1 files changed, 279 insertions, 0 deletions

diff --git a/C/Ppmd7aDec.c b/C/Ppmd7aDec.c
new file mode 100644
index 0000000..c424578
--- /dev/null
+++ b/C/Ppmd7aDec.c
@@ -0,0 +1,279 @@
+/* Ppmd7aDec.c -- PPMd7a (PPMdH) Decoder
+2021-04-13 : Igor Pavlov : Public domain
+This code is based on:
+  PPMd var.H (2001): Dmitry Shkarin : Public domain
+  Carryless rangecoder (1999): Dmitry Subbotin : Public domain */
+
+#include "Precomp.h"
+
+#include "Ppmd7.h"
+
+#define kTop (1 << 24)
+#define kBot (1 << 15)
+
+#define READ_BYTE(p) IByteIn_Read((p)->Stream)
+
+BoolInt Ppmd7a_RangeDec_Init(CPpmd7_RangeDec *p)
+{
+  unsigned i;
+  p->Code = 0;
+  p->Range = 0xFFFFFFFF;
+  p->Low = 0;
+  
+  for (i = 0; i < 4; i++)
+    p->Code = (p->Code << 8) | READ_BYTE(p);
+  return (p->Code < 0xFFFFFFFF);
+}
+
+#define RC_NORM(p) \
+  while ((p->Low ^ (p->Low + p->Range)) < kTop \
+    || (p->Range < kBot && ((p->Range = (0 - p->Low) & (kBot - 1)), 1))) { \
+      p->Code = (p->Code << 8) | READ_BYTE(p); \
+      p->Range <<= 8; p->Low <<= 8; }
+
+// we must use only one type of Normalization from two: LOCAL or REMOTE
+#define RC_NORM_LOCAL(p)    // RC_NORM(p)
+#define RC_NORM_REMOTE(p)   RC_NORM(p)
+
+#define R (&p->rc.dec)
+
+MY_FORCE_INLINE
+// MY_NO_INLINE
+static void RangeDec_Decode(CPpmd7 *p, UInt32 start, UInt32 size)
+{
+  start *= R->Range;
+  R->Low += start;
+  R->Code -= start;
+  R->Range *= size;
+  RC_NORM_LOCAL(R)
+}
+
+#define RC_Decode(start, size) RangeDec_Decode(p, start, size);
+#define RC_DecodeFinal(start, size) RC_Decode(start, size) RC_NORM_REMOTE(R)
+#define RC_GetThreshold(total) (R->Code / (R->Range /= (total)))
+
+
+#define CTX(ref) ((CPpmd7_Context *)Ppmd7_GetContext(p, ref))
+typedef CPpmd7_Context * CTX_PTR;
+#define SUCCESSOR(p) Ppmd_GET_SUCCESSOR(p)
+void Ppmd7_UpdateModel(CPpmd7 *p);
+
+#define MASK(sym) ((unsigned char *)charMask)[sym]
+
+
+int Ppmd7a_DecodeSymbol(CPpmd7 *p)
+{
+  size_t charMask[256 / sizeof(size_t)];
+
+  if (p->MinContext->NumStats != 1)
+  {
+    CPpmd_State *s = Ppmd7_GetStats(p, p->MinContext);
+    unsigned i;
+    UInt32 count, hiCnt;
+    UInt32 summFreq = p->MinContext->Union2.SummFreq;
+
+    if (summFreq > R->Range)
+      return PPMD7_SYM_ERROR;
+
+    count = RC_GetThreshold(summFreq);
+    hiCnt = count;
+    
+    if ((Int32)(count -= s->Freq) < 0)
+    {
+      Byte sym;
+      RC_DecodeFinal(0, s->Freq);
+      p->FoundState = s;
+      sym = s->Symbol;
+      Ppmd7_Update1_0(p);
+      return sym;
+    }
+  
+    p->PrevSuccess = 0;
+    i = (unsigned)p->MinContext->NumStats - 1;
+    
+    do
+    {
+      if ((Int32)(count -= (++s)->Freq) < 0)
+      {
+        Byte sym;
+        RC_DecodeFinal((hiCnt - count) - s->Freq, s->Freq);
+        p->FoundState = s;
+        sym = s->Symbol;
+        Ppmd7_Update1(p);
+        return sym;
+      }
+    }
+    while (--i);
+    
+    if (hiCnt >= summFreq)
+      return PPMD7_SYM_ERROR;
+    
+    hiCnt -= count;
+    RC_Decode(hiCnt, summFreq - hiCnt);
+
+    p->HiBitsFlag = PPMD7_HiBitsFlag_3(p->FoundState->Symbol);
+    PPMD_SetAllBitsIn256Bytes(charMask);
+    // i = p->MinContext->NumStats - 1;
+    // do { MASK((--s)->Symbol) = 0; } while (--i);
+    {
+      CPpmd_State *s2 = Ppmd7_GetStats(p, p->MinContext);
+      MASK(s->Symbol) = 0;
+      do
+      {
+        unsigned sym0 = s2[0].Symbol;
+        unsigned sym1 = s2[1].Symbol;
+        s2 += 2;
+        MASK(sym0) = 0;
+        MASK(sym1) = 0;
+      }
+      while (s2 < s);
+    }
+  }
+  else
+  {
+    CPpmd_State *s = Ppmd7Context_OneState(p->MinContext);
+    UInt16 *prob = Ppmd7_GetBinSumm(p);
+    UInt32 pr = *prob;
+    UInt32 size0 = (R->Range >> 14) * pr;
+    pr = PPMD_UPDATE_PROB_1(pr);
+
+    if (R->Code < size0)
+    {
+      Byte sym;
+      *prob = (UInt16)(pr + (1 << PPMD_INT_BITS));
+      
+      // RangeDec_DecodeBit0(size0);
+      R->Range = size0;
+      RC_NORM(R)
+      
+        
+        
+      // sym = (p->FoundState = Ppmd7Context_OneState(p->MinContext))->Symbol;
+      // Ppmd7_UpdateBin(p);
+      {
+        unsigned freq = s->Freq;
+        CTX_PTR c = CTX(SUCCESSOR(s));
+        sym = s->Symbol;
+        p->FoundState = s;
+        p->PrevSuccess = 1;
+        p->RunLength++;
+        s->Freq = (Byte)(freq + (freq < 128));
+        // NextContext(p);
+        if (p->OrderFall == 0 && (const Byte *)c > p->Text)
+          p->MaxContext = p->MinContext = c;
+        else
+          Ppmd7_UpdateModel(p);
+      }
+      return sym;
+    }
+
+    *prob = (UInt16)pr;
+    p->InitEsc = p->ExpEscape[pr >> 10];
+
+    // RangeDec_DecodeBit1(size0);
+    R->Low += size0;
+    R->Code -= size0;
+    R->Range = (R->Range & ~((UInt32)PPMD_BIN_SCALE - 1)) - size0;
+    RC_NORM_LOCAL(R)
+    
+    PPMD_SetAllBitsIn256Bytes(charMask);
+    MASK(Ppmd7Context_OneState(p->MinContext)->Symbol) = 0;
+    p->PrevSuccess = 0;
+  }
+
+  for (;;)
+  {
+    CPpmd_State *s, *s2;
+    UInt32 freqSum, count, hiCnt;
+
+    CPpmd_See *see;
+    CPpmd7_Context *mc;
+    unsigned numMasked;
+    RC_NORM_REMOTE(R)
+    mc = p->MinContext;
+    numMasked = mc->NumStats;
+
+    do
+    {
+      p->OrderFall++;
+      if (!mc->Suffix)
+        return PPMD7_SYM_END;
+      mc = Ppmd7_GetContext(p, mc->Suffix);
+    }
+    while (mc->NumStats == numMasked);
+    
+    s = Ppmd7_GetStats(p, mc);
+
+    {
+      unsigned num = mc->NumStats;
+      unsigned num2 = num / 2;
+      
+      num &= 1;
+      hiCnt = (s->Freq & (unsigned)(MASK(s->Symbol))) & (0 - (UInt32)num);
+      s += num;
+      p->MinContext = mc;
+
+      do
+      {
+        unsigned sym0 = s[0].Symbol;
+        unsigned sym1 = s[1].Symbol;
+        s += 2;
+        hiCnt += (s[-2].Freq & (unsigned)(MASK(sym0)));
+        hiCnt += (s[-1].Freq & (unsigned)(MASK(sym1)));
+      }
+      while (--num2);
+    }
+
+    see = Ppmd7_MakeEscFreq(p, numMasked, &freqSum);
+    freqSum += hiCnt;
+
+    if (freqSum > R->Range)
+      return PPMD7_SYM_ERROR;
+
+    count = RC_GetThreshold(freqSum);
+    
+    if (count < hiCnt)
+    {
+      Byte sym;
+
+      s = Ppmd7_GetStats(p, p->MinContext);
+      hiCnt = count;
+      // count -= s->Freq & (unsigned)(MASK(s->Symbol));
+      // if ((Int32)count >= 0)
+      {
+        for (;;)
+        {
+          count -= s->Freq & (unsigned)(MASK((s)->Symbol)); s++; if ((Int32)count < 0) break;
+          // count -= s->Freq & (unsigned)(MASK((s)->Symbol)); s++; if ((Int32)count < 0) break;
+        };
+      }
+      s--;
+      RC_DecodeFinal((hiCnt - count) - s->Freq, s->Freq);
+
+      // new (see->Summ) value can overflow over 16-bits in some rare cases
+      Ppmd_See_Update(see);
+      p->FoundState = s;
+      sym = s->Symbol;
+      Ppmd7_Update2(p);
+      return sym;
+    }
+
+    if (count >= freqSum)
+      return PPMD7_SYM_ERROR;
+    
+    RC_Decode(hiCnt, freqSum - hiCnt);
+
+    // We increase (see->Summ) for sum of Freqs of all non_Masked symbols.
+    // new (see->Summ) value can overflow over 16-bits in some rare cases
+    see->Summ = (UInt16)(see->Summ + freqSum);
+
+    s = Ppmd7_GetStats(p, p->MinContext);
+    s2 = s + p->MinContext->NumStats;
+    do
+    {
+      MASK(s->Symbol) = 0;
+      s++;
+    }
+    while (s != s2);
+  }
+}