1 /* 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
10 static const char inflate_copyright[] =
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 */
18 struct 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
25 local int huft_build OF((
26 uIntf *, /* code lengths in bits */
27 uInt, /* number of codes */
28 uInt, /* number of "simple" codes */
29 const uIntf *, /* list of base values for non-simple codes */
30 const uIntf *, /* list of extra bits for non-simple codes */
31 inflate_huft * FAR*,/* result: starting table */
32 uIntf *, /* maximum lookup bits (returns actual) */
33 inflate_huft *, /* space for trees */
34 uInt *, /* hufts used in space */
35 uIntf * )); /* space for values */
36
37 /* Tables for deflate from PKZIP's appnote.txt. */
38 local 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 */
42 local 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 */
45 local 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};
49 local 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
huft_build(b,n,s,d,e,t,m,hp,hn,v)90 local int huft_build(b, n, s, d, e, t, m, hp, hn, v)
91 uIntf *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 uIntf *d; /* list of base values for non-simple codes */
95 const uIntf *e; /* list of extra bits for non-simple codes */
96 inflate_huft * FAR *t; /* result: starting table */
97 uIntf *m; /* maximum lookup bits, returns actual */
98 inflate_huft *hp; /* space for trees */
99 uInt *hn; /* hufts used in space */
100 uIntf *v; /* working area: values in order of bit length */
101 /* Given a list of code lengths and a maximum table size, make a set of
102 tables to decode that set of codes. Return Z_OK on success, Z_BUF_ERROR
103 if the given code set is incomplete (the tables are still built in this
104 case), Z_DATA_ERROR if the input is invalid (an over-subscribed set of
105 lengths), or Z_MEM_ERROR if not enough memory. */
106 {
107
108 uInt a; /* counter for codes of length k */
109 uInt c[BMAX+1]; /* bit length count table */
110 uInt f; /* i repeats in table every f entries */
111 int g; /* maximum code length */
112 int h; /* table level */
113 register uInt i; /* counter, current code */
114 register uInt j; /* counter */
115 register int k; /* number of bits in current code */
116 int l; /* bits per table (returned in m) */
117 uInt mask; /* (1 << w) - 1, to avoid cc -O bug on HP */
118 register uIntf *p; /* pointer into c[], b[], or v[] */
119 inflate_huft *q; /* points to current table */
120 struct inflate_huft_s r; /* table entry for structure assignment */
121 inflate_huft *u[BMAX]; /* table stack */
122 register int w; /* bits before this table == (l * h) */
123 uInt x[BMAX+1]; /* bit offsets, then code stack */
124 uIntf *xp; /* pointer into x */
125 int y; /* number of dummy codes added */
126 uInt z; /* number of entries in current table */
127
128
129 /* Generate counts for each bit length */
130 p = c;
131 #define C0 *p++ = 0;
132 #define C2 C0 C0 C0 C0
133 #define C4 C2 C2 C2 C2
134 C4 /* clear c[]--assume BMAX+1 is 16 */
135 p = b; i = n;
136 do {
137 c[*p++]++; /* assume all entries <= BMAX */
138 } while (--i);
139 if (c[0] == n) /* null input--all zero length codes */
140 {
141 *t = (inflate_huft *)Z_NULL;
142 *m = 0;
143 return Z_OK;
144 }
145
146
147 /* Find minimum and maximum length, bound *m by those */
148 l = *m;
149 for (j = 1; j <= BMAX; j++)
150 if (c[j])
151 break;
152 k = j; /* minimum code length */
153 if ((uInt)l < j)
154 l = j;
155 for (i = BMAX; i; i--)
156 if (c[i])
157 break;
158 g = i; /* maximum code length */
159 if ((uInt)l > i)
160 l = i;
161 *m = l;
162
163
164 /* Adjust last length count to fill out codes, if needed */
165 for (y = 1 << j; j < i; j++, y <<= 1)
166 if ((y -= c[j]) < 0)
167 return Z_DATA_ERROR;
168 if ((y -= c[i]) < 0)
169 return Z_DATA_ERROR;
170 c[i] += y;
171
172
173 /* Generate starting offsets into the value table for each length */
174 x[1] = j = 0;
175 p = c + 1; xp = x + 2;
176 while (--i) { /* note that i == g from above */
177 *xp++ = (j += *p++);
178 }
179
180
181 /* Make a table of values in order of bit lengths */
182 p = b; i = 0;
183 do {
184 if ((j = *p++) != 0)
185 v[x[j]++] = i;
186 } while (++i < n);
187 n = x[g]; /* set n to length of v */
188
189
190 /* Generate the Huffman codes and for each, make the table entries */
191 x[0] = i = 0; /* first Huffman code is zero */
192 p = v; /* grab values in bit order */
193 h = -1; /* no tables yet--level -1 */
194 w = -l; /* bits decoded == (l * h) */
195 u[0] = (inflate_huft *)Z_NULL; /* just to keep compilers happy */
196 q = (inflate_huft *)Z_NULL; /* ditto */
197 z = 0; /* ditto */
198
199 /* go through the bit lengths (k already is bits in shortest code) */
200 for (; k <= g; k++)
201 {
202 a = c[k];
203 while (a--)
204 {
205 /* here i is the Huffman code of length k bits for value *p */
206 /* make tables up to required level */
207 while (k > w + l)
208 {
209 h++;
210 w += l; /* previous table always l bits */
211
212 /* compute minimum size table less than or equal to l bits */
213 z = g - w;
214 z = z > (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 new table */
230 if (*hn + z > MANY) /* (note: doesn't matter for fixed) */
231 return Z_MEM_ERROR; /* not enough memory */
232 u[h] = q = hp + *hn;
233 *hn += z;
234
235 /* connect to last table, if there is one */
236 if (h)
237 {
238 x[h] = i; /* save pattern for backing up */
239 r.bits = (Byte)l; /* bits to dump before this table */
240 r.exop = (Byte)j; /* bits in this table */
241 j = i >> (w - l);
242 r.base = (uInt)(q - u[h-1] - j); /* offset to this table */
243 u[h-1][j] = r; /* connect to last table */
244 }
245 else
246 *t = q; /* first table is returned result */
247 }
248
249 /* set up table entry in r */
250 r.bits = (Byte)(k - w);
251 if (p >= v + n)
252 r.exop = 128 + 64; /* out of values--invalid code */
253 else if (*p < s)
254 {
255 r.exop = (Byte)(*p < 256 ? 0 : 32 + 64); /* 256 is end-of-block */
256 r.base = *p++; /* simple code is just the value */
257 }
258 else
259 {
260 r.exop = (Byte)(e[*p - s] + 16 + 64);/* non-simple--look up in lists */
261 r.base = d[*p++ - s];
262 }
263
264 /* fill code-like entries with r */
265 f = 1 << (k - w);
266 for (j = i >> w; j < z; j += f)
267 q[j] = r;
268
269 /* backwards increment the k-bit code i */
270 for (j = 1 << (k - 1); i & j; j >>= 1)
271 i ^= j;
272 i ^= j;
273
274 /* backup over finished tables */
275 mask = (1 << w) - 1; /* needed on HP, cc -O bug */
276 while ((i & mask) != x[h])
277 {
278 h--; /* don't need to update q */
279 w -= l;
280 mask = (1 << w) - 1;
281 }
282 }
283 }
284
285
286 /* Return Z_BUF_ERROR if we were given an incomplete table */
287 return y != 0 && g != 1 ? Z_BUF_ERROR : Z_OK;
288 }
289
290
zlib_inflate_trees_bits(c,bb,tb,hp,z)291 int zlib_inflate_trees_bits(c, bb, tb, hp, z)
292 uIntf *c; /* 19 code lengths */
293 uIntf *bb; /* bits tree desired/actual depth */
294 inflate_huft * FAR *tb; /* bits tree result */
295 inflate_huft *hp; /* space for trees */
296 z_streamp z; /* for messages */
297 {
298 int r;
299 uInt hn = 0; /* hufts used in space */
300 uIntf *v; /* work area for huft_build */
301
302 v = WS(z)->tree_work_area_1;
303 r = huft_build(c, 19, 19, (uIntf*)Z_NULL, (uIntf*)Z_NULL,
304 tb, bb, hp, &hn, v);
305 if (r == Z_DATA_ERROR)
306 z->msg = (char*)"oversubscribed dynamic bit lengths tree";
307 else if (r == Z_BUF_ERROR || *bb == 0)
308 {
309 z->msg = (char*)"incomplete dynamic bit lengths tree";
310 r = Z_DATA_ERROR;
311 }
312 return r;
313 }
314
zlib_inflate_trees_dynamic(nl,nd,c,bl,bd,tl,td,hp,z)315 int zlib_inflate_trees_dynamic(nl, nd, c, bl, bd, tl, td, hp, z)
316 uInt nl; /* number of literal/length codes */
317 uInt nd; /* number of distance codes */
318 uIntf *c; /* that many (total) code lengths */
319 uIntf *bl; /* literal desired/actual bit depth */
320 uIntf *bd; /* distance desired/actual bit depth */
321 inflate_huft * FAR *tl; /* literal/length tree result */
322 inflate_huft * FAR *td; /* distance tree result */
323 inflate_huft *hp; /* space for trees */
324 z_streamp z; /* for messages */
325 {
326 int r;
327 uInt hn = 0; /* hufts used in space */
328 uIntf *v; /* work area for huft_build */
329
330 /* allocate work area */
331 v = WS(z)->tree_work_area_2;
332
333 /* build literal/length tree */
334 r = huft_build(c, nl, 257, cplens, cplext, tl, bl, hp, &hn, v);
335 if (r != Z_OK || *bl == 0)
336 {
337 if (r == Z_DATA_ERROR)
338 z->msg = (char*)"oversubscribed literal/length tree";
339 else if (r != Z_MEM_ERROR)
340 {
341 z->msg = (char*)"incomplete literal/length tree";
342 r = Z_DATA_ERROR;
343 }
344 return r;
345 }
346
347 /* build distance tree */
348 r = huft_build(c + nl, nd, 0, cpdist, cpdext, td, bd, hp, &hn, v);
349 if (r != Z_OK || (*bd == 0 && nl > 257))
350 {
351 if (r == Z_DATA_ERROR)
352 z->msg = (char*)"oversubscribed distance tree";
353 else if (r == Z_BUF_ERROR) {
354 #ifdef PKZIP_BUG_WORKAROUND
355 r = Z_OK;
356 }
357 #else
358 z->msg = (char*)"incomplete distance tree";
359 r = Z_DATA_ERROR;
360 }
361 else if (r != Z_MEM_ERROR)
362 {
363 z->msg = (char*)"empty distance tree with lengths";
364 r = Z_DATA_ERROR;
365 }
366 return r;
367 #endif
368 }
369
370 /* done */
371 return Z_OK;
372 }
373
374
375 /* build fixed tables only once--keep them here */
376 #include "inffixed.h"
377
378
zlib_inflate_trees_fixed(bl,bd,tl,td,z)379 int zlib_inflate_trees_fixed(bl, bd, tl, td, z)
380 uIntf *bl; /* literal desired/actual bit depth */
381 uIntf *bd; /* distance desired/actual bit depth */
382 inflate_huft * FAR *tl; /* literal/length tree result */
383 inflate_huft * FAR *td; /* distance tree result */
384 z_streamp z; /* for memory allocation */
385 {
386 *bl = fixed_bl;
387 *bd = fixed_bd;
388 *tl = fixed_tl;
389 *td = fixed_td;
390 return Z_OK;
391 }
392