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///////////////////////////////////////////////////////////////////////////////
//
/// \file range_encoder.h
/// \brief Range Encoder
//
// Copyright (C) 1999-2006 Igor Pavlov
// Copyright (C) 2007-2008 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_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
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