text: /* Ppmd7.c -- PPMdH codec
  2017-04-03 : Igor Pavlov : Public domain
  This code is based on PPMd var.H (2001): Dmitry Shkarin : Public domain */
  
  #include <string.h>
  
  #include "Ppmd7.h"
  
  const Byte PPMD7_kExpEscape[16] = { 25, 14, 9, 7, 5, 5, 4, 4, 4, 3, 3, 3, 2, 2, 2, 2 };
  static const UInt16 kInitBinEsc[] = { 0x3CDD, 0x1F3F, 0x59BF, 0x48F3, 0x64A1, 0x5ABC, 0x6632, 0x6051};
  
  #define MAX_FREQ 124
  #define UNIT_SIZE 12
  
  #define U2B(nu) ((UInt32)(nu) * UNIT_SIZE)
  #define U2I(nu) (p->Units2Indx[(size_t)(nu) - 1])
  #define I2U(indx) (p->Indx2Units[indx])
  
  #ifdef PPMD_32BIT
    #define REF(ptr) (ptr)
  #else
    #define REF(ptr) ((UInt32)((Byte *)(ptr) - (p)->Base))
  #endif
  
  #define STATS_REF(ptr) ((CPpmd_State_Ref)REF(ptr))
  
  #define CTX(ref) ((CPpmd7_Context *)Ppmd7_GetContext(p, ref))
  #define STATS(ctx) Ppmd7_GetStats(p, ctx)
  #define ONE_STATE(ctx) Ppmd7Context_OneState(ctx)
  #define SUFFIX(ctx) CTX((ctx)->Suffix)
  
  typedef CPpmd7_Context * CTX_PTR;
  
  struct CPpmd7_Node_;
  
  typedef
    #ifdef PPMD_32BIT
      struct CPpmd7_Node_ *
    #else
      UInt32
    #endif
    CPpmd7_Node_Ref;
  
  typedef struct CPpmd7_Node_
  {
    UInt16 Stamp; /* must be at offset 0 as CPpmd7_Context::NumStats. Stamp=0 means free */
    UInt16 NU;
    CPpmd7_Node_Ref Next; /* must be at offset >= 4 */
    CPpmd7_Node_Ref Prev;
  } CPpmd7_Node;
  
  #ifdef PPMD_32BIT
    #define NODE(ptr) (ptr)
  #else
    #define NODE(offs) ((CPpmd7_Node *)(p->Base + (offs)))
  #endif
  
  void Ppmd7_Construct(CPpmd7 *p)
  {
    unsigned i, k, m;
  
    p->Base = 0;
  
    for (i = 0, k = 0; i < PPMD_NUM_INDEXES; i++)
    {
      unsigned step = (i >= 12 ? 4 : (i >> 2) + 1);
      do { p->Units2Indx[k++] = (Byte)i; } while (--step);
      p->Indx2Units[i] = (Byte)k;
    }
  
    p->NS2BSIndx[0] = (0 << 1);
    p->NS2BSIndx[1] = (1 << 1);
    memset(p->NS2BSIndx + 2, (2 << 1), 9);
    memset(p->NS2BSIndx + 11, (3 << 1), 256 - 11);
  
    for (i = 0; i < 3; i++)
      p->NS2Indx[i] = (Byte)i;
    for (m = i, k = 1; i < 256; i++)
    {
      p->NS2Indx[i] = (Byte)m;
      if (--k == 0)
        k = (++m) - 2;
    }
  
    memset(p->HB2Flag, 0, 0x40);
    memset(p->HB2Flag + 0x40, 8, 0x100 - 0x40);
  }
  
  void Ppmd7_Free(CPpmd7 *p, ISzAllocPtr alloc)
  {
    ISzAlloc_Free(alloc, p->Base);
    p->Size = 0;
    p->Base = 0;
  }
  
  Bool Ppmd7_Alloc(CPpmd7 *p, UInt32 size, ISzAllocPtr alloc)
  {
    if (!p->Base || p->Size != size)
    {
      size_t size2;
      Ppmd7_Free(p, alloc);
      size2 = 0
        #ifndef PPMD_32BIT
        + UNIT_SIZE
        #endif
        ;
      p->AlignOffset =
        #ifdef PPMD_32BIT
          (4 - size) & 3;
        #else
          4 - (size & 3);
        #endif
      if ((p->Base = (Byte *)ISzAlloc_Alloc(alloc, p->AlignOffset + size + size2)) == 0)
        return False;
      p->Size = size;
    }
    return True;
  }
  
  static void InsertNode(CPpmd7 *p, void *node, unsigned indx)
  {
    *((CPpmd_Void_Ref *)node) = p->FreeList[indx];
    p->FreeList[indx] = REF(node);
  }
  
  static void *RemoveNode(CPpmd7 *p, unsigned indx)
  {
    CPpmd_Void_Ref *node = (CPpmd_Void_Ref *)Ppmd7_GetPtr(p, p->FreeList[indx]);
    p->FreeList[indx] = *node;
    return node;
  }
  
  static void SplitBlock(CPpmd7 *p, void *ptr, unsigned oldIndx, unsigned newIndx)
  {
    unsigned i, nu = I2U(oldIndx) - I2U(newIndx);
    ptr = (Byte *)ptr + U2B(I2U(newIndx));
    if (I2U(i = U2I(nu)) != nu)
    {
      unsigned k = I2U(--i);
      InsertNode(p, ((Byte *)ptr) + U2B(k), nu - k - 1);
    }
    InsertNode(p, ptr, i);
  }
  
  static void GlueFreeBlocks(CPpmd7 *p)
  {
    #ifdef PPMD_32BIT
    CPpmd7_Node headItem;
    CPpmd7_Node_Ref head = &headItem;
    #else
    CPpmd7_Node_Ref head = p->AlignOffset + p->Size;
    #endif
    
    CPpmd7_Node_Ref n = head;
    unsigned i;
  
    p->GlueCount = 255;
  
    /* create doubly-linked list of free blocks */
    for (i = 0; i < PPMD_NUM_INDEXES; i++)
    {
      UInt16 nu = I2U(i);
      CPpmd7_Node_Ref next = (CPpmd7_Node_Ref)p->FreeList[i];
      p->FreeList[i] = 0;
      while (next != 0)
      {
        CPpmd7_Node *node = NODE(next);
        node->Next = n;
        n = NODE(n)->Prev = next;
        next = *(const CPpmd7_Node_Ref *)node;
        node->Stamp = 0;
        node->NU = (UInt16)nu;
      }
    }
    NODE(head)->Stamp = 1;
    NODE(head)->Next = n;
    NODE(n)->Prev = head;
    if (p->LoUnit != p->HiUnit)
      ((CPpmd7_Node *)p->LoUnit)->Stamp = 1;
    
    /* Glue free blocks */
    while (n != head)
    {
      CPpmd7_Node *node = NODE(n);
      UInt32 nu = (UInt32)node->NU;
      for (;;)
      {
        CPpmd7_Node *node2 = NODE(n) + nu;
        nu += node2->NU;
        if (node2->Stamp != 0 || nu >= 0x10000)
          break;
        NODE(node2->Prev)->Next = node2->Next;
        NODE(node2->Next)->Prev = node2->Prev;
        node->NU = (UInt16)nu;
      }
      n = node->Next;
    }
    
    /* Fill lists of free blocks */
    for (n = NODE(head)->Next; n != head;)
    {
      CPpmd7_Node *node = NODE(n);
      unsigned nu;
      CPpmd7_Node_Ref next = node->Next;
      for (nu = node->NU; nu > 128; nu -= 128, node += 128)
        InsertNode(p, node, PPMD_NUM_INDEXES - 1);
      if (I2U(i = U2I(nu)) != nu)
      {
        unsigned k = I2U(--i);
        InsertNode(p, node + k, nu - k - 1);
      }
      InsertNode(p, node, i);
      n = next;
    }
  }
  
  static void *AllocUnitsRare(CPpmd7 *p, unsigned indx)
  {
    unsigned i;
    void *retVal;
    if (p->GlueCount == 0)
    {
      GlueFreeBlocks(p);
      if (p->FreeList[indx] != 0)
        return RemoveNode(p, indx);
    }
    i = indx;
    do
    {
      if (++i == PPMD_NUM_INDEXES)
      {
        UInt32 numBytes = U2B(I2U(indx));
        p->GlueCount--;
        return ((UInt32)(p->UnitsStart - p->Text) > numBytes) ? (p->UnitsStart -= numBytes) : (NULL);
      }
    }
    while (p->FreeList[i] == 0);
    retVal = RemoveNode(p, i);
    SplitBlock(p, retVal, i, indx);
    return retVal;
  }
  
  static void *AllocUnits(CPpmd7 *p, unsigned indx)
  {
    UInt32 numBytes;
    if (p->FreeList[indx] != 0)
      return RemoveNode(p, indx);
    numBytes = U2B(I2U(indx));
    if (numBytes <= (UInt32)(p->HiUnit - p->LoUnit))
    {
      void *retVal = p->LoUnit;
      p->LoUnit += numBytes;
      return retVal;
    }
    return AllocUnitsRare(p, indx);
  }
  
  #define MyMem12Cpy(dest, src, num) \
    { UInt32 *d = (UInt32 *)dest; const UInt32 *s = (const UInt32 *)src; UInt32 n = num; \
      do { d[0] = s[0]; d[1] = s[1]; d[2] = s[2]; s += 3; d += 3; } while (--n); }
  
  static void *ShrinkUnits(CPpmd7 *p, void *oldPtr, unsigned oldNU, unsigned newNU)
  {
    unsigned i0 = U2I(oldNU);
    unsigned i1 = U2I(newNU);
    if (i0 == i1)
      return oldPtr;
    if (p->FreeList[i1] != 0)
    {
      void *ptr = RemoveNode(p, i1);
      MyMem12Cpy(ptr, oldPtr, newNU);
      InsertNode(p, oldPtr, i0);
      return ptr;
    }
    SplitBlock(p, oldPtr, i0, i1);
    return oldPtr;
  }
  
  #define SUCCESSOR(p) ((CPpmd_Void_Ref)((p)->SuccessorLow | ((UInt32)(p)->SuccessorHigh << 16)))
  
  static void SetSuccessor(CPpmd_State *p, CPpmd_Void_Ref v)
  {
    (p)->SuccessorLow = (UInt16)((UInt32)(v) & 0xFFFF);
    (p)->SuccessorHigh = (UInt16)(((UInt32)(v) >> 16) & 0xFFFF);
  }
  
  static void RestartModel(CPpmd7 *p)
  {
    unsigned i, k, m;
  
    memset(p->FreeList, 0, sizeof(p->FreeList));
    p->Text = p->Base + p->AlignOffset;
    p->HiUnit = p->Text + p->Size;
    p->LoUnit = p->UnitsStart = p->HiUnit - p->Size / 8 / UNIT_SIZE * 7 * UNIT_SIZE;
    p->GlueCount = 0;
  
    p->OrderFall = p->MaxOrder;
    p->RunLength = p->InitRL = -(Int32)((p->MaxOrder < 12) ? p->MaxOrder : 12) - 1;
    p->PrevSuccess = 0;
  
    p->MinContext = p->MaxContext = (CTX_PTR)(p->HiUnit -= UNIT_SIZE); /* AllocContext(p); */
    p->MinContext->Suffix = 0;
    p->MinContext->NumStats = 256;
    p->MinContext->SummFreq = 256 + 1;
    p->FoundState = (CPpmd_State *)p->LoUnit; /* AllocUnits(p, PPMD_NUM_INDEXES - 1); */
    p->LoUnit += U2B(256 / 2);
    p->MinContext->Stats = REF(p->FoundState);
    for (i = 0; i < 256; i++)
    {
      CPpmd_State *s = &p->FoundState[i];
      s->Symbol = (Byte)i;
      s->Freq = 1;
      SetSuccessor(s, 0);
    }
  
    for (i = 0; i < 128; i++)
      for (k = 0; k < 8; k++)
      {
        UInt16 *dest = p->BinSumm[i] + k;
        UInt16 val = (UInt16)(PPMD_BIN_SCALE - kInitBinEsc[k] / (i + 2));
        for (m = 0; m < 64; m += 8)
          dest[m] = val;
      }
    
    for (i = 0; i < 25; i++)
      for (k = 0; k < 16; k++)
      {
        CPpmd_See *s = &p->See[i][k];
        s->Summ = (UInt16)((5 * i + 10) << (s->Shift = PPMD_PERIOD_BITS - 4));
        s->Count = 4;
      }
  }
  
  void Ppmd7_Init(CPpmd7 *p, unsigned maxOrder)
  {
    p->MaxOrder = maxOrder;
    RestartModel(p);
    p->DummySee.Shift = PPMD_PERIOD_BITS;
    p->DummySee.Summ = 0; /* unused */
    p->DummySee.Count = 64; /* unused */
  }
  
  static CTX_PTR CreateSuccessors(CPpmd7 *p, Bool skip)
  {
    CPpmd_State upState;
    CTX_PTR c = p->MinContext;
    CPpmd_Byte_Ref upBranch = (CPpmd_Byte_Ref)SUCCESSOR(p->FoundState);
    CPpmd_State *ps[PPMD7_MAX_ORDER];
    unsigned numPs = 0;
    
    if (!skip)
      ps[numPs++] = p->FoundState;
    
    while (c->Suffix)
    {
      CPpmd_Void_Ref successor;
      CPpmd_State *s;
      c = SUFFIX(c);
      if (c->NumStats != 1)
      {
        for (s = STATS(c); s->Symbol != p->FoundState->Symbol; s++);
      }
      else
        s = ONE_STATE(c);
      successor = SUCCESSOR(s);
      if (successor != upBranch)
      {
        c = CTX(successor);
        if (numPs == 0)
          return c;
        break;
      }
      ps[numPs++] = s;
    }
    
    upState.Symbol = *(const Byte *)Ppmd7_GetPtr(p, upBranch);
    SetSuccessor(&upState, upBranch + 1);
    
    if (c->NumStats == 1)
      upState.Freq = ONE_STATE(c)->Freq;
    else
    {
      UInt32 cf, s0;
      CPpmd_State *s;
      for (s = STATS(c); s->Symbol != upState.Symbol; s++);
      cf = s->Freq - 1;
      s0 = c->SummFreq - c->NumStats - cf;
      upState.Freq = (Byte)(1 + ((2 * cf <= s0) ? (5 * cf > s0) : ((2 * cf + 3 * s0 - 1) / (2 * s0))));
    }
  
    do
    {
      /* Create Child */
      CTX_PTR c1; /* = AllocContext(p); */
      if (p->HiUnit != p->LoUnit)
        c1 = (CTX_PTR)(p->HiUnit -= UNIT_SIZE);
      else if (p->FreeList[0] != 0)
        c1 = (CTX_PTR)RemoveNode(p, 0);
      else
      {
        c1 = (CTX_PTR)AllocUnitsRare(p, 0);
        if (!c1)
          return NULL;
      }
      c1->NumStats = 1;
      *ONE_STATE(c1) = upState;
      c1->Suffix = REF(c);
      SetSuccessor(ps[--numPs], REF(c1));
      c = c1;
    }
    while (numPs != 0);
    
    return c;
  }
  
  static void SwapStates(CPpmd_State *t1, CPpmd_State *t2)
  {
    CPpmd_State tmp = *t1;
    *t1 = *t2;
    *t2 = tmp;
  }
  
  static void UpdateModel(CPpmd7 *p)
  {
    CPpmd_Void_Ref successor, fSuccessor = SUCCESSOR(p->FoundState);
    CTX_PTR c;
    unsigned s0, ns;
    
    if (p->FoundState->Freq < MAX_FREQ / 4 && p->MinContext->Suffix != 0)
    {
      c = SUFFIX(p->MinContext);
      
      if (c->NumStats == 1)
      {
        CPpmd_State *s = ONE_STATE(c);
        if (s->Freq < 32)
          s->Freq++;
      }
      else
      {
        CPpmd_State *s = STATS(c);
        if (s->Symbol != p->FoundState->Symbol)
        {
          do { s++; } while (s->Symbol != p->FoundState->Symbol);
          if (s[0].Freq >= s[-1].Freq)
          {
            SwapStates(&s[0], &s[-1]);
            s--;
          }
        }
        if (s->Freq < MAX_FREQ - 9)
        {
          s->Freq += 2;
          c->SummFreq += 2;
        }
      }
    }
  
    if (p->OrderFall == 0)
    {
      p->MinContext = p->MaxContext = CreateSuccessors(p, True);
      if (p->MinContext == 0)
      {
        RestartModel(p);
        return;
      }
      SetSuccessor(p->FoundState, REF(p->MinContext));
      return;
    }
    
    *p->Text++ = p->FoundState->Symbol;
    successor = REF(p->Text);
    if (p->Text >= p->UnitsStart)
    {
      RestartModel(p);
      return;
    }
    
    if (fSuccessor)
    {
      if (fSuccessor <= successor)
      {
        CTX_PTR cs = CreateSuccessors(p, False);
        if (cs == NULL)
        {
          RestartModel(p);
          return;
        }
        fSuccessor = REF(cs);
      }
      if (--p->OrderFall == 0)
      {
        successor = fSuccessor;
        p->Text -= (p->MaxContext != p->MinContext);
      }
    }
    else
    {
      SetSuccessor(p->FoundState, successor);
      fSuccessor = REF(p->MinContext);
    }
    
    s0 = p->MinContext->SummFreq - (ns = p->MinContext->NumStats) - (p->FoundState->Freq - 1);
    
    for (c = p->MaxContext; c != p->MinContext; c = SUFFIX(c))
    {
      unsigned ns1;
      UInt32 cf, sf;
      if ((ns1 = c->NumStats) != 1)
      {
        if ((ns1 & 1) == 0)
        {
          /* Expand for one UNIT */
          unsigned oldNU = ns1 >> 1;
          unsigned i = U2I(oldNU);
          if (i != U2I((size_t)oldNU + 1))
          {
            void *ptr = AllocUnits(p, i + 1);
            void *oldPtr;
            if (!ptr)
            {
              RestartModel(p);
              return;
            }
            oldPtr = STATS(c);
            MyMem12Cpy(ptr, oldPtr, oldNU);
            InsertNode(p, oldPtr, i);
            c->Stats = STATS_REF(ptr);
          }
        }
        c->SummFreq = (UInt16)(c->SummFreq + (2 * ns1 < ns) + 2 * ((4 * ns1 <= ns) & (c->SummFreq <= 8 * ns1)));
      }
      else
      {
        CPpmd_State *s = (CPpmd_State*)AllocUnits(p, 0);
        if (!s)
        {
          RestartModel(p);
          return;
        }
        *s = *ONE_STATE(c);
        c->Stats = REF(s);
        if (s->Freq < MAX_FREQ / 4 - 1)
          s->Freq <<= 1;
        else
          s->Freq = MAX_FREQ - 4;
        c->SummFreq = (UInt16)(s->Freq + p->InitEsc + (ns > 3));
      }
      cf = 2 * (UInt32)p->FoundState->Freq * (c->SummFreq + 6);
      sf = (UInt32)s0 + c->SummFreq;
      if (cf < 6 * sf)
      {
        cf = 1 + (cf > sf) + (cf >= 4 * sf);
        c->SummFreq += 3;
      }
      else
      {
        cf = 4 + (cf >= 9 * sf) + (cf >= 12 * sf) + (cf >= 15 * sf);
        c->SummFreq = (UInt16)(c->SummFreq + cf);
      }
      {
        CPpmd_State *s = STATS(c) + ns1;
        SetSuccessor(s, successor);
        s->Symbol = p->FoundState->Symbol;
        s->Freq = (Byte)cf;
        c->NumStats = (UInt16)(ns1 + 1);
      }
    }
    p->MaxContext = p->MinContext = CTX(fSuccessor);
  }
    
  static void Rescale(CPpmd7 *p)
  {
    unsigned i, adder, sumFreq, escFreq;
    CPpmd_State *stats = STATS(p->MinContext);
    CPpmd_State *s = p->FoundState;
    {
      CPpmd_State tmp = *s;
      for (; s != stats; s--)
        s[0] = s[-1];
      *s = tmp;
    }
    escFreq = p->MinContext->SummFreq - s->Freq;
    s->Freq += 4;
    adder = (p->OrderFall != 0);
    s->Freq = (Byte)((s->Freq + adder) >> 1);
    sumFreq = s->Freq;
    
    i = p->MinContext->NumStats - 1;
    do
    {
      escFreq -= (++s)->Freq;
      s->Freq = (Byte)((s->Freq + adder) >> 1);
      sumFreq += s->Freq;
      if (s[0].Freq > s[-1].Freq)
      {
        CPpmd_State *s1 = s;
        CPpmd_State tmp = *s1;
        do
          s1[0] = s1[-1];
        while (--s1 != stats && tmp.Freq > s1[-1].Freq);
        *s1 = tmp;
      }
    }
    while (--i);
    
    if (s->Freq == 0)
    {
      unsigned numStats = p->MinContext->NumStats;
      unsigned n0, n1;
      do { i++; } while ((--s)->Freq == 0);
      escFreq += i;
      p->MinContext->NumStats = (UInt16)(p->MinContext->NumStats - i);
      if (p->MinContext->NumStats == 1)
      {
        CPpmd_State tmp = *stats;
        do
        {
          tmp.Freq = (Byte)(tmp.Freq - (tmp.Freq >> 1));
          escFreq >>= 1;
        }
        while (escFreq > 1);
        InsertNode(p, stats, U2I(((numStats + 1) >> 1)));
        *(p->FoundState = ONE_STATE(p->MinContext)) = tmp;
        return;
      }
      n0 = (numStats + 1) >> 1;
      n1 = (p->MinContext->NumStats + 1) >> 1;
      if (n0 != n1)
        p->MinContext->Stats = STATS_REF(ShrinkUnits(p, stats, n0, n1));
    }
    p->MinContext->SummFreq = (UInt16)(sumFreq + escFreq - (escFreq >> 1));
    p->FoundState = STATS(p->MinContext);
  }
  
  CPpmd_See *Ppmd7_MakeEscFreq(CPpmd7 *p, unsigned numMasked, UInt32 *escFreq)
  {
    CPpmd_See *see;
    unsigned nonMasked = p->MinContext->NumStats - numMasked;
    if (p->MinContext->NumStats != 256)
    {
      see = p->See[(unsigned)p->NS2Indx[(size_t)nonMasked - 1]] +
          (nonMasked < (unsigned)SUFFIX(p->MinContext)->NumStats - p->MinContext->NumStats) +
          2 * (unsigned)(p->MinContext->SummFreq < 11 * p->MinContext->NumStats) +
          4 * (unsigned)(numMasked > nonMasked) +
          p->HiBitsFlag;
      {
        unsigned r = (see->Summ >> see->Shift);
        see->Summ = (UInt16)(see->Summ - r);
        *escFreq = r + (r == 0);
      }
    }
    else
    {
      see = &p->DummySee;
      *escFreq = 1;
    }
    return see;
  }
  
  static void NextContext(CPpmd7 *p)
  {
    CTX_PTR c = CTX(SUCCESSOR(p->FoundState));
    if (p->OrderFall == 0 && (Byte *)c > p->Text)
      p->MinContext = p->MaxContext = c;
    else
      UpdateModel(p);
  }
  
  void Ppmd7_Update1(CPpmd7 *p)
  {
    CPpmd_State *s = p->FoundState;
    s->Freq += 4;
    p->MinContext->SummFreq += 4;
    if (s[0].Freq > s[-1].Freq)
    {
      SwapStates(&s[0], &s[-1]);
      p->FoundState = --s;
      if (s->Freq > MAX_FREQ)
        Rescale(p);
    }
    NextContext(p);
  }
  
  void Ppmd7_Update1_0(CPpmd7 *p)
  {
    p->PrevSuccess = (2 * p->FoundState->Freq > p->MinContext->SummFreq);
    p->RunLength += p->PrevSuccess;
    p->MinContext->SummFreq += 4;
    if ((p->FoundState->Freq += 4) > MAX_FREQ)
      Rescale(p);
    NextContext(p);
  }
  
  void Ppmd7_UpdateBin(CPpmd7 *p)
  {
    p->FoundState->Freq = (Byte)(p->FoundState->Freq + (p->FoundState->Freq < 128 ? 1: 0));
    p->PrevSuccess = 1;
    p->RunLength++;
    NextContext(p);
  }
  
  void Ppmd7_Update2(CPpmd7 *p)
  {
    p->MinContext->SummFreq += 4;
    if ((p->FoundState->Freq += 4) > MAX_FREQ)
      Rescale(p);
    p->RunLength = p->InitRL;
    UpdateModel(p);
  }
  