Initial revision

fs/jffs2/mini_inflate.c

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+/*-------------------------------------------------------------------------
+ * 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 */