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xz/src/liblzma/lzma/lzma_decoder.c

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///////////////////////////////////////////////////////////////////////////////
//
/// \file lzma_decoder.c
/// \brief LZMA decoder
//
// Copyright (C) 1999-2006 Igor Pavlov
// Copyright (C) 2007 Lasse Collin
//
// This library 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 2.1 of the License, or (at your option) any later version.
//
// This library 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.
//
///////////////////////////////////////////////////////////////////////////////
// NOTE: If you want to keep the line length in 80 characters, set
// tab width to 4 or less in your editor when editing this file.
#include "lzma_common.h"
#include "lzma_decoder.h"
#include "lz_decoder.h"
#include "range_decoder.h"
/// REQUIRED_IN_BUFFER_SIZE is the number of required input bytes
/// for the worst case: longest match with longest distance.
/// LZMA_IN_BUFFER_SIZE must be larger than REQUIRED_IN_BUFFER_SIZE.
/// 23 bits = 2 (match select) + 10 (len) + 6 (distance) + 4 (align)
/// + 1 (rc_normalize)
///
/// \todo Is this correct for sure?
///
#define REQUIRED_IN_BUFFER_SIZE \
((23 * (BIT_MODEL_TOTAL_BITS - MOVE_BITS + 1) + 26 + 9) / 8)
// Length decoders are easiest to have as macros, because they use range
// decoder macros, which use local variables rc_range and rc_code.
#define length_decode(target, len_decoder, pos_state) \
do { \
if_bit_0(len_decoder.choice) { \
update_bit_0(len_decoder.choice); \
target = MATCH_MIN_LEN; \
bittree_decode(target, len_decoder.low[pos_state], LEN_LOW_BITS); \
} else { \
update_bit_1(len_decoder.choice); \
if_bit_0(len_decoder.choice2) { \
update_bit_0(len_decoder.choice2); \
target = MATCH_MIN_LEN + LEN_LOW_SYMBOLS; \
bittree_decode(target, len_decoder.mid[pos_state], LEN_MID_BITS); \
} else { \
update_bit_1(len_decoder.choice2); \
target = MATCH_MIN_LEN + LEN_LOW_SYMBOLS + LEN_MID_SYMBOLS; \
bittree_decode(target, len_decoder.high, LEN_HIGH_BITS); \
} \
} \
} while (0)
#define length_decode_dummy(target, len_decoder, pos_state) \
do { \
if_bit_0(len_decoder.choice) { \
update_bit_0_dummy(); \
target = MATCH_MIN_LEN; \
bittree_decode_dummy(target, \
len_decoder.low[pos_state], LEN_LOW_BITS); \
} else { \
update_bit_1_dummy(); \
if_bit_0(len_decoder.choice2) { \
update_bit_0_dummy(); \
target = MATCH_MIN_LEN + LEN_LOW_SYMBOLS; \
bittree_decode_dummy(target, len_decoder.mid[pos_state], \
LEN_MID_BITS); \
} else { \
update_bit_1_dummy(); \
target = MATCH_MIN_LEN + LEN_LOW_SYMBOLS + LEN_MID_SYMBOLS; \
bittree_decode_dummy(target, len_decoder.high, LEN_HIGH_BITS); \
} \
} \
} while (0)
typedef struct {
probability choice;
probability choice2;
probability low[POS_STATES_MAX][LEN_LOW_SYMBOLS];
probability mid[POS_STATES_MAX][LEN_MID_SYMBOLS];
probability high[LEN_HIGH_SYMBOLS];
} lzma_length_decoder;
struct lzma_coder_s {
/// Data of the next coder, if any.
lzma_next_coder next;
/// Sliding output window a.k.a. dictionary a.k.a. history buffer.
lzma_lz_decoder lz;
// Range coder
lzma_range_decoder rc;
// State
uint32_t state;
uint32_t rep0; ///< Distance of the latest match
uint32_t rep1; ///< Distance of second latest match
uint32_t rep2; ///< Distance of third latest match
uint32_t rep3; ///< Distance of fourth latest match
uint32_t pos_bits;
uint32_t pos_mask;
uint32_t now_pos; // Lowest 32-bits are enough here.
lzma_literal_coder *literal_coder;
/// If 1, it's a match. Otherwise it's a single 8-bit literal.
probability is_match[STATES][POS_STATES_MAX];
/// If 1, it's a repeated match. The distance is one of rep0 .. rep3.
probability is_rep[STATES];
/// If 0, distance of a repeated match is rep0.
/// Otherwise check is_rep1.
probability is_rep0[STATES];
/// If 0, distance of a repeated match is rep1.
/// Otherwise check is_rep2.
probability is_rep1[STATES];
/// If 0, distance of a repeated match is rep2. Otherwise it is rep3.
probability is_rep2[STATES];
/// If 1, the repeated match has length of one byte. Otherwise
/// the length is decoded from rep_match_len_decoder.
probability is_rep0_long[STATES][POS_STATES_MAX];
probability pos_slot_decoder[LEN_TO_POS_STATES][1 << POS_SLOT_BITS];
probability pos_decoders[FULL_DISTANCES - END_POS_MODEL_INDEX];
probability pos_align_decoder[1 << ALIGN_BITS];
/// Length of a match
lzma_length_decoder len_decoder;
/// Length of a repeated match.
lzma_length_decoder rep_match_len_decoder;
/// True when we have produced at least one byte of output since the
/// beginning of the stream or the latest flush marker.
bool has_produced_output;
};
/// \brief Check if the next iteration of the decoder loop can be run.
///
/// \note There must always be REQUIRED_IN_BUFFER_SIZE bytes
/// readable space!
///
static bool lzma_attribute((pure))
decode_dummy(const lzma_coder *restrict coder,
const uint8_t *restrict in, size_t in_pos_local,
const size_t in_size, lzma_range_decoder rc,
uint32_t state, uint32_t rep0, const uint32_t now_pos)
{
uint32_t rc_bound;
do {
const uint32_t pos_state = now_pos & coder->pos_mask;
if_bit_0(coder->is_match[state][pos_state]) {
// It's a literal i.e. a single 8-bit byte.
update_bit_0_dummy();
const probability *subcoder = literal_get_subcoder(
coder->literal_coder, now_pos, lz_get_byte(coder->lz, 0));
uint32_t symbol = 1;
if (!is_char_state(state)) {
// Decode literal with match byte.
assert(rep0 != UINT32_MAX);
uint32_t match_byte = lz_get_byte(coder->lz, rep0);
do {
match_byte <<= 1;
const uint32_t match_bit = match_byte & 0x100;
const uint32_t subcoder_index = 0x100 + match_bit + symbol;
if_bit_0(subcoder[subcoder_index]) {
update_bit_0_dummy();
symbol <<= 1;
if (match_bit != 0)
break;
} else {
update_bit_1_dummy();
symbol = (symbol << 1) | 1;
if (match_bit == 0)
break;
}
} while (symbol < 0x100);
}
// Decode literal without match byte. This is also
// the tail of the with-match-byte function.
while (symbol < 0x100) {
if_bit_0(subcoder[symbol]) {
update_bit_0_dummy();
symbol <<= 1;
} else {
update_bit_1_dummy();
symbol = (symbol << 1) | 1;
}
}
break;
}
update_bit_1_dummy();
uint32_t len;
if_bit_0(coder->is_rep[state]) {
update_bit_0_dummy();
length_decode_dummy(len, coder->len_decoder, pos_state);
update_match(state);
const uint32_t len_to_pos_state = get_len_to_pos_state(len);
uint32_t pos_slot = 0;
bittree_decode_dummy(pos_slot,
coder->pos_slot_decoder[len_to_pos_state], POS_SLOT_BITS);
assert(pos_slot <= 63);
if (pos_slot >= START_POS_MODEL_INDEX) {
uint32_t direct_bits = (pos_slot >> 1) - 1;
assert(direct_bits >= 1 && direct_bits <= 31);
rep0 = 2 | (pos_slot & 1);
if (pos_slot < END_POS_MODEL_INDEX) {
assert(direct_bits <= 5);
rep0 <<= direct_bits;
assert(rep0 <= 96);
// -1 is fine, because bittree_reverse_decode()
// starts from table index [1] (not [0]).
assert((int32_t)(rep0 - pos_slot - 1) >= -1);
assert((int32_t)(rep0 - pos_slot - 1) <= 82);
// We add the result to rep0, so rep0
// must not be part of second argument
// of the macro.
const int32_t offset = rep0 - pos_slot - 1;
bittree_reverse_decode_dummy(coder->pos_decoders + offset,
direct_bits);
} else {
assert(pos_slot >= 14);
assert(direct_bits >= 6);
direct_bits -= ALIGN_BITS;
assert(direct_bits >= 2);
rc_decode_direct_dummy(direct_bits);
bittree_reverse_decode_dummy(coder->pos_align_decoder,
ALIGN_BITS);
}
}
} else {
update_bit_1_dummy();
if_bit_0(coder->is_rep0[state]) {
update_bit_0_dummy();
if_bit_0(coder->is_rep0_long[state][pos_state]) {
update_bit_0_dummy();
break;
} else {
update_bit_1_dummy();
}
} else {
update_bit_1_dummy();
if_bit_0(coder->is_rep1[state]) {
update_bit_0_dummy();
} else {
update_bit_1_dummy();
if_bit_0(coder->is_rep2[state]) {
update_bit_0_dummy();
} else {
update_bit_1_dummy();
}
}
}
length_decode_dummy(len, coder->rep_match_len_decoder, pos_state);
}
} while (0);
rc_normalize();
return in_pos_local <= in_size;
}
static bool
decode_real(lzma_coder *restrict coder, const uint8_t *restrict in,
size_t *restrict in_pos, size_t in_size, bool has_safe_buffer)
{
////////////////////
// Initialization //
////////////////////
if (!rc_read_init(&coder->rc, in, in_pos, in_size))
return false;
///////////////
// Variables //
///////////////
// Making local copies of often-used variables improves both
// speed and readability.
// Range decoder
rc_to_local(coder->rc);
// State
uint32_t state = coder->state;
uint32_t rep0 = coder->rep0;
uint32_t rep1 = coder->rep1;
uint32_t rep2 = coder->rep2;
uint32_t rep3 = coder->rep3;
// Misc
uint32_t now_pos = coder->now_pos;
bool has_produced_output = coder->has_produced_output;
// Variables derived from decoder settings
const uint32_t pos_mask = coder->pos_mask;
size_t in_pos_local = *in_pos; // Local copy
size_t in_limit;
if (in_size <= REQUIRED_IN_BUFFER_SIZE)
in_limit = 0;
else
in_limit = in_size - REQUIRED_IN_BUFFER_SIZE;
while (coder->lz.pos < coder->lz.limit
&& (in_pos_local < in_limit || (has_safe_buffer
&& decode_dummy(coder, in, in_pos_local, in_size,
rc, state, rep0, now_pos)))) {
/////////////////////
// Actual decoding //
/////////////////////
const uint32_t pos_state = now_pos & pos_mask;
if_bit_0(coder->is_match[state][pos_state]) {
update_bit_0(coder->is_match[state][pos_state]);
// It's a literal i.e. a single 8-bit byte.
probability *subcoder = literal_get_subcoder(coder->literal_coder,
now_pos, lz_get_byte(coder->lz, 0));
uint32_t symbol = 1;
if (!is_char_state(state)) {
// Decode literal with match byte.
assert(rep0 != UINT32_MAX);
uint32_t match_byte = lz_get_byte(coder->lz, rep0);
do {
match_byte <<= 1;
const uint32_t match_bit = match_byte & 0x100;
const uint32_t subcoder_index = 0x100 + match_bit + symbol;
if_bit_0(subcoder[subcoder_index]) {
update_bit_0(subcoder[subcoder_index]);
symbol <<= 1;
if (match_bit != 0)
break;
} else {
update_bit_1(subcoder[subcoder_index]);
symbol = (symbol << 1) | 1;
if (match_bit == 0)
break;
}
} while (symbol < 0x100);
}
// Decode literal without match byte. This is also
// the tail of the with-match-byte function.
while (symbol < 0x100) {
if_bit_0(subcoder[symbol]) {
update_bit_0(subcoder[symbol]);
symbol <<= 1;
} else {
update_bit_1(subcoder[symbol]);
symbol = (symbol << 1) | 1;
}
}
// Put the decoded byte to the dictionary, update the
// decoder state, and start a new decoding loop.
coder->lz.dict[coder->lz.pos++] = (uint8_t)(symbol);
++now_pos;
update_char(state);
has_produced_output = true;
continue;
}
// Instead of a new byte we are going to get a byte range
// (distance and length) which will be repeated from our
// output history.
update_bit_1(coder->is_match[state][pos_state]);
uint32_t len;
if_bit_0(coder->is_rep[state]) {
update_bit_0(coder->is_rep[state]);
// Not a repeated match
//
// We will decode a new distance and store
// the value to distance.
// Decode the length of the match.
length_decode(len, coder->len_decoder, pos_state);
update_match(state);
const uint32_t len_to_pos_state = get_len_to_pos_state(len);
uint32_t pos_slot = 0;
bittree_decode(pos_slot,
coder->pos_slot_decoder[len_to_pos_state], POS_SLOT_BITS);
assert(pos_slot <= 63);
if (pos_slot >= START_POS_MODEL_INDEX) {
uint32_t direct_bits = (pos_slot >> 1) - 1;
assert(direct_bits >= 1 && direct_bits <= 30);
uint32_t distance = 2 | (pos_slot & 1);
if (pos_slot < END_POS_MODEL_INDEX) {
assert(direct_bits <= 5);
distance <<= direct_bits;
assert(distance <= 96);
// -1 is fine, because
// bittree_reverse_decode()
// starts from table index [1]
// (not [0]).
assert((int32_t)(distance - pos_slot - 1) >= -1);
assert((int32_t)(distance - pos_slot - 1) <= 82);
// We add the result to distance, so distance
// must not be part of second argument
// of the macro.
const int32_t offset = distance - pos_slot - 1;
bittree_reverse_decode(distance, coder->pos_decoders + offset,
direct_bits);
} else {
assert(pos_slot >= 14);
assert(direct_bits >= 6);
direct_bits -= ALIGN_BITS;
assert(direct_bits >= 2);
rc_decode_direct(distance, direct_bits);
distance <<= ALIGN_BITS;
bittree_reverse_decode(distance, coder->pos_align_decoder,
ALIGN_BITS);
if (distance == UINT32_MAX) {
if (len == LEN_SPECIAL_EOPM) {
// End of Payload Marker found.
coder->lz.eopm_detected = true;
break;
} else if (len == LEN_SPECIAL_FLUSH) {
// Flush marker detected. We must have produced
// at least one byte of output since the previous
// flush marker or the beginning of the stream.
// This is to prevent hanging the decoder with
// malicious input files.
if (!has_produced_output)
return true;
has_produced_output = false;
// We know that we have enough input to call
// this macro, because it is tested at the
// end of decode_dummy().
rc_normalize();
rc_reset(rc);
// If we don't have enough input here, we jump
// out of the loop. Note that while there is a
// useless call to rc_normalize(), it does nothing
// since we have just reset the range decoder.
if (!rc_read_init(&rc, in, &in_pos_local, in_size))
break;
continue;
} else {
return true;
}
}
}
// The latest three match distances are kept in
// memory in case there are repeated matches.
rep3 = rep2;
rep2 = rep1;
rep1 = rep0;
rep0 = distance;
} else {
rep3 = rep2;
rep2 = rep1;
rep1 = rep0;
rep0 = pos_slot;
}
} else {
update_bit_1(coder->is_rep[state]);
// Repeated match
//
// The match distance is a value that we have had
// earlier. The latest four match distances are
// available as rep0, rep1, rep2 and rep3. We will
// now decode which of them is the new distance.
if_bit_0(coder->is_rep0[state]) {
update_bit_0(coder->is_rep0[state]);
// The distance is rep0.
if_bit_0(coder->is_rep0_long[state][pos_state]) {
update_bit_0(coder->is_rep0_long[state][pos_state]);
// Repeating exactly one byte. For
// simplicity, it is done here inline
// instead of at the end of the main
// loop.
update_short_rep(state);
// Security/sanity checks. See the end
// of the main loop for explanation
// of these.
if ((rep0 >= coder->lz.pos && !coder->lz.is_full)
|| in_pos_local > in_size)
return true;
// Repeat one byte and start a new
// decoding loop.
coder->lz.dict[coder->lz.pos]
= lz_get_byte(coder->lz, rep0);
++coder->lz.pos;
++now_pos;
has_produced_output = true;
continue;
} else {
update_bit_1(coder->is_rep0_long[state][pos_state]);
// Repeating more than one byte at
// distance of rep0.
}
} else {
update_bit_1(coder->is_rep0[state]);
// The distance is rep1, rep2 or rep3. Once
// we find out which one of these three, it
// is stored to rep0 and rep1, rep2 and rep3
// are updated accordingly.
uint32_t distance;
if_bit_0(coder->is_rep1[state]) {
update_bit_0(coder->is_rep1[state]);
distance = rep1;
} else {
update_bit_1(coder->is_rep1[state]);
if_bit_0(coder->is_rep2[state]) {
update_bit_0(coder->is_rep2[state]);
distance = rep2;
} else {
update_bit_1(coder->is_rep2[state]);
distance = rep3;
rep3 = rep2;
}
rep2 = rep1;
}
rep1 = rep0;
rep0 = distance;
}
// Decode the length of the repeated match.
length_decode(len, coder->rep_match_len_decoder, pos_state);
update_rep(state);
}
/////////////////////////////////
// Repeat from history buffer. //
/////////////////////////////////
// The length is always between these limits. There is no way
// to trigger the algorithm to set len outside this range.
assert(len >= MATCH_MIN_LEN);
assert(len <= MATCH_MAX_LEN);
now_pos += len;
has_produced_output = true;
// Validate the buffer position to avoid buffer overflows
// on corrupted input data.
if (in_pos_local > in_size)
return true;
// Repeat len bytes from distance of rep0.
if (!lzma_lz_out_repeat(&coder->lz, rep0, len))
return true;
}
rc_normalize();
/////////////////////////////////
// Update the *data structure. //
/////////////////////////////////
// Range decoder
rc_from_local(coder->rc);
// State
coder->state = state;
coder->rep0 = rep0;
coder->rep1 = rep1;
coder->rep2 = rep2;
coder->rep3 = rep3;
// Misc
coder->now_pos = now_pos;
coder->has_produced_output = has_produced_output;
*in_pos = in_pos_local;
return false;
}
static void
lzma_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
{
lzma_next_coder_end(&coder->next, allocator);
lzma_lz_decoder_end(&coder->lz, allocator);
lzma_literal_end(&coder->literal_coder, allocator);
lzma_free(coder, allocator);
return;
}
extern lzma_ret
lzma_lzma_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
const lzma_filter_info *filters)
{
// Validate pos_bits. Other options are validated by the
// respective initialization functions.
const lzma_options_lzma *options = filters[0].options;
if (options->pos_bits > LZMA_POS_BITS_MAX)
return LZMA_HEADER_ERROR;
// Allocate memory for the decoder if needed.
if (next->coder == NULL) {
next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
if (next->coder == NULL)
return LZMA_MEM_ERROR;
// Initialize variables so that we know later that we don't
// have an existing decoder initialized.
next->coder->next = LZMA_NEXT_CODER_INIT;
next->coder->lz = LZMA_LZ_DECODER_INIT;
next->coder->literal_coder = NULL;
}
// Store the pos_bits and calculate pos_mask.
next->coder->pos_bits = options->pos_bits;
next->coder->pos_mask = (1U << next->coder->pos_bits) - 1;
// Allocate (if needed) and initialize the literal decoder.
{
const lzma_ret ret = lzma_literal_init(
&next->coder->literal_coder, allocator,
options->literal_context_bits,
options->literal_pos_bits);
if (ret != LZMA_OK) {
lzma_free(next->coder, allocator);
next->coder = NULL;
return ret;
}
}
// Allocate and initialize the LZ decoder.
{
const lzma_ret ret = lzma_lz_decoder_reset(
&next->coder->lz, allocator, &decode_real,
filters[0].uncompressed_size,
options->dictionary_size, MATCH_MAX_LEN);
if (ret != LZMA_OK) {
lzma_literal_end(&next->coder->literal_coder,
allocator);
lzma_free(next->coder, allocator);
next->coder = NULL;
return ret;
}
}
// State
next->coder->state = 0;
next->coder->rep0 = 0;
next->coder->rep1 = 0;
next->coder->rep2 = 0;
next->coder->rep3 = 0;
next->coder->pos_bits = options->pos_bits;
next->coder->pos_mask = (1 << next->coder->pos_bits) - 1;
next->coder->now_pos = 0;
// Range decoder
rc_reset(next->coder->rc);
// Bit and bittree decoders
for (uint32_t i = 0; i < STATES; ++i) {
for (uint32_t j = 0; j <= next->coder->pos_mask; ++j) {
bit_reset(next->coder->is_match[i][j]);
bit_reset(next->coder->is_rep0_long[i][j]);
}
bit_reset(next->coder->is_rep[i]);
bit_reset(next->coder->is_rep0[i]);
bit_reset(next->coder->is_rep1[i]);
bit_reset(next->coder->is_rep2[i]);
}
for (uint32_t i = 0; i < LEN_TO_POS_STATES; ++i)
bittree_reset(next->coder->pos_slot_decoder[i], POS_SLOT_BITS);
for (uint32_t i = 0; i < FULL_DISTANCES - END_POS_MODEL_INDEX; ++i)
bit_reset(next->coder->pos_decoders[i]);
bittree_reset(next->coder->pos_align_decoder, ALIGN_BITS);
// Len decoders (also bit/bittree)
const uint32_t num_pos_states = 1 << next->coder->pos_bits;
bit_reset(next->coder->len_decoder.choice);
bit_reset(next->coder->len_decoder.choice2);
bit_reset(next->coder->rep_match_len_decoder.choice);
bit_reset(next->coder->rep_match_len_decoder.choice2);
for (uint32_t pos_state = 0; pos_state < num_pos_states; ++pos_state) {
bittree_reset(next->coder->len_decoder.low[pos_state], LEN_LOW_BITS);
bittree_reset(next->coder->len_decoder.mid[pos_state], LEN_MID_BITS);
bittree_reset(next->coder->rep_match_len_decoder.low[pos_state],
LEN_LOW_BITS);
bittree_reset(next->coder->rep_match_len_decoder.mid[pos_state],
LEN_MID_BITS);
}
bittree_reset(next->coder->len_decoder.high, LEN_HIGH_BITS);
bittree_reset(next->coder->rep_match_len_decoder.high, LEN_HIGH_BITS);
next->coder->has_produced_output = false;
// Initialize the next decoder in the chain, if any.
{
const lzma_ret ret = lzma_next_filter_init(&next->coder->next,
allocator, filters + 1);
if (ret != LZMA_OK) {
lzma_decoder_end(next->coder, allocator);
return ret;
}
}
// Initialization successful. Set the function pointers.
next->code = &lzma_lz_decode;
next->end = &lzma_decoder_end;
return LZMA_OK;
}
extern bool
lzma_lzma_decode_properties(lzma_options_lzma *options, uint8_t byte)
{
if (byte > (4 * 5 + 4) * 9 + 8)
return true;
// See the file format specification to understand this.
options->pos_bits = byte / (9 * 5);
byte -= options->pos_bits * 9 * 5;
options->literal_pos_bits = byte / 9;
options->literal_context_bits = byte - options->literal_pos_bits * 9;
return false;
}
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