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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* inftrees.c -- generate Huffman trees for efficient decoding
2 * Copyright (C) 1995-1998 Mark Adler
3 * For conditions of distribution and use, see copyright notice in zlib.h
4 */
5
6#include <linux/zutil.h>
7#include "inftrees.h"
8#include "infutil.h"
9
10static const char inflate_copyright[] __attribute_used__ =
11 " inflate 1.1.3 Copyright 1995-1998 Mark Adler ";
12/*
13 If you use the zlib library in a product, an acknowledgment is welcome
14 in the documentation of your product. If for some reason you cannot
15 include such an acknowledgment, I would appreciate that you keep this
16 copyright string in the executable of your product.
17 */
18struct internal_state;
19
20/* simplify the use of the inflate_huft type with some defines */
21#define exop word.what.Exop
22#define bits word.what.Bits
23
24
25static int huft_build (
26 uInt *, /* code lengths in bits */
27 uInt, /* number of codes */
28 uInt, /* number of "simple" codes */
29 const uInt *, /* list of base values for non-simple codes */
30 const uInt *, /* list of extra bits for non-simple codes */
31 inflate_huft **, /* result: starting table */
32 uInt *, /* maximum lookup bits (returns actual) */
33 inflate_huft *, /* space for trees */
34 uInt *, /* hufts used in space */
35 uInt * ); /* space for values */
36
37/* Tables for deflate from PKZIP's appnote.txt. */
38static const uInt cplens[31] = { /* 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 /* see note #13 above about 258 */
42static const uInt cplext[31] = { /* 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, 112, 112}; /* 112==invalid */
45static const uInt cpdist[30] = { /* 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};
49static const uInt cpdext[30] = { /* 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
90static int huft_build(
91 uInt *b, /* code lengths in bits (all assumed <= BMAX) */
92 uInt n, /* number of codes (assumed <= 288) */
93 uInt s, /* number of simple-valued codes (0..s-1) */
94 const uInt *d, /* list of base values for non-simple codes */
95 const uInt *e, /* list of extra bits for non-simple codes */
96 inflate_huft **t, /* result: starting table */
97 uInt *m, /* maximum lookup bits, returns actual */
98 inflate_huft *hp, /* space for trees */
99 uInt *hn, /* hufts used in space */
100 uInt *v /* working area: values in order of bit length */
101)
102/* Given a list of code lengths and a maximum table size, make a set of
103 tables to decode that set of codes. Return Z_OK on success, Z_BUF_ERROR
104 if the given code set is incomplete (the tables are still built in this
105 case), Z_DATA_ERROR if the input is invalid (an over-subscribed set of
106 lengths), or Z_MEM_ERROR if not enough memory. */
107{
108
109 uInt a; /* counter for codes of length k */
110 uInt c[BMAX+1]; /* bit length count table */
111 uInt f; /* i repeats in table every f entries */
112 int g; /* maximum code length */
113 int h; /* table level */
114 register uInt i; /* counter, current code */
115 register uInt j; /* counter */
116 register int k; /* number of bits in current code */
117 int l; /* bits per table (returned in m) */
118 uInt mask; /* (1 << w) - 1, to avoid cc -O bug on HP */
119 register uInt *p; /* pointer into c[], b[], or v[] */
120 inflate_huft *q; /* points to current table */
121 struct inflate_huft_s r; /* table entry for structure assignment */
122 inflate_huft *u[BMAX]; /* table stack */
123 register int w; /* bits before this table == (l * h) */
124 uInt x[BMAX+1]; /* bit offsets, then code stack */
125 uInt *xp; /* pointer into x */
126 int y; /* number of dummy codes added */
127 uInt z; /* number of entries in current table */
128
129
130 /* Generate counts for each bit length */
131 p = c;
132#define C0 *p++ = 0;
133#define C2 C0 C0 C0 C0
134#define C4 C2 C2 C2 C2
135 C4 /* clear c[]--assume BMAX+1 is 16 */
136 p = b; i = n;
137 do {
138 c[*p++]++; /* assume all entries <= BMAX */
139 } while (--i);
140 if (c[0] == n) /* null input--all zero length codes */
141 {
142 *t = NULL;
143 *m = 0;
Linus Torvaldsc231c7db2005-08-17 13:07:28 -0700144 return Z_OK;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700145 }
146
147
148 /* Find minimum and maximum length, bound *m by those */
149 l = *m;
150 for (j = 1; j <= BMAX; j++)
151 if (c[j])
152 break;
153 k = j; /* minimum code length */
154 if ((uInt)l < j)
155 l = j;
156 for (i = BMAX; i; i--)
157 if (c[i])
158 break;
159 g = i; /* maximum code length */
160 if ((uInt)l > i)
161 l = i;
162 *m = l;
163
164
165 /* Adjust last length count to fill out codes, if needed */
166 for (y = 1 << j; j < i; j++, y <<= 1)
167 if ((y -= c[j]) < 0)
168 return Z_DATA_ERROR;
169 if ((y -= c[i]) < 0)
170 return Z_DATA_ERROR;
171 c[i] += y;
172
173
174 /* Generate starting offsets into the value table for each length */
175 x[1] = j = 0;
176 p = c + 1; xp = x + 2;
177 while (--i) { /* note that i == g from above */
178 *xp++ = (j += *p++);
179 }
180
181
182 /* Make a table of values in order of bit lengths */
183 p = b; i = 0;
184 do {
185 if ((j = *p++) != 0)
186 v[x[j]++] = i;
187 } while (++i < n);
188 n = x[g]; /* set n to length of v */
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] = NULL; /* just to keep compilers happy */
197 q = 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 = g - w;
215 z = z > (uInt)l ? l : z; /* table size upper limit */
216 if ((f = 1 << (j = k - w)) > a + 1) /* try a k-w bit table */
217 { /* too few codes for k-w bit table */
218 f -= a + 1; /* deduct codes from patterns left */
219 xp = c + k;
220 if (j < z)
221 while (++j < z) /* try smaller tables up to z bits */
222 {
223 if ((f <<= 1) <= *++xp)
224 break; /* enough codes to use up j bits */
225 f -= *xp; /* else deduct codes from patterns */
226 }
227 }
228 z = 1 << j; /* table entries for j-bit table */
229
230 /* allocate new table */
231 if (*hn + z > MANY) /* (note: doesn't matter for fixed) */
232 return Z_DATA_ERROR; /* overflow of MANY */
233 u[h] = q = hp + *hn;
234 *hn += z;
235
236 /* connect to last table, if there is one */
237 if (h)
238 {
239 x[h] = i; /* save pattern for backing up */
240 r.bits = (Byte)l; /* bits to dump before this table */
241 r.exop = (Byte)j; /* bits in this table */
242 j = i >> (w - l);
243 r.base = (uInt)(q - u[h-1] - j); /* offset to this table */
244 u[h-1][j] = r; /* connect to last table */
245 }
246 else
247 *t = q; /* first table is returned result */
248 }
249
250 /* set up table entry in r */
251 r.bits = (Byte)(k - w);
252 if (p >= v + n)
253 r.exop = 128 + 64; /* out of values--invalid code */
254 else if (*p < s)
255 {
256 r.exop = (Byte)(*p < 256 ? 0 : 32 + 64); /* 256 is end-of-block */
257 r.base = *p++; /* simple code is just the value */
258 }
259 else
260 {
261 r.exop = (Byte)(e[*p - s] + 16 + 64);/* non-simple--look up in lists */
262 r.base = d[*p++ - s];
263 }
264
265 /* fill code-like entries with r */
266 f = 1 << (k - w);
267 for (j = i >> w; j < z; j += f)
268 q[j] = r;
269
270 /* backwards increment the k-bit code i */
271 for (j = 1 << (k - 1); i & j; j >>= 1)
272 i ^= j;
273 i ^= j;
274
275 /* backup over finished tables */
276 mask = (1 << w) - 1; /* needed on HP, cc -O bug */
277 while ((i & mask) != x[h])
278 {
279 h--; /* don't need to update q */
280 w -= l;
281 mask = (1 << w) - 1;
282 }
283 }
284 }
285
286
287 /* Return Z_BUF_ERROR if we were given an incomplete table */
288 return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK;
289}
290
291
292int zlib_inflate_trees_bits(
293 uInt *c, /* 19 code lengths */
294 uInt *bb, /* bits tree desired/actual depth */
295 inflate_huft **tb, /* bits tree result */
296 inflate_huft *hp, /* space for trees */
297 z_streamp z /* for messages */
298)
299{
300 int r;
301 uInt hn = 0; /* hufts used in space */
302 uInt *v; /* work area for huft_build */
303
304 v = WS(z)->tree_work_area_1;
305 r = huft_build(c, 19, 19, NULL, NULL, tb, bb, hp, &hn, v);
306 if (r == Z_DATA_ERROR)
307 z->msg = (char*)"oversubscribed dynamic bit lengths tree";
308 else if (r == Z_BUF_ERROR || *bb == 0)
309 {
310 z->msg = (char*)"incomplete dynamic bit lengths tree";
311 r = Z_DATA_ERROR;
312 }
313 return r;
314}
315
316int zlib_inflate_trees_dynamic(
317 uInt nl, /* number of literal/length codes */
318 uInt nd, /* number of distance codes */
319 uInt *c, /* that many (total) code lengths */
320 uInt *bl, /* literal desired/actual bit depth */
321 uInt *bd, /* distance desired/actual bit depth */
322 inflate_huft **tl, /* literal/length tree result */
323 inflate_huft **td, /* distance tree result */
324 inflate_huft *hp, /* space for trees */
325 z_streamp z /* for messages */
326)
327{
328 int r;
329 uInt hn = 0; /* hufts used in space */
330 uInt *v; /* work area for huft_build */
331
332 /* allocate work area */
333 v = WS(z)->tree_work_area_2;
334
335 /* build literal/length tree */
336 r = huft_build(c, nl, 257, cplens, cplext, tl, bl, hp, &hn, v);
337 if (r != Z_OK || *bl == 0)
338 {
339 if (r == Z_DATA_ERROR)
340 z->msg = (char*)"oversubscribed literal/length tree";
341 else if (r != Z_MEM_ERROR)
342 {
343 z->msg = (char*)"incomplete literal/length tree";
344 r = Z_DATA_ERROR;
345 }
346 return r;
347 }
348
349 /* build distance tree */
350 r = huft_build(c + nl, nd, 0, cpdist, cpdext, td, bd, hp, &hn, v);
351 if (r != Z_OK || (*bd == 0 && nl > 257))
352 {
353 if (r == Z_DATA_ERROR)
354 z->msg = (char*)"oversubscribed distance tree";
355 else if (r == Z_BUF_ERROR) {
356#ifdef PKZIP_BUG_WORKAROUND
357 r = Z_OK;
358 }
359#else
360 z->msg = (char*)"incomplete distance tree";
361 r = Z_DATA_ERROR;
362 }
363 else if (r != Z_MEM_ERROR)
364 {
365 z->msg = (char*)"empty distance tree with lengths";
366 r = Z_DATA_ERROR;
367 }
368 return r;
369#endif
370 }
371
372 /* done */
373 return Z_OK;
374}
375
376
377int zlib_inflate_trees_fixed(
378 uInt *bl, /* literal desired/actual bit depth */
379 uInt *bd, /* distance desired/actual bit depth */
380 inflate_huft **tl, /* literal/length tree result */
381 inflate_huft **td, /* distance tree result */
382 inflate_huft *hp, /* space for trees */
383 z_streamp z /* for memory allocation */
384)
385{
386 int i; /* temporary variable */
387 unsigned l[288]; /* length list for huft_build */
388 uInt *v; /* work area for huft_build */
389
390 /* set up literal table */
391 for (i = 0; i < 144; i++)
392 l[i] = 8;
393 for (; i < 256; i++)
394 l[i] = 9;
395 for (; i < 280; i++)
396 l[i] = 7;
397 for (; i < 288; i++) /* make a complete, but wrong code set */
398 l[i] = 8;
399 *bl = 9;
400 v = WS(z)->tree_work_area_1;
401 if ((i = huft_build(l, 288, 257, cplens, cplext, tl, bl, hp, &i, v)) != 0)
402 return i;
403
404 /* set up distance table */
405 for (i = 0; i < 30; i++) /* make an incomplete code set */
406 l[i] = 5;
407 *bd = 5;
408 if ((i = huft_build(l, 30, 0, cpdist, cpdext, td, bd, hp, &i, v)) > 1)
409 return i;
410
411 return Z_OK;
412}