/*
* LZX is a LZ77 and Huffman-code based compression format that has many
* similarities to the DEFLATE format used in zlib. The compression ratio is as
- * good or better than DEFLATE. However, in WIM files only up to 32768 bytes of
- * data can ever compressed be in the same LZX block, so a .tar.gz file could
- * potentially be smaller than a WIM file that uses LZX compression because it
- * can use a larger LZ77 window size.
+ * good or better than DEFLATE.
*
* Some notes on the LZX compression format as used in Windows Imaging (WIM)
* files:
*
* A compressed WIM resource consists of a table of chunk offsets followed by
* the compressed chunks themselves. All compressed chunks except possibly the
- * last decompress to 32768 bytes. This is quite similar to the cabinet (.cab)
- * file format, but they are not the same. According to the cabinet format
- * documentation, the LZX block size is independent from the CFDATA blocks, and
- * a LZX block may span several CFDATA blocks. However, in WIMs, LZX blocks do
- * not appear to ever span multiple WIM chunks. Note that this means any WIM
- * chunk may be decompressed or compressed independently from any other chunk,
- * which is convenient.
+ * last decompress to a fixed number of bytes, by default 32768. This is quite
+ * similar to the cabinet (.cab) file format, but they are not the same.
+ * According to the cabinet format documentation, the LZX block size is
+ * independent from the CFDATA blocks, and a LZX block may span several CFDATA
+ * blocks. However, in WIMs, LZX blocks do not appear to ever span multiple WIM
+ * chunks. Note that this means any WIM chunk may be decompressed or compressed
+ * independently from any other chunk, which allows random access.
*
* A LZX compressed WIM chunk contains one or more LZX blocks of the aligned,
* verbatim, or uncompressed block types. For aligned and verbatim blocks, the
* size of the block in uncompressed bytes is specified by a bit following the 3
* bits that specify the block type, possibly followed by an additional 16 bits.
- * '1' means to use the default block size (equal to 32768, the size of a WIM
- * chunk--- and this seems to only be valid for the first LZX block in a WIM
- * chunk), while '0' means that the block size is provided by the next 16 bits.
+ * '1' means to use the default block size (equal to 32768, the default size of
+ * a WIM chunk), while '0' means that the block size is provided by the next 16
+ * bits.
*
* The cabinet format, as documented, allows for the possibility that a
* compressed CFDATA chunk is up to 6144 bytes larger than the data it
* defined in the specification.
*
* The LZX document states that aligned offset blocks have their aligned offset
- * huffman tree AFTER the main and length trees. The implementation suggests
+ * Huffman tree AFTER the main and length trees. The implementation suggests
* that the aligned offset tree is BEFORE the main and length trees.
*
* The LZX document decoding algorithm states that, in an aligned offset block,
* if an extra_bits value is 1, 2 or 3, then that number of bits should be read
* and the result added to the match offset. This is correct for 1 and 2, but
- * not 3, where just a huffman symbol (using the aligned tree) should be read.
+ * not 3, where just a Huffman symbol (using the aligned tree) should be read.
*
* Regarding the E8 preprocessing, the LZX document states 'No translation may
* be performed on the last 6 bytes of the input block'. This is correct.
* would cause the next four bytes to be modified, at least one of which would
* be in the last 6 bytes, which is not allowed according to the spec.
*
- * The specification states that the huffman trees must always contain at least
+ * The specification states that the Huffman trees must always contain at least
* one element. However, many CAB files contain blocks where the length tree is
* completely empty (because there are no matches), and this is expected to
* succeed.
struct lzx_tables {
u16 maintree_decode_table[(1 << LZX_MAINCODE_TABLEBITS) +
- (LZX_MAINCODE_NUM_SYMBOLS * 2)]
+ (LZX_MAINCODE_MAX_NUM_SYMBOLS * 2)]
_aligned_attribute(DECODE_TABLE_ALIGNMENT);
- u8 maintree_lens[LZX_MAINCODE_NUM_SYMBOLS];
+ u8 maintree_lens[LZX_MAINCODE_MAX_NUM_SYMBOLS];
u16 lentree_decode_table[(1 << LZX_LENCODE_TABLEBITS) +
static inline int
read_huffsym_using_maintree(struct input_bitstream *istream,
const struct lzx_tables *tables,
- unsigned *n)
+ unsigned *n,
+ unsigned num_main_syms)
{
return read_huffsym(istream, tables->maintree_decode_table,
- tables->maintree_lens, LZX_MAINCODE_NUM_SYMBOLS,
+ tables->maintree_lens, num_main_syms,
LZX_MAINCODE_TABLEBITS, n, LZX_MAX_MAIN_CODEWORD_LEN);
}
_aligned_attribute(DECODE_TABLE_ALIGNMENT);
u8 pretree_lens[LZX_PRECODE_NUM_SYMBOLS];
unsigned i;
- unsigned len;
+ u32 len;
int ret;
/* Read the code lengths of the pretree codes. There are 20 lengths of
* the next lengths are all equal to the next symbol in the
* input. */
unsigned tree_code;
- unsigned num_zeroes;
+ u32 num_zeroes;
unsigned code;
- unsigned num_same;
+ u32 num_same;
signed char value;
ret = read_huffsym_using_pretree(istream, pretree_decode_table,
*/
static int
lzx_read_block_header(struct input_bitstream *istream,
+ unsigned num_main_syms,
+ unsigned max_window_size,
unsigned *block_size_ret,
unsigned *block_type_ret,
struct lzx_tables *tables,
int ret;
unsigned block_type;
unsigned block_size;
- unsigned s;
- unsigned i;
- unsigned len;
- ret = bitstream_ensure_bits(istream, LZX_BLOCKTYPE_NBITS + 1);
- if (ret) {
- LZX_DEBUG("LZX input stream overrun");
+ ret = bitstream_ensure_bits(istream, 4);
+ if (ret)
return ret;
- }
/* The first three bits tell us what kind of block it is, and are one
* of the LZX_BLOCKTYPE_* values. */
- block_type = bitstream_read_bits_nocheck(istream, LZX_BLOCKTYPE_NBITS);
-
- /* 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. */
- s = bitstream_read_bits_nocheck(istream, 1);
+ block_type = bitstream_read_bits_nocheck(istream, 3);
- if (s) {
- block_size = 32768;
+ /* Read the block size. This mirrors the behavior
+ * lzx_write_compressed_block() in lzx-compress.c; see that for more
+ * details. */
+ if (bitstream_read_bits_nocheck(istream, 1)) {
+ block_size = LZX_DEFAULT_BLOCK_SIZE;
} else {
- ret = bitstream_read_bits(istream, LZX_BLOCKSIZE_NBITS, &block_size);
+ u32 tmp;
+ block_size = 0;
+
+ ret = bitstream_read_bits(istream, 8, &tmp);
+ if (ret)
+ return ret;
+ block_size |= tmp;
+
+ ret = bitstream_read_bits(istream, 8, &tmp);
if (ret)
return ret;
- block_size = le16_to_cpu(block_size);
+ block_size <<= 8;
+ block_size |= tmp;
+
+ if (max_window_size >= 65536) {
+ ret = bitstream_read_bits(istream, 8, &tmp);
+ if (ret)
+ return ret;
+ block_size <<= 8;
+ block_size |= tmp;
+ }
}
switch (block_type) {
/* Read the path lengths for the elements of the aligned tree,
* then build it. */
- for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) {
+ for (unsigned i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) {
+ u32 len;
+
ret = bitstream_read_bits(istream,
LZX_ALIGNEDCODE_ELEMENT_SIZE,
&len);
* tree. */
LZX_DEBUG("Reading path lengths for remaining elements of "
"main tree (%d elements).",
- LZX_MAINCODE_NUM_SYMBOLS - LZX_NUM_CHARS);
+ num_main_syms - LZX_NUM_CHARS);
ret = lzx_read_code_lens(istream,
tables->maintree_lens + LZX_NUM_CHARS,
- LZX_MAINCODE_NUM_SYMBOLS - LZX_NUM_CHARS);
+ num_main_syms - LZX_NUM_CHARS);
if (ret) {
LZX_DEBUG("Failed to read the path lengths for the "
"remaining elements of the main tree");
"table for the main tree.");
ret = make_huffman_decode_table(tables->maintree_decode_table,
- LZX_MAINCODE_NUM_SYMBOLS,
+ num_main_syms,
LZX_MAINCODE_TABLEBITS,
tables->maintree_lens,
LZX_MAX_MAIN_CODEWORD_LEN);
istream->bitsleft = 0;
istream->bitbuf = 0;
}
- queue->R[0] = le32_to_cpu(*(u32*)(istream->data + 0));
- queue->R[1] = le32_to_cpu(*(u32*)(istream->data + 4));
- queue->R[2] = le32_to_cpu(*(u32*)(istream->data + 8));
+ queue->R[0] = le32_to_cpu(*(le32*)(istream->data + 0));
+ queue->R[1] = le32_to_cpu(*(le32*)(istream->data + 4));
+ queue->R[2] = le32_to_cpu(*(le32*)(istream->data + 8));
istream->data += 12;
istream->data_bytes_left -= 12;
/* The uncompressed data of this block directly follows and will
unsigned match_offset;
unsigned additional_len;
unsigned num_extra_bits;
- unsigned verbatim_bits;
- unsigned aligned_bits;
+ u32 verbatim_bits;
+ u32 aligned_bits;
unsigned i;
int ret;
u8 *match_dest;
* @block_type: The type of the block (LZX_BLOCKTYPE_VERBATIM or
* LZX_BLOCKTYPE_ALIGNED)
* @block_size: The size of the block, in bytes.
+ * @num_main_syms: Number of symbols in the main alphabet.
* @window: Pointer to the decompression window.
* @window_pos: The current position in the window. Will be 0 for the first
* block.
*/
static int
lzx_decompress_block(int block_type, unsigned block_size,
+ unsigned num_main_syms,
u8 *window,
unsigned window_pos,
const struct lzx_tables *tables,
end = window_pos + block_size;
while (window_pos < end) {
ret = read_huffsym_using_maintree(istream, tables,
- &main_element);
+ &main_element,
+ num_main_syms);
if (ret)
return ret;
/* literal: 0 to LZX_NUM_CHARS - 1 */
window[window_pos++] = main_element;
} else {
- /* match: LZX_NUM_CHARS to LZX_MAINCODE_NUM_SYMBOLS - 1 */
+ /* match: LZX_NUM_CHARS to num_main_syms - 1 */
match_len = lzx_decode_match(main_element,
block_type,
end - window_pos,
/* API function documented in wimlib.h */
WIMLIBAPI int
-wimlib_lzx_decompress(const void *compressed_data, unsigned compressed_len,
- void *uncompressed_data, unsigned uncompressed_len)
+wimlib_lzx_decompress2(const void *compressed_data, unsigned compressed_len,
+ void *uncompressed_data, unsigned uncompressed_len,
+ u32 max_window_size)
{
struct lzx_tables tables;
struct input_bitstream istream;
unsigned window_pos;
unsigned block_size;
unsigned block_type;
+ unsigned num_main_syms;
int ret;
bool e8_preprocessing_done;
- LZX_DEBUG("lzx_decompress (compressed_data = %p, compressed_len = %d, "
- "uncompressed_data = %p, uncompressed_len = %d).",
+ LZX_DEBUG("compressed_data = %p, compressed_len = %u, "
+ "uncompressed_data = %p, uncompressed_len = %u, "
+ "max_window_size=%u).",
compressed_data, compressed_len,
- uncompressed_data, uncompressed_len);
+ uncompressed_data, uncompressed_len, max_window_size);
- wimlib_assert(uncompressed_len <= 32768);
+ if (!lzx_window_size_valid(max_window_size)) {
+ LZX_DEBUG("Window size of %u is invalid!",
+ max_window_size);
+ return -1;
+ }
+
+ num_main_syms = lzx_get_num_main_syms(max_window_size);
+
+ if (uncompressed_len > max_window_size) {
+ LZX_DEBUG("Uncompressed chunk size of %u exceeds "
+ "window size of %u!",
+ uncompressed_len, max_window_size);
+ return -1;
+ }
memset(tables.maintree_lens, 0, sizeof(tables.maintree_lens));
memset(tables.lentree_lens, 0, sizeof(tables.lentree_lens));
window_pos += block_size)
{
LZX_DEBUG("Reading block header.");
- ret = lzx_read_block_header(&istream, &block_size,
+ ret = lzx_read_block_header(&istream, num_main_syms,
+ max_window_size, &block_size,
&block_type, &tables, &queue);
if (ret)
return ret;
LZX_DEBUG("LZX_BLOCKTYPE_ALIGNED");
ret = lzx_decompress_block(block_type,
block_size,
+ num_main_syms,
uncompressed_data,
window_pos,
&tables,
&istream);
if (ret)
return ret;
+
if (tables.maintree_lens[0xe8] != 0)
e8_preprocessing_done = true;
break;
undo_call_insn_preprocessing(uncompressed_data, uncompressed_len);
return 0;
}
+
+/* API function documented in wimlib.h */
+WIMLIBAPI int
+wimlib_lzx_decompress(const void *compressed_data, unsigned compressed_len,
+ void *uncompressed_data, unsigned uncompressed_len)
+{
+ return wimlib_lzx_decompress2(compressed_data, compressed_len,
+ uncompressed_data, uncompressed_len,
+ 32768);
+}
git://wimlib.net / wimlib / blobdiff