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///////////////////////////////////////////////////////////////////////////////
//
/// \file range_decoder.h
/// \brief Range 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.
//
///////////////////////////////////////////////////////////////////////////////
#ifndef LZMA_RANGE_DECODER_H
#define LZMA_RANGE_DECODER_H
#include "range_common.h"
typedef struct {
uint32_t range;
uint32_t code;
uint32_t init_bytes_left;
} lzma_range_decoder;
static inline bool
rc_read_init(lzma_range_decoder *rc, const uint8_t *restrict in,
size_t *restrict in_pos, size_t in_size)
{
while (rc->init_bytes_left > 0) {
if (*in_pos == in_size)
return false;
rc->code = (rc->code << 8) | in[*in_pos];
++*in_pos;
--rc->init_bytes_left;
}
return true;
}
/// Makes local copies of range decoder variables.
#define rc_to_local(range_decoder) \
lzma_range_decoder rc = range_decoder; \
uint32_t rc_bound
/// Stores the local copes back to the range decoder structure.
#define rc_from_local(range_decoder) \
range_decoder = rc
/// Resets the range decoder structure.
#define rc_reset(range_decoder) \
do { \
(range_decoder).range = UINT32_MAX; \
(range_decoder).code = 0; \
(range_decoder).init_bytes_left = 5; \
} while (0)
// All of the macros in this file expect the following variables being defined:
// - lzma_range_decoder range_decoder;
// - uint32_t rc_bound; // Temporary variable
// - uint8_t *in;
// - size_t in_pos_local; // Local alias for *in_pos
//////////////////
// Buffer "I/O" //
//////////////////
// Read the next byte of compressed data from buffer_in, if needed.
#define rc_normalize() \
do { \
if (rc.range < TOP_VALUE) { \
rc.range <<= SHIFT_BITS; \
rc.code = (rc.code << SHIFT_BITS) | in[in_pos_local++]; \
} \
} while (0)
//////////////////
// Bit decoding //
//////////////////
// Range decoder's DecodeBit() is splitted into three macros:
// if_bit_0(prob) {
// update_bit_0(prob)
// ...
// } else {
// update_bit_1(prob)
// ...
// }
#define if_bit_0(prob) \
rc_normalize(); \
rc_bound = (rc.range >> BIT_MODEL_TOTAL_BITS) * (prob); \
if (rc.code < rc_bound)
#define update_bit_0(prob) \
do { \
rc.range = rc_bound; \
prob += (BIT_MODEL_TOTAL - (prob)) >> MOVE_BITS; \
} while (0)
#define update_bit_1(prob) \
do { \
rc.range -= rc_bound; \
rc.code -= rc_bound; \
prob -= (prob) >> MOVE_BITS; \
} while (0)
#define rc_decode_direct(dest, count) \
do { \
rc_normalize(); \
rc.range >>= 1; \
rc_bound = (rc.code - rc.range) >> 31; \
rc.code -= rc.range & (rc_bound - 1); \
dest = ((dest) << 1) | (1 - rc_bound);\
} while (--count > 0)
// Dummy versions don't update prob or dest.
#define update_bit_0_dummy() \
rc.range = rc_bound
#define update_bit_1_dummy() \
do { \
rc.range -= rc_bound; \
rc.code -= rc_bound; \
} while (0)
#define rc_decode_direct_dummy(count) \
do { \
rc_normalize(); \
rc.range >>= 1; \
rc_bound = (rc.code - rc.range) >> 31; \
rc.code -= rc.range & (rc_bound - 1); \
} while (--count > 0)
///////////////////////
// Bit tree decoding //
///////////////////////
#define bittree_decode(target, probs, bit_levels) \
do { \
uint32_t model_index = 1; \
for (uint32_t bit_index = (bit_levels); bit_index != 0; --bit_index) { \
if_bit_0((probs)[model_index]) { \
update_bit_0((probs)[model_index]); \
model_index <<= 1; \
} else { \
update_bit_1((probs)[model_index]); \
model_index = (model_index << 1) | 1; \
} \
} \
target += model_index - (1 << bit_levels); \
} while (0)
#define bittree_reverse_decode(target, probs, bit_levels) \
do { \
uint32_t model_index = 1; \
for (uint32_t bit_index = 0; bit_index < bit_levels; ++bit_index) { \
if_bit_0((probs)[model_index]) { \
update_bit_0((probs)[model_index]); \
model_index <<= 1; \
} else { \
update_bit_1((probs)[model_index]); \
model_index = (model_index << 1) | 1; \
target += 1 << bit_index; \
} \
} \
} while (0)
// Dummy versions don't update prob.
#define bittree_decode_dummy(target, probs, bit_levels) \
do { \
uint32_t model_index = 1; \
for (uint32_t bit_index = (bit_levels); bit_index != 0; --bit_index) { \
if_bit_0((probs)[model_index]) { \
update_bit_0_dummy(); \
model_index <<= 1; \
} else { \
update_bit_1_dummy(); \
model_index = (model_index << 1) | 1; \
} \
} \
target += model_index - (1 << bit_levels); \
} while (0)
#define bittree_reverse_decode_dummy(probs, bit_levels) \
do { \
uint32_t model_index = 1; \
for (uint32_t bit_index = 0; bit_index < bit_levels; ++bit_index) { \
if_bit_0((probs)[model_index]) { \
update_bit_0_dummy(); \
model_index <<= 1; \
} else { \
update_bit_1_dummy(); \
model_index = (model_index << 1) | 1; \
} \
} \
} while (0)
#endif
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