fs/jffs2/mini_inflate.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*-------------------------------------------------------------------------
   3  * Filename:      mini_inflate.c
   4  * Version:       $Id: mini_inflate.c,v 1.3 2002/01/24 22:58:42 rfeany Exp $
   5  * Copyright:     Copyright (C) 2001, Russ Dill
   6  * Author:        Russ Dill <Russ.Dill@asu.edu>
   7  * Description:   Mini inflate implementation (RFC 1951)
   8  *-----------------------------------------------------------------------*/
   9
  10 #include <config.h>
  11 #include <jffs2/mini_inflate.h>
  12
  13 /* The order that the code lengths in section 3.2.7 are in */
  14 static unsigned char huffman_order[] = {16, 17, 18,  0,  8,  7,  9,  6, 10,  5,
  15                                         11,  4, 12,  3, 13,  2, 14,  1, 15};
  16
  17 static inline void cramfs_memset(int *s, const int c, size n)
  18 {
  19         n--;
  20         for (;n > 0; n--) s[n] = c;
  21         s[0] = c;
  22 }
  23
  24 /* associate a stream with a block of data and reset the stream */
  25 static void init_stream(struct bitstream *stream, unsigned char *data,
  26                         void *(*inflate_memcpy)(void *, const void *, size))
  27 {
  28         stream->error = NO_ERROR;
  29         stream->memcpy = inflate_memcpy;
  30         stream->decoded = 0;
  31         stream->data = data;
  32         stream->bit = 0;        /* The first bit of the stream is the lsb of the
  33                                  * first byte */
  34
  35         /* really sorry about all this initialization, think of a better way,
  36          * let me know and it will get cleaned up */
  37         stream->codes.bits = 8;
  38         stream->codes.num_symbols = 19;
  39         stream->codes.lengths = stream->code_lengths;
  40         stream->codes.symbols = stream->code_symbols;
  41         stream->codes.count = stream->code_count;
  42         stream->codes.first = stream->code_first;
  43         stream->codes.pos = stream->code_pos;
  44
  45         stream->lengths.bits = 16;
  46         stream->lengths.num_symbols = 288;
  47         stream->lengths.lengths = stream->length_lengths;
  48         stream->lengths.symbols = stream->length_symbols;
  49         stream->lengths.count = stream->length_count;
  50         stream->lengths.first = stream->length_first;
  51         stream->lengths.pos = stream->length_pos;
  52
  53         stream->distance.bits = 16;
  54         stream->distance.num_symbols = 32;
  55         stream->distance.lengths = stream->distance_lengths;
  56         stream->distance.symbols = stream->distance_symbols;
  57         stream->distance.count = stream->distance_count;
  58         stream->distance.first = stream->distance_first;
  59         stream->distance.pos = stream->distance_pos;
  60
  61 }
  62
  63 /* pull 'bits' bits out of the stream. The last bit pulled it returned as the
  64  * msb. (section 3.1.1)
  65  */
  66 static inline unsigned long pull_bits(struct bitstream *stream,
  67                                       const unsigned int bits)
  68 {
  69         unsigned long ret;
  70         int i;
  71
  72         ret = 0;
  73         for (i = 0; i < bits; i++) {
  74                 ret += ((*(stream->data) >> stream->bit) & 1) << i;
  75
  76                 /* if, before incrementing, we are on bit 7,
  77                  * go to the lsb of the next byte */
  78                 if (stream->bit++ == 7) {
  79                         stream->bit = 0;
  80                         stream->data++;
  81                 }
  82         }
  83         return ret;
  84 }
  85
  86 static inline int pull_bit(struct bitstream *stream)
  87 {
  88         int ret = ((*(stream->data) >> stream->bit) & 1);
  89         if (stream->bit++ == 7) {
  90                 stream->bit = 0;
  91                 stream->data++;
  92         }
  93         return ret;
  94 }
  95
  96 /* discard bits up to the next whole byte */
  97 static void discard_bits(struct bitstream *stream)
  98 {
  99         if (stream->bit != 0) {
 100                 stream->bit = 0;
 101                 stream->data++;
 102         }
 103 }
 104
 105 /* No decompression, the data is all literals (section 3.2.4) */
 106 static void decompress_none(struct bitstream *stream, unsigned char *dest)
 107 {
 108         unsigned int length;
 109
 110         discard_bits(stream);
 111         length = *(stream->data++);
 112         length += *(stream->data++) << 8;
 113         pull_bits(stream, 16);  /* throw away the inverse of the size */
 114
 115         stream->decoded += length;
 116         stream->memcpy(dest, stream->data, length);
 117         stream->data += length;
 118 }
 119
 120 /* Read in a symbol from the stream (section 3.2.2) */
 121 static int read_symbol(struct bitstream *stream, struct huffman_set *set)
 122 {
 123         int bits = 0;
 124         int code = 0;
 125         while (!(set->count[bits] && code < set->first[bits] +
 126                                              set->count[bits])) {
 127                 code = (code << 1) + pull_bit(stream);
 128                 if (++bits > set->bits) {
 129                         /* error decoding (corrupted data?) */
 130                         stream->error = CODE_NOT_FOUND;
 131                         return -1;
 132                 }
 133         }
 134         return set->symbols[set->pos[bits] + code - set->first[bits]];
 135 }
 136
 137 /* decompress a stream of data encoded with the passed length and distance
 138  * huffman codes */
 139 static void decompress_huffman(struct bitstream *stream, unsigned char *dest)
 140 {
 141         struct huffman_set *lengths = &(stream->lengths);
 142         struct huffman_set *distance = &(stream->distance);
 143
 144         int symbol, length, dist, i;
 145
 146         do {
 147                 if ((symbol = read_symbol(stream, lengths)) < 0) return;
 148                 if (symbol < 256) {
 149                         *(dest++) = symbol; /* symbol is a literal */
 150                         stream->decoded++;
 151                 } else if (symbol > 256) {
 152                         /* Determine the length of the repitition
 153                          * (section 3.2.5) */
 154                         if (symbol < 265) length = symbol - 254;
 155                         else if (symbol == 285) length = 258;
 156                         else {
 157                                 length = pull_bits(stream, (symbol - 261) >> 2);
 158                                 length += (4 << ((symbol - 261) >> 2)) + 3;
 159                                 length += ((symbol - 1) % 4) <<
 160                                           ((symbol - 261) >> 2);
 161                         }
 162
 163                         /* Determine how far back to go */
 164                         if ((symbol = read_symbol(stream, distance)) < 0)
 165                                 return;
 166                         if (symbol < 4) dist = symbol + 1;
 167                         else {
 168                                 dist = pull_bits(stream, (symbol - 2) >> 1);
 169                                 dist += (2 << ((symbol - 2) >> 1)) + 1;
 170                                 dist += (symbol % 2) << ((symbol - 2) >> 1);
 171                         }
 172                         stream->decoded += length;
 173                         for (i = 0; i < length; i++) {
 174                                 *dest = dest[-dist];
 175                                 dest++;
 176                         }
 177                 }
 178         } while (symbol != 256); /* 256 is the end of the data block */
 179 }
 180
 181 /* Fill the lookup tables (section 3.2.2) */
 182 static void fill_code_tables(struct huffman_set *set)
 183 {
 184         int code = 0, i, length;
 185
 186         /* fill in the first code of each bit length, and the pos pointer */
 187         set->pos[0] = 0;
 188         for (i = 1; i < set->bits; i++) {
 189                 code = (code + set->count[i - 1]) << 1;
 190                 set->first[i] = code;
 191                 set->pos[i] = set->pos[i - 1] + set->count[i - 1];
 192         }
 193
 194         /* Fill in the table of symbols in order of their huffman code */
 195         for (i = 0; i < set->num_symbols; i++) {
 196                 if ((length = set->lengths[i]))
 197                         set->symbols[set->pos[length]++] = i;
 198         }
 199
 200         /* reset the pos pointer */
 201         for (i = 1; i < set->bits; i++) set->pos[i] -= set->count[i];
 202 }
 203
 204 static void init_code_tables(struct huffman_set *set)
 205 {
 206         cramfs_memset(set->lengths, 0, set->num_symbols);
 207         cramfs_memset(set->count, 0, set->bits);
 208         cramfs_memset(set->first, 0, set->bits);
 209 }
 210
 211 /* read in the huffman codes for dynamic decoding (section 3.2.7) */
 212 static void decompress_dynamic(struct bitstream *stream, unsigned char *dest)
 213 {
 214         /* I tried my best to minimize the memory footprint here, while still
 215          * keeping up performance. I really dislike the _lengths[] tables, but
 216          * I see no way of eliminating them without a sizable performance
 217          * impact. The first struct table keeps track of stats on each bit
 218          * length. The _length table keeps a record of the bit length of each
 219          * symbol. The _symbols table is for looking up symbols by the huffman
 220          * code (the pos element points to the first place in the symbol table
 221          * where that bit length occurs). I also hate the initization of these
 222          * structs, if someone knows how to compact these, lemme know. */
 223
 224         struct huffman_set *codes = &(stream->codes);
 225         struct huffman_set *lengths = &(stream->lengths);
 226         struct huffman_set *distance = &(stream->distance);
 227
 228         int hlit = pull_bits(stream, 5) + 257;
 229         int hdist = pull_bits(stream, 5) + 1;
 230         int hclen = pull_bits(stream, 4) + 4;
 231         int length, curr_code, symbol, i, last_code;
 232
 233         last_code = 0;
 234
 235         init_code_tables(codes);
 236         init_code_tables(lengths);
 237         init_code_tables(distance);
 238
 239         /* fill in the count of each bit length' as well as the lengths
 240          * table */
 241         for (i = 0; i < hclen; i++) {
 242                 length = pull_bits(stream, 3);
 243                 codes->lengths[huffman_order[i]] = length;
 244                 if (length) codes->count[length]++;
 245
 246         }
 247         fill_code_tables(codes);
 248
 249         /* Do the same for the length codes, being carefull of wrap through
 250          * to the distance table */
 251         curr_code = 0;
 252         while (curr_code < hlit) {
 253                 if ((symbol = read_symbol(stream, codes)) < 0) return;
 254                 if (symbol == 0) {
 255                         curr_code++;
 256                         last_code = 0;
 257                 } else if (symbol < 16) { /* Literal length */
 258                         lengths->lengths[curr_code] =  last_code = symbol;
 259                         lengths->count[symbol]++;
 260                         curr_code++;
 261                 } else if (symbol == 16) { /* repeat the last symbol 3 - 6
 262                                             * times */
 263                         length = 3 + pull_bits(stream, 2);
 264                         for (;length; length--, curr_code++)
 265                                 if (curr_code < hlit) {
 266                                         lengths->lengths[curr_code] =
 267                                                 last_code;
 268                                         lengths->count[last_code]++;
 269                                 } else { /* wrap to the distance table */
 270                                         distance->lengths[curr_code - hlit] =
 271                                                 last_code;
 272                                         distance->count[last_code]++;
 273                                 }
 274                 } else if (symbol == 17) { /* repeat a bit length 0 */
 275                         curr_code += 3 + pull_bits(stream, 3);
 276                         last_code = 0;
 277                 } else { /* same, but more times */
 278                         curr_code += 11 + pull_bits(stream, 7);
 279                         last_code = 0;
 280                 }
 281         }
 282         fill_code_tables(lengths);
 283
 284         /* Fill the distance table, don't need to worry about wrapthrough
 285          * here */
 286         curr_code -= hlit;
 287         while (curr_code < hdist) {
 288                 if ((symbol = read_symbol(stream, codes)) < 0) return;
 289                 if (symbol == 0) {
 290                         curr_code++;
 291                         last_code = 0;
 292                 } else if (symbol < 16) {
 293                         distance->lengths[curr_code] = last_code = symbol;
 294                         distance->count[symbol]++;
 295                         curr_code++;
 296                 } else if (symbol == 16) {
 297                         length = 3 + pull_bits(stream, 2);
 298                         for (;length; length--, curr_code++) {
 299                                 distance->lengths[curr_code] =
 300                                         last_code;
 301                                 distance->count[last_code]++;
 302                         }
 303                 } else if (symbol == 17) {
 304                         curr_code += 3 + pull_bits(stream, 3);
 305                         last_code = 0;
 306                 } else {
 307                         curr_code += 11 + pull_bits(stream, 7);
 308                         last_code = 0;
 309                 }
 310         }
 311         fill_code_tables(distance);
 312
 313         decompress_huffman(stream, dest);
 314 }
 315
 316 /* fill in the length and distance huffman codes for fixed encoding
 317  * (section 3.2.6) */
 318 static void decompress_fixed(struct bitstream *stream, unsigned char *dest)
 319 {
 320         /* let gcc fill in the initial values */
 321         struct huffman_set *lengths = &(stream->lengths);
 322         struct huffman_set *distance = &(stream->distance);
 323
 324         cramfs_memset(lengths->count, 0, 16);
 325         cramfs_memset(lengths->first, 0, 16);
 326         cramfs_memset(lengths->lengths, 8, 144);
 327         cramfs_memset(lengths->lengths + 144, 9, 112);
 328         cramfs_memset(lengths->lengths + 256, 7, 24);
 329         cramfs_memset(lengths->lengths + 280, 8, 8);
 330         lengths->count[7] = 24;
 331         lengths->count[8] = 152;
 332         lengths->count[9] = 112;
 333
 334         cramfs_memset(distance->count, 0, 16);
 335         cramfs_memset(distance->first, 0, 16);
 336         cramfs_memset(distance->lengths, 5, 32);
 337         distance->count[5] = 32;
 338
 339
 340         fill_code_tables(lengths);
 341         fill_code_tables(distance);
 342
 343
 344         decompress_huffman(stream, dest);
 345 }
 346
 347 /* returns the number of bytes decoded, < 0 if there was an error. Note that
 348  * this function assumes that the block starts on a byte boundry
 349  * (non-compliant, but I don't see where this would happen). section 3.2.3 */
 350 long decompress_block(unsigned char *dest, unsigned char *source,
 351                       void *(*inflate_memcpy)(void *, const void *, size))
 352 {
 353         int bfinal, btype;
 354         struct bitstream stream;
 355
 356         init_stream(&stream, source, inflate_memcpy);
 357         do {
 358                 bfinal = pull_bit(&stream);
 359                 btype = pull_bits(&stream, 2);
 360                 if (btype == NO_COMP) decompress_none(&stream, dest + stream.decoded);
 361                 else if (btype == DYNAMIC_COMP)
 362                         decompress_dynamic(&stream, dest + stream.decoded);
 363                 else if (btype == FIXED_COMP) decompress_fixed(&stream, dest + stream.decoded);
 364                 else stream.error = COMP_UNKNOWN;
 365         } while (!bfinal && !stream.error);
 366
 367 #if 0
 368         putstr("decompress_block start\r\n");
 369         putLabeledWord("stream.error = ",stream.error);
 370         putLabeledWord("stream.decoded = ",stream.decoded);
 371         putLabeledWord("dest = ",dest);
 372         putstr("decompress_block end\r\n");
 373 #endif
 374         return stream.error ? -stream.error : stream.decoded;
 375 }