1/* Ppmd.h -- PPMD codec common code
 22013-01-18 : Igor Pavlov : Public domain
 3This code is based on PPMd var.H (2001): Dmitry Shkarin : Public domain */
 4
 5#ifndef __PPMD_H
 6#define __PPMD_H
 7
 8#include "CpuArch.h"
 9
10EXTERN_C_BEGIN
11
12#ifdef MY_CPU_32BIT
13  #define PPMD_32BIT
14#endif
15
16#define PPMD_INT_BITS 7
17#define PPMD_PERIOD_BITS 7
18#define PPMD_BIN_SCALE (1 << (PPMD_INT_BITS + PPMD_PERIOD_BITS))
19
20#define PPMD_GET_MEAN_SPEC(summ, shift, round) (((summ) + (1 << ((shift) - (round)))) >> (shift))
21#define PPMD_GET_MEAN(summ) PPMD_GET_MEAN_SPEC((summ), PPMD_PERIOD_BITS, 2)
22#define PPMD_UPDATE_PROB_0(prob) ((prob) + (1 << PPMD_INT_BITS) - PPMD_GET_MEAN(prob))
23#define PPMD_UPDATE_PROB_1(prob) ((prob) - PPMD_GET_MEAN(prob))
24
25#define PPMD_N1 4
26#define PPMD_N2 4
27#define PPMD_N3 4
28#define PPMD_N4 ((128 + 3 - 1 * PPMD_N1 - 2 * PPMD_N2 - 3 * PPMD_N3) / 4)
29#define PPMD_NUM_INDEXES (PPMD_N1 + PPMD_N2 + PPMD_N3 + PPMD_N4)
30
31#pragma pack(push, 1)
32/* Most compilers works OK here even without #pragma pack(push, 1), but some GCC compilers need it. */
33
34/* SEE-contexts for PPM-contexts with masked symbols */
35typedef struct
36{
37  UInt16 Summ; /* Freq */
38  Byte Shift;  /* Speed of Freq change; low Shift is for fast change */
39  Byte Count;  /* Count to next change of Shift */
40} CPpmd_See;
41
42#define Ppmd_See_Update(p)  if ((p)->Shift < PPMD_PERIOD_BITS && --(p)->Count == 0) \
43    { (p)->Summ <<= 1; (p)->Count = (Byte)(3 << (p)->Shift++); }
44
45typedef struct
46{
47  Byte Symbol;
48  Byte Freq;
49  UInt16 SuccessorLow;
50  UInt16 SuccessorHigh;
51} CPpmd_State;
52
53#pragma pack(pop)
54
55typedef
56  #ifdef PPMD_32BIT
57    CPpmd_State *
58  #else
59    UInt32
60  #endif
61  CPpmd_State_Ref;
62
63typedef
64  #ifdef PPMD_32BIT
65    void *
66  #else
67    UInt32
68  #endif
69  CPpmd_Void_Ref;
70
71typedef
72  #ifdef PPMD_32BIT
73    Byte *
74  #else
75    UInt32
76  #endif
77  CPpmd_Byte_Ref;
78
79#define PPMD_SetAllBitsIn256Bytes(p) \
80  { unsigned i; for (i = 0; i < 256 / sizeof(p[0]); i += 8) { \
81  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; }}
82
83EXTERN_C_END
84 
85#endif