/*
* lzx-compress.c
*
* LZX compression routines, originally based on code written by Matthew T.
* Russotto (liblzxcomp), but heavily modified.
*/
/*
* Copyright (C) 2002 Matthew T. Russotto
* Copyright (C) 2012 Eric Biggers
*
* This file is part of wimlib, a library for working with WIM files.
*
* wimlib 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 3 of the License, or (at your option)
* any later version.
*
* wimlib 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 wimlib; if not, see http://www.gnu.org/licenses/.
*/
/*
* This file provides lzx_compress(), a function to compress an in-memory buffer
* of data using LZX compression, as used in the WIM file format.
*
* Please see the comments in lzx-decompress.c for more information about this
* compression format.
*
* One thing to keep in mind is that there is no sliding window, since the
* window is always the entirety of a WIM chunk, which is at most WIM_CHUNK_SIZE
* ( = 32768) bytes.
*
* The basic compression algorithm used here should be familiar if you are
* familiar with Huffman trees and with other LZ77 and Huffman-based formats
* such as DEFLATE. Otherwise it can be quite tricky to understand. Basically
* it is the following:
*
* - Preprocess the input data (LZX-specific)
* - Go through the input data and determine matches. This part is based on
* code from zlib, and a hash table of 3-character strings is used to
* accelerate the process of finding matches.
* - Build the Huffman trees based on the frequencies of symbols determined
* while recording matches.
* - Output the block header, including the Huffman trees; then output the
* compressed stream of matches and literal characters.
*
* It is possible for a WIM chunk to include multiple LZX blocks, since for some
* input data this will produce a better compression ratio (especially since
* each block can include new Huffman codes). However, producing multiple LZX
* blocks from one input chunk is not yet implemented.
*/
#include "lzx.h"
#include "compress.h"
#include
#include
/* Structure to contain the Huffman codes for the main, length, and aligned
* offset trees. */
struct lzx_codes {
u16 main_codewords[LZX_MAINTREE_NUM_SYMBOLS];
u8 main_lens[LZX_MAINTREE_NUM_SYMBOLS];
u16 len_codewords[LZX_LENTREE_NUM_SYMBOLS];
u8 len_lens[LZX_LENTREE_NUM_SYMBOLS];
u16 aligned_codewords[LZX_ALIGNEDTREE_NUM_SYMBOLS];
u8 aligned_lens[LZX_ALIGNEDTREE_NUM_SYMBOLS];
};
struct lzx_freq_tables {
freq_t main_freq_table[LZX_MAINTREE_NUM_SYMBOLS];
freq_t len_freq_table[LZX_LENTREE_NUM_SYMBOLS];
freq_t aligned_freq_table[LZX_ALIGNEDTREE_NUM_SYMBOLS];
};
/* Returns the LZX position slot that corresponds to a given formatted offset.
*
* Logically, this returns the smallest i such that
* formatted_offset >= lzx_position_base[i].
*
* The actual implementation below takes advantage of the regularity of the
* numbers in the lzx_position_base array to calculate the slot directly from
* the formatted offset without actually looking at the array.
*/
static inline unsigned lzx_get_position_slot(unsigned formatted_offset)
{
#if 0
/*
* Slots 36-49 (formatted_offset >= 262144) can be found by
* (formatted_offset/131072) + 34 == (formatted_offset >> 17) + 34;
* however, this check for formatted_offset >= 262144 is commented out
* because WIM chunks cannot be that large.
*/
if (formatted_offset >= 262144) {
return (formatted_offset >> 17) + 34;
} else
#endif
{
/* Note: this part here only works if:
*
* 2 <= formatted_offset < 655360
*
* It is < 655360 because the frequency of the position bases
* increases starting at the 655360 entry, and it is >= 2
* because the below calculation fails if the most significant
* bit is lower than the 2's place. */
wimlib_assert(formatted_offset >= 2 && formatted_offset < 655360);
unsigned mssb_idx = bsr32(formatted_offset);
return (mssb_idx << 1) |
((formatted_offset >> (mssb_idx - 1)) & 1);
}
}
static u32 lzx_record_literal(u8 literal, void *__main_freq_tab)
{
freq_t *main_freq_tab = __main_freq_tab;
main_freq_tab[literal]++;
return literal;
}
/* Constructs a match from an offset and a length, and updates the LRU queue and
* the frequency of symbols in the main, length, and aligned offset alphabets.
* The return value is a 32-bit number that provides the match in an
* intermediate representation documented below. */
static u32 lzx_record_match(unsigned match_offset, unsigned match_len,
void *__freq_tabs, void *__queue)
{
struct lzx_freq_tables *freq_tabs = __freq_tabs;
struct lru_queue *queue = __queue;
unsigned formatted_offset;
unsigned position_slot;
unsigned position_footer = 0;
u32 match;
u32 len_header;
u32 len_pos_header;
unsigned len_footer;
unsigned adjusted_match_len;
wimlib_assert(match_len >= LZX_MIN_MATCH && match_len <= LZX_MAX_MATCH);
wimlib_assert(match_offset != 0);
/* If possible, encode this offset as a repeated offset. */
if (match_offset == queue->R0) {
formatted_offset = 0;
position_slot = 0;
} else if (match_offset == queue->R1) {
swap(queue->R0, queue->R1);
formatted_offset = 1;
position_slot = 1;
} else if (match_offset == queue->R2) {
swap(queue->R0, queue->R2);
formatted_offset = 2;
position_slot = 2;
} else {
/* Not a repeated offset. */
/* offsets of 0, 1, and 2 are reserved for the repeated offset
* codes, so non-repeated offsets must be encoded as 3+. The
* minimum offset is 1, so encode the offsets offset by 2. */
formatted_offset = match_offset + LZX_MIN_MATCH;
queue->R2 = queue->R1;
queue->R1 = queue->R0;
queue->R0 = match_offset;
/* The (now-formatted) offset will actually be encoded as a
* small position slot number that maps to a certain hard-coded
* offset (position base), followed by a number of extra bits---
* the position footer--- that are added to the position base to
* get the original formatted offset. */
position_slot = lzx_get_position_slot(formatted_offset);
position_footer = formatted_offset &
((1 << lzx_get_num_extra_bits(position_slot)) - 1);
}
adjusted_match_len = match_len - LZX_MIN_MATCH;
/* Pack the position slot, position footer, and match length into an
* intermediate representation.
*
* bits description
* ---- -----------------------------------------------------------
*
* 31 1 if a match, 0 if a literal.
*
* 30-25 position slot. This can be at most 50, so it will fit in 6
* bits.
*
* 8-24 position footer. This is the offset of the real formatted
* offset from the position base. This can be at most 17 bits
* (since lzx_extra_bits[LZX_NUM_POSITION_SLOTS - 1] is 17).
*
* 0-7 length of match, offset by 2. This can be at most
* (LZX_MAX_MATCH - 2) == 255, so it will fit in 8 bits. */
match = 0x80000000 |
(position_slot << 25) |
(position_footer << 8) |
(adjusted_match_len);
/* The match length must be at least 2, so let the adjusted match length
* be the match length minus 2.
*
* If it is less than 7, the adjusted match length is encoded as a 3-bit
* number offset by 2. Otherwise, the 3-bit length header is all 1's
* and the actual adjusted length is given as a symbol encoded with the
* length tree, offset by 7.
*/
if (adjusted_match_len < LZX_NUM_PRIMARY_LENS) {
len_header = adjusted_match_len;
} else {
len_header = LZX_NUM_PRIMARY_LENS;
len_footer = adjusted_match_len - LZX_NUM_PRIMARY_LENS;
freq_tabs->len_freq_table[len_footer]++;
}
len_pos_header = (position_slot << 3) | len_header;
wimlib_assert(len_pos_header < LZX_MAINTREE_NUM_SYMBOLS - LZX_NUM_CHARS);
freq_tabs->main_freq_table[len_pos_header + LZX_NUM_CHARS]++;
/* Equivalent to:
* if (lzx_extra_bits[position_slot] >= 3) */
if (position_slot >= 8)
freq_tabs->aligned_freq_table[position_footer & 7]++;
return match;
}
/*
* Writes a compressed literal match to the output.
*
* @out: The output bitstream.
* @block_type: The type of the block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM)
* @match: The match, encoded as a 32-bit number.
* @codes: Pointer to a structure that contains the codewords for the
* main, length, and aligned offset Huffman codes.
*/
static int lzx_write_match(struct output_bitstream *out, int block_type,
u32 match, const struct lzx_codes *codes)
{
/* low 8 bits are the match length minus 2 */
unsigned match_len_minus_2 = match & 0xff;
/* Next 17 bits are the position footer */
unsigned position_footer = (match >> 8) & 0x1ffff; /* 17 bits */
/* Next 6 bits are the position slot. */
unsigned position_slot = (match >> 25) & 0x3f; /* 6 bits */
unsigned len_header;
unsigned len_footer;
unsigned len_pos_header;
unsigned main_symbol;
unsigned num_extra_bits;
unsigned verbatim_bits;
unsigned aligned_bits;
int ret;
/* If the match length is less than MIN_MATCH (= 2) +
* NUM_PRIMARY_LENS (= 7), the length header contains
* the match length minus MIN_MATCH, and there is no
* length footer.
*
* Otherwise, the length header contains
* NUM_PRIMARY_LENS, and the length footer contains
* the match length minus NUM_PRIMARY_LENS minus
* MIN_MATCH. */
if (match_len_minus_2 < LZX_NUM_PRIMARY_LENS) {
len_header = match_len_minus_2;
/* No length footer-- mark it with a special
* value. */
len_footer = (unsigned)(-1);
} else {
len_header = LZX_NUM_PRIMARY_LENS;
len_footer = match_len_minus_2 - LZX_NUM_PRIMARY_LENS;
}
/* Combine the position slot with the length header into
* a single symbol that will be encoded with the main
* tree. */
len_pos_header = (position_slot << 3) | len_header;
/* The actual main symbol is offset by LZX_NUM_CHARS because
* values under LZX_NUM_CHARS are used to indicate a literal
* byte rather than a match. */
main_symbol = len_pos_header + LZX_NUM_CHARS;
/* Output main symbol. */
ret = bitstream_put_bits(out, codes->main_codewords[main_symbol],
codes->main_lens[main_symbol]);
if (ret != 0)
return ret;
/* If there is a length footer, output it using the
* length Huffman code. */
if (len_footer != (unsigned)(-1)) {
ret = bitstream_put_bits(out, codes->len_codewords[len_footer],
codes->len_lens[len_footer]);
if (ret != 0)
return ret;
}
wimlib_assert(position_slot < LZX_NUM_POSITION_SLOTS);
num_extra_bits = lzx_get_num_extra_bits(position_slot);
/* For aligned offset blocks with at least 3 extra bits, output the
* verbatim bits literally, then the aligned bits encoded using the
* aligned offset tree. Otherwise, only the verbatim bits need to be
* output. */
if ((block_type == LZX_BLOCKTYPE_ALIGNED) && (num_extra_bits >= 3)) {
verbatim_bits = position_footer >> 3;
ret = bitstream_put_bits(out, verbatim_bits,
num_extra_bits - 3);
if (ret != 0)
return ret;
aligned_bits = (position_footer & 7);
ret = bitstream_put_bits(out,
codes->aligned_codewords[aligned_bits],
codes->aligned_lens[aligned_bits]);
if (ret != 0)
return ret;
} else {
/* verbatim bits is the same as the position
* footer, in this case. */
ret = bitstream_put_bits(out, position_footer, num_extra_bits);
if (ret != 0)
return ret;
}
return 0;
}
/*
* Writes all compressed literals in a block, both matches and literal bytes, to
* the output bitstream.
*
* @out: The output bitstream.
* @block_type: The type of the block (LZX_BLOCKTYPE_ALIGNED or LZX_BLOCKTYPE_VERBATIM)
* @match_tab[]: The array of matches that will be output. It has length
* of @num_compressed_literals.
* @num_compressed_literals: Number of compressed literals to be output.
* @codes: Pointer to a structure that contains the codewords for the
* main, length, and aligned offset Huffman codes.
*/
static int lzx_write_compressed_literals(struct output_bitstream *ostream,
int block_type,
const u32 match_tab[],
unsigned num_compressed_literals,
const struct lzx_codes *codes)
{
unsigned i;
u32 match;
int ret;
for (i = 0; i < num_compressed_literals; i++) {
match = match_tab[i];
/* High bit of the match indicates whether the match is an
* actual match (1) or a literal uncompressed byte (0) */
if (match & 0x80000000) {
/* match */
ret = lzx_write_match(ostream, block_type, match,
codes);
if (ret != 0)
return ret;
} else {
/* literal byte */
wimlib_assert(match < LZX_NUM_CHARS);
ret = bitstream_put_bits(ostream,
codes->main_codewords[match],
codes->main_lens[match]);
if (ret != 0)
return ret;
}
}
return 0;
}
/*
* Writes a compressed Huffman tree to the output, preceded by the pretree for
* it.
*
* The Huffman tree is represented in the output as a series of path lengths
* from which the canonical Huffman code can be reconstructed. The path lengths
* themselves are compressed using a separate Huffman code, the pretree, which
* consists of LZX_PRETREE_NUM_SYMBOLS (= 20) symbols that cover all possible code
* lengths, plus extra codes for repeated lengths. The path lengths of the
* pretree precede the path lengths of the larger code and are uncompressed,
* consisting of 20 entries of 4 bits each.
*
* @out: The bitstream for the compressed output.
* @lens: The code lengths for the Huffman tree, indexed by symbol.
* @num_symbols: The number of symbols in the code.
*/
static int lzx_write_compressed_tree(struct output_bitstream *out,
const u8 lens[], unsigned num_symbols)
{
/* Frequencies of the length symbols, including the RLE symbols (NOT the
* actual lengths themselves). */
freq_t pretree_freqs[LZX_PRETREE_NUM_SYMBOLS];
u8 pretree_lens[LZX_PRETREE_NUM_SYMBOLS];
u16 pretree_codewords[LZX_PRETREE_NUM_SYMBOLS];
u8 output_syms[num_symbols * 2];
unsigned output_syms_idx;
unsigned cur_run_len;
unsigned i;
unsigned len_in_run;
unsigned additional_bits;
char delta;
u8 pretree_sym;
ZERO_ARRAY(pretree_freqs);
/* Since the code word lengths use a form of RLE encoding, the goal here
* is to find each run of identical lengths when going through them in
* symbol order (including runs of length 1). For each run, as many
* lengths are encoded using RLE as possible, and the rest are output
* literally.
*
* output_syms[] will be filled in with the length symbols that will be
* output, including RLE codes, not yet encoded using the pre-tree.
*
* cur_run_len keeps track of how many code word lengths are in the
* current run of identical lengths.
*/
output_syms_idx = 0;
cur_run_len = 1;
for (i = 1; i <= num_symbols; i++) {
if (i != num_symbols && lens[i] == lens[i - 1]) {
/* Still in a run--- keep going. */
cur_run_len++;
continue;
}
/* Run ended! Check if it is a run of zeroes or a run of
* nonzeroes. */
/* The symbol that was repeated in the run--- not to be confused
* with the length *of* the run (cur_run_len) */
len_in_run = lens[i - 1];
if (len_in_run == 0) {
/* A run of 0's. Encode it in as few length
* codes as we can. */
/* The magic length 18 indicates a run of 20 + n zeroes,
* where n is an uncompressed literal 5-bit integer that
* follows the magic length. */
while (cur_run_len >= 20) {
additional_bits = min(cur_run_len - 20, 0x1f);
pretree_freqs[18]++;
output_syms[output_syms_idx++] = 18;
output_syms[output_syms_idx++] = additional_bits;
cur_run_len -= 20 + additional_bits;
}
/* The magic length 17 indicates a run of 4 + n zeroes,
* where n is an uncompressed literal 4-bit integer that
* follows the magic length. */
while (cur_run_len >= 4) {
additional_bits = min(cur_run_len - 4, 0xf);
pretree_freqs[17]++;
output_syms[output_syms_idx++] = 17;
output_syms[output_syms_idx++] = additional_bits;
cur_run_len -= 4 + additional_bits;
}
} else {
/* A run of nonzero lengths. */
/* The magic length 19 indicates a run of 4 + n
* nonzeroes, where n is a literal bit that follows the
* magic length, and where the value of the lengths in
* the run is given by an extra length symbol, encoded
* with the pretree, that follows the literal bit.
*
* The extra length symbol is encoded as a difference
* from the length of the codeword for the first symbol
* in the run in the previous tree.
* */
while (cur_run_len >= 4) {
additional_bits = (cur_run_len > 4);
delta = -(char)len_in_run;
if (delta < 0)
delta += 17;
pretree_freqs[19]++;
pretree_freqs[(unsigned char)delta]++;
output_syms[output_syms_idx++] = 19;
output_syms[output_syms_idx++] = additional_bits;
output_syms[output_syms_idx++] = delta;
cur_run_len -= 4 + additional_bits;
}
}
/* Any remaining lengths in the run are outputted without RLE,
* as a difference from the length of that codeword in the
* previous tree. */
while (cur_run_len--) {
delta = -(char)len_in_run;
if (delta < 0)
delta += 17;
pretree_freqs[(unsigned char)delta]++;
output_syms[output_syms_idx++] = delta;
}
cur_run_len = 1;
}
wimlib_assert(output_syms_idx < ARRAY_LEN(output_syms));
/* Build the pretree from the frequencies of the length symbols. */
make_canonical_huffman_code(LZX_PRETREE_NUM_SYMBOLS,
LZX_MAX_CODEWORD_LEN,
pretree_freqs, pretree_lens,
pretree_codewords);
/* Write the lengths of the pretree codes to the output. */
for (i = 0; i < LZX_PRETREE_NUM_SYMBOLS; i++)
bitstream_put_bits(out, pretree_lens[i],
LZX_PRETREE_ELEMENT_SIZE);
/* Write the length symbols, encoded with the pretree, to the output. */
i = 0;
while (i < output_syms_idx) {
pretree_sym = output_syms[i++];
bitstream_put_bits(out, pretree_codewords[pretree_sym],
pretree_lens[pretree_sym]);
switch (pretree_sym) {
case 17:
bitstream_put_bits(out, output_syms[i++], 4);
break;
case 18:
bitstream_put_bits(out, output_syms[i++], 5);
break;
case 19:
bitstream_put_bits(out, output_syms[i++], 1);
bitstream_put_bits(out,
pretree_codewords[output_syms[i]],
pretree_lens[output_syms[i]]);
i++;
break;
default:
break;
}
}
return 0;
}
/* Builds the canonical Huffman code for the main tree, the length tree, and the
* aligned offset tree. */
static void lzx_make_huffman_codes(const struct lzx_freq_tables *freq_tabs,
struct lzx_codes *codes)
{
make_canonical_huffman_code(LZX_MAINTREE_NUM_SYMBOLS,
LZX_MAX_CODEWORD_LEN,
freq_tabs->main_freq_table,
codes->main_lens,
codes->main_codewords);
make_canonical_huffman_code(LZX_LENTREE_NUM_SYMBOLS,
LZX_MAX_CODEWORD_LEN,
freq_tabs->len_freq_table,
codes->len_lens,
codes->len_codewords);
make_canonical_huffman_code(LZX_ALIGNEDTREE_NUM_SYMBOLS, 8,
freq_tabs->aligned_freq_table,
codes->aligned_lens,
codes->aligned_codewords);
}
static void do_call_insn_translation(u32 *call_insn_target, int input_pos,
int32_t file_size)
{
int32_t abs_offset;
int32_t rel_offset;
rel_offset = le32_to_cpu(*call_insn_target);
if (rel_offset >= -input_pos && rel_offset < file_size) {
if (rel_offset < file_size - input_pos) {
/* "good translation" */
abs_offset = rel_offset + input_pos;
} else {
/* "compensating translation" */
abs_offset = rel_offset - file_size;
}
*call_insn_target = cpu_to_le32(abs_offset);
}
}
/* This is the reverse of undo_call_insn_preprocessing() in lzx-decompress.c.
* See the comment above that function for more information. */
static void do_call_insn_preprocessing(u8 uncompressed_data[],
int uncompressed_data_len)
{
for (int i = 0; i < uncompressed_data_len - 10; i++) {
if (uncompressed_data[i] == 0xe8) {
do_call_insn_translation((u32*)&uncompressed_data[i + 1],
i,
LZX_WIM_MAGIC_FILESIZE);
i += 4;
}
}
}
static const struct lz_params lzx_lz_params = {
/* LZX_MIN_MATCH == 2, but 2-character matches are rarely useful; the
* minimum match for compression is set to 3 instead. */
.min_match = 3,
.max_match = LZX_MAX_MATCH,
.good_match = LZX_MAX_MATCH,
.nice_match = LZX_MAX_MATCH,
.max_chain_len = LZX_MAX_MATCH,
.max_lazy_match = LZX_MAX_MATCH,
.too_far = 4096,
};
/*
* Performs LZX compression on a block of data.
*
* @__uncompressed_data: Pointer to the data to be compressed.
* @uncompressed_len: Length, in bytes, of the data to be compressed.
* @compressed_data: Pointer to a location at least (@uncompressed_len - 1)
* bytes long into which the compressed data may be
* written.
* @compressed_len_ret: A pointer to an unsigned int into which the length of
* the compressed data may be returned.
*
* Returns zero if compression was successfully performed. In that case
* @compressed_data and @compressed_len_ret will contain the compressed data and
* its length. A return value of nonzero means that compressing the data did
* not reduce its size, and @compressed_data will not contain the full
* compressed data.
*/
int lzx_compress(const void *__uncompressed_data, unsigned uncompressed_len,
void *compressed_data, unsigned *compressed_len_ret)
{
struct output_bitstream ostream;
u8 uncompressed_data[uncompressed_len + 8];
struct lzx_freq_tables freq_tabs;
struct lzx_codes codes;
u32 match_tab[uncompressed_len];
struct lru_queue queue;
unsigned num_matches;
unsigned compressed_len;
unsigned i;
int ret;
int block_type = LZX_BLOCKTYPE_ALIGNED;
if (uncompressed_len < 100)
return 1;
memset(&freq_tabs, 0, sizeof(freq_tabs));
queue.R0 = 1;
queue.R1 = 1;
queue.R2 = 1;
/* The input data must be preprocessed. To avoid changing the original
* input, copy it to a temporary buffer. */
memcpy(uncompressed_data, __uncompressed_data, uncompressed_len);
/* Before doing any actual compression, do the call instruction (0xe8
* byte) translation on the uncompressed data. */
do_call_insn_preprocessing(uncompressed_data, uncompressed_len);
/* Determine the sequence of matches and literals that will be output,
* and in the process, keep counts of the number of times each symbol
* will be output, so that the Huffman trees can be made. */
num_matches = lz_analyze_block(uncompressed_data, uncompressed_len,
match_tab, lzx_record_match,
lzx_record_literal, &freq_tabs,
&queue, freq_tabs.main_freq_table,
&lzx_lz_params);
lzx_make_huffman_codes(&freq_tabs, &codes);
/* Initialize the output bitstream. */
init_output_bitstream(&ostream, compressed_data, uncompressed_len - 1);
/* The first three bits tell us what kind of block it is, and are one
* of the LZX_BLOCKTYPE_* values. */
bitstream_put_bits(&ostream, block_type, 3);
/* The next bit indicates whether the block size is the default (32768),
* indicated by a 1 bit, or whether the block size is given by the next
* 16 bits, indicated by a 0 bit. */
if (uncompressed_len == 32768) {
bitstream_put_bits(&ostream, 1, 1);
} else {
bitstream_put_bits(&ostream, 0, 1);
bitstream_put_bits(&ostream, uncompressed_len, 16);
}
/* Write out the aligned offset tree. Note that M$ lies and says that
* the aligned offset tree comes after the length tree, but that is
* wrong; it actually is before the main tree. */
if (block_type == LZX_BLOCKTYPE_ALIGNED)
for (i = 0; i < LZX_ALIGNEDTREE_NUM_SYMBOLS; i++)
bitstream_put_bits(&ostream, codes.aligned_lens[i],
LZX_ALIGNEDTREE_ELEMENT_SIZE);
/* Write the pre-tree and lengths for the first LZX_NUM_CHARS symbols in the
* main tree. */
ret = lzx_write_compressed_tree(&ostream, codes.main_lens,
LZX_NUM_CHARS);
if (ret != 0)
return ret;
/* Write the pre-tree and symbols for the rest of the main tree. */
ret = lzx_write_compressed_tree(&ostream, codes.main_lens +
LZX_NUM_CHARS,
LZX_MAINTREE_NUM_SYMBOLS -
LZX_NUM_CHARS);
if (ret != 0)
return ret;
/* Write the pre-tree and symbols for the length tree. */
ret = lzx_write_compressed_tree(&ostream, codes.len_lens,
LZX_LENTREE_NUM_SYMBOLS);
if (ret != 0)
return ret;
/* Write the compressed literals. */
ret = lzx_write_compressed_literals(&ostream, block_type,
match_tab, num_matches, &codes);
if (ret != 0)
return ret;
ret = flush_output_bitstream(&ostream);
if (ret != 0)
return ret;
compressed_len = ostream.bit_output - (u8*)compressed_data;
*compressed_len_ret = compressed_len;
#ifdef ENABLE_VERIFY_COMPRESSION
/* Verify that we really get the same thing back when decompressing. */
u8 buf[uncompressed_len];
ret = lzx_decompress(compressed_data, compressed_len, buf,
uncompressed_len);
if (ret != 0) {
ERROR("lzx_compress(): Failed to decompress data we compressed");
abort();
}
for (i = 0; i < uncompressed_len; i++) {
if (buf[i] != *((u8*)__uncompressed_data + i)) {
ERROR("lzx_compress(): Data we compressed didn't "
"decompress to the original data (difference at "
"byte %u of %u)", i + 1, uncompressed_len);
abort();
}
}
#endif
return 0;
}