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      1 /* Ppmd.h -- PPMD codec common code
      2 2016-05-16 : 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   { unsigned 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