--- /dev/null
+/*
+ * lzx_decompress.c
+ *
+ * A decompressor for the LZX compression format, as used in WIM files.
+ */
+
+/*
+ * Copyright (C) 2012, 2013, 2014 Eric Biggers
+ *
+ * This file is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the Free
+ * Software Foundation; either version 3 of the License, or (at your option) any
+ * later version.
+ *
+ * This file 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 Lesser General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this file; if not, see http://www.gnu.org/licenses/.
+ */
+
+/*
+ * LZX is an LZ77 and Huffman-code based compression format that has many
+ * similarities to DEFLATE (the format used by zlib/gzip). The compression
+ * ratio is as good or better than DEFLATE. See lzx_compress.c for a format
+ * overview, and see https://en.wikipedia.org/wiki/LZX_(algorithm) for a
+ * historical overview. Here I make some pragmatic notes.
+ *
+ * The old specification for LZX is the document "Microsoft LZX Data Compression
+ * Format" (1997). It defines the LZX format as used in cabinet files. Allowed
+ * window sizes are 2^n where 15 <= n <= 21. However, this document contains
+ * several errors, so don't read too much into it...
+ *
+ * The new specification for LZX is the document "[MS-PATCH]: LZX DELTA
+ * Compression and Decompression" (2014). It defines the LZX format as used by
+ * Microsoft's binary patcher. It corrects several errors in the 1997 document
+ * and extends the format in several ways --- namely, optional reference data,
+ * up to 2^25 byte windows, and longer match lengths.
+ *
+ * WIM files use a more restricted form of LZX. No LZX DELTA extensions are
+ * present, the window is not "sliding", E8 preprocessing is done
+ * unconditionally with a fixed file size, and the maximum window size is always
+ * 2^15 bytes (equal to the size of each "chunk" in a compressed WIM resource).
+ * This code is primarily intended to implement this form of LZX. But although
+ * not compatible with WIMGAPI, this code also supports maximum window sizes up
+ * to 2^21 bytes.
+ *
+ * TODO: Add support for window sizes up to 2^25 bytes.
+ */
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include "wimlib/decompressor_ops.h"
+#include "wimlib/decompress_common.h"
+#include "wimlib/error.h"
+#include "wimlib/lzx_common.h"
+#include "wimlib/util.h"
+
+#include <string.h>
+
+/* These values are chosen for fast decompression. */
+#define LZX_MAINCODE_TABLEBITS 11
+#define LZX_LENCODE_TABLEBITS 10
+#define LZX_PRECODE_TABLEBITS 6
+#define LZX_ALIGNEDCODE_TABLEBITS 7
+
+#define LZX_READ_LENS_MAX_OVERRUN 50
+
+/* Huffman decoding tables, and arrays that map symbols to codeword lengths. */
+struct lzx_tables {
+
+ u16 maincode_decode_table[(1 << LZX_MAINCODE_TABLEBITS) +
+ (LZX_MAINCODE_MAX_NUM_SYMBOLS * 2)]
+ _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+ u8 maincode_lens[LZX_MAINCODE_MAX_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN];
+
+
+ u16 lencode_decode_table[(1 << LZX_LENCODE_TABLEBITS) +
+ (LZX_LENCODE_NUM_SYMBOLS * 2)]
+ _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+ u8 lencode_lens[LZX_LENCODE_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN];
+
+
+ u16 alignedcode_decode_table[(1 << LZX_ALIGNEDCODE_TABLEBITS) +
+ (LZX_ALIGNEDCODE_NUM_SYMBOLS * 2)]
+ _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+ u8 alignedcode_lens[LZX_ALIGNEDCODE_NUM_SYMBOLS];
+} _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+
+/* The main LZX decompressor structure.
+ *
+ * Note: we keep track of most of the decompression state outside this
+ * structure. This structure only exists so that (1) we can store @window_order
+ * and @num_main_syms for multiple calls to lzx_decompress(); and (2) so that we
+ * don't have to allocate the large 'struct lzx_tables' on the stack. */
+struct lzx_decompressor {
+ unsigned window_order;
+ unsigned num_main_syms;
+ struct lzx_tables tables;
+};
+
+/* Read a Huffman-encoded symbol using the precode. */
+static inline u16
+read_huffsym_using_precode(struct input_bitstream *istream,
+ const u16 precode_decode_table[])
+{
+ return read_huffsym(istream, precode_decode_table,
+ LZX_PRECODE_TABLEBITS, LZX_MAX_PRE_CODEWORD_LEN);
+}
+
+/* Read a Huffman-encoded symbol using the main code. */
+static inline u16
+read_huffsym_using_maincode(struct input_bitstream *istream,
+ const struct lzx_tables *tables)
+{
+ return read_huffsym(istream, tables->maincode_decode_table,
+ LZX_MAINCODE_TABLEBITS, LZX_MAX_MAIN_CODEWORD_LEN);
+}
+
+/* Read a Huffman-encoded symbol using the length code. */
+static inline u16
+read_huffsym_using_lencode(struct input_bitstream *istream,
+ const struct lzx_tables *tables)
+{
+ return read_huffsym(istream, tables->lencode_decode_table,
+ LZX_LENCODE_TABLEBITS, LZX_MAX_LEN_CODEWORD_LEN);
+}
+
+/* Read a Huffman-encoded symbol using the aligned offset code. */
+static inline u16
+read_huffsym_using_alignedcode(struct input_bitstream *istream,
+ const struct lzx_tables *tables)
+{
+ return read_huffsym(istream, tables->alignedcode_decode_table,
+ LZX_ALIGNEDCODE_TABLEBITS, LZX_MAX_ALIGNED_CODEWORD_LEN);
+}
+
+/*
+ * Read the precode from the compressed input bitstream, then use it to decode
+ * @num_lens codeword length values.
+ *
+ * @istream:
+ * The input bitstream.
+ *
+ * @lens:
+ * An array that contains the length values from the previous time the
+ * codeword lengths for this Huffman code were read, or all 0's if this is
+ * the first time. This array must have at least (@num_lens +
+ * LZX_READ_LENS_MAX_OVERRUN) entries.
+ *
+ * @num_lens:
+ * Number of length values to decode.
+ *
+ * Returns 0 on success, or -1 if the data was invalid.
+ */
+static int
+lzx_read_codeword_lens(struct input_bitstream *istream, u8 *lens, unsigned num_lens)
+{
+ u16 precode_decode_table[(1 << LZX_PRECODE_TABLEBITS) +
+ (LZX_PRECODE_NUM_SYMBOLS * 2)]
+ _aligned_attribute(DECODE_TABLE_ALIGNMENT);
+ u8 precode_lens[LZX_PRECODE_NUM_SYMBOLS];
+ u8 *len_ptr = lens;
+ u8 *lens_end = lens + num_lens;
+ int ret;
+
+ /* Read the lengths of the precode codewords. These are given
+ * explicitly. */
+ for (int i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++) {
+ precode_lens[i] = bitstream_read_bits(istream,
+ LZX_PRECODE_ELEMENT_SIZE);
+ }
+
+ /* Make the decoding table for the precode. */
+ ret = make_huffman_decode_table(precode_decode_table,
+ LZX_PRECODE_NUM_SYMBOLS,
+ LZX_PRECODE_TABLEBITS,
+ precode_lens,
+ LZX_MAX_PRE_CODEWORD_LEN);
+ if (ret)
+ return ret;
+
+ /* Decode the codeword lengths. */
+ do {
+ unsigned presym;
+ u8 len;
+
+ /* Read the next precode symbol. */
+ presym = read_huffsym_using_precode(istream,
+ precode_decode_table);
+ if (presym < 17) {
+ /* Difference from old length */
+ len = *len_ptr - presym;
+ if ((s8)len < 0)
+ len += 17;
+ *len_ptr++ = len;
+ } else {
+ /* Special RLE values */
+
+ unsigned run_len;
+
+ if (presym == 17) {
+ /* Run of 0's */
+ run_len = 4 + bitstream_read_bits(istream, 4);
+ len = 0;
+ } else if (presym == 18) {
+ /* Longer run of 0's */
+ run_len = 20 + bitstream_read_bits(istream, 5);
+ len = 0;
+ } else {
+ /* Run of identical lengths */
+ run_len = 4 + bitstream_read_bits(istream, 1);
+ presym = read_huffsym_using_precode(istream,
+ precode_decode_table);
+ len = *len_ptr - presym;
+ if ((s8)len < 0)
+ len += 17;
+ }
+
+ do {
+ *len_ptr++ = len;
+ } while (--run_len);
+ /* Worst case overrun is when presym == 18,
+ * run_len == 20 + 31, and only 1 length was remaining.
+ * So LZX_READ_LENS_MAX_OVERRUN == 50.
+ *
+ * Overrun while reading the first half of maincode_lens
+ * can corrupt the previous values in the second half.
+ * This doesn't really matter because the resulting
+ * lengths will still be in range, and data that
+ * generates overruns is invalid anyway. */
+ }
+ } while (len_ptr < lens_end);
+ return 0;
+}
+
+/*
+ * Read the header of an LZX block and save the block type and size in
+ * *block_type_ret and *block_size_ret, respectively.
+ *
+ * If the block is compressed, also update the Huffman decode @tables with the
+ * new Huffman codes.
+ *
+ * If the block is uncompressed, also update the match offset @queue with the
+ * new match offsets.
+ *
+ * Return 0 on success, or -1 if the data was invalid.
+ */
+static int
+lzx_read_block_header(struct input_bitstream *istream,
+ unsigned num_main_syms,
+ unsigned window_order,
+ int *block_type_ret,
+ u32 *block_size_ret,
+ struct lzx_tables *tables,
+ struct lzx_lru_queue *queue)
+{
+ int block_type;
+ u32 block_size;
+ int ret;
+
+ bitstream_ensure_bits(istream, 4);
+
+ /* The first three bits tell us what kind of block it is, and should be
+ * one of the LZX_BLOCKTYPE_* values. */
+ block_type = bitstream_pop_bits(istream, 3);
+
+ /* Read the block size. This mirrors the behavior of
+ * lzx_write_compressed_block() in lzx_compress.c; see that for more
+ * details. */
+ if (bitstream_pop_bits(istream, 1)) {
+ block_size = LZX_DEFAULT_BLOCK_SIZE;
+ } else {
+ u32 tmp;
+ block_size = 0;
+
+ tmp = bitstream_read_bits(istream, 8);
+ block_size |= tmp;
+ tmp = bitstream_read_bits(istream, 8);
+ block_size <<= 8;
+ block_size |= tmp;
+
+ if (window_order >= 16) {
+ tmp = bitstream_read_bits(istream, 8);
+ block_size <<= 8;
+ block_size |= tmp;
+ }
+ }
+
+ switch (block_type) {
+
+ case LZX_BLOCKTYPE_ALIGNED:
+
+ /* Read the aligned offset code and prepare its decode table.
+ */
+
+ for (int i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) {
+ tables->alignedcode_lens[i] =
+ bitstream_read_bits(istream,
+ LZX_ALIGNEDCODE_ELEMENT_SIZE);
+ }
+
+ ret = make_huffman_decode_table(tables->alignedcode_decode_table,
+ LZX_ALIGNEDCODE_NUM_SYMBOLS,
+ LZX_ALIGNEDCODE_TABLEBITS,
+ tables->alignedcode_lens,
+ LZX_MAX_ALIGNED_CODEWORD_LEN);
+ if (ret)
+ return ret;
+
+ /* Fall though, since the rest of the header for aligned offset
+ * blocks is the same as that for verbatim blocks. */
+
+ case LZX_BLOCKTYPE_VERBATIM:
+
+ /* Read the main code and prepare its decode table.
+ *
+ * Note that the codeword lengths in the main code are encoded
+ * in two parts: one part for literal symbols, and one part for
+ * match symbols. */
+
+ ret = lzx_read_codeword_lens(istream, tables->maincode_lens,
+ LZX_NUM_CHARS);
+ if (ret)
+ return ret;
+
+ ret = lzx_read_codeword_lens(istream,
+ tables->maincode_lens + LZX_NUM_CHARS,
+ num_main_syms - LZX_NUM_CHARS);
+ if (ret)
+ return ret;
+
+ ret = make_huffman_decode_table(tables->maincode_decode_table,
+ num_main_syms,
+ LZX_MAINCODE_TABLEBITS,
+ tables->maincode_lens,
+ LZX_MAX_MAIN_CODEWORD_LEN);
+ if (ret)
+ return ret;
+
+ /* Read the length code and prepare its decode table. */
+
+ ret = lzx_read_codeword_lens(istream, tables->lencode_lens,
+ LZX_LENCODE_NUM_SYMBOLS);
+ if (ret)
+ return ret;
+
+ ret = make_huffman_decode_table(tables->lencode_decode_table,
+ LZX_LENCODE_NUM_SYMBOLS,
+ LZX_LENCODE_TABLEBITS,
+ tables->lencode_lens,
+ LZX_MAX_LEN_CODEWORD_LEN);
+ if (ret)
+ return ret;
+
+ break;
+
+ case LZX_BLOCKTYPE_UNCOMPRESSED:
+
+ /* Before reading the three LRU match offsets from the
+ * uncompressed block header, the stream must be aligned on a
+ * 16-bit boundary. But, unexpectedly, if the stream is
+ * *already* aligned, the correct thing to do is to throw away
+ * the next 16 bits. */
+
+ bitstream_ensure_bits(istream, 1);
+ bitstream_align(istream);
+ queue->R[0] = bitstream_read_u32(istream);
+ queue->R[1] = bitstream_read_u32(istream);
+ queue->R[2] = bitstream_read_u32(istream);
+
+ /* Offsets of 0 are invalid. */
+ if (queue->R[0] == 0 || queue->R[1] == 0 || queue->R[2] == 0)
+ return -1;
+ break;
+
+ default:
+ /* Unrecognized block type. */
+ return -1;
+ }
+
+ *block_type_ret = block_type;
+ *block_size_ret = block_size;
+ return 0;
+}
+
+/*
+ * Decompress an LZX-compressed block of data.
+ *
+ * @block_type:
+ * The type of the block (LZX_BLOCKTYPE_VERBATIM or LZX_BLOCKTYPE_ALIGNED).
+ *
+ * @block_size:
+ * The size of the block, in bytes.
+ *
+ * @window:
+ * Pointer to the beginning of the decompression window.
+ *
+ * @window_pos:
+ * The position in the window at which the block starts.
+ *
+ * @tables:
+ * The Huffman decoding tables for the block.
+ *
+ * @queue:
+ * The least-recently-used queue for match offsets.
+ *
+ * @istream:
+ * The input bitstream, positioned at the start of the block data.
+ *
+ * Returns 0 on success, or -1 if the data was invalid.
+ */
+static int
+lzx_decompress_block(int block_type, u32 block_size,
+ u8 *window, u32 window_pos,
+ const struct lzx_tables *tables,
+ struct lzx_lru_queue *queue,
+ struct input_bitstream *istream)
+{
+ u8 *window_ptr = &window[window_pos];
+ u8 *window_end = window_ptr + block_size;
+ unsigned mainsym;
+ u32 match_len;
+ unsigned offset_slot;
+ u32 match_offset;
+ unsigned num_extra_bits;
+ unsigned ones_if_aligned = 0U - (block_type == LZX_BLOCKTYPE_ALIGNED);
+
+ while (window_ptr != window_end) {
+
+ mainsym = read_huffsym_using_maincode(istream, tables);
+ if (mainsym < LZX_NUM_CHARS) {
+ /* Literal */
+ *window_ptr++ = mainsym;
+ continue;
+ }
+
+ /* Match */
+
+ /* Decode the length header and offset slot. */
+ mainsym -= LZX_NUM_CHARS;
+ match_len = mainsym & 0x7;
+ offset_slot = mainsym >> 3;
+
+ /* If needed, read a length symbol to decode the full length. */
+ if (match_len == 0x7)
+ match_len += read_huffsym_using_lencode(istream, tables);
+ match_len += LZX_MIN_MATCH_LEN;
+
+ if (offset_slot <= 2) {
+ /* Repeat offset */
+
+ /* Note: This isn't a real LRU queue, since using the R2
+ * offset doesn't bump the R1 offset down to R2. This
+ * quirk allows all 3 recent offsets to be handled by
+ * the same code. (For R0, the swap is a no-op.) */
+ match_offset = queue->R[offset_slot];
+ queue->R[offset_slot] = queue->R[0];
+ queue->R[0] = match_offset;
+ } else {
+ /* Explicit offset */
+
+ /* Look up the number of extra bits that need to be read
+ * to decode offsets with this offset slot. */
+ num_extra_bits = lzx_extra_offset_bits[offset_slot];
+
+ /* Start with the offset slot base value. */
+ match_offset = lzx_offset_slot_base[offset_slot];
+
+ /* In aligned offset blocks, the low-order 3 bits of
+ * each offset are encoded using the aligned offset
+ * code. Otherwise, all the extra bits are literal. */
+
+ /*if (block_type == LZX_BLOCKTYPE_ALIGNED && num_extra_bits >= 3) {*/
+ if ((num_extra_bits & ones_if_aligned) >= 3) {
+ match_offset += bitstream_read_bits(istream, num_extra_bits - 3) << 3;
+ match_offset += read_huffsym_using_alignedcode(istream, tables);
+ } else {
+ match_offset += bitstream_read_bits(istream, num_extra_bits);
+ }
+
+ /* Adjust the offset. */
+ match_offset -= LZX_OFFSET_OFFSET;
+
+ /* Update the match offset LRU queue. */
+ queue->R[2] = queue->R[1];
+ queue->R[1] = queue->R[0];
+ queue->R[0] = match_offset;
+ }
+
+ /* Validate the match, then copy it to the current position. */
+
+ if (unlikely(match_len > window_end - window_ptr))
+ return -1;
+
+ if (unlikely(match_offset > window_ptr - window))
+ return -1;
+
+ lz_copy(window_ptr, match_len, match_offset, window_end,
+ LZX_MIN_MATCH_LEN);
+
+ window_ptr += match_len;
+ }
+ return 0;
+}
+
+static int
+lzx_decompress(const void *compressed_data, size_t compressed_size,
+ void *uncompressed_data, size_t uncompressed_size,
+ void *_dec)
+{
+ struct lzx_decompressor *dec = _dec;
+ struct input_bitstream istream;
+ struct lzx_lru_queue queue;
+ u32 window_pos;
+ int block_type;
+ u32 block_size;
+ bool may_have_e8_byte;
+ int ret;
+
+ init_input_bitstream(&istream, compressed_data, compressed_size);
+
+ /* Initialize the recent offsets queue. */
+ lzx_lru_queue_init(&queue);
+
+ /* Codeword lengths begin as all 0's for delta encoding purposes. */
+ memset(dec->tables.maincode_lens, 0, dec->num_main_syms);
+ memset(dec->tables.lencode_lens, 0, LZX_LENCODE_NUM_SYMBOLS);
+
+ /* Set this to true if there may be 0xe8 bytes in the uncompressed data.
+ */
+ may_have_e8_byte = false;
+
+ /* The compressed data will consist of one or more blocks. The
+ * following loop decompresses one block, and it runs until there all
+ * the compressed data has been decompressed, so there are no more
+ * blocks. */
+
+ for (window_pos = 0;
+ window_pos < uncompressed_size;
+ window_pos += block_size)
+ {
+ ret = lzx_read_block_header(&istream, dec->num_main_syms,
+ dec->window_order, &block_type,
+ &block_size, &dec->tables, &queue);
+ if (ret)
+ return ret;
+
+ if (block_size > uncompressed_size - window_pos)
+ return -1;
+
+ if (block_type != LZX_BLOCKTYPE_UNCOMPRESSED) {
+
+ /* Compressed block. */
+
+ ret = lzx_decompress_block(block_type,
+ block_size,
+ uncompressed_data,
+ window_pos,
+ &dec->tables,
+ &queue,
+ &istream);
+ if (ret)
+ return ret;
+
+ /* If the first 0xe8 byte was in this block, it must
+ * have been encoded as a literal using mainsym 0xe8. */
+ if (dec->tables.maincode_lens[0xe8] != 0)
+ may_have_e8_byte = true;
+ } else {
+
+ /* Uncompressed block. */
+ const u8 *p;
+
+ p = bitstream_read_bytes(&istream, block_size);
+ if (!p)
+ return -1;
+
+ memcpy(&((u8*)uncompressed_data)[window_pos], p, block_size);
+
+ /* Re-align the bitstream if an odd number of bytes was
+ * read. */
+ if (block_size & 1)
+ bitstream_read_byte(&istream);
+
+ may_have_e8_byte = true;
+ }
+ }
+
+ /* Postprocess the data unless it cannot possibly contain 0xe8 bytes */
+ if (may_have_e8_byte)
+ lzx_undo_e8_preprocessing(uncompressed_data, uncompressed_size);
+
+ return 0;
+}
+
+static void
+lzx_free_decompressor(void *_dec)
+{
+ struct lzx_decompressor *dec = _dec;
+
+ ALIGNED_FREE(dec);
+}
+
+static int
+lzx_create_decompressor(size_t max_block_size, void **dec_ret)
+{
+ struct lzx_decompressor *dec;
+ unsigned window_order;
+
+ window_order = lzx_get_window_order(max_block_size);
+ if (window_order == 0)
+ return WIMLIB_ERR_INVALID_PARAM;
+
+ /* The aligned allocation is needed to ensure that the lzx_tables are
+ * aligned properly. */
+ dec = ALIGNED_MALLOC(sizeof(struct lzx_decompressor),
+ DECODE_TABLE_ALIGNMENT);
+ if (!dec)
+ return WIMLIB_ERR_NOMEM;
+
+ dec->window_order = window_order;
+ dec->num_main_syms = lzx_get_num_main_syms(window_order);
+
+ *dec_ret = dec;
+ return 0;
+}
+
+const struct decompressor_ops lzx_decompressor_ops = {
+ .create_decompressor = lzx_create_decompressor,
+ .decompress = lzx_decompress,
+ .free_decompressor = lzx_free_decompressor,
+};
git://wimlib.net / wimlib / blobdiff