diff options
Diffstat (limited to 'fs/jffs2')
| -rw-r--r-- | fs/jffs2/mini_inflate.c | 396 |
1 files changed, 396 insertions, 0 deletions
diff --git a/fs/jffs2/mini_inflate.c b/fs/jffs2/mini_inflate.c new file mode 100644 index 0000000..4f511ec --- /dev/null +++ b/fs/jffs2/mini_inflate.c @@ -0,0 +1,396 @@ +/*------------------------------------------------------------------------- + * Filename: mini_inflate.c + * Version: $Id: mini_inflate.c,v 1.3 2002/01/24 22:58:42 rfeany Exp $ + * Copyright: Copyright (C) 2001, Russ Dill + * Author: Russ Dill <Russ.Dill@asu.edu> + * Description: Mini inflate implementation (RFC 1951) + *-----------------------------------------------------------------------*/ +/* + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + * + */ + +#include <config.h> + +#if (CONFIG_COMMANDS & CFG_CMD_JFFS2) + +#include <jffs2/mini_inflate.h> + +/* The order that the code lengths in section 3.2.7 are in */ +static unsigned char huffman_order[] = {16, 17, 18, 0, 8, 7, 9, 6, 10, 5, + 11, 4, 12, 3, 13, 2, 14, 1, 15}; + +inline void cramfs_memset(int *s, const int c, size n) +{ + n--; + for (;n > 0; n--) s[n] = c; + s[0] = c; +} + +/* associate a stream with a block of data and reset the stream */ +static void init_stream(struct bitstream *stream, unsigned char *data, + void *(*inflate_memcpy)(void *, const void *, size)) +{ + stream->error = NO_ERROR; + stream->memcpy = inflate_memcpy; + stream->decoded = 0; + stream->data = data; + stream->bit = 0; /* The first bit of the stream is the lsb of the + * first byte */ + + /* really sorry about all this initialization, think of a better way, + * let me know and it will get cleaned up */ + stream->codes.bits = 8; + stream->codes.num_symbols = 19; + stream->codes.lengths = stream->code_lengths; + stream->codes.symbols = stream->code_symbols; + stream->codes.count = stream->code_count; + stream->codes.first = stream->code_first; + stream->codes.pos = stream->code_pos; + + stream->lengths.bits = 16; + stream->lengths.num_symbols = 288; + stream->lengths.lengths = stream->length_lengths; + stream->lengths.symbols = stream->length_symbols; + stream->lengths.count = stream->length_count; + stream->lengths.first = stream->length_first; + stream->lengths.pos = stream->length_pos; + + stream->distance.bits = 16; + stream->distance.num_symbols = 32; + stream->distance.lengths = stream->distance_lengths; + stream->distance.symbols = stream->distance_symbols; + stream->distance.count = stream->distance_count; + stream->distance.first = stream->distance_first; + stream->distance.pos = stream->distance_pos; + +} + +/* pull 'bits' bits out of the stream. The last bit pulled it returned as the + * msb. (section 3.1.1) + */ +inline unsigned long pull_bits(struct bitstream *stream, + const unsigned int bits) +{ + unsigned long ret; + int i; + + ret = 0; + for (i = 0; i < bits; i++) { + ret += ((*(stream->data) >> stream->bit) & 1) << i; + + /* if, before incrementing, we are on bit 7, + * go to the lsb of the next byte */ + if (stream->bit++ == 7) { + stream->bit = 0; + stream->data++; + } + } + return ret; +} + +inline int pull_bit(struct bitstream *stream) +{ + int ret = ((*(stream->data) >> stream->bit) & 1); + if (stream->bit++ == 7) { + stream->bit = 0; + stream->data++; + } + return ret; +} + +/* discard bits up to the next whole byte */ +static void discard_bits(struct bitstream *stream) +{ + if (stream->bit != 0) { + stream->bit = 0; + stream->data++; + } +} + +/* No decompression, the data is all literals (section 3.2.4) */ +static void decompress_none(struct bitstream *stream, unsigned char *dest) +{ + unsigned int length; + + discard_bits(stream); + length = *(stream->data++); + length += *(stream->data++) << 8; + pull_bits(stream, 16); /* throw away the inverse of the size */ + + stream->decoded += length; + stream->memcpy(dest, stream->data, length); + stream->data += length; +} + +/* Read in a symbol from the stream (section 3.2.2) */ +static int read_symbol(struct bitstream *stream, struct huffman_set *set) +{ + int bits = 0; + int code = 0; + while (!(set->count[bits] && code < set->first[bits] + + set->count[bits])) { + code = (code << 1) + pull_bit(stream); + if (++bits > set->bits) { + /* error decoding (corrupted data?) */ + stream->error = CODE_NOT_FOUND; + return -1; + } + } + return set->symbols[set->pos[bits] + code - set->first[bits]]; +} + +/* decompress a stream of data encoded with the passed length and distance + * huffman codes */ +static void decompress_huffman(struct bitstream *stream, unsigned char *dest) +{ + struct huffman_set *lengths = &(stream->lengths); + struct huffman_set *distance = &(stream->distance); + + int symbol, length, dist, i; + + do { + if ((symbol = read_symbol(stream, lengths)) < 0) return; + if (symbol < 256) { + *(dest++) = symbol; /* symbol is a literal */ + stream->decoded++; + } else if (symbol > 256) { + /* Determine the length of the repitition + * (section 3.2.5) */ + if (symbol < 265) length = symbol - 254; + else if (symbol == 285) length = 258; + else { + length = pull_bits(stream, (symbol - 261) >> 2); + length += (4 << ((symbol - 261) >> 2)) + 3; + length += ((symbol - 1) % 4) << + ((symbol - 261) >> 2); + } + + /* Determine how far back to go */ + if ((symbol = read_symbol(stream, distance)) < 0) + return; + if (symbol < 4) dist = symbol + 1; + else { + dist = pull_bits(stream, (symbol - 2) >> 1); + dist += (2 << ((symbol - 2) >> 1)) + 1; + dist += (symbol % 2) << ((symbol - 2) >> 1); + } + stream->decoded += length; + for (i = 0; i < length; i++) { + *dest = dest[-dist]; + dest++; + } + } + } while (symbol != 256); /* 256 is the end of the data block */ +} + +/* Fill the lookup tables (section 3.2.2) */ +static void fill_code_tables(struct huffman_set *set) +{ + int code = 0, i, length; + + /* fill in the first code of each bit length, and the pos pointer */ + set->pos[0] = 0; + for (i = 1; i < set->bits; i++) { + code = (code + set->count[i - 1]) << 1; + set->first[i] = code; + set->pos[i] = set->pos[i - 1] + set->count[i - 1]; + } + + /* Fill in the table of symbols in order of their huffman code */ + for (i = 0; i < set->num_symbols; i++) { + if ((length = set->lengths[i])) + set->symbols[set->pos[length]++] = i; + } + + /* reset the pos pointer */ + for (i = 1; i < set->bits; i++) set->pos[i] -= set->count[i]; +} + +static void init_code_tables(struct huffman_set *set) +{ + cramfs_memset(set->lengths, 0, set->num_symbols); + cramfs_memset(set->count, 0, set->bits); + cramfs_memset(set->first, 0, set->bits); +} + +/* read in the huffman codes for dynamic decoding (section 3.2.7) */ +static void decompress_dynamic(struct bitstream *stream, unsigned char *dest) +{ + /* I tried my best to minimize the memory footprint here, while still + * keeping up performance. I really dislike the _lengths[] tables, but + * I see no way of eliminating them without a sizable performance + * impact. The first struct table keeps track of stats on each bit + * length. The _length table keeps a record of the bit length of each + * symbol. The _symbols table is for looking up symbols by the huffman + * code (the pos element points to the first place in the symbol table + * where that bit length occurs). I also hate the initization of these + * structs, if someone knows how to compact these, lemme know. */ + + struct huffman_set *codes = &(stream->codes); + struct huffman_set *lengths = &(stream->lengths); + struct huffman_set *distance = &(stream->distance); + + int hlit = pull_bits(stream, 5) + 257; + int hdist = pull_bits(stream, 5) + 1; + int hclen = pull_bits(stream, 4) + 4; + int length, curr_code, symbol, i, last_code; + + last_code = 0; + + init_code_tables(codes); + init_code_tables(lengths); + init_code_tables(distance); + + /* fill in the count of each bit length' as well as the lengths + * table */ + for (i = 0; i < hclen; i++) { + length = pull_bits(stream, 3); + codes->lengths[huffman_order[i]] = length; + if (length) codes->count[length]++; + + } + fill_code_tables(codes); + + /* Do the same for the length codes, being carefull of wrap through + * to the distance table */ + curr_code = 0; + while (curr_code < hlit) { + if ((symbol = read_symbol(stream, codes)) < 0) return; + if (symbol == 0) { + curr_code++; + last_code = 0; + } else if (symbol < 16) { /* Literal length */ + lengths->lengths[curr_code] = last_code = symbol; + lengths->count[symbol]++; + curr_code++; + } else if (symbol == 16) { /* repeat the last symbol 3 - 6 + * times */ + length = 3 + pull_bits(stream, 2); + for (;length; length--, curr_code++) + if (curr_code < hlit) { + lengths->lengths[curr_code] = + last_code; + lengths->count[last_code]++; + } else { /* wrap to the distance table */ + distance->lengths[curr_code - hlit] = + last_code; + distance->count[last_code]++; + } + } else if (symbol == 17) { /* repeat a bit length 0 */ + curr_code += 3 + pull_bits(stream, 3); + last_code = 0; + } else { /* same, but more times */ + curr_code += 11 + pull_bits(stream, 7); + last_code = 0; + } + } + fill_code_tables(lengths); + + /* Fill the distance table, don't need to worry about wrapthrough + * here */ + curr_code -= hlit; + while (curr_code < hdist) { + if ((symbol = read_symbol(stream, codes)) < 0) return; + if (symbol == 0) { + curr_code++; + last_code = 0; + } else if (symbol < 16) { + distance->lengths[curr_code] = last_code = symbol; + distance->count[symbol]++; + curr_code++; + } else if (symbol == 16) { + length = 3 + pull_bits(stream, 2); + for (;length; length--, curr_code++) { + distance->lengths[curr_code] = + last_code; + distance->count[last_code]++; + } + } else if (symbol == 17) { + curr_code += 3 + pull_bits(stream, 3); + last_code = 0; + } else { + curr_code += 11 + pull_bits(stream, 7); + last_code = 0; + } + } + fill_code_tables(distance); + + decompress_huffman(stream, dest); +} + +/* fill in the length and distance huffman codes for fixed encoding + * (section 3.2.6) */ +static void decompress_fixed(struct bitstream *stream, unsigned char *dest) +{ + /* let gcc fill in the initial values */ + struct huffman_set *lengths = &(stream->lengths); + struct huffman_set *distance = &(stream->distance); + + cramfs_memset(lengths->count, 0, 16); + cramfs_memset(lengths->first, 0, 16); + cramfs_memset(lengths->lengths, 8, 144); + cramfs_memset(lengths->lengths + 144, 9, 112); + cramfs_memset(lengths->lengths + 256, 7, 24); + cramfs_memset(lengths->lengths + 280, 8, 8); + lengths->count[7] = 24; + lengths->count[8] = 152; + lengths->count[9] = 112; + + cramfs_memset(distance->count, 0, 16); + cramfs_memset(distance->first, 0, 16); + cramfs_memset(distance->lengths, 5, 32); + distance->count[5] = 32; + + + fill_code_tables(lengths); + fill_code_tables(distance); + + + decompress_huffman(stream, dest); +} + +/* returns the number of bytes decoded, < 0 if there was an error. Note that + * this function assumes that the block starts on a byte boundry + * (non-compliant, but I don't see where this would happen). section 3.2.3 */ +long decompress_block(unsigned char *dest, unsigned char *source, + void *(*inflate_memcpy)(void *, const void *, size)) +{ + int bfinal, btype; + struct bitstream stream; + + init_stream(&stream, source, inflate_memcpy); + do { + bfinal = pull_bit(&stream); + btype = pull_bits(&stream, 2); + if (btype == NO_COMP) decompress_none(&stream, dest + stream.decoded); + else if (btype == DYNAMIC_COMP) + decompress_dynamic(&stream, dest + stream.decoded); + else if (btype == FIXED_COMP) decompress_fixed(&stream, dest + stream.decoded); + else stream.error = COMP_UNKNOWN; + } while (!bfinal && !stream.error); + +#if 0 + putstr("decompress_block start\r\n"); + putLabeledWord("stream.error = ",stream.error); + putLabeledWord("stream.decoded = ",stream.decoded); + putLabeledWord("dest = ",dest); + putstr("decompress_block end\r\n"); +#endif + return stream.error ? -stream.error : stream.decoded; +} + +#endif /* CFG_CMD_JFFS2 */ |