The R Project SVN R

///////////////////////////////////////////////////////////////////////////////
//
/// \file       price.h
/// \brief      Probability price calculation
//
//  Author:     Igor Pavlov
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#ifndef LZMA_PRICE_H
#define LZMA_PRICE_H


#define RC_MOVE_REDUCING_BITS 4
#define RC_BIT_PRICE_SHIFT_BITS 4
#define RC_PRICE_TABLE_SIZE (RC_BIT_MODEL_TOTAL >> RC_MOVE_REDUCING_BITS)

#define RC_INFINITY_PRICE (UINT32_C(1) << 30)


/// Lookup table for the inline functions defined in this file.
extern const uint8_t lzma_rc_prices[RC_PRICE_TABLE_SIZE];


static inline uint32_t
rc_bit_price(const probability prob, const uint32_t bit)
{
    return lzma_rc_prices[(prob ^ ((UINT32_C(0) - bit)
            & (RC_BIT_MODEL_TOTAL - 1))) >> RC_MOVE_REDUCING_BITS];
}


static inline uint32_t
rc_bit_0_price(const probability prob)
{
    return lzma_rc_prices[prob >> RC_MOVE_REDUCING_BITS];
}


static inline uint32_t
rc_bit_1_price(const probability prob)
{
    return lzma_rc_prices[(prob ^ (RC_BIT_MODEL_TOTAL - 1))
            >> RC_MOVE_REDUCING_BITS];
}


static inline uint32_t
rc_bittree_price(const probability *const probs,
        const uint32_t bit_levels, uint32_t symbol)
{
    uint32_t price = 0;
    symbol += UINT32_C(1) << bit_levels;

    do {
        const uint32_t bit = symbol & 1;
        symbol >>= 1;
        price += rc_bit_price(probs[symbol], bit);
    } while (symbol != 1);

    return price;
}


static inline uint32_t
rc_bittree_reverse_price(const probability *const probs,
        uint32_t bit_levels, uint32_t symbol)
{
    uint32_t price = 0;
    uint32_t model_index = 1;

    do {
        const uint32_t bit = symbol & 1;
        symbol >>= 1;
        price += rc_bit_price(probs[model_index], bit);
        model_index = (model_index << 1) + bit;
    } while (--bit_levels != 0);

    return price;
}


static inline uint32_t
rc_direct_price(const uint32_t bits)
{
     return bits << RC_BIT_PRICE_SHIFT_BITS;
}

#endif