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      1 /* Ppmd.h -- PPMD codec common code
      2 2010-03-12 : 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 "Types.h"
      9 #include "CpuArch.h"
     10 
     11 EXTERN_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 /* SEE-contexts for PPM-contexts with masked symbols */
     33 typedef struct
     34 {
     35   UInt16 Summ; /* Freq */
     36   Byte Shift;  /* Speed of Freq change; low Shift is for fast change */
     37   Byte Count;  /* Count to next change of Shift */
     38 } CPpmd_See;
     39 
     40 #define Ppmd_See_Update(p)  if ((p)->Shift < PPMD_PERIOD_BITS && --(p)->Count == 0) \
     41     { (p)->Summ <<= 1; (p)->Count = (Byte)(3 << (p)->Shift++); }
     42 
     43 typedef struct
     44 {
     45   Byte Symbol;
     46   Byte Freq;
     47   UInt16 SuccessorLow;
     48   UInt16 SuccessorHigh;
     49 } CPpmd_State;
     50 
     51 typedef
     52   #ifdef PPMD_32BIT
     53     CPpmd_State *
     54   #else
     55     UInt32
     56   #endif
     57   CPpmd_State_Ref;
     58 
     59 typedef
     60   #ifdef PPMD_32BIT
     61     void *
     62   #else
     63     UInt32
     64   #endif
     65   CPpmd_Void_Ref;
     66 
     67 typedef
     68   #ifdef PPMD_32BIT
     69     Byte *
     70   #else
     71     UInt32
     72   #endif
     73   CPpmd_Byte_Ref;
     74 
     75 #define PPMD_SetAllBitsIn256Bytes(p) \
     76   { unsigned i; for (i = 0; i < 256 / sizeof(p[0]); i += 8) { \
     77   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; }}
     78 
     79 EXTERN_C_END
     80 
     81 #endif
     82