visualboyadvance-m/fex/7z_C/Ppmd.h

/* Ppmd.h -- PPMD codec common code
2011-01-27 : Igor Pavlov : Public domain
This code is based on PPMd var.H (2001): Dmitry Shkarin : Public domain */

#ifndef __PPMD_H
#define __PPMD_H

#include "CpuArch.h"
#include "Types.h"

EXTERN_C_BEGIN

#ifdef MY_CPU_32BIT
#define PPMD_32BIT
#endif

#define PPMD_INT_BITS 7
#define PPMD_PERIOD_BITS 7
#define PPMD_BIN_SCALE (1 << (PPMD_INT_BITS + PPMD_PERIOD_BITS))

#define PPMD_GET_MEAN_SPEC(summ, shift, round) (((summ) + (1 << ((shift) - (round)))) >> (shift))
#define PPMD_GET_MEAN(summ) PPMD_GET_MEAN_SPEC((summ), PPMD_PERIOD_BITS, 2)
#define PPMD_UPDATE_PROB_0(prob) ((prob) + (1 << PPMD_INT_BITS) - PPMD_GET_MEAN(prob))
#define PPMD_UPDATE_PROB_1(prob) ((prob)-PPMD_GET_MEAN(prob))

#define PPMD_N1 4
#define PPMD_N2 4
#define PPMD_N3 4
#define PPMD_N4 ((128 + 3 - 1 * PPMD_N1 - 2 * PPMD_N2 - 3 * PPMD_N3) / 4)
#define PPMD_NUM_INDEXES (PPMD_N1 + PPMD_N2 + PPMD_N3 + PPMD_N4)

#pragma pack(push, 1)
/* Most compilers works OK here even without #pragma pack(push, 1), but some GCC compilers need it. */

/* SEE-contexts for PPM-contexts with masked symbols */
typedef struct
{
    UInt16 Summ; /* Freq */
    Byte Shift; /* Speed of Freq change; low Shift is for fast change */
    Byte Count; /* Count to next change of Shift */
} CPpmd_See;

#define Ppmd_See_Update(p)                                    \
    if ((p)->Shift < PPMD_PERIOD_BITS && --(p)->Count == 0) { \
        (p)->Summ <<= 1;                                      \
        (p)->Count = (Byte)(3 << (p)->Shift++);               \
    }

typedef struct
{
    Byte Symbol;
    Byte Freq;
    UInt16 SuccessorLow;
    UInt16 SuccessorHigh;
} CPpmd_State;

#pragma pack(pop)

typedef
#ifdef PPMD_32BIT
    CPpmd_State*
#else
    UInt32
#endif
        CPpmd_State_Ref;

typedef
#ifdef PPMD_32BIT
    void*
#else
    UInt32
#endif
        CPpmd_Void_Ref;

typedef
#ifdef PPMD_32BIT
    Byte*
#else
    UInt32
#endif
        CPpmd_Byte_Ref;

#define PPMD_SetAllBitsIn256Bytes(p)                                                                            \
    {                                                                                                           \
        unsigned i;                                                                                             \
        for (i = 0; i < 256 / sizeof(p[0]); i += 8) {                                                           \
            p[i + 7] = p[i + 6] = p[i + 5] = p[i + 4] = p[i + 3] = p[i + 2] = p[i + 1] = p[i + 0] = ~(size_t)0; \
        }                                                                                                       \
    }

EXTERN_C_END

#endif