1 /* Ppmd.h -- PPMD codec common code
2 2017-04-03 : Igor Pavlov : Public domain
3 This 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 
10 EXTERN_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 */
35 typedef 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 
45 typedef struct
46 {
47   Byte Symbol;
48   Byte Freq;
49   UInt16 SuccessorLow;
50   UInt16 SuccessorHigh;
51 } CPpmd_State;
52 
53 #pragma pack(pop)
54 
55 typedef
56   #ifdef PPMD_32BIT
57     CPpmd_State *
58   #else
59     UInt32
60   #endif
61   CPpmd_State_Ref;
62 
63 typedef
64   #ifdef PPMD_32BIT
65     void *
66   #else
67     UInt32
68   #endif
69   CPpmd_Void_Ref;
70 
71 typedef
72   #ifdef PPMD_32BIT
73     Byte *
74   #else
75     UInt32
76   #endif
77   CPpmd_Byte_Ref;
78 
79 #define PPMD_SetAllBitsIn256Bytes(p) \
80   { size_t z; for (z = 0; z < 256 / sizeof(p[0]); z += 8) { \
81   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; }}
82 
83 EXTERN_C_END
84 
85 #endif
86