X-Git-Url: https://wimlib.net/git/?a=blobdiff_plain;f=src%2Flzx-decompress.c;h=0c95ac03ecefa1489ee9e69a76a5d9197245e7ad;hb=3ee9acdab75547655dd7fb9d3c423daeb3051642;hp=5a3c78a7baa9265303f5e8848b3225b1a91acba0;hpb=af940b1ab45d16ad97e3a5530dd8559bcad86958;p=wimlib diff --git a/src/lzx-decompress.c b/src/lzx-decompress.c index 5a3c78a7..0c95ac03 100644 --- a/src/lzx-decompress.c +++ b/src/lzx-decompress.c @@ -1,13 +1,11 @@ /* * lzx-decompress.c * - * LZX decompression routines, originally based on code taken from cabextract - * v0.5, which was, itself, a modified version of the lzx decompression code - * from unlzx. + * A very fast decompressor for LZX, as used in WIM files. */ /* - * Copyright (C) 2012, 2013 Eric Biggers + * Copyright (C) 2012, 2013, 2014 Eric Biggers * * This file is part of wimlib, a library for working with WIM files. * @@ -26,275 +24,222 @@ */ /* - * 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. - * - * 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 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 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 - * uncompresses to. However, in the WIM format it appears that every chunk that - * would be 32768 bytes or more when compressed is actually stored fully - * uncompressed. - * - * The 'e8' preprocessing step that changes x86 call instructions to use - * absolute offsets instead of relative offsets relies on a filesize parameter. - * There is no such parameter for this in the WIM files (even though the size of - * the file resource could be used for this purpose), and instead a magic file - * size of 12000000 is used. The 'e8' preprocessing is always done, and there - * is no bit to indicate whether it is done or not. - */ - -/* - * Some more notes about errors in Microsoft's LZX documentation: - * - * Microsoft's LZX document and their implementation of the com.ms.util.cab Java - * package do not concur. - * - * In the LZX document, there is a table showing the correlation between window - * size and the number of position slots. It states that the 1MB window = 40 - * slots and the 2MB window = 42 slots. In the implementation, 1MB = 42 slots, - * 2MB = 50 slots. The actual calculation is 'find the first slot whose position - * base is equal to or more than the required window size'. This would explain - * why other tables in the document refer to 50 slots rather than 42. - * - * The constant NUM_PRIMARY_LENS used in the decompression pseudocode is not - * 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 - * 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. - * - * 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. - * However, the pseudocode provided checks for the *E8 leader* up to the last 6 - * bytes. If the leader appears between -10 and -7 bytes from the end, this - * 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 - * 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. + * 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.h" -#include "wimlib/decompress.h" +#include "wimlib/decompressor_ops.h" +#include "wimlib/decompress_common.h" +#include "wimlib/error.h" #include "wimlib/lzx.h" #include "wimlib/util.h" #include -/* Huffman decoding tables and maps from symbols to code lengths. */ +/* 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 + +/* Huffman decoding tables, and arrays that map symbols to codeword lengths. */ struct lzx_tables { - u16 maintree_decode_table[(1 << LZX_MAINCODE_TABLEBITS) + + u16 maincode_decode_table[(1 << LZX_MAINCODE_TABLEBITS) + (LZX_MAINCODE_MAX_NUM_SYMBOLS * 2)] _aligned_attribute(DECODE_TABLE_ALIGNMENT); - u8 maintree_lens[LZX_MAINCODE_MAX_NUM_SYMBOLS]; + u8 maincode_lens[LZX_MAINCODE_MAX_NUM_SYMBOLS]; - u16 lentree_decode_table[(1 << LZX_LENCODE_TABLEBITS) + + u16 lencode_decode_table[(1 << LZX_LENCODE_TABLEBITS) + (LZX_LENCODE_NUM_SYMBOLS * 2)] _aligned_attribute(DECODE_TABLE_ALIGNMENT); - u8 lentree_lens[LZX_LENCODE_NUM_SYMBOLS]; + u8 lencode_lens[LZX_LENCODE_NUM_SYMBOLS]; - u16 alignedtree_decode_table[(1 << LZX_ALIGNEDCODE_TABLEBITS) + + u16 alignedcode_decode_table[(1 << LZX_ALIGNEDCODE_TABLEBITS) + (LZX_ALIGNEDCODE_NUM_SYMBOLS * 2)] _aligned_attribute(DECODE_TABLE_ALIGNMENT); - u8 alignedtree_lens[LZX_ALIGNEDCODE_NUM_SYMBOLS]; + 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 + * @max_window_size 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 { + u32 max_window_size; + unsigned num_main_syms; + struct lzx_tables tables; +}; -/* - * Reads a Huffman-encoded symbol using the pre-tree. - */ -static inline int -read_huffsym_using_pretree(struct input_bitstream *istream, - const u16 pretree_decode_table[], - const u8 pretree_lens[], unsigned *n) +/* 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, pretree_decode_table, pretree_lens, - LZX_PRECODE_NUM_SYMBOLS, LZX_PRECODE_TABLEBITS, n, - LZX_MAX_PRE_CODEWORD_LEN); + return read_huffsym(istream, precode_decode_table, + LZX_PRECODE_TABLEBITS, LZX_MAX_PRE_CODEWORD_LEN); } -/* Reads a Huffman-encoded symbol using the main tree. */ -static inline int -read_huffsym_using_maintree(struct input_bitstream *istream, - const struct lzx_tables *tables, - unsigned *n, - unsigned num_main_syms) +/* 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->maintree_decode_table, - tables->maintree_lens, num_main_syms, - LZX_MAINCODE_TABLEBITS, n, LZX_MAX_MAIN_CODEWORD_LEN); + return read_huffsym(istream, tables->maincode_decode_table, + LZX_MAINCODE_TABLEBITS, LZX_MAX_MAIN_CODEWORD_LEN); } -/* Reads a Huffman-encoded symbol using the length tree. */ -static inline int -read_huffsym_using_lentree(struct input_bitstream *istream, - const struct lzx_tables *tables, - unsigned *n) +/* 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->lentree_decode_table, - tables->lentree_lens, LZX_LENCODE_NUM_SYMBOLS, - LZX_LENCODE_TABLEBITS, n, LZX_MAX_LEN_CODEWORD_LEN); + return read_huffsym(istream, tables->lencode_decode_table, + LZX_LENCODE_TABLEBITS, LZX_MAX_LEN_CODEWORD_LEN); } -/* Reads a Huffman-encoded symbol using the aligned offset tree. */ -static inline int -read_huffsym_using_alignedtree(struct input_bitstream *istream, - const struct lzx_tables *tables, - unsigned *n) +/* 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->alignedtree_decode_table, - tables->alignedtree_lens, - LZX_ALIGNEDCODE_NUM_SYMBOLS, - LZX_ALIGNEDCODE_TABLEBITS, n, - LZX_MAX_ALIGNED_CODEWORD_LEN); + return read_huffsym(istream, tables->alignedcode_decode_table, + LZX_ALIGNEDCODE_TABLEBITS, LZX_MAX_ALIGNED_CODEWORD_LEN); } /* - * Reads the pretree from the input, then uses the pretree to decode @num_lens - * code length values from the input. + * Read the precode from the compressed input bitstream, then use it to decode + * @num_lens codeword length values. + * + * @istream: + * The input bitstream. * - * @istream: The bit stream for the input. It is positioned on the beginning - * of the pretree for the code length values. - * @lens: An array that contains the length values from the previous time - * the code lengths for this Huffman tree were read, or all - * 0's if this is the first time. - * @num_lens: Number of length values to decode and return. + * @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. * + * @num_lens: + * Number of length values to decode. + * + * Returns 0 on success, or -1 if the data was invalid. */ static int -lzx_read_code_lens(struct input_bitstream *istream, u8 lens[], - unsigned num_lens) +lzx_read_codeword_lens(struct input_bitstream *istream, u8 lens[], unsigned num_lens) { - /* Declare the decoding table and length table for the pretree. */ - u16 pretree_decode_table[(1 << LZX_PRECODE_TABLEBITS) + + /* Declare the decoding table and length table for the precode. */ + u16 precode_decode_table[(1 << LZX_PRECODE_TABLEBITS) + (LZX_PRECODE_NUM_SYMBOLS * 2)] _aligned_attribute(DECODE_TABLE_ALIGNMENT); - u8 pretree_lens[LZX_PRECODE_NUM_SYMBOLS]; - unsigned i; - u32 len; + u8 precode_lens[LZX_PRECODE_NUM_SYMBOLS]; int ret; - /* Read the code lengths of the pretree codes. There are 20 lengths of - * 4 bits each. */ - for (i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++) { - ret = bitstream_read_bits(istream, LZX_PRECODE_ELEMENT_SIZE, - &len); - if (ret) - return ret; - pretree_lens[i] = len; + /* 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 pretree. */ - ret = make_huffman_decode_table(pretree_decode_table, + /* Make the decoding table for the precode. */ + ret = make_huffman_decode_table(precode_decode_table, LZX_PRECODE_NUM_SYMBOLS, LZX_PRECODE_TABLEBITS, - pretree_lens, + precode_lens, LZX_MAX_PRE_CODEWORD_LEN); if (ret) return ret; - /* Pointer past the last length value that needs to be filled in. */ + /* Pointer past the last length value that needs to be filled in. */ u8 *lens_end = lens + num_lens; - while (1) { - - /* Decode a symbol from the input. If the symbol is between 0 - * and 16, it is the difference from the old length. If it is - * between 17 and 19, it is a special code that indicates that - * some number of the next lengths are all 0, or some number of - * the next lengths are all equal to the next symbol in the - * input. */ - unsigned tree_code; - u32 num_zeroes; - unsigned code; - u32 num_same; + for (;;) { + + unsigned presym; + unsigned run_len; signed char value; - ret = read_huffsym_using_pretree(istream, pretree_decode_table, - pretree_lens, &tree_code); - if (ret) - return ret; - switch (tree_code) { - case 17: /* Run of 0's */ - ret = bitstream_read_bits(istream, 4, &num_zeroes); - if (ret) - return ret; - num_zeroes += 4; - while (num_zeroes--) { + /* Decode a symbol from the input. + * + * If the symbol is between 0 and 16, it is the difference from + * the old length, modulo 17. + * + * If the symbol is between 17 and 19, it is a special symbol + * that indicates that some number of the next lengths are all + * 0, or that some number of the next lengths are all equal to + * the next symbol. */ + + presym = read_huffsym_using_precode(istream, + precode_decode_table); + switch (presym) { + + case 17: /* Run of 0's */ + run_len = 4 + bitstream_read_bits(istream, 4); + do { *lens = 0; if (++lens == lens_end) return 0; - } + } while (--run_len); break; - case 18: /* Longer run of 0's */ - ret = bitstream_read_bits(istream, 5, &num_zeroes); - if (ret) - return ret; - num_zeroes += 20; - while (num_zeroes--) { + + case 18: /* Longer run of 0's */ + run_len = 20 + bitstream_read_bits(istream, 5); + do { *lens = 0; if (++lens == lens_end) return 0; - } + } while (--run_len); break; - case 19: /* Run of identical lengths */ - ret = bitstream_read_bits(istream, 1, &num_same); - if (ret) - return ret; - num_same += 4; - ret = read_huffsym_using_pretree(istream, - pretree_decode_table, - pretree_lens, - &code); - if (ret) - return ret; - value = (signed char)*lens - (signed char)code; + + case 19: /* Run of identical lengths */ + run_len = 4 + bitstream_read_bits(istream, 1); + presym = read_huffsym_using_precode(istream, + precode_decode_table); + value = (signed char)*lens - (signed char)presym; if (value < 0) value += 17; - while (num_same--) { + do { *lens = value; if (++lens == lens_end) return 0; - } + } while (--run_len); break; - default: /* Difference from old length. */ - value = (signed char)*lens - (signed char)tree_code; + + default: /* Difference from old length */ + value = (signed char)*lens - (signed char)presym; if (value < 0) value += 17; *lens = value; @@ -306,188 +251,142 @@ lzx_read_code_lens(struct input_bitstream *istream, u8 lens[], } /* - * Reads the header for an LZX-compressed block. + * 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. * - * @istream: The input bitstream. - * @block_size_ret: A pointer to an int into which the size of the block, - * in bytes, will be returned. - * @block_type_ret: A pointer to an int into which the type of the block - * (LZX_BLOCKTYPE_*) will be returned. - * @tables: A pointer to a lzx_tables structure in which the - * main tree, the length tree, and possibly the - * aligned offset tree will be constructed. - * @queue: A pointer to the least-recently-used queue into which - * R0, R1, and R2 will be written (only for uncompressed - * blocks, which contain this information in the header) + * 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 max_window_size, - unsigned *block_size_ret, - unsigned *block_type_ret, + u32 max_window_size, + 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; - unsigned block_type; - unsigned block_size; - ret = bitstream_ensure_bits(istream, 4); - if (ret) - return ret; + bitstream_ensure_bits(istream, 4); - /* 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, 3); + /* 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 + /* Read the block size. This mirrors the behavior of * lzx_write_compressed_block() in lzx-compress.c; see that for more * details. */ - if (bitstream_read_bits_nocheck(istream, 1)) { + if (bitstream_pop_bits(istream, 1)) { block_size = LZX_DEFAULT_BLOCK_SIZE; } else { u32 tmp; block_size = 0; - ret = bitstream_read_bits(istream, 8, &tmp); - if (ret) - return ret; + tmp = bitstream_read_bits(istream, 8); block_size |= tmp; - - ret = bitstream_read_bits(istream, 8, &tmp); - if (ret) - return ret; + tmp = bitstream_read_bits(istream, 8); block_size <<= 8; block_size |= tmp; if (max_window_size >= 65536) { - ret = bitstream_read_bits(istream, 8, &tmp); - if (ret) - return ret; + tmp = bitstream_read_bits(istream, 8); block_size <<= 8; block_size |= tmp; } } switch (block_type) { + case LZX_BLOCKTYPE_ALIGNED: - /* Read the path lengths for the elements of the aligned tree, - * then build it. */ - for (unsigned i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) { - u32 len; + /* Read the aligned offset code and prepare its decode table. + */ - ret = bitstream_read_bits(istream, - LZX_ALIGNEDCODE_ELEMENT_SIZE, - &len); - if (ret) - return ret; - tables->alignedtree_lens[i] = len; + for (int i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) { + tables->alignedcode_lens[i] = + bitstream_read_bits(istream, + LZX_ALIGNEDCODE_ELEMENT_SIZE); } - LZX_DEBUG("Building the aligned tree."); - ret = make_huffman_decode_table(tables->alignedtree_decode_table, + ret = make_huffman_decode_table(tables->alignedcode_decode_table, LZX_ALIGNEDCODE_NUM_SYMBOLS, LZX_ALIGNEDCODE_TABLEBITS, - tables->alignedtree_lens, + tables->alignedcode_lens, LZX_MAX_ALIGNED_CODEWORD_LEN); - if (ret) { - LZX_DEBUG("Failed to make the decode table for the " - "aligned offset tree"); + if (ret) return ret; - } /* Fall though, since the rest of the header for aligned offset - * blocks is the same as that for verbatim blocks */ + * blocks is the same as that for verbatim blocks. */ case LZX_BLOCKTYPE_VERBATIM: - if (block_type == LZX_BLOCKTYPE_VERBATIM) - LZX_DEBUG("Found verbatim block."); - - LZX_DEBUG("Reading path lengths for main tree."); - /* Read the path lengths for the first 256 elements of the main - * tree. */ - ret = lzx_read_code_lens(istream, tables->maintree_lens, - LZX_NUM_CHARS); - if (ret) { - LZX_DEBUG("Failed to read the code lengths for the " - "first 256 elements of the main tree"); - return ret; - } - /* Read the path lengths for the remaining elements of the main - * tree. */ - LZX_DEBUG("Reading path lengths for remaining elements of " - "main tree (%d elements).", - num_main_syms - LZX_NUM_CHARS); - ret = lzx_read_code_lens(istream, - tables->maintree_lens + 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"); + /* 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; - } - LZX_DEBUG("Building the Huffman decoding " - "table for the main tree."); + 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->maintree_decode_table, + ret = make_huffman_decode_table(tables->maincode_decode_table, num_main_syms, LZX_MAINCODE_TABLEBITS, - tables->maintree_lens, + tables->maincode_lens, LZX_MAX_MAIN_CODEWORD_LEN); - if (ret) { - LZX_DEBUG("Failed to make the decode " - "table for the main tree"); + if (ret) return ret; - } - LZX_DEBUG("Reading path lengths for the length tree."); - ret = lzx_read_code_lens(istream, tables->lentree_lens, - LZX_LENCODE_NUM_SYMBOLS); - if (ret) { - LZX_DEBUG("Failed to read the path " - "lengths for the length tree"); + /* 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; - } - LZX_DEBUG("Building the length tree."); - ret = make_huffman_decode_table(tables->lentree_decode_table, + ret = make_huffman_decode_table(tables->lencode_decode_table, LZX_LENCODE_NUM_SYMBOLS, LZX_LENCODE_TABLEBITS, - tables->lentree_lens, + tables->lencode_lens, LZX_MAX_LEN_CODEWORD_LEN); - if (ret) { - LZX_DEBUG("Failed to build the length Huffman tree"); + if (ret) return ret; - } - /* The bitstream of compressed literals and matches for this - * block directly follows and will be read in - * lzx_decompress_block(). */ + break; + case LZX_BLOCKTYPE_UNCOMPRESSED: - LZX_DEBUG("Found uncompressed block."); + /* Before reading the three LRU match offsets from the - * uncompressed block header, the stream needs to be aligned on - * a 16-bit boundary. But, unexpectedly, if the stream is + * 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. */ + * the next 16 bits. */ + if (istream->bitsleft == 0) { - if (istream->data_bytes_left < 14) { - LZX_DEBUG("Insufficient length in " - "uncompressed block"); + if (istream->data_bytes_left < 14) return -1; - } istream->data += 2; istream->data_bytes_left -= 2; } else { - if (istream->data_bytes_left < 12) { - LZX_DEBUG("Insufficient length in " - "uncompressed block"); + if (istream->data_bytes_left < 12) return -1; - } istream->bitsleft = 0; istream->bitbuf = 0; } @@ -496,117 +395,69 @@ lzx_read_block_header(struct input_bitstream *istream, 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 - * be read in lzx_decompress(). */ break; + default: - LZX_DEBUG("Found invalid block"); + /* Unrecognized block type. */ return -1; } + *block_type_ret = block_type; *block_size_ret = block_size; return 0; } /* - * Decodes a compressed match from a block of LZX-compressed data. A match - * refers to some match_offset to a point earlier in the window as well as some - * match_len, for which the data is to be copied to the current position in the - * window. - * - * @main_element: The start of the match data, as decoded using the main - * tree. - * - * @block_type: The type of the block (LZX_BLOCKTYPE_ALIGNED or - * LZX_BLOCKTYPE_VERBATIM) - * - * @bytes_remaining: The amount of uncompressed data remaining to be - * uncompressed in this block. It is an error if the match - * is longer than this number. - * - * @window: A pointer to the window into which the uncompressed - * data is being written. - * - * @window_pos: The current byte offset in the window. - * - * @tables: The Huffman decoding tables for this LZX block (main - * code, length code, and for LZX_BLOCKTYPE_ALIGNED blocks, - * also the aligned offset code). - * - * @queue: The least-recently used queue for match offsets. - * - * @istream: The input bitstream. + * Decode a match and copy its bytes into the decompression window. * - * Returns the length of the match, or a negative number on error. The possible - * error cases are: - * - Match would exceed the amount of data remaining to be uncompressed. - * - Match refers to data before the window. - * - The input bitstream ended unexpectedly. + * Return the length of the match in bytes, or 0 if the match underflowed the + * window or overflowed the current block. */ -static int -lzx_decode_match(unsigned main_element, int block_type, - unsigned bytes_remaining, u8 *window, - unsigned window_pos, +static u32 +lzx_decode_match(unsigned main_symbol, int block_type, + u32 bytes_remaining, u8 *window, u32 window_pos, const struct lzx_tables *tables, struct lzx_lru_queue *queue, struct input_bitstream *istream) { unsigned length_header; unsigned position_slot; - unsigned match_len; - unsigned match_offset; - unsigned additional_len; + u32 match_len; + u32 match_offset; unsigned num_extra_bits; u32 verbatim_bits; u32 aligned_bits; - unsigned i; - int ret; - u8 *match_dest; - u8 *match_src; - /* The main element is offset by 256 because values under 256 indicate a - * literal value. */ - main_element -= LZX_NUM_CHARS; + /* The main symbol is offset by 256 because values under 256 indicate a + * literal value. */ + main_symbol -= LZX_NUM_CHARS; /* The length header consists of the lower 3 bits of the main element. * The position slot is the rest of it. */ - length_header = main_element & LZX_NUM_PRIMARY_LENS; - position_slot = main_element >> 3; + length_header = main_symbol & LZX_NUM_PRIMARY_LENS; + position_slot = main_symbol >> 3; /* If the length_header is less than LZX_NUM_PRIMARY_LENS (= 7), it * gives the match length as the offset from LZX_MIN_MATCH_LEN. * Otherwise, the length is given by an additional symbol encoded using - * the length tree, offset by 9 (LZX_MIN_MATCH_LEN + + * the length code, offset by 9 (LZX_MIN_MATCH_LEN + * LZX_NUM_PRIMARY_LENS) */ match_len = LZX_MIN_MATCH_LEN + length_header; - if (length_header == LZX_NUM_PRIMARY_LENS) { - ret = read_huffsym_using_lentree(istream, tables, - &additional_len); - if (ret) - return ret; - match_len += additional_len; - } - + if (length_header == LZX_NUM_PRIMARY_LENS) + match_len += read_huffsym_using_lencode(istream, tables); /* If the position_slot is 0, 1, or 2, the match offset is retrieved * from the LRU queue. Otherwise, the match offset is not in the LRU * queue. */ - switch (position_slot) { - case 0: - match_offset = queue->R[0]; - break; - case 1: - match_offset = queue->R[1]; - swap(queue->R[0], queue->R[1]); - break; - case 2: - /* The queue doesn't work quite the same as a real LRU queue, - * since using the R2 offset doesn't bump the R1 offset down to - * R2. */ - match_offset = queue->R[2]; - swap(queue->R[0], queue->R[2]); - break; - default: + if (position_slot <= 2) { + /* 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[position_slot]; + queue->R[position_slot] = queue->R[0]; + queue->R[0] = match_offset; + } else { /* Otherwise, the offset was not encoded as one the offsets in * the queue. Depending on the position slot, there is a * certain number of extra bits that need to be read to fully @@ -618,8 +469,8 @@ lzx_decode_match(unsigned main_element, int block_type, /* For aligned blocks, if there are at least 3 extra bits, the * actual number of extra bits is 3 less, and they encode a * number of 8-byte words that are added to the offset; there - * is then an additional symbol read using the aligned tree that - * specifies the actual byte alignment. */ + * is then an additional symbol read using the aligned offset + * code that specifies the actual byte alignment. */ if (block_type == LZX_BLOCKTYPE_ALIGNED && num_extra_bits >= 3) { /* There is an error in the LZX "specification" at this @@ -629,27 +480,17 @@ lzx_decode_match(unsigned main_element, int block_type, * equal to 3. (Note that in the case with * num_extra_bits == 3, the assignment to verbatim_bits * will just set it to 0. ) */ - ret = bitstream_read_bits(istream, num_extra_bits - 3, - &verbatim_bits); - if (ret) - return ret; - + verbatim_bits = bitstream_read_bits(istream, + num_extra_bits - 3); verbatim_bits <<= 3; - - ret = read_huffsym_using_alignedtree(istream, tables, - &aligned_bits); - if (ret) - return ret; + aligned_bits = read_huffsym_using_alignedcode(istream, + tables); } else { /* For non-aligned blocks, or for aligned blocks with * less than 3 extra bits, the extra bits are added * directly to the match offset, and the correction for * the alignment is taken to be 0. */ - ret = bitstream_read_bits(istream, num_extra_bits, - &verbatim_bits); - if (ret) - return ret; - + verbatim_bits = bitstream_read_bits(istream, num_extra_bits); aligned_bits = 0; } @@ -661,207 +502,112 @@ lzx_decode_match(unsigned main_element, int block_type, queue->R[2] = queue->R[1]; queue->R[1] = queue->R[0]; queue->R[0] = match_offset; - break; } - /* Verify that the match is in the bounds of the part of the window - * currently in use, then copy the source of the match to the current - * position. */ + /* Validate the match, then copy it to the current position. */ - if (match_len > bytes_remaining) { - LZX_DEBUG("Match of length %u bytes overflows " - "uncompressed block size", match_len); - return -1; - } + if (unlikely(match_len > bytes_remaining)) + return 0; - if (match_offset > window_pos) { - LZX_DEBUG("Match of length %u bytes references " - "data before window (match_offset = %u, " - "window_pos = %u)", - match_len, match_offset, window_pos); - return -1; - } + if (unlikely(match_offset > window_pos)) + return 0; - match_dest = window + window_pos; - match_src = match_dest - match_offset; - -#if 0 - printf("Match: src %u, dst %u, len %u\n", match_src - window, - match_dest - window, - match_len); - putchar('|'); - for (i = 0; i < match_len; i++) { - match_dest[i] = match_src[i]; - putchar(match_src[i]); - } - putchar('|'); - putchar('\n'); -#else - for (i = 0; i < match_len; i++) - match_dest[i] = match_src[i]; -#endif + lz_copy(&window[window_pos], match_len, match_offset, + &window[window_pos + bytes_remaining]); return match_len; } -static void -undo_call_insn_translation(u32 *call_insn_target, int input_pos, - s32 file_size) -{ - s32 abs_offset; - s32 rel_offset; - - abs_offset = le32_to_cpu(*call_insn_target); - if (abs_offset >= -input_pos && abs_offset < file_size) { - if (abs_offset >= 0) { - /* "good translation" */ - rel_offset = abs_offset - input_pos; - } else { - /* "compensating translation" */ - rel_offset = abs_offset + file_size; - } - *call_insn_target = cpu_to_le32(rel_offset); - } -} - -/* Undo the 'E8' preprocessing, where the targets of x86 CALL instructions were - * changed from relative offsets to absolute offsets. +/* + * Decompress an LZX-compressed block of data. * - * Note that this call instruction preprocessing can and will be used on any - * data even if it is not actually x86 machine code. In fact, this type of - * preprocessing appears to always be used in LZX-compressed resources in WIM - * files; there is no bit to indicate whether it is used or not, unlike in the - * LZX compressed format as used in cabinet files, where a bit is reserved for - * that purpose. + * @block_type: + * The type of the block (LZX_BLOCKTYPE_VERBATIM or LZX_BLOCKTYPE_ALIGNED). * - * Call instruction preprocessing is disabled in the last 6 bytes of the - * uncompressed data, which really means the 5-byte call instruction cannot - * start in the last 10 bytes of the uncompressed data. This is one of the - * errors in the LZX documentation. + * @block_size: + * The size of the block, in bytes. * - * Call instruction preprocessing does not appear to be disabled after the - * 32768th chunk of a WIM stream, which is apparently is yet another difference - * from the LZX compression used in cabinet files. + * @window: + * Pointer to the beginning of the decompression window. * - * Call instruction processing is supposed to take the file size as a parameter, - * as it is used in calculating the translated jump targets. But in WIM files, - * this file size is always the same (LZX_WIM_MAGIC_FILESIZE == 12000000).*/ -static void -undo_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) { - undo_call_insn_translation((u32*)&uncompressed_data[i + 1], - i, - LZX_WIM_MAGIC_FILESIZE); - i += 4; - } - } -} - -/* - * Decompresses a LZX-compressed block of data from which the header has already - * been read. + * @window_pos: + * The position in the window at which the block starts. + * + * @tables: + * The Huffman decoding tables for the block. * - * @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. - * @tables: The Huffman decoding tables for the block (main, length, and - * aligned offset, the latter only for LZX_BLOCKTYPE_ALIGNED) - * @queue: The least-recently-used queue for match offsets. - * @istream: The input bitstream for the compressed literals. + * @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, unsigned block_size, - unsigned num_main_syms, - u8 *window, - unsigned window_pos, +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) { - unsigned main_element; - unsigned end; - int ret; - int match_len; - - end = window_pos + block_size; - while (window_pos < end) { - ret = read_huffsym_using_maintree(istream, tables, - &main_element, - num_main_syms); - if (ret) - return ret; - - if (main_element < LZX_NUM_CHARS) { - /* literal: 0 to LZX_NUM_CHARS - 1 */ - window[window_pos++] = main_element; + u32 block_end; + unsigned main_symbol; + u32 match_len; + + block_end = window_pos + block_size; + while (window_pos < block_end) { + main_symbol = read_huffsym_using_maincode(istream, tables); + if (main_symbol < LZX_NUM_CHARS) { + /* Literal */ + window[window_pos++] = main_symbol; } else { - /* match: LZX_NUM_CHARS to num_main_syms - 1 */ - match_len = lzx_decode_match(main_element, + /* Match */ + match_len = lzx_decode_match(main_symbol, block_type, - end - window_pos, + block_end - window_pos, window, window_pos, tables, queue, istream); - if (match_len < 0) - return match_len; + if (unlikely(match_len == 0)) + return -1; window_pos += match_len; } } return 0; } -/* API function documented in wimlib.h */ -WIMLIBAPI int -wimlib_lzx_decompress2(const void *compressed_data, unsigned compressed_len, - void *uncompressed_data, unsigned uncompressed_len, - u32 max_window_size) +static int +lzx_decompress(const void *compressed_data, size_t compressed_size, + void *uncompressed_data, size_t uncompressed_size, + void *_dec) { - struct lzx_tables tables; + struct lzx_decompressor *dec = _dec; struct input_bitstream istream; struct lzx_lru_queue queue; - unsigned window_pos; - unsigned block_size; - unsigned block_type; - unsigned num_main_syms; + u32 window_pos; + int block_type; + u32 block_size; + bool may_have_e8_byte; int ret; - bool e8_preprocessing_done; - 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, max_window_size); - - if (!lzx_window_size_valid(max_window_size)) { - LZX_DEBUG("Window size of %u is invalid!", - max_window_size); + if (uncompressed_size > dec->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; - } + init_input_bitstream(&istream, compressed_data, compressed_size); - memset(tables.maintree_lens, 0, sizeof(tables.maintree_lens)); - memset(tables.lentree_lens, 0, sizeof(tables.lentree_lens)); + /* Initialize the recent offsets queue. */ lzx_lru_queue_init(&queue); - init_input_bitstream(&istream, compressed_data, compressed_len); - e8_preprocessing_done = false; /* Set to true if there may be 0xe8 bytes - in the uncompressed data. */ + /* Codeword lengths begin as all 0's for delta encoding purposes. */ + memset(dec->tables.maincode_lens, 0, sizeof(dec->tables.maincode_lens)); + memset(dec->tables.lencode_lens, 0, sizeof(dec->tables.lencode_lens)); + + /* 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 @@ -869,81 +615,97 @@ wimlib_lzx_decompress2(const void *compressed_data, unsigned compressed_len, * blocks. */ for (window_pos = 0; - window_pos < uncompressed_len; + window_pos < uncompressed_size; window_pos += block_size) { - LZX_DEBUG("Reading block header."); - ret = lzx_read_block_header(&istream, num_main_syms, - max_window_size, &block_size, - &block_type, &tables, &queue); + ret = lzx_read_block_header(&istream, dec->num_main_syms, + dec->max_window_size, &block_type, + &block_size, &dec->tables, &queue); if (ret) return ret; - LZX_DEBUG("block_size = %u, window_pos = %u", - block_size, window_pos); - - if (block_size > uncompressed_len - window_pos) { - LZX_DEBUG("Expected a block size of at " - "most %u bytes (found %u bytes)", - uncompressed_len - window_pos, block_size); + if (block_size > uncompressed_size - window_pos) return -1; - } - switch (block_type) { - case LZX_BLOCKTYPE_VERBATIM: - case LZX_BLOCKTYPE_ALIGNED: - if (block_type == LZX_BLOCKTYPE_VERBATIM) - LZX_DEBUG("LZX_BLOCKTYPE_VERBATIM"); - else - LZX_DEBUG("LZX_BLOCKTYPE_ALIGNED"); + if (block_type != LZX_BLOCKTYPE_UNCOMPRESSED) { + + /* Compressed block. */ + ret = lzx_decompress_block(block_type, block_size, - num_main_syms, uncompressed_data, window_pos, - &tables, + &dec->tables, &queue, &istream); if (ret) return ret; - if (tables.maintree_lens[0xe8] != 0) - e8_preprocessing_done = true; - break; - case LZX_BLOCKTYPE_UNCOMPRESSED: - LZX_DEBUG("LZX_BLOCKTYPE_UNCOMPRESSED"); - if (istream.data_bytes_left < block_size) { - LZX_DEBUG("Unexpected end of input when " - "reading %u bytes from LZX bitstream " - "(only have %u bytes left)", - block_size, istream.data_bytes_left); + /* 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. */ + + if (istream.data_bytes_left < block_size) return -1; - } + memcpy(&((u8*)uncompressed_data)[window_pos], istream.data, block_size); istream.data += block_size; istream.data_bytes_left -= block_size; - /* Re-align bitstream if an odd number of bytes were + + /* Re-align the bitstream if an odd number of bytes was * read. */ if (istream.data_bytes_left && (block_size & 1)) { istream.data_bytes_left--; istream.data++; } - e8_preprocessing_done = true; - break; + may_have_e8_byte = true; } } - if (e8_preprocessing_done) - undo_call_insn_preprocessing(uncompressed_data, uncompressed_len); + + /* 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; } -/* API function documented in wimlib.h */ -WIMLIBAPI int -wimlib_lzx_decompress(const void *compressed_data, unsigned compressed_len, - void *uncompressed_data, unsigned uncompressed_len) +static void +lzx_free_decompressor(void *_dec) { - return wimlib_lzx_decompress2(compressed_data, compressed_len, - uncompressed_data, uncompressed_len, - 32768); + struct lzx_decompressor *dec = _dec; + + ALIGNED_FREE(dec); } + +static int +lzx_create_decompressor(size_t max_window_size, void **dec_ret) +{ + struct lzx_decompressor *dec; + + if (!lzx_window_size_valid(max_window_size)) + 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->max_window_size = max_window_size; + dec->num_main_syms = lzx_get_num_main_syms(max_window_size); + + *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, +};