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/* Ppmd.h -- PPMD codec common code
2016-05-16 : 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"
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 z; for (z = 0; z < 256 / sizeof(p[0]); z += 8) { \
p[z+7] = p[z+6] = p[z+5] = p[z+4] = p[z+3] = p[z+2] = p[z+1] = p[z+0] = ~(size_t)0; }}
EXTERN_C_END
#endif
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