1/* Ppmd.h -- PPMD codec common code
22011-01-27 : 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 "Types.h"
9#include "CpuArch.h"
10
11EXTERN_C_BEGIN
12
13#ifdef MY_CPU_32BIT
14 #define PPMD_32BIT
15#endif
16
17#define PPMD_INT_BITS 7
18#define PPMD_PERIOD_BITS 7
19#define PPMD_BIN_SCALE (1 << (PPMD_INT_BITS + PPMD_PERIOD_BITS))
20
21#define PPMD_GET_MEAN_SPEC(summ, shift, round) (((summ) + (1 << ((shift) - (round)))) >> (shift))
22#define PPMD_GET_MEAN(summ) PPMD_GET_MEAN_SPEC((summ), PPMD_PERIOD_BITS, 2)
23#define PPMD_UPDATE_PROB_0(prob) ((prob) + (1 << PPMD_INT_BITS) - PPMD_GET_MEAN(prob))
24#define PPMD_UPDATE_PROB_1(prob) ((prob) - PPMD_GET_MEAN(prob))
25
26#define PPMD_N1 4
27#define PPMD_N2 4
28#define PPMD_N3 4
29#define PPMD_N4 ((128 + 3 - 1 * PPMD_N1 - 2 * PPMD_N2 - 3 * PPMD_N3) / 4)
30#define PPMD_NUM_INDEXES (PPMD_N1 + PPMD_N2 + PPMD_N3 + PPMD_N4)
31
32#pragma pack(push, 1)
33/* Most compilers works OK here even without #pragma pack(push, 1), but some GCC compilers need it. */
34
35/* SEE-contexts for PPM-contexts with masked symbols */
36typedef struct
37{
38 UInt16 Summ; /* Freq */
39 Byte Shift; /* Speed of Freq change; low Shift is for fast change */
40 Byte Count; /* Count to next change of Shift */
41} CPpmd_See;
42
43#define Ppmd_See_Update(p) if ((p)->Shift < PPMD_PERIOD_BITS && --(p)->Count == 0) \
44 { (p)->Summ <<= 1; (p)->Count = (Byte)(3 << (p)->Shift++); }
45
46typedef struct
47{
48 Byte Symbol;
49 Byte Freq;
50 UInt16 SuccessorLow;
51 UInt16 SuccessorHigh;
52} CPpmd_State;
53
54#pragma pack(pop)
55
56typedef
57 #ifdef PPMD_32BIT
58 CPpmd_State *
59 #else
60 UInt32
61 #endif
62 CPpmd_State_Ref;
63
64typedef
65 #ifdef PPMD_32BIT
66 void *
67 #else
68 UInt32
69 #endif
70 CPpmd_Void_Ref;
71
72typedef
73 #ifdef PPMD_32BIT
74 Byte *
75 #else
76 UInt32
77 #endif
78 CPpmd_Byte_Ref;
79
80#define PPMD_SetAllBitsIn256Bytes(p) \
81 { unsigned i; for (i = 0; i < 256 / sizeof(p[0]); i += 8) { \
82 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; }}
83
84EXTERN_C_END
85
86#endif
87