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wdenkae644802002-03-08 23:11:41 +00001/*-------------------------------------------------------------------------
2 * Filename: mini_inflate.c
3 * Version: $Id: mini_inflate.c,v 1.3 2002/01/24 22:58:42 rfeany Exp $
4 * Copyright: Copyright (C) 2001, Russ Dill
5 * Author: Russ Dill <Russ.Dill@asu.edu>
6 * Description: Mini inflate implementation (RFC 1951)
7 *-----------------------------------------------------------------------*/
8/*
9 *
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License as published by
12 * the Free Software Foundation; either version 2 of the License, or
13 * (at your option) any later version.
14 *
15 * This program is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 * GNU General Public License for more details.
19 *
20 * You should have received a copy of the GNU General Public License
21 * along with this program; if not, write to the Free Software
22 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
23 *
24 */
25
26#include <config.h>
wdenkae644802002-03-08 23:11:41 +000027#include <jffs2/mini_inflate.h>
28
29/* The order that the code lengths in section 3.2.7 are in */
30static unsigned char huffman_order[] = {16, 17, 18, 0, 8, 7, 9, 6, 10, 5,
31 11, 4, 12, 3, 13, 2, 14, 1, 15};
32
33inline void cramfs_memset(int *s, const int c, size n)
34{
35 n--;
36 for (;n > 0; n--) s[n] = c;
37 s[0] = c;
38}
39
40/* associate a stream with a block of data and reset the stream */
41static void init_stream(struct bitstream *stream, unsigned char *data,
42 void *(*inflate_memcpy)(void *, const void *, size))
43{
44 stream->error = NO_ERROR;
45 stream->memcpy = inflate_memcpy;
46 stream->decoded = 0;
47 stream->data = data;
48 stream->bit = 0; /* The first bit of the stream is the lsb of the
49 * first byte */
50
51 /* really sorry about all this initialization, think of a better way,
52 * let me know and it will get cleaned up */
53 stream->codes.bits = 8;
54 stream->codes.num_symbols = 19;
55 stream->codes.lengths = stream->code_lengths;
56 stream->codes.symbols = stream->code_symbols;
57 stream->codes.count = stream->code_count;
58 stream->codes.first = stream->code_first;
59 stream->codes.pos = stream->code_pos;
60
61 stream->lengths.bits = 16;
62 stream->lengths.num_symbols = 288;
63 stream->lengths.lengths = stream->length_lengths;
64 stream->lengths.symbols = stream->length_symbols;
65 stream->lengths.count = stream->length_count;
66 stream->lengths.first = stream->length_first;
67 stream->lengths.pos = stream->length_pos;
68
69 stream->distance.bits = 16;
70 stream->distance.num_symbols = 32;
71 stream->distance.lengths = stream->distance_lengths;
72 stream->distance.symbols = stream->distance_symbols;
73 stream->distance.count = stream->distance_count;
74 stream->distance.first = stream->distance_first;
75 stream->distance.pos = stream->distance_pos;
76
77}
78
79/* pull 'bits' bits out of the stream. The last bit pulled it returned as the
80 * msb. (section 3.1.1)
81 */
82inline unsigned long pull_bits(struct bitstream *stream,
83 const unsigned int bits)
84{
85 unsigned long ret;
86 int i;
87
88 ret = 0;
89 for (i = 0; i < bits; i++) {
90 ret += ((*(stream->data) >> stream->bit) & 1) << i;
91
92 /* if, before incrementing, we are on bit 7,
93 * go to the lsb of the next byte */
94 if (stream->bit++ == 7) {
95 stream->bit = 0;
96 stream->data++;
97 }
98 }
99 return ret;
100}
101
102inline int pull_bit(struct bitstream *stream)
103{
104 int ret = ((*(stream->data) >> stream->bit) & 1);
105 if (stream->bit++ == 7) {
106 stream->bit = 0;
107 stream->data++;
108 }
109 return ret;
110}
111
112/* discard bits up to the next whole byte */
113static void discard_bits(struct bitstream *stream)
114{
115 if (stream->bit != 0) {
116 stream->bit = 0;
117 stream->data++;
118 }
119}
120
121/* No decompression, the data is all literals (section 3.2.4) */
122static void decompress_none(struct bitstream *stream, unsigned char *dest)
123{
124 unsigned int length;
125
126 discard_bits(stream);
127 length = *(stream->data++);
128 length += *(stream->data++) << 8;
129 pull_bits(stream, 16); /* throw away the inverse of the size */
130
131 stream->decoded += length;
132 stream->memcpy(dest, stream->data, length);
133 stream->data += length;
134}
135
136/* Read in a symbol from the stream (section 3.2.2) */
137static int read_symbol(struct bitstream *stream, struct huffman_set *set)
138{
139 int bits = 0;
140 int code = 0;
141 while (!(set->count[bits] && code < set->first[bits] +
142 set->count[bits])) {
143 code = (code << 1) + pull_bit(stream);
144 if (++bits > set->bits) {
145 /* error decoding (corrupted data?) */
146 stream->error = CODE_NOT_FOUND;
147 return -1;
148 }
149 }
150 return set->symbols[set->pos[bits] + code - set->first[bits]];
151}
152
153/* decompress a stream of data encoded with the passed length and distance
154 * huffman codes */
155static void decompress_huffman(struct bitstream *stream, unsigned char *dest)
156{
157 struct huffman_set *lengths = &(stream->lengths);
158 struct huffman_set *distance = &(stream->distance);
159
160 int symbol, length, dist, i;
161
162 do {
163 if ((symbol = read_symbol(stream, lengths)) < 0) return;
164 if (symbol < 256) {
165 *(dest++) = symbol; /* symbol is a literal */
166 stream->decoded++;
167 } else if (symbol > 256) {
168 /* Determine the length of the repitition
169 * (section 3.2.5) */
170 if (symbol < 265) length = symbol - 254;
171 else if (symbol == 285) length = 258;
172 else {
173 length = pull_bits(stream, (symbol - 261) >> 2);
174 length += (4 << ((symbol - 261) >> 2)) + 3;
175 length += ((symbol - 1) % 4) <<
176 ((symbol - 261) >> 2);
177 }
178
179 /* Determine how far back to go */
180 if ((symbol = read_symbol(stream, distance)) < 0)
181 return;
182 if (symbol < 4) dist = symbol + 1;
183 else {
184 dist = pull_bits(stream, (symbol - 2) >> 1);
185 dist += (2 << ((symbol - 2) >> 1)) + 1;
186 dist += (symbol % 2) << ((symbol - 2) >> 1);
187 }
188 stream->decoded += length;
189 for (i = 0; i < length; i++) {
190 *dest = dest[-dist];
191 dest++;
192 }
193 }
194 } while (symbol != 256); /* 256 is the end of the data block */
195}
196
197/* Fill the lookup tables (section 3.2.2) */
198static void fill_code_tables(struct huffman_set *set)
199{
200 int code = 0, i, length;
201
202 /* fill in the first code of each bit length, and the pos pointer */
203 set->pos[0] = 0;
204 for (i = 1; i < set->bits; i++) {
205 code = (code + set->count[i - 1]) << 1;
206 set->first[i] = code;
207 set->pos[i] = set->pos[i - 1] + set->count[i - 1];
208 }
209
210 /* Fill in the table of symbols in order of their huffman code */
211 for (i = 0; i < set->num_symbols; i++) {
212 if ((length = set->lengths[i]))
213 set->symbols[set->pos[length]++] = i;
214 }
215
216 /* reset the pos pointer */
217 for (i = 1; i < set->bits; i++) set->pos[i] -= set->count[i];
218}
219
220static void init_code_tables(struct huffman_set *set)
221{
222 cramfs_memset(set->lengths, 0, set->num_symbols);
223 cramfs_memset(set->count, 0, set->bits);
224 cramfs_memset(set->first, 0, set->bits);
225}
226
227/* read in the huffman codes for dynamic decoding (section 3.2.7) */
228static void decompress_dynamic(struct bitstream *stream, unsigned char *dest)
229{
230 /* I tried my best to minimize the memory footprint here, while still
231 * keeping up performance. I really dislike the _lengths[] tables, but
232 * I see no way of eliminating them without a sizable performance
233 * impact. The first struct table keeps track of stats on each bit
234 * length. The _length table keeps a record of the bit length of each
235 * symbol. The _symbols table is for looking up symbols by the huffman
236 * code (the pos element points to the first place in the symbol table
237 * where that bit length occurs). I also hate the initization of these
238 * structs, if someone knows how to compact these, lemme know. */
239
240 struct huffman_set *codes = &(stream->codes);
241 struct huffman_set *lengths = &(stream->lengths);
242 struct huffman_set *distance = &(stream->distance);
243
244 int hlit = pull_bits(stream, 5) + 257;
245 int hdist = pull_bits(stream, 5) + 1;
246 int hclen = pull_bits(stream, 4) + 4;
247 int length, curr_code, symbol, i, last_code;
248
249 last_code = 0;
250
251 init_code_tables(codes);
252 init_code_tables(lengths);
253 init_code_tables(distance);
254
255 /* fill in the count of each bit length' as well as the lengths
256 * table */
257 for (i = 0; i < hclen; i++) {
258 length = pull_bits(stream, 3);
259 codes->lengths[huffman_order[i]] = length;
260 if (length) codes->count[length]++;
261
262 }
263 fill_code_tables(codes);
264
265 /* Do the same for the length codes, being carefull of wrap through
266 * to the distance table */
267 curr_code = 0;
268 while (curr_code < hlit) {
269 if ((symbol = read_symbol(stream, codes)) < 0) return;
270 if (symbol == 0) {
271 curr_code++;
272 last_code = 0;
273 } else if (symbol < 16) { /* Literal length */
274 lengths->lengths[curr_code] = last_code = symbol;
275 lengths->count[symbol]++;
276 curr_code++;
277 } else if (symbol == 16) { /* repeat the last symbol 3 - 6
278 * times */
279 length = 3 + pull_bits(stream, 2);
280 for (;length; length--, curr_code++)
281 if (curr_code < hlit) {
282 lengths->lengths[curr_code] =
283 last_code;
284 lengths->count[last_code]++;
285 } else { /* wrap to the distance table */
286 distance->lengths[curr_code - hlit] =
287 last_code;
288 distance->count[last_code]++;
289 }
290 } else if (symbol == 17) { /* repeat a bit length 0 */
291 curr_code += 3 + pull_bits(stream, 3);
292 last_code = 0;
293 } else { /* same, but more times */
294 curr_code += 11 + pull_bits(stream, 7);
295 last_code = 0;
296 }
297 }
298 fill_code_tables(lengths);
299
300 /* Fill the distance table, don't need to worry about wrapthrough
301 * here */
302 curr_code -= hlit;
303 while (curr_code < hdist) {
304 if ((symbol = read_symbol(stream, codes)) < 0) return;
305 if (symbol == 0) {
306 curr_code++;
307 last_code = 0;
308 } else if (symbol < 16) {
309 distance->lengths[curr_code] = last_code = symbol;
310 distance->count[symbol]++;
311 curr_code++;
312 } else if (symbol == 16) {
313 length = 3 + pull_bits(stream, 2);
314 for (;length; length--, curr_code++) {
315 distance->lengths[curr_code] =
316 last_code;
317 distance->count[last_code]++;
318 }
319 } else if (symbol == 17) {
320 curr_code += 3 + pull_bits(stream, 3);
321 last_code = 0;
322 } else {
323 curr_code += 11 + pull_bits(stream, 7);
324 last_code = 0;
325 }
326 }
327 fill_code_tables(distance);
328
329 decompress_huffman(stream, dest);
330}
331
332/* fill in the length and distance huffman codes for fixed encoding
333 * (section 3.2.6) */
334static void decompress_fixed(struct bitstream *stream, unsigned char *dest)
335{
336 /* let gcc fill in the initial values */
337 struct huffman_set *lengths = &(stream->lengths);
338 struct huffman_set *distance = &(stream->distance);
339
340 cramfs_memset(lengths->count, 0, 16);
341 cramfs_memset(lengths->first, 0, 16);
342 cramfs_memset(lengths->lengths, 8, 144);
343 cramfs_memset(lengths->lengths + 144, 9, 112);
344 cramfs_memset(lengths->lengths + 256, 7, 24);
345 cramfs_memset(lengths->lengths + 280, 8, 8);
346 lengths->count[7] = 24;
347 lengths->count[8] = 152;
348 lengths->count[9] = 112;
349
350 cramfs_memset(distance->count, 0, 16);
351 cramfs_memset(distance->first, 0, 16);
352 cramfs_memset(distance->lengths, 5, 32);
353 distance->count[5] = 32;
354
355
356 fill_code_tables(lengths);
357 fill_code_tables(distance);
358
359
360 decompress_huffman(stream, dest);
361}
362
363/* returns the number of bytes decoded, < 0 if there was an error. Note that
364 * this function assumes that the block starts on a byte boundry
365 * (non-compliant, but I don't see where this would happen). section 3.2.3 */
366long decompress_block(unsigned char *dest, unsigned char *source,
367 void *(*inflate_memcpy)(void *, const void *, size))
368{
369 int bfinal, btype;
370 struct bitstream stream;
371
372 init_stream(&stream, source, inflate_memcpy);
373 do {
374 bfinal = pull_bit(&stream);
375 btype = pull_bits(&stream, 2);
376 if (btype == NO_COMP) decompress_none(&stream, dest + stream.decoded);
377 else if (btype == DYNAMIC_COMP)
378 decompress_dynamic(&stream, dest + stream.decoded);
379 else if (btype == FIXED_COMP) decompress_fixed(&stream, dest + stream.decoded);
380 else stream.error = COMP_UNKNOWN;
381 } while (!bfinal && !stream.error);
382
383#if 0
384 putstr("decompress_block start\r\n");
385 putLabeledWord("stream.error = ",stream.error);
386 putLabeledWord("stream.decoded = ",stream.decoded);
387 putLabeledWord("dest = ",dest);
388 putstr("decompress_block end\r\n");
389#endif
390 return stream.error ? -stream.error : stream.decoded;
391}