already (multiple overlapped executions ok) */
403 int k; /* temporary variable */
404 unsigned c[288]; /* length list for huft_build */
405 z_stream z; /* for falloc function */
406 int f = FIXEDH; /* number of hufts left in fixed_mem */
408 /* set up fake z_stream for memory routines */
411 z.opaque = (voidpf)&f;
414 for (k = 0; k < 144; k++)
423 huft_build(c, 288, 257, cplens, cplext, &fixed_tl, &fixed_bl, &z);
426 for (k = 0; k < 30; k++)
429 huft_build(c, 30, 0, cpdist, cpdext, &fixed_td, &fixed_bd, &z);
432 Assert(f == 0, "invalid build of fixed tables");
443 int inflate_trees_free(t, z)
444 inflate_huft *t; /* table to free */
445 z_stream *z; /* for zfree function */
446 /* Free the malloc'ed tables built by huft_build(), which makes a linked
447 list of the tables it made, with the links in a dummy first entry of
450 register inflate_huft *p, *q, *r;
452 /* Reverse linked list */
462 /* Go through linked list, freeing from the malloced (t[-1]) address. */