1 /*-------------------------------------------------------------------------
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 *-----------------------------------------------------------------------*/
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.
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.
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
27 #include <jffs2/mini_inflate.h>
29 /* The order that the code lengths in section 3.2.7 are in */
30 static unsigned char huffman_order[] = {16, 17, 18, 0, 8, 7, 9, 6, 10, 5,
31 11, 4, 12, 3, 13, 2, 14, 1, 15};
33 inline void cramfs_memset(int *s, const int c, size n)
36 for (;n > 0; n--) s[n] = c;
40 /* associate a stream with a block of data and reset the stream */
41 static void init_stream(struct bitstream *stream, unsigned char *data,
42 void *(*inflate_memcpy)(void *, const void *, size))
44 stream->error = NO_ERROR;
45 stream->memcpy = inflate_memcpy;
48 stream->bit = 0; /* The first bit of the stream is the lsb of the
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;
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;
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;
79 /* pull 'bits' bits out of the stream. The last bit pulled it returned as the
80 * msb. (section 3.1.1)
82 inline unsigned long pull_bits(struct bitstream *stream,
83 const unsigned int bits)
89 for (i = 0; i < bits; i++) {
90 ret += ((*(stream->data) >> stream->bit) & 1) << i;
92 /* if, before incrementing, we are on bit 7,
93 * go to the lsb of the next byte */
94 if (stream->bit++ == 7) {
102 inline int pull_bit(struct bitstream *stream)
104 int ret = ((*(stream->data) >> stream->bit) & 1);
105 if (stream->bit++ == 7) {
112 /* discard bits up to the next whole byte */
113 static void discard_bits(struct bitstream *stream)
115 if (stream->bit != 0) {
121 /* No decompression, the data is all literals (section 3.2.4) */
122 static void decompress_none(struct bitstream *stream, unsigned char *dest)
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 */
131 stream->decoded += length;
132 stream->memcpy(dest, stream->data, length);
133 stream->data += length;
136 /* Read in a symbol from the stream (section 3.2.2) */
137 static int read_symbol(struct bitstream *stream, struct huffman_set *set)
141 while (!(set->count[bits] && code < set->first[bits] +
143 code = (code << 1) + pull_bit(stream);
144 if (++bits > set->bits) {
145 /* error decoding (corrupted data?) */
146 stream->error = CODE_NOT_FOUND;
150 return set->symbols[set->pos[bits] + code - set->first[bits]];
153 /* decompress a stream of data encoded with the passed length and distance
155 static void decompress_huffman(struct bitstream *stream, unsigned char *dest)
157 struct huffman_set *lengths = &(stream->lengths);
158 struct huffman_set *distance = &(stream->distance);
160 int symbol, length, dist, i;
163 if ((symbol = read_symbol(stream, lengths)) < 0) return;
165 *(dest++) = symbol; /* symbol is a literal */
167 } else if (symbol > 256) {
168 /* Determine the length of the repitition
170 if (symbol < 265) length = symbol - 254;
171 else if (symbol == 285) length = 258;
173 length = pull_bits(stream, (symbol - 261) >> 2);
174 length += (4 << ((symbol - 261) >> 2)) + 3;
175 length += ((symbol - 1) % 4) <<
176 ((symbol - 261) >> 2);
179 /* Determine how far back to go */
180 if ((symbol = read_symbol(stream, distance)) < 0)
182 if (symbol < 4) dist = symbol + 1;
184 dist = pull_bits(stream, (symbol - 2) >> 1);
185 dist += (2 << ((symbol - 2) >> 1)) + 1;
186 dist += (symbol % 2) << ((symbol - 2) >> 1);
188 stream->decoded += length;
189 for (i = 0; i < length; i++) {
194 } while (symbol != 256); /* 256 is the end of the data block */
197 /* Fill the lookup tables (section 3.2.2) */
198 static void fill_code_tables(struct huffman_set *set)
200 int code = 0, i, length;
202 /* fill in the first code of each bit length, and the pos pointer */
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];
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;
216 /* reset the pos pointer */
217 for (i = 1; i < set->bits; i++) set->pos[i] -= set->count[i];
220 static void init_code_tables(struct huffman_set *set)
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);
227 /* read in the huffman codes for dynamic decoding (section 3.2.7) */
228 static void decompress_dynamic(struct bitstream *stream, unsigned char *dest)
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. */
240 struct huffman_set *codes = &(stream->codes);
241 struct huffman_set *lengths = &(stream->lengths);
242 struct huffman_set *distance = &(stream->distance);
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;
251 init_code_tables(codes);
252 init_code_tables(lengths);
253 init_code_tables(distance);
255 /* fill in the count of each bit length' as well as the lengths
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]++;
263 fill_code_tables(codes);
265 /* Do the same for the length codes, being carefull of wrap through
266 * to the distance table */
268 while (curr_code < hlit) {
269 if ((symbol = read_symbol(stream, codes)) < 0) return;
273 } else if (symbol < 16) { /* Literal length */
274 lengths->lengths[curr_code] = last_code = symbol;
275 lengths->count[symbol]++;
277 } else if (symbol == 16) { /* repeat the last symbol 3 - 6
279 length = 3 + pull_bits(stream, 2);
280 for (;length; length--, curr_code++)
281 if (curr_code < hlit) {
282 lengths->lengths[curr_code] =
284 lengths->count[last_code]++;
285 } else { /* wrap to the distance table */
286 distance->lengths[curr_code - hlit] =
288 distance->count[last_code]++;
290 } else if (symbol == 17) { /* repeat a bit length 0 */
291 curr_code += 3 + pull_bits(stream, 3);
293 } else { /* same, but more times */
294 curr_code += 11 + pull_bits(stream, 7);
298 fill_code_tables(lengths);
300 /* Fill the distance table, don't need to worry about wrapthrough
303 while (curr_code < hdist) {
304 if ((symbol = read_symbol(stream, codes)) < 0) return;
308 } else if (symbol < 16) {
309 distance->lengths[curr_code] = last_code = symbol;
310 distance->count[symbol]++;
312 } else if (symbol == 16) {
313 length = 3 + pull_bits(stream, 2);
314 for (;length; length--, curr_code++) {
315 distance->lengths[curr_code] =
317 distance->count[last_code]++;
319 } else if (symbol == 17) {
320 curr_code += 3 + pull_bits(stream, 3);
323 curr_code += 11 + pull_bits(stream, 7);
327 fill_code_tables(distance);
329 decompress_huffman(stream, dest);
332 /* fill in the length and distance huffman codes for fixed encoding
334 static void decompress_fixed(struct bitstream *stream, unsigned char *dest)
336 /* let gcc fill in the initial values */
337 struct huffman_set *lengths = &(stream->lengths);
338 struct huffman_set *distance = &(stream->distance);
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;
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;
356 fill_code_tables(lengths);
357 fill_code_tables(distance);
360 decompress_huffman(stream, dest);
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 */
366 long decompress_block(unsigned char *dest, unsigned char *source,
367 void *(*inflate_memcpy)(void *, const void *, size))
370 struct bitstream stream;
372 init_stream(&stream, source, inflate_memcpy);
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);
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");
390 return stream.error ? -stream.error : stream.decoded;