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