--- /dev/null
+/*-------------------------------------------------------------------------
+ * 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)
+ *-----------------------------------------------------------------------*/
+/*
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+#include <config.h>
+#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;
+}
Code Review / kvmfornfv.git / blobdiff