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85 lines
2 KiB
C
85 lines
2 KiB
C
/* Ppmd.h -- PPMD codec common code
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2013-01-18 : Igor Pavlov : Public domain
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This code is based on PPMd var.H (2001): Dmitry Shkarin : Public domain */
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#ifndef __PPMD_H
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#define __PPMD_H
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#include "CpuArch.h"
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EXTERN_C_BEGIN
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#ifdef MY_CPU_32BIT
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#define PPMD_32BIT
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#endif
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#define PPMD_INT_BITS 7
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#define PPMD_PERIOD_BITS 7
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#define PPMD_BIN_SCALE (1 << (PPMD_INT_BITS + PPMD_PERIOD_BITS))
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#define PPMD_GET_MEAN_SPEC(summ, shift, round) (((summ) + (1 << ((shift) - (round)))) >> (shift))
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#define PPMD_GET_MEAN(summ) PPMD_GET_MEAN_SPEC((summ), PPMD_PERIOD_BITS, 2)
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#define PPMD_UPDATE_PROB_0(prob) ((prob) + (1 << PPMD_INT_BITS) - PPMD_GET_MEAN(prob))
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#define PPMD_UPDATE_PROB_1(prob) ((prob) - PPMD_GET_MEAN(prob))
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#define PPMD_N1 4
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#define PPMD_N2 4
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#define PPMD_N3 4
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#define PPMD_N4 ((128 + 3 - 1 * PPMD_N1 - 2 * PPMD_N2 - 3 * PPMD_N3) / 4)
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#define PPMD_NUM_INDEXES (PPMD_N1 + PPMD_N2 + PPMD_N3 + PPMD_N4)
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#pragma pack(push, 1)
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/* Most compilers works OK here even without #pragma pack(push, 1), but some GCC compilers need it. */
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/* SEE-contexts for PPM-contexts with masked symbols */
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typedef struct
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{
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UInt16 Summ; /* Freq */
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Byte Shift; /* Speed of Freq change; low Shift is for fast change */
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Byte Count; /* Count to next change of Shift */
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} CPpmd_See;
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#define Ppmd_See_Update(p) if ((p)->Shift < PPMD_PERIOD_BITS && --(p)->Count == 0) \
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{ (p)->Summ <<= 1; (p)->Count = (Byte)(3 << (p)->Shift++); }
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typedef struct
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{
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Byte Symbol;
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Byte Freq;
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UInt16 SuccessorLow;
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UInt16 SuccessorHigh;
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} CPpmd_State;
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#pragma pack(pop)
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typedef
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#ifdef PPMD_32BIT
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CPpmd_State *
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#else
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UInt32
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#endif
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CPpmd_State_Ref;
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typedef
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#ifdef PPMD_32BIT
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void *
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#else
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UInt32
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#endif
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CPpmd_Void_Ref;
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typedef
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#ifdef PPMD_32BIT
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Byte *
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#else
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UInt32
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#endif
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CPpmd_Byte_Ref;
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#define PPMD_SetAllBitsIn256Bytes(p) \
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{ unsigned i; for (i = 0; i < 256 / sizeof(p[0]); i += 8) { \
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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; }}
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EXTERN_C_END
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#endif
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