You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
231 lines
4.5 KiB
231 lines
4.5 KiB
/////////////////////////////////////////////////////////////////////////////// |
|
// |
|
/// \file range_encoder.h |
|
/// \brief Range Encoder |
|
/// |
|
// Authors: Igor Pavlov |
|
// Lasse Collin |
|
// |
|
// This file has been put into the public domain. |
|
// You can do whatever you want with this file. |
|
// |
|
/////////////////////////////////////////////////////////////////////////////// |
|
|
|
#ifndef LZMA_RANGE_ENCODER_H |
|
#define LZMA_RANGE_ENCODER_H |
|
|
|
#include "range_common.h" |
|
#include "price.h" |
|
|
|
|
|
/// Maximum number of symbols that can be put pending into lzma_range_encoder |
|
/// structure between calls to lzma_rc_encode(). For LZMA, 52+5 is enough |
|
/// (match with big distance and length followed by range encoder flush). |
|
#define RC_SYMBOLS_MAX 58 |
|
|
|
|
|
typedef struct { |
|
uint64_t low; |
|
uint64_t cache_size; |
|
uint32_t range; |
|
uint8_t cache; |
|
|
|
/// Number of symbols in the tables |
|
size_t count; |
|
|
|
/// rc_encode()'s position in the tables |
|
size_t pos; |
|
|
|
/// Symbols to encode |
|
enum { |
|
RC_BIT_0, |
|
RC_BIT_1, |
|
RC_DIRECT_0, |
|
RC_DIRECT_1, |
|
RC_FLUSH, |
|
} symbols[RC_SYMBOLS_MAX]; |
|
|
|
/// Probabilities associated with RC_BIT_0 or RC_BIT_1 |
|
probability *probs[RC_SYMBOLS_MAX]; |
|
|
|
} lzma_range_encoder; |
|
|
|
|
|
static inline void |
|
rc_reset(lzma_range_encoder *rc) |
|
{ |
|
rc->low = 0; |
|
rc->cache_size = 1; |
|
rc->range = UINT32_MAX; |
|
rc->cache = 0; |
|
rc->count = 0; |
|
rc->pos = 0; |
|
} |
|
|
|
|
|
static inline void |
|
rc_bit(lzma_range_encoder *rc, probability *prob, uint32_t bit) |
|
{ |
|
rc->symbols[rc->count] = bit; |
|
rc->probs[rc->count] = prob; |
|
++rc->count; |
|
} |
|
|
|
|
|
static inline void |
|
rc_bittree(lzma_range_encoder *rc, probability *probs, |
|
uint32_t bit_count, uint32_t symbol) |
|
{ |
|
uint32_t model_index = 1; |
|
|
|
do { |
|
const uint32_t bit = (symbol >> --bit_count) & 1; |
|
rc_bit(rc, &probs[model_index], bit); |
|
model_index = (model_index << 1) + bit; |
|
} while (bit_count != 0); |
|
} |
|
|
|
|
|
static inline void |
|
rc_bittree_reverse(lzma_range_encoder *rc, probability *probs, |
|
uint32_t bit_count, uint32_t symbol) |
|
{ |
|
uint32_t model_index = 1; |
|
|
|
do { |
|
const uint32_t bit = symbol & 1; |
|
symbol >>= 1; |
|
rc_bit(rc, &probs[model_index], bit); |
|
model_index = (model_index << 1) + bit; |
|
} while (--bit_count != 0); |
|
} |
|
|
|
|
|
static inline void |
|
rc_direct(lzma_range_encoder *rc, |
|
uint32_t value, uint32_t bit_count) |
|
{ |
|
do { |
|
rc->symbols[rc->count++] |
|
= RC_DIRECT_0 + ((value >> --bit_count) & 1); |
|
} while (bit_count != 0); |
|
} |
|
|
|
|
|
static inline void |
|
rc_flush(lzma_range_encoder *rc) |
|
{ |
|
for (size_t i = 0; i < 5; ++i) |
|
rc->symbols[rc->count++] = RC_FLUSH; |
|
} |
|
|
|
|
|
static inline bool |
|
rc_shift_low(lzma_range_encoder *rc, |
|
uint8_t *out, size_t *out_pos, size_t out_size) |
|
{ |
|
if ((uint32_t)(rc->low) < (uint32_t)(0xFF000000) |
|
|| (uint32_t)(rc->low >> 32) != 0) { |
|
do { |
|
if (*out_pos == out_size) |
|
return true; |
|
|
|
out[*out_pos] = rc->cache + (uint8_t)(rc->low >> 32); |
|
++*out_pos; |
|
rc->cache = 0xFF; |
|
|
|
} while (--rc->cache_size != 0); |
|
|
|
rc->cache = (rc->low >> 24) & 0xFF; |
|
} |
|
|
|
++rc->cache_size; |
|
rc->low = (rc->low & 0x00FFFFFF) << RC_SHIFT_BITS; |
|
|
|
return false; |
|
} |
|
|
|
|
|
static inline bool |
|
rc_encode(lzma_range_encoder *rc, |
|
uint8_t *out, size_t *out_pos, size_t out_size) |
|
{ |
|
assert(rc->count <= RC_SYMBOLS_MAX); |
|
|
|
while (rc->pos < rc->count) { |
|
// Normalize |
|
if (rc->range < RC_TOP_VALUE) { |
|
if (rc_shift_low(rc, out, out_pos, out_size)) |
|
return true; |
|
|
|
rc->range <<= RC_SHIFT_BITS; |
|
} |
|
|
|
// Encode a bit |
|
switch (rc->symbols[rc->pos]) { |
|
case RC_BIT_0: { |
|
probability prob = *rc->probs[rc->pos]; |
|
rc->range = (rc->range >> RC_BIT_MODEL_TOTAL_BITS) |
|
* prob; |
|
prob += (RC_BIT_MODEL_TOTAL - prob) >> RC_MOVE_BITS; |
|
*rc->probs[rc->pos] = prob; |
|
break; |
|
} |
|
|
|
case RC_BIT_1: { |
|
probability prob = *rc->probs[rc->pos]; |
|
const uint32_t bound = prob * (rc->range |
|
>> RC_BIT_MODEL_TOTAL_BITS); |
|
rc->low += bound; |
|
rc->range -= bound; |
|
prob -= prob >> RC_MOVE_BITS; |
|
*rc->probs[rc->pos] = prob; |
|
break; |
|
} |
|
|
|
case RC_DIRECT_0: |
|
rc->range >>= 1; |
|
break; |
|
|
|
case RC_DIRECT_1: |
|
rc->range >>= 1; |
|
rc->low += rc->range; |
|
break; |
|
|
|
case RC_FLUSH: |
|
// Prevent further normalizations. |
|
rc->range = UINT32_MAX; |
|
|
|
// Flush the last five bytes (see rc_flush()). |
|
do { |
|
if (rc_shift_low(rc, out, out_pos, out_size)) |
|
return true; |
|
} while (++rc->pos < rc->count); |
|
|
|
// Reset the range encoder so we are ready to continue |
|
// encoding if we weren't finishing the stream. |
|
rc_reset(rc); |
|
return false; |
|
|
|
default: |
|
assert(0); |
|
break; |
|
} |
|
|
|
++rc->pos; |
|
} |
|
|
|
rc->count = 0; |
|
rc->pos = 0; |
|
|
|
return false; |
|
} |
|
|
|
|
|
static inline uint64_t |
|
rc_pending(const lzma_range_encoder *rc) |
|
{ |
|
return rc->cache_size + 5 - 1; |
|
} |
|
|
|
#endif
|
|
|