/*
* lzms-decompress.c
*/
/*
* Copyright (C) 2013 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 is a decompressor for the LZMS compression format used by Microsoft.
* This format is not documented, but it is one of the formats supported by the
* compression API available in Windows 8, and as of Windows 8 it is one of the
* formats that can be used in WIM files.
*
* This decompressor only implements "raw" decompression, which decompresses a
* single LZMS-compressed block. This behavior is the same as that of
* Decompress() in the Windows 8 compression API when using a compression handle
* created with CreateDecompressor() with the Algorithm parameter specified as
* COMPRESS_ALGORITHM_LZMS | COMPRESS_RAW. Presumably, non-raw LZMS data
* is a container format from which the locations and sizes (both compressed and
* uncompressed) of the constituent blocks can be determined.
*
* A LZMS-compressed block must be read in 16-bit little endian units from both
* directions. One logical bitstream starts at the front of the block and
* proceeds forwards. Another logical bitstream starts at the end of the block
* and proceeds backwards. Bits read from the forwards bitstream constitute
* range-encoded data, whereas bits read from the backwards bitstream constitute
* Huffman-encoded symbols or verbatim bits. For both bitstreams, the ordering
* of the bits within the 16-bit coding units is such that the first bit is the
* high-order bit and the last bit is the low-order bit.
*
* From these two logical bitstreams, an LZMS decompressor can reconstitute the
* series of items that make up the LZMS data representation. Each such item
* may be a literal byte or a match. Matches may be either traditional LZ77
* matches or "delta" matches, either of which can have its offset encoded
* explicitly or encoded via a reference to a recently used (repeat) offset.
*
* A traditional LZ match consists of a length and offset; it asserts that the
* sequence of bytes beginning at the current position and extending for the
* length is exactly equal to the equal-length sequence of bytes at the offset
* back in the window. On the other hand, a delta match consists of a length,
* raw offset, and power. It asserts that the sequence of bytes beginning at
* the current position and extending for the length is equal to the bytewise
* sum of the two equal-length sequences of bytes (2**power) and (raw_offset *
* 2**power) bytes before the current position, minus bytewise the sequence of
* bytes beginning at (2**power + raw_offset * 2**power) bytes before the
* current position. Although not generally as useful as traditional LZ
* matches, delta matches can be helpful on some types of data. Both LZ and
* delta matches may overlap with the current position; in fact, the minimum
* offset is 1, regardless of match length.
*
* For LZ matches, up to 3 repeat offsets are allowed, similar to some other
* LZ-based formats such as LZX and LZMA. They must updated in a LRU fashion,
* except for a quirk: updates to the queue must be delayed by one LZMS item,
* except for the removal of a repeat match. As a result, 4 entries are
* actually needed in the queue, even though it is only possible to decode
* references to the first 3 at any given time. The queue must be initialized
* to the offsets {1, 2, 3, 4}.
*
* Repeat delta matches are handled similarly, but for them there are two queues
* updated in lock-step: one for powers and one for raw offsets. The power
* queue must be initialized to {0, 0, 0, 0}, and the raw offset queue must be
* initialized to {1, 2, 3, 4}.
*
* Bits from the range decoder must be used to disambiguate item types. The
* range decoder must hold two state variables: the range, which must initially
* be set to 0xffffffff, and the current code, which must initially be set to
* the first 32 bits read from the forwards bitstream. The range must be
* maintained above 0xffff; when it falls below 0xffff, both the range and code
* must be left-shifted by 16 bits and the low 16 bits of the code must be
* filled in with the next 16 bits from the forwards bitstream.
*
* To decode each bit, the range decoder requires a probability that is
* logically a real number between 0 and 1. Multiplying this probability by the
* current range and taking the floor gives the bound between the 0-bit region
* of the range and the 1-bit region of the range. However, in LZMS,
* probabilities are restricted to values of n/64 where n is an integer is
* between 1 and 63 inclusively, so the implementation may use integer
* operations instead. Following calculation of the bound, if the current code
* is in the 0-bit region, the new range becomes the current code and the
* decoded bit is 0; otherwise, the bound must be subtracted from both the range
* and the code, and the decoded bit is 1. More information about range coding
* can be found at https://en.wikipedia.org/wiki/Range_encoding. Furthermore,
* note that the LZMA format also uses range coding and has public domain code
* available for it.
*
* The probability used to range-decode each bit must be taken from a table, of
* which one instance must exist for each distinct context in which a
* range-decoded bit is needed. At each call of the range decoder, the
* appropriate probability must be obtained by indexing the appropriate
* probability table with the last 4 (in the context disambiguating literals
* from matches), 5 (in the context disambiguating LZ matches from delta
* matches), or 6 (in all other contexts) bits recently range-decoded in that
* context, ordered such that the most recently decoded bit is the low-order bit
* of the index.
*
* Furthermore, each probability entry itself is variable, as its value must be
* maintained as n/64 where n is the number of 0 bits in the most recently
* decoded 64 bits with that same entry. This allows the compressed
* representation to adapt to the input and use fewer bits to represent the most
* likely data; note that LZMA uses a similar scheme. Initially, the most
* recently 64 decoded bits for each probability entry are assumed to be
* 0x0000000055555555 (high order to low order); therefore, all probabilities
* are initially 48/64. During the course of decoding, each probability may be
* updated to as low as 0/64 (as a result of reading many consecutive 1 bits
* with that entry) or as high as 64/64 (as a result of reading many consecutive
* 0 bits with that entry); however, probabilities of 0/64 and 64/64 cannot be
* used as-is but rather must be adjusted to 1/64 and 63/64, respectively,
* before being used for range decoding.
*
* Representations of the LZMS items themselves must be read from the backwards
* bitstream. For this, there are 5 different Huffman codes used:
*
* - The literal code, used for decoding literal bytes. Each of the 256
* symbols represents a literal byte. This code must be rebuilt whenever
* 1024 symbols have been decoded with it.
*
* - The LZ offset code, used for decoding the offsets of standard LZ77
* matches. Each symbol represents a position slot, which corresponds to a
* base value and some number of extra bits which must be read and added to
* the base value to reconstitute the full offset. The number of symbols in
* this code is the number of position slots needed to represent all possible
* offsets in the uncompressed block. This code must be rebuilt whenever
* 1024 symbols have been decoded with it.
*
* - The length code, used for decoding length symbols. Each of the 54 symbols
* represents a length slot, which corresponds to a base value and some
* number of extra bits which must be read and added to the base value to
* reconstitute the full length. This code must be rebuilt whenever 512
* symbols have been decoded with it.
*
* - The delta offset code, used for decoding the offsets of delta matches.
* Each symbol corresponds to a position slot, which corresponds to a base
* value and some number of extra bits which must be read and added to the
* base value to reconstitute the full offset. The number of symbols in this
* code is equal to the number of symbols in the LZ offset code. This code
* must be rebuilt whenever 1024 symbols have been decoded with it.
*
* - The delta power code, used for decoding the powers of delta matches. Each
* of the 8 symbols corresponds to a power. This code must be rebuilt
* whenever 512 symbols have been decoded with it.
*
* All the LZMS Huffman codes must be built adaptively based on symbol
* frequencies. Initially, each code must be built assuming that all symbols
* have equal frequency. Following that, each code must be rebuilt whenever a
* certain number of symbols has been decoded with it.
*
* In general, multiple valid Huffman codes can be constructed from a set of
* symbol frequencies. Like other compression formats such as XPRESS, LZX, and
* DEFLATE, the LZMS format solves this ambiguity by requiring that all Huffman
* codes be constructed in canonical form. This form requires that same-length
* codewords be lexicographically ordered the same way as the corresponding
* symbols and that all shorter codewords lexicographically precede longer
* codewords.
*
* Codewords in all the LZMS Huffman codes are limited to 15 bits. If the
* canonical code for a given set of symbol frequencies has any codewords longer
* than 15 bits, then all frequencies must be divided by 2, rounding up, and the
* code construction must be attempted again.
*
* A LZMS-compressed block seemingly cannot have a compressed size greater than
* or equal to the uncompressed size. In such cases the block must be stored
* uncompressed.
*
* After all LZMS items have been decoded, the data must be postprocessed to
* translate absolute address encoded in x86 instructions into their original
* relative addresses.
*
* Details omitted above can be found in the code. Note that in the absence of
* an official specification there is no guarantee that this decompressor
* handles all possible cases.
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include "wimlib.h"
#include "wimlib/compress_common.h"
#include "wimlib/decompressor_ops.h"
#include "wimlib/decompress_common.h"
#include "wimlib/error.h"
#include "wimlib/lzms.h"
#include "wimlib/util.h"
#include
#define LZMS_DECODE_TABLE_BITS 10
/* Structure used for range decoding, reading bits forwards. This is the first
* logical bitstream mentioned above. */
struct lzms_range_decoder_raw {
/* The relevant part of the current range. Although the logical range
* for range decoding is a very large integer, only a small portion
* matters at any given time, and it can be normalized (shifted left)
* whenever it gets too small. */
u32 range;
/* The current position in the range encoded by the portion of the input
* read so far. */
u32 code;
/* Pointer to the next little-endian 16-bit integer in the compressed
* input data (reading forwards). */
const le16 *in;
/* Number of 16-bit integers remaining in the compressed input data
* (reading forwards). */
size_t num_le16_remaining;
};
/* Structure used for reading raw bits backwards. This is the second logical
* bitstream mentioned above. */
struct lzms_input_bitstream {
/* Holding variable for bits that have been read from the compressed
* data. The bits are ordered from high-order to low-order. */
/* XXX: Without special-case code to handle reading more than 17 bits
* at a time, this needs to be 64 bits rather than 32 bits. */
u64 bitbuf;
/* Number of bits in @bitbuf that are are used. */
unsigned num_filled_bits;
/* Pointer to the one past the next little-endian 16-bit integer in the
* compressed input data (reading backwards). */
const le16 *in;
/* Number of 16-bit integers remaining in the compressed input data
* (reading backwards). */
size_t num_le16_remaining;
};
/* Structure used for range decoding. This wraps around `struct
* lzms_range_decoder_raw' to use and maintain probability entries. */
struct lzms_range_decoder {
/* Pointer to the raw range decoder, which has no persistent knowledge
* of probabilities. Multiple lzms_range_decoder's share the same
* lzms_range_decoder_raw. */
struct lzms_range_decoder_raw *rd;
/* Bits recently decoded by this range decoder. This are used as in
* index into @prob_entries. */
u32 state;
/* Bitmask for @state to prevent its value from exceeding the number of
* probability entries. */
u32 mask;
/* Probability entries being used for this range decoder. */
struct lzms_probability_entry prob_entries[LZMS_MAX_NUM_STATES];
};
/* Structure used for Huffman decoding, optionally using the decoded symbols as
* slots into a base table to determine how many extra bits need to be read to
* reconstitute the full value. */
struct lzms_huffman_decoder {
/* Bitstream to read Huffman-encoded symbols and verbatim bits from.
* Multiple lzms_huffman_decoder's share the same lzms_input_bitstream.
*/
struct lzms_input_bitstream *is;
/* Pointer to the slot base table to use. It is indexed by the decoded
* Huffman symbol that specifies the slot. The entry specifies the base
* value to use, and the position of its high bit is the number of
* additional bits that must be read to reconstitute the full value.
*
* This member need not be set if only raw Huffman symbols are being
* read using this decoder. */
const u32 *slot_base_tab;
/* Number of symbols that have been read using this code far. Reset to
* 0 whenever the code is rebuilt. */
u32 num_syms_read;
/* When @num_syms_read reaches this number, the Huffman code must be
* rebuilt. */
u32 rebuild_freq;
/* Number of symbols in the represented Huffman code. */
unsigned num_syms;
/* Running totals of symbol frequencies. These are diluted slightly
* whenever the code is rebuilt. */
u32 sym_freqs[LZMS_MAX_NUM_SYMS];
/* The length, in bits, of each symbol in the Huffman code. */
u8 lens[LZMS_MAX_NUM_SYMS];
/* The codeword of each symbol in the Huffman code. */
u16 codewords[LZMS_MAX_NUM_SYMS];
/* A table for quickly decoding symbols encoded using the Huffman code.
*/
u16 decode_table[(1U << LZMS_DECODE_TABLE_BITS) + 2 * LZMS_MAX_NUM_SYMS]
_aligned_attribute(DECODE_TABLE_ALIGNMENT);
};
/* State of the LZMS decompressor. */
struct lzms_decompressor {
/* Pointer to the beginning of the uncompressed data buffer. */
u8 *out_begin;
/* Pointer to the next position in the uncompressed data buffer. */
u8 *out_next;
/* Pointer to one past the end of the uncompressed data buffer. */
u8 *out_end;
/* Range decoder, which reads bits from the beginning of the compressed
* block, going forwards. */
struct lzms_range_decoder_raw rd;
/* Input bitstream, which reads from the end of the compressed block,
* going backwards. */
struct lzms_input_bitstream is;
/* Range decoders. */
struct lzms_range_decoder main_range_decoder;
struct lzms_range_decoder match_range_decoder;
struct lzms_range_decoder lz_match_range_decoder;
struct lzms_range_decoder lz_repeat_match_range_decoders[LZMS_NUM_RECENT_OFFSETS - 1];
struct lzms_range_decoder delta_match_range_decoder;
struct lzms_range_decoder delta_repeat_match_range_decoders[LZMS_NUM_RECENT_OFFSETS - 1];
/* Huffman decoders. */
struct lzms_huffman_decoder literal_decoder;
struct lzms_huffman_decoder lz_offset_decoder;
struct lzms_huffman_decoder length_decoder;
struct lzms_huffman_decoder delta_power_decoder;
struct lzms_huffman_decoder delta_offset_decoder;
/* LRU (least-recently-used) queues for match information. */
struct lzms_lru_queues lru;
/* Used for postprocessing. */
s32 last_target_usages[65536];
};
/* Initialize the input bitstream @is to read forwards from the specified
* compressed data buffer @in that is @in_limit 16-bit integers long. */
static void
lzms_input_bitstream_init(struct lzms_input_bitstream *is,
const le16 *in, size_t in_limit)
{
is->bitbuf = 0;
is->num_filled_bits = 0;
is->in = in + in_limit;
is->num_le16_remaining = in_limit;
}
/* Ensures that @num_bits bits are buffered in the input bitstream. */
static int
lzms_input_bitstream_ensure_bits(struct lzms_input_bitstream *is,
unsigned num_bits)
{
while (is->num_filled_bits < num_bits) {
u64 next;
LZMS_ASSERT(is->num_filled_bits + 16 <= sizeof(is->bitbuf) * 8);
if (unlikely(is->num_le16_remaining == 0))
return -1;
next = le16_to_cpu(*--is->in);
is->num_le16_remaining--;
is->bitbuf |= next << (sizeof(is->bitbuf) * 8 - is->num_filled_bits - 16);
is->num_filled_bits += 16;
}
return 0;
}
/* Returns the next @num_bits bits that are buffered in the input bitstream. */
static u32
lzms_input_bitstream_peek_bits(struct lzms_input_bitstream *is,
unsigned num_bits)
{
LZMS_ASSERT(is->num_filled_bits >= num_bits);
return is->bitbuf >> (sizeof(is->bitbuf) * 8 - num_bits);
}
/* Removes the next @num_bits bits that are buffered in the input bitstream. */
static void
lzms_input_bitstream_remove_bits(struct lzms_input_bitstream *is,
unsigned num_bits)
{
LZMS_ASSERT(is->num_filled_bits >= num_bits);
is->bitbuf <<= num_bits;
is->num_filled_bits -= num_bits;
}
/* Removes and returns the next @num_bits bits that are buffered in the input
* bitstream. */
static u32
lzms_input_bitstream_pop_bits(struct lzms_input_bitstream *is,
unsigned num_bits)
{
u32 bits = lzms_input_bitstream_peek_bits(is, num_bits);
lzms_input_bitstream_remove_bits(is, num_bits);
return bits;
}
/* Reads the next @num_bits from the input bitstream. */
static u32
lzms_input_bitstream_read_bits(struct lzms_input_bitstream *is,
unsigned num_bits)
{
if (unlikely(lzms_input_bitstream_ensure_bits(is, num_bits)))
return 0;
return lzms_input_bitstream_pop_bits(is, num_bits);
}
/* Initialize the range decoder @rd to read forwards from the specified
* compressed data buffer @in that is @in_limit 16-bit integers long. */
static void
lzms_range_decoder_raw_init(struct lzms_range_decoder_raw *rd,
const le16 *in, size_t in_limit)
{
rd->range = 0xffffffff;
rd->code = ((u32)le16_to_cpu(in[0]) << 16) |
((u32)le16_to_cpu(in[1]) << 0);
rd->in = in + 2;
rd->num_le16_remaining = in_limit - 2;
}
/* Ensures the current range of the range decoder has at least 16 bits of
* precision. */
static int
lzms_range_decoder_raw_normalize(struct lzms_range_decoder_raw *rd)
{
if (rd->range <= 0xffff) {
rd->range <<= 16;
if (unlikely(rd->num_le16_remaining == 0))
return -1;
rd->code = (rd->code << 16) | le16_to_cpu(*rd->in++);
rd->num_le16_remaining--;
}
return 0;
}
/* Decode and return the next bit from the range decoder (raw version).
*
* @prob is the chance out of LZMS_PROBABILITY_MAX that the next bit is 0.
*/
static int
lzms_range_decoder_raw_decode_bit(struct lzms_range_decoder_raw *rd, u32 prob)
{
u32 bound;
/* Ensure the range has at least 16 bits of precision. */
lzms_range_decoder_raw_normalize(rd);
/* Based on the probability, calculate the bound between the 0-bit
* region and the 1-bit region of the range. */
bound = (rd->range >> LZMS_PROBABILITY_BITS) * prob;
if (rd->code < bound) {
/* Current code is in the 0-bit region of the range. */
rd->range = bound;
return 0;
} else {
/* Current code is in the 1-bit region of the range. */
rd->range -= bound;
rd->code -= bound;
return 1;
}
}
/* Decode and return the next bit from the range decoder. This wraps around
* lzms_range_decoder_raw_decode_bit() to handle using and updating the
* appropriate probability table. */
static int
lzms_range_decode_bit(struct lzms_range_decoder *dec)
{
struct lzms_probability_entry *prob_entry;
u32 prob;
int bit;
/* Load the probability entry corresponding to the current state. */
prob_entry = &dec->prob_entries[dec->state];
/* Treat the number of zero bits in the most recently decoded
* LZMS_PROBABILITY_MAX bits with this probability entry as the chance,
* out of LZMS_PROBABILITY_MAX, that the next bit will be a 0. However,
* don't allow 0% or 100% probabilities. */
prob = prob_entry->num_recent_zero_bits;
if (prob == LZMS_PROBABILITY_MAX)
prob = LZMS_PROBABILITY_MAX - 1;
else if (prob == 0)
prob = 1;
/* Decode the next bit. */
bit = lzms_range_decoder_raw_decode_bit(dec->rd, prob);
/* Update the state based on the newly decoded bit. */
dec->state = (((dec->state << 1) | bit) & dec->mask);
/* Update the recent bits, including the cached count of 0's. */
BUILD_BUG_ON(LZMS_PROBABILITY_MAX > sizeof(prob_entry->recent_bits) * 8);
if (bit == 0) {
if (prob_entry->recent_bits & (1ULL << (LZMS_PROBABILITY_MAX - 1))) {
/* Replacing 1 bit with 0 bit; increment the zero count.
*/
prob_entry->num_recent_zero_bits++;
}
} else {
if (!(prob_entry->recent_bits & (1ULL << (LZMS_PROBABILITY_MAX - 1)))) {
/* Replacing 0 bit with 1 bit; decrement the zero count.
*/
prob_entry->num_recent_zero_bits--;
}
}
prob_entry->recent_bits = (prob_entry->recent_bits << 1) | bit;
/* Return the decoded bit. */
return bit;
}
/* Build the decoding table for a new adaptive Huffman code using the alphabet
* used in the specified Huffman decoder, with the symbol frequencies
* dec->sym_freqs. */
static void
lzms_rebuild_adaptive_huffman_code(struct lzms_huffman_decoder *dec)
{
/* XXX: This implementation makes use of code already implemented for
* the XPRESS and LZX compression formats. However, since for the
* adaptive codes used in LZMS we don't actually need the explicit codes
* themselves, only the decode tables, it may be possible to optimize
* this by somehow directly building or updating the Huffman decode
* table. This may be a worthwhile optimization because the adaptive
* codes change many times throughout a decompression run. */
LZMS_DEBUG("Rebuilding adaptive Huffman code (num_syms=%u)",
dec->num_syms);
make_canonical_huffman_code(dec->num_syms, LZMS_MAX_CODEWORD_LEN,
dec->sym_freqs, dec->lens, dec->codewords);
#if defined(ENABLE_LZMS_DEBUG)
int ret =
#endif
make_huffman_decode_table(dec->decode_table, dec->num_syms,
LZMS_DECODE_TABLE_BITS, dec->lens,
LZMS_MAX_CODEWORD_LEN);
LZMS_ASSERT(ret == 0);
}
/* Decode and return the next Huffman-encoded symbol from the LZMS-compressed
* block using the specified Huffman decoder. */
static u32
lzms_huffman_decode_symbol(struct lzms_huffman_decoder *dec)
{
const u8 *lens = dec->lens;
const u16 *decode_table = dec->decode_table;
struct lzms_input_bitstream *is = dec->is;
/* The Huffman codes used in LZMS are adaptive and must be rebuilt
* whenever a certain number of symbols have been read. Each such
* rebuild uses the current symbol frequencies, but the format also
* requires that the symbol frequencies be halved after each code
* rebuild. This diminishes the effect of old symbols on the current
* Huffman codes, thereby causing the Huffman codes to be more locally
* adaptable. */
if (dec->num_syms_read == dec->rebuild_freq) {
lzms_rebuild_adaptive_huffman_code(dec);
for (unsigned i = 0; i < dec->num_syms; i++) {
dec->sym_freqs[i] >>= 1;
dec->sym_freqs[i] += 1;
}
dec->num_syms_read = 0;
}
/* In the following Huffman decoding implementation, the first
* LZMS_DECODE_TABLE_BITS of the input are used as an offset into a
* decode table. The entry will either provide the decoded symbol
* directly, or else a "real" Huffman binary tree will be searched to
* decode the symbol. */
lzms_input_bitstream_ensure_bits(is, LZMS_MAX_CODEWORD_LEN);
u16 key_bits = lzms_input_bitstream_peek_bits(is, LZMS_DECODE_TABLE_BITS);
u16 sym = decode_table[key_bits];
if (sym < dec->num_syms) {
/* Fast case: The decode table directly provided the symbol. */
lzms_input_bitstream_remove_bits(is, lens[sym]);
} else {
/* Slow case: The symbol took too many bits to include directly
* in the decode table, so search for it in a binary tree at the
* end of the decode table. */
lzms_input_bitstream_remove_bits(is, LZMS_DECODE_TABLE_BITS);
do {
key_bits = sym + lzms_input_bitstream_pop_bits(is, 1);
} while ((sym = decode_table[key_bits]) >= dec->num_syms);
}
/* Tally and return the decoded symbol. */
++dec->sym_freqs[sym];
++dec->num_syms_read;
return sym;
}
/* Decode a number from the LZMS bitstream, encoded as a Huffman-encoded symbol
* specifying a "slot" (whose corresponding value is looked up in a static
* table) plus the number specified by a number of extra bits depending on the
* slot. */
static u32
lzms_decode_value(struct lzms_huffman_decoder *dec)
{
unsigned slot;
unsigned num_extra_bits;
u32 extra_bits;
/* Read the slot (position slot, length slot, etc.), which is encoded as
* a Huffman symbol. */
slot = lzms_huffman_decode_symbol(dec);
LZMS_ASSERT(dec->slot_base_tab != NULL);
/* Get the number of extra bits needed to represent the range of values
* that share the slot. */
num_extra_bits = bsr32(dec->slot_base_tab[slot + 1] -
dec->slot_base_tab[slot]);
/* Read the number of extra bits and add them to the slot to form the
* final decoded value. */
extra_bits = lzms_input_bitstream_read_bits(dec->is, num_extra_bits);
return dec->slot_base_tab[slot] + extra_bits;
}
/* Copy a literal to the output buffer. */
static int
lzms_copy_literal(struct lzms_decompressor *ctx, u8 literal)
{
*ctx->out_next++ = literal;
return 0;
}
/* Validate an LZ match and copy it to the output buffer. */
static int
lzms_copy_lz_match(struct lzms_decompressor *ctx, u32 length, u32 offset)
{
u8 *out_next;
u8 *matchptr;
if (length > ctx->out_end - ctx->out_next) {
LZMS_DEBUG("Match overrun!");
return -1;
}
if (offset > ctx->out_next - ctx->out_begin) {
LZMS_DEBUG("Match underrun!");
return -1;
}
out_next = ctx->out_next;
matchptr = out_next - offset;
while (length--)
*out_next++ = *matchptr++;
ctx->out_next = out_next;
return 0;
}
/* Validate a delta match and copy it to the output buffer. */
static int
lzms_copy_delta_match(struct lzms_decompressor *ctx, u32 length,
u32 power, u32 raw_offset)
{
u32 offset1 = 1U << power;
u32 offset2 = raw_offset << power;
u32 offset = offset1 + offset2;
u8 *out_next;
u8 *matchptr1;
u8 *matchptr2;
u8 *matchptr;
if (length > ctx->out_end - ctx->out_next) {
LZMS_DEBUG("Match overrun!");
return -1;
}
if (offset > ctx->out_next - ctx->out_begin) {
LZMS_DEBUG("Match underrun!");
return -1;
}
out_next = ctx->out_next;
matchptr1 = out_next - offset1;
matchptr2 = out_next - offset2;
matchptr = out_next - offset;
while (length--)
*out_next++ = *matchptr1++ + *matchptr2++ - *matchptr++;
ctx->out_next = out_next;
return 0;
}
/* Decode a (length, offset) pair from the input. */
static int
lzms_decode_lz_match(struct lzms_decompressor *ctx)
{
int bit;
u32 length, offset;
/* Decode the match offset. The next range-encoded bit indicates
* whether it's a repeat offset or an explicit offset. */
bit = lzms_range_decode_bit(&ctx->lz_match_range_decoder);
if (bit == 0) {
/* Explicit offset. */
offset = lzms_decode_value(&ctx->lz_offset_decoder);
} else {
/* Repeat offset. */
int i;
for (i = 0; i < LZMS_NUM_RECENT_OFFSETS - 1; i++)
if (!lzms_range_decode_bit(&ctx->lz_repeat_match_range_decoders[i]))
break;
offset = ctx->lru.lz.recent_offsets[i];
for (; i < LZMS_NUM_RECENT_OFFSETS; i++)
ctx->lru.lz.recent_offsets[i] = ctx->lru.lz.recent_offsets[i + 1];
}
/* Decode match length, which is always given explicitly (there is no
* LRU queue for repeat lengths). */
length = lzms_decode_value(&ctx->length_decoder);
ctx->lru.lz.upcoming_offset = offset;
LZMS_DEBUG("Decoded %s LZ match: length=%u, offset=%u",
(bit ? "repeat" : "explicit"), length, offset);
/* Validate the match and copy it to the output. */
return lzms_copy_lz_match(ctx, length, offset);
}
/* Decodes a "delta" match from the input. */
static int
lzms_decode_delta_match(struct lzms_decompressor *ctx)
{
int bit;
u32 length, power, raw_offset;
/* Decode the match power and raw offset. The next range-encoded bit
* indicates whether these data are a repeat, or given explicitly. */
bit = lzms_range_decode_bit(&ctx->delta_match_range_decoder);
if (bit == 0) {
power = lzms_huffman_decode_symbol(&ctx->delta_power_decoder);
raw_offset = lzms_decode_value(&ctx->delta_offset_decoder);
} else {
int i;
for (i = 0; i < LZMS_NUM_RECENT_OFFSETS - 1; i++)
if (!lzms_range_decode_bit(&ctx->delta_repeat_match_range_decoders[i]))
break;
power = ctx->lru.delta.recent_powers[i];
raw_offset = ctx->lru.delta.recent_offsets[i];
for (; i < LZMS_NUM_RECENT_OFFSETS; i++) {
ctx->lru.delta.recent_powers[i] = ctx->lru.delta.recent_powers[i + 1];
ctx->lru.delta.recent_offsets[i] = ctx->lru.delta.recent_offsets[i + 1];
}
}
length = lzms_decode_value(&ctx->length_decoder);
ctx->lru.delta.upcoming_power = power;
ctx->lru.delta.upcoming_offset = raw_offset;
LZMS_DEBUG("Decoded %s delta match: length=%u, power=%u, raw_offset=%u",
(bit ? "repeat" : "explicit"), length, power, raw_offset);
/* Validate the match and copy it to the output. */
return lzms_copy_delta_match(ctx, length, power, raw_offset);
}
static int
lzms_decode_match(struct lzms_decompressor *ctx)
{
if (!lzms_range_decode_bit(&ctx->match_range_decoder))
return lzms_decode_lz_match(ctx);
else
return lzms_decode_delta_match(ctx);
}
/* Decode a literal byte encoded using the literal Huffman code. */
static int
lzms_decode_literal(struct lzms_decompressor *ctx)
{
u8 literal = lzms_huffman_decode_symbol(&ctx->literal_decoder);
LZMS_DEBUG("Decoded literal: 0x%02x", literal);
return lzms_copy_literal(ctx, literal);
}
/* Decode the next LZMS match or literal. */
static int
lzms_decode_item(struct lzms_decompressor *ctx)
{
int ret;
ctx->lru.lz.upcoming_offset = 0;
ctx->lru.delta.upcoming_power = 0;
ctx->lru.delta.upcoming_offset = 0;
if (lzms_range_decode_bit(&ctx->main_range_decoder))
ret = lzms_decode_match(ctx);
else
ret = lzms_decode_literal(ctx);
if (ret)
return ret;
/* Update LRU queues */
lzms_update_lru_queues(&ctx->lru);
return 0;
}
static void
lzms_init_range_decoder(struct lzms_range_decoder *dec,
struct lzms_range_decoder_raw *rd, u32 num_states)
{
dec->rd = rd;
dec->state = 0;
dec->mask = num_states - 1;
for (u32 i = 0; i < num_states; i++) {
dec->prob_entries[i].num_recent_zero_bits = LZMS_INITIAL_PROBABILITY;
dec->prob_entries[i].recent_bits = LZMS_INITIAL_RECENT_BITS;
}
}
static void
lzms_init_huffman_decoder(struct lzms_huffman_decoder *dec,
struct lzms_input_bitstream *is,
const u32 *slot_base_tab, unsigned num_syms,
unsigned rebuild_freq)
{
dec->is = is;
dec->slot_base_tab = slot_base_tab;
dec->num_syms = num_syms;
dec->num_syms_read = rebuild_freq;
dec->rebuild_freq = rebuild_freq;
for (unsigned i = 0; i < num_syms; i++)
dec->sym_freqs[i] = 1;
}
/* Prepare to decode items from an LZMS-compressed block. */
static void
lzms_init_decompressor(struct lzms_decompressor *ctx,
const void *cdata, unsigned clen,
void *ubuf, unsigned ulen)
{
unsigned num_position_slots;
LZMS_DEBUG("Initializing decompressor (clen=%u, ulen=%u)", clen, ulen);
/* Initialize output pointers. */
ctx->out_begin = ubuf;
ctx->out_next = ubuf;
ctx->out_end = (u8*)ubuf + ulen;
/* Initialize the raw range decoder (reading forwards). */
lzms_range_decoder_raw_init(&ctx->rd, cdata, clen / 2);
/* Initialize the input bitstream for Huffman symbols (reading
* backwards) */
lzms_input_bitstream_init(&ctx->is, cdata, clen / 2);
/* Initialize position and length slot bases if not done already. */
lzms_init_slot_bases();
/* Calculate the number of position slots needed for this compressed
* block. */
num_position_slots = lzms_get_position_slot(ulen - 1) + 1;
LZMS_DEBUG("Using %u position slots", num_position_slots);
/* Initialize Huffman decoders for each alphabet used in the compressed
* representation. */
lzms_init_huffman_decoder(&ctx->literal_decoder, &ctx->is,
NULL, LZMS_NUM_LITERAL_SYMS,
LZMS_LITERAL_CODE_REBUILD_FREQ);
lzms_init_huffman_decoder(&ctx->lz_offset_decoder, &ctx->is,
lzms_position_slot_base, num_position_slots,
LZMS_LZ_OFFSET_CODE_REBUILD_FREQ);
lzms_init_huffman_decoder(&ctx->length_decoder, &ctx->is,
lzms_length_slot_base, LZMS_NUM_LEN_SYMS,
LZMS_LENGTH_CODE_REBUILD_FREQ);
lzms_init_huffman_decoder(&ctx->delta_offset_decoder, &ctx->is,
lzms_position_slot_base, num_position_slots,
LZMS_DELTA_OFFSET_CODE_REBUILD_FREQ);
lzms_init_huffman_decoder(&ctx->delta_power_decoder, &ctx->is,
NULL, LZMS_NUM_DELTA_POWER_SYMS,
LZMS_DELTA_POWER_CODE_REBUILD_FREQ);
/* Initialize range decoders, all of which wrap around the same
* lzms_range_decoder_raw. */
lzms_init_range_decoder(&ctx->main_range_decoder,
&ctx->rd, LZMS_NUM_MAIN_STATES);
lzms_init_range_decoder(&ctx->match_range_decoder,
&ctx->rd, LZMS_NUM_MATCH_STATES);
lzms_init_range_decoder(&ctx->lz_match_range_decoder,
&ctx->rd, LZMS_NUM_LZ_MATCH_STATES);
for (size_t i = 0; i < ARRAY_LEN(ctx->lz_repeat_match_range_decoders); i++)
lzms_init_range_decoder(&ctx->lz_repeat_match_range_decoders[i],
&ctx->rd, LZMS_NUM_LZ_REPEAT_MATCH_STATES);
lzms_init_range_decoder(&ctx->delta_match_range_decoder,
&ctx->rd, LZMS_NUM_DELTA_MATCH_STATES);
for (size_t i = 0; i < ARRAY_LEN(ctx->delta_repeat_match_range_decoders); i++)
lzms_init_range_decoder(&ctx->delta_repeat_match_range_decoders[i],
&ctx->rd, LZMS_NUM_DELTA_REPEAT_MATCH_STATES);
/* Initialize LRU match information. */
lzms_init_lru_queues(&ctx->lru);
LZMS_DEBUG("Decompressor successfully initialized");
}
/* Decode the series of literals and matches from the LZMS-compressed data.
* Returns 0 on success; nonzero if the compressed data is invalid. */
static int
lzms_decode_items(const u8 *cdata, size_t clen, u8 *ubuf, size_t ulen,
struct lzms_decompressor *ctx)
{
/* Initialize the LZMS decompressor. */
lzms_init_decompressor(ctx, cdata, clen, ubuf, ulen);
/* Decode the sequence of items. */
while (ctx->out_next != ctx->out_end) {
LZMS_DEBUG("Position %u", ctx->out_next - ctx->out_begin);
if (lzms_decode_item(ctx))
return -1;
}
return 0;
}
static int
lzms_decompress(const void *compressed_data, size_t compressed_size,
void *uncompressed_data, size_t uncompressed_size, void *_ctx)
{
struct lzms_decompressor *ctx = _ctx;
/* The range decoder requires that a minimum of 4 bytes of compressed
* data be initially available. */
if (compressed_size < 4) {
LZMS_DEBUG("Compressed size too small (got %zu, expected >= 4)",
compressed_size);
return -1;
}
/* A LZMS-compressed data block should be evenly divisible into 16-bit
* integers. */
if (compressed_size % 2 != 0) {
LZMS_DEBUG("Compressed size not divisible by 2 (got %zu)",
compressed_size);
return -1;
}
/* Handle the trivial case where nothing needs to be decompressed.
* (Necessary because a window of size 0 does not have a valid position
* slot.) */
if (uncompressed_size == 0)
return 0;
/* The x86 post-processor requires that the uncompressed length fit into
* a signed 32-bit integer. Also, the position slot table cannot be
* searched for a position of INT32_MAX or greater. */
if (uncompressed_size >= INT32_MAX) {
LZMS_DEBUG("Uncompressed length too large "
"(got %zu, expected < INT32_MAX)",
uncompressed_size);
return -1;
}
/* Decode the literals and matches. */
if (lzms_decode_items(compressed_data, compressed_size,
uncompressed_data, uncompressed_size, ctx))
return -1;
/* Postprocess the data. */
lzms_x86_filter(uncompressed_data, uncompressed_size,
ctx->last_target_usages, true);
LZMS_DEBUG("Decompression successful.");
return 0;
}
static void
lzms_free_decompressor(void *_ctx)
{
struct lzms_decompressor *ctx = _ctx;
FREE(ctx);
}
static int
lzms_create_decompressor(size_t max_block_size,
const struct wimlib_decompressor_params_header *params,
void **ctx_ret)
{
struct lzms_decompressor *ctx;
ctx = MALLOC(sizeof(struct lzms_decompressor));
if (ctx == NULL)
return WIMLIB_ERR_NOMEM;
*ctx_ret = ctx;
return 0;
}
const struct decompressor_ops lzms_decompressor_ops = {
.create_decompressor = lzms_create_decompressor,
.decompress = lzms_decompress,
.free_decompressor = lzms_free_decompressor,
};