'21.07'21.07

1 files changed, 1104 insertions, 0 deletions

diff --git a/C/Ppmd7.c b/C/Ppmd7.c
new file mode 100644
index 0000000..cf401cb
--- /dev/null
+++ b/C/Ppmd7.c
@@ -0,0 +1,1104 @@
+/* Ppmd7.c -- PPMdH codec
+2021-04-13 : Igor Pavlov : Public domain
+This code is based on PPMd var.H (2001): Dmitry Shkarin : Public domain */
+
+#include "Precomp.h"
+
+#include <string.h>
+
+#include "Ppmd7.h"
+
+/* define PPMD7_ORDER_0_SUPPPORT to suport order-0 mode, unsupported by orignal PPMd var.H. code */
+// #define PPMD7_ORDER_0_SUPPPORT
+ 
+MY_ALIGN(16)
+static const Byte PPMD7_kExpEscape[16] = { 25, 14, 9, 7, 5, 5, 4, 4, 4, 3, 3, 3, 2, 2, 2, 2 };
+MY_ALIGN(16)
+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) ((unsigned)p->Indx2Units[indx])
+#define I2U_UInt16(indx) ((UInt16)p->Indx2Units[indx])
+
+#define REF(ptr) Ppmd_GetRef(p, ptr)
+
+#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 Ppmd_Ref_Type(struct CPpmd7_Node_) 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;
+
+#define NODE(r)  Ppmd_GetPtr_Type(p, r, CPpmd7_Node)
+
+void Ppmd7_Construct(CPpmd7 *p)
+{
+  unsigned i, k, m;
+
+  p->Base = NULL;
+
+  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;
+  }
+
+  memcpy(p->ExpEscape, PPMD7_kExpEscape, 16);
+}
+
+
+void Ppmd7_Free(CPpmd7 *p, ISzAllocPtr alloc)
+{
+  ISzAlloc_Free(alloc, p->Base);
+  p->Size = 0;
+  p->Base = NULL;
+}
+
+
+BoolInt Ppmd7_Alloc(CPpmd7 *p, UInt32 size, ISzAllocPtr alloc)
+{
+  if (!p->Base || p->Size != size)
+  {
+    Ppmd7_Free(p, alloc);
+    p->AlignOffset = (4 - size) & 3;
+    if ((p->Base = (Byte *)ISzAlloc_Alloc(alloc, p->AlignOffset + size)) == NULL)
+      return False;
+    p->Size = size;
+  }
+  return True;
+}
+
+
+
+// ---------- Internal Memory Allocator ----------
+
+/* We can use CPpmd7_Node in list of free units (as in Ppmd8)
+   But we still need one additional list walk pass in GlueFreeBlocks().
+   So we use simple CPpmd_Void_Ref instead of CPpmd7_Node in InsertNode() / RemoveNode()
+*/
+
+#define EMPTY_NODE 0
+
+
+static void InsertNode(CPpmd7 *p, void *node, unsigned indx)
+{
+  *((CPpmd_Void_Ref *)node) = p->FreeList[indx];
+  // ((CPpmd7_Node *)node)->Next = (CPpmd7_Node_Ref)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;
+  // CPpmd7_Node *node = NODE((CPpmd7_Node_Ref)p->FreeList[indx]);
+  // p->FreeList[indx] = node->Next;
+  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);
+}
+
+
+/* we use CPpmd7_Node_Union union to solve XLC -O2 strict pointer aliasing problem */
+
+typedef union _CPpmd7_Node_Union
+{
+  CPpmd7_Node     Node;
+  CPpmd7_Node_Ref NextRef;
+} CPpmd7_Node_Union;
+
+/* Original PPmdH (Ppmd7) code uses doubly linked list in GlueFreeBlocks()
+   we use single linked list similar to Ppmd8 code */
+
+
+static void GlueFreeBlocks(CPpmd7 *p)
+{
+  /*
+  we use first UInt16 field of 12-bytes UNITs as record type stamp
+    CPpmd_State    { Byte Symbol; Byte Freq; : Freq != 0
+    CPpmd7_Context { UInt16 NumStats;        : NumStats != 0
+    CPpmd7_Node    { UInt16 Stamp            : Stamp == 0 for free record
+                                             : Stamp == 1 for head record and guard
+    Last 12-bytes UNIT in array is always contains 12-bytes order-0 CPpmd7_Context record.
+  */
+  CPpmd7_Node_Ref head, n = 0;
+ 
+  p->GlueCount = 255;
+
+  
+  /* we set guard NODE at LoUnit */
+  if (p->LoUnit != p->HiUnit)
+    ((CPpmd7_Node *)(void *)p->LoUnit)->Stamp = 1;
+
+  {
+    /* Create list of free blocks.
+       We still need one additional list walk pass before Glue. */
+    unsigned i;
+    for (i = 0; i < PPMD_NUM_INDEXES; i++)
+    {
+      const UInt16 nu = I2U_UInt16(i);
+      CPpmd7_Node_Ref next = (CPpmd7_Node_Ref)p->FreeList[i];
+      p->FreeList[i] = 0;
+      while (next != 0)
+      {
+        /* Don't change the order of the following commands: */
+        CPpmd7_Node_Union *un = (CPpmd7_Node_Union *)NODE(next);
+        const CPpmd7_Node_Ref tmp = next;
+        next = un->NextRef;
+        un->Node.Stamp = EMPTY_NODE;
+        un->Node.NU = nu;
+        un->Node.Next = n;
+        n = tmp;
+      }
+    }
+  }
+
+  head = n;
+  /* Glue and Fill must walk the list in same direction */
+  {
+    /* Glue free blocks */
+    CPpmd7_Node_Ref *prev = &head;
+    while (n)
+    {
+      CPpmd7_Node *node = NODE(n);
+      UInt32 nu = node->NU;
+      n = node->Next;
+      if (nu == 0)
+      {
+        *prev = n;
+        continue;
+      }
+      prev = &node->Next;
+      for (;;)
+      {
+        CPpmd7_Node *node2 = node + nu;
+        nu += node2->NU;
+        if (node2->Stamp != EMPTY_NODE || nu >= 0x10000)
+          break;
+        node->NU = (UInt16)nu;
+        node2->NU = 0;
+      }
+    }
+  }
+
+  /* Fill lists of free blocks */
+  for (n = head; n != 0;)
+  {
+    CPpmd7_Node *node = NODE(n);
+    UInt32 nu = node->NU;
+    unsigned i;
+    n = node->Next;
+    if (nu == 0)
+      continue;
+    for (; 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, (unsigned)nu - k - 1);
+    }
+    InsertNode(p, node, i);
+  }
+}
+
+
+MY_NO_INLINE
+static void *AllocUnitsRare(CPpmd7 *p, unsigned indx)
+{
+  unsigned i;
+  
+  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));
+      Byte *us = p->UnitsStart;
+      p->GlueCount--;
+      return ((UInt32)(us - p->Text) > numBytes) ? (p->UnitsStart = us - numBytes) : NULL;
+    }
+  }
+  while (p->FreeList[i] == 0);
+
+  {
+    void *block = RemoveNode(p, i);
+    SplitBlock(p, block, i, indx);
+    return block;
+  }
+}
+
+
+static void *AllocUnits(CPpmd7 *p, unsigned indx)
+{
+  if (p->FreeList[indx] != 0)
+    return RemoveNode(p, indx);
+  {
+    UInt32 numBytes = U2B(I2U(indx));
+    Byte *lo = p->LoUnit;
+    if ((UInt32)(p->HiUnit - lo) >= numBytes)
+    {
+      p->LoUnit = lo + numBytes;
+      return lo;
+    }
+  }
+  return AllocUnitsRare(p, indx);
+}
+
+
+#define MyMem12Cpy(dest, src, num) \
+  { UInt32 *d = (UInt32 *)dest; const UInt32 *z = (const UInt32 *)src; UInt32 n = num; \
+    do { d[0] = z[0]; d[1] = z[1]; d[2] = z[2]; z += 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) Ppmd_GET_SUCCESSOR(p)
+static void SetSuccessor(CPpmd_State *p, CPpmd_Void_Ref v)
+{
+  Ppmd_SET_SUCCESSOR(p, v);
+}
+
+
+
+MY_NO_INLINE
+static
+void RestartModel(CPpmd7 *p)
+{
+  unsigned i, k;
+
+  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;
+
+  {
+    CPpmd7_Context *mc = (CTX_PTR)(void *)(p->HiUnit -= UNIT_SIZE); /* AllocContext(p); */
+    CPpmd_State *s = (CPpmd_State *)p->LoUnit; /* AllocUnits(p, PPMD_NUM_INDEXES - 1); */
+    
+    p->LoUnit += U2B(256 / 2);
+    p->MaxContext = p->MinContext = mc;
+    p->FoundState = s;
+
+    mc->NumStats = 256;
+    mc->Union2.SummFreq = 256 + 1;
+    mc->Union4.Stats = REF(s);
+    mc->Suffix = 0;
+
+    for (i = 0; i < 256; i++, s++)
+    {
+      s->Symbol = (Byte)i;
+      s->Freq = 1;
+      SetSuccessor(s, 0);
+    }
+
+    #ifdef PPMD7_ORDER_0_SUPPPORT
+    if (p->MaxOrder == 0)
+    {
+      CPpmd_Void_Ref r = REF(mc);
+      s = p->FoundState;
+      for (i = 0; i < 256; i++, s++)
+        SetSuccessor(s, r);
+      return;
+    }
+    #endif
+  }
+
+  for (i = 0; i < 128; i++)
+    
+    
+    
+    for (k = 0; k < 8; k++)
+    {
+      unsigned m;
+      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++)
+  {
+
+    CPpmd_See *s = p->See[i];
+    
+    
+    
+    unsigned summ = ((5 * i + 10) << (PPMD_PERIOD_BITS - 4));
+    for (k = 0; k < 16; k++, s++)
+    {
+      s->Summ = (UInt16)summ;
+      s->Shift = (PPMD_PERIOD_BITS - 4);
+      s->Count = 4;
+    }
+  }
+  
+  p->DummySee.Summ = 0; /* unused */
+  p->DummySee.Shift = PPMD_PERIOD_BITS;
+  p->DummySee.Count = 64; /* unused */
+}
+
+
+void Ppmd7_Init(CPpmd7 *p, unsigned maxOrder)
+{
+  p->MaxOrder = maxOrder;
+
+  RestartModel(p);
+}
+
+
+
+/*
+  CreateSuccessors()
+  It's called when (FoundState->Successor) is RAW-Successor,
+  that is the link to position in Raw text.
+  So we create Context records and write the links to
+  FoundState->Successor and to identical RAW-Successors in suffix
+  contexts of MinContex.
+  
+  The function returns:
+  if (OrderFall == 0) then MinContext is already at MAX order,
+    { return pointer to new or existing context of same MAX order }
+  else
+    { return pointer to new real context that will be (Order+1) in comparison with MinContext
+
+  also it can return pointer to real context of same order,
+*/
+
+MY_NO_INLINE
+static CTX_PTR CreateSuccessors(CPpmd7 *p)
+{
+  CTX_PTR c = p->MinContext;
+  CPpmd_Byte_Ref upBranch = (CPpmd_Byte_Ref)SUCCESSOR(p->FoundState);
+  Byte newSym, newFreq;
+  unsigned numPs = 0;
+  CPpmd_State *ps[PPMD7_MAX_ORDER];
+
+  if (p->OrderFall != 0)
+    ps[numPs++] = p->FoundState;
+  
+  while (c->Suffix)
+  {
+    CPpmd_Void_Ref successor;
+    CPpmd_State *s;
+    c = SUFFIX(c);
+    
+
+    if (c->NumStats != 1)
+    {
+      Byte sym = p->FoundState->Symbol;
+      for (s = STATS(c); s->Symbol != sym; s++);
+
+    }
+    else
+    {
+      s = ONE_STATE(c);
+
+    }
+    successor = SUCCESSOR(s);
+    if (successor != upBranch)
+    {
+      // (c) is real record Context here,
+      c = CTX(successor);
+      if (numPs == 0)
+      {
+        // (c) is real record MAX Order Context here,
+        // So we don't need to create any new contexts.
+        return c;
+      }
+      break;
+    }
+    ps[numPs++] = s;
+  }
+  
+  // All created contexts will have single-symbol with new RAW-Successor
+  // All new RAW-Successors will point to next position in RAW text
+  // after FoundState->Successor
+
+  newSym = *(const Byte *)Ppmd7_GetPtr(p, upBranch);
+  upBranch++;
+  
+  
+  if (c->NumStats == 1)
+    newFreq = ONE_STATE(c)->Freq;
+  else
+  {
+    UInt32 cf, s0;
+    CPpmd_State *s;
+    for (s = STATS(c); s->Symbol != newSym; s++);
+    cf = (UInt32)s->Freq - 1;
+    s0 = (UInt32)c->Union2.SummFreq - c->NumStats - cf;
+    /*
+      cf - is frequency of symbol that will be Successor in new context records.
+      s0 - is commulative frequency sum of another symbols from parent context.
+      max(newFreq)= (s->Freq + 1), when (s0 == 1)
+      we have requirement (Ppmd7Context_OneState()->Freq <= 128) in BinSumm[]
+      so (s->Freq < 128) - is requirement for multi-symbol contexts
+    */
+    newFreq = (Byte)(1 + ((2 * cf <= s0) ? (5 * cf > s0) : (2 * cf + s0 - 1) / (2 * s0) + 1));
+  }
+
+  // Create new single-symbol contexts from low order to high order in loop
+
+  do
+  {
+    CTX_PTR c1;
+    /* = AllocContext(p); */
+    if (p->HiUnit != p->LoUnit)
+      c1 = (CTX_PTR)(void *)(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)->Symbol = newSym;
+    ONE_STATE(c1)->Freq = newFreq;
+    SetSuccessor(ONE_STATE(c1), upBranch);
+    c1->Suffix = REF(c);
+    SetSuccessor(ps[--numPs], REF(c1));
+    c = c1;
+  }
+  while (numPs != 0);
+  
+  return c;
+}
+
+
+
+#define SwapStates(s) \
+  { CPpmd_State tmp = s[0]; s[0] = s[-1]; s[-1] = tmp; }
+
+
+void Ppmd7_UpdateModel(CPpmd7 *p);
+MY_NO_INLINE
+void Ppmd7_UpdateModel(CPpmd7 *p)
+{
+  CPpmd_Void_Ref maxSuccessor, minSuccessor;
+  CTX_PTR c, mc;
+  unsigned s0, ns;
+
+
+
+  if (p->FoundState->Freq < MAX_FREQ / 4 && p->MinContext->Suffix != 0)
+  {
+    /* Update Freqs in Suffix Context */
+
+    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);
+      Byte sym = p->FoundState->Symbol;
+      
+      if (s->Symbol != sym)
+      {
+        do
+        {
+          // s++; if (s->Symbol == sym) break;
+          s++;
+        }
+        while (s->Symbol != sym);
+        
+        if (s[0].Freq >= s[-1].Freq)
+        {
+          SwapStates(s);
+          s--;
+        }
+      }
+
+      if (s->Freq < MAX_FREQ - 9)
+      {
+        s->Freq = (Byte)(s->Freq + 2);
+        c->Union2.SummFreq = (UInt16)(c->Union2.SummFreq + 2);
+      }
+    }
+  }
+
+  
+  if (p->OrderFall == 0)
+  {
+    /* MAX ORDER context */
+    /* (FoundState->Successor) is RAW-Successor. */
+    p->MaxContext = p->MinContext = CreateSuccessors(p);
+    if (!p->MinContext)
+    {
+      RestartModel(p);
+      return;
+    }
+    SetSuccessor(p->FoundState, REF(p->MinContext));
+    return;
+  }
+
+  
+  /* NON-MAX ORDER context */
+  
+  {
+    Byte *text = p->Text;
+    *text++ = p->FoundState->Symbol;
+    p->Text = text;
+    if (text >= p->UnitsStart)
+    {
+      RestartModel(p);
+      return;
+    }
+    maxSuccessor = REF(text);
+  }
+  
+  minSuccessor = SUCCESSOR(p->FoundState);
+
+  if (minSuccessor)
+  {
+    // there is Successor for FoundState in MinContext.
+    // So the next context will be one order higher than MinContext.
+    
+    if (minSuccessor <= maxSuccessor)
+    {
+      // minSuccessor is RAW-Successor. So we will create real contexts records:
+      CTX_PTR cs = CreateSuccessors(p);
+      if (!cs)
+      {
+        RestartModel(p);
+        return;
+      }
+      minSuccessor = REF(cs);
+    }
+
+    // minSuccessor now is real Context pointer that points to existing (Order+1) context
+    
+    if (--p->OrderFall == 0)
+    {
+      /*
+      if we move to MaxOrder context, then minSuccessor will be common Succesor for both:
+        MinContext that is (MaxOrder - 1)
+        MaxContext that is (MaxOrder)
+      so we don't need new RAW-Successor, and we can use real minSuccessor
+      as succssors for both MinContext and MaxContext.
+      */
+      maxSuccessor = minSuccessor;
+      
+      /*
+      if (MaxContext != MinContext)
+      {
+        there was order fall from MaxOrder and we don't need current symbol
+        to transfer some RAW-Succesors to real contexts.
+        So we roll back pointer in raw data for one position.
+      }
+      */
+      p->Text -= (p->MaxContext != p->MinContext);
+    }
+  }
+  else
+  {
+    /*
+    FoundState has NULL-Successor here.
+    And only root 0-order context can contain NULL-Successors.
+    We change Successor in FoundState to RAW-Successor,
+    And next context will be same 0-order root Context.
+    */
+    SetSuccessor(p->FoundState, maxSuccessor);
+    minSuccessor = REF(p->MinContext);
+  }
+
+  mc = p->MinContext;
+  c = p->MaxContext;
+
+  p->MaxContext = p->MinContext = CTX(minSuccessor);
+
+  if (c == mc)
+    return;
+
+  // s0 : is pure Escape Freq
+  s0 = mc->Union2.SummFreq - (ns = mc->NumStats) - ((unsigned)p->FoundState->Freq - 1);
+
+  do
+  {
+    unsigned ns1;
+    UInt32 sum;
+    
+    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->Union4.Stats = STATS_REF(ptr);
+        }
+      }
+      sum = c->Union2.SummFreq;
+      /* max increase of Escape_Freq is 3 here.
+         total increase of Union2.SummFreq for all symbols is less than 256 here */
+      sum += (UInt32)(2 * ns1 < ns) + 2 * ((unsigned)(4 * ns1 <= ns) & (sum <= 8 * ns1));
+      /* original PPMdH uses 16-bit variable for (sum) here.
+         But (sum < 0x9000). So we don't truncate (sum) to 16-bit */
+      // sum = (UInt16)sum;
+    }
+    else
+    {
+      // instead of One-symbol context we create 2-symbol context
+      CPpmd_State *s = (CPpmd_State*)AllocUnits(p, 0);
+      if (!s)
+      {
+        RestartModel(p);
+        return;
+      }
+      {
+        unsigned freq = c->Union2.State2.Freq;
+        // s = *ONE_STATE(c);
+        s->Symbol = c->Union2.State2.Symbol;
+        s->Successor_0 = c->Union4.State4.Successor_0;
+        s->Successor_1 = c->Union4.State4.Successor_1;
+        // SetSuccessor(s, c->Union4.Stats);  // call it only for debug purposes to check the order of
+                                              // (Successor_0 and Successor_1) in LE/BE.
+        c->Union4.Stats = REF(s);
+        if (freq < MAX_FREQ / 4 - 1)
+          freq <<= 1;
+        else
+          freq = MAX_FREQ - 4;
+        // (max(s->freq) == 120), when we convert from 1-symbol into 2-symbol context
+        s->Freq = (Byte)freq;
+        // max(InitEsc = PPMD7_kExpEscape[*]) is 25. So the max(escapeFreq) is 26 here
+        sum = freq + p->InitEsc + (ns > 3);
+      }
+    }
+    
+    {
+      CPpmd_State *s = STATS(c) + ns1;
+      UInt32 cf = 2 * (sum + 6) * (UInt32)p->FoundState->Freq;
+      UInt32 sf = (UInt32)s0 + sum;
+      s->Symbol = p->FoundState->Symbol;
+      c->NumStats = (UInt16)(ns1 + 1);
+      SetSuccessor(s, maxSuccessor);
+      
+      if (cf < 6 * sf)
+      {
+        cf = (UInt32)1 + (cf > sf) + (cf >= 4 * sf);
+        sum += 3;
+        /* It can add (0, 1, 2) to Escape_Freq */
+      }
+      else
+      {
+        cf = (UInt32)4 + (cf >= 9 * sf) + (cf >= 12 * sf) + (cf >= 15 * sf);
+        sum += cf;
+      }
+     
+      c->Union2.SummFreq = (UInt16)sum;
+      s->Freq = (Byte)cf;
+    }
+    c = SUFFIX(c);
+  }
+  while (c != mc);
+}
+  
+
+
+MY_NO_INLINE
+static void Rescale(CPpmd7 *p)
+{
+  unsigned i, adder, sumFreq, escFreq;
+  CPpmd_State *stats = STATS(p->MinContext);
+  CPpmd_State *s = p->FoundState;
+
+  /* Sort the list by Freq */
+  if (s != stats)
+  {
+    CPpmd_State tmp = *s;
+    do
+      s[0] = s[-1];
+    while (--s != stats);
+    *s = tmp;
+  }
+
+  sumFreq = s->Freq;
+  escFreq = p->MinContext->Union2.SummFreq - sumFreq;
+  
+  /*
+  if (p->OrderFall == 0), adder = 0 : it's     allowed to remove symbol from     MAX Order context
+  if (p->OrderFall != 0), adder = 1 : it's NOT allowed to remove symbol from NON-MAX Order context
+  */
+
+  adder = (p->OrderFall != 0);
+
+  #ifdef PPMD7_ORDER_0_SUPPPORT
+  adder |= (p->MaxOrder == 0); // we don't remove symbols from order-0 context
+  #endif
+
+  sumFreq = (sumFreq + 4 + adder) >> 1;
+  i = (unsigned)p->MinContext->NumStats - 1;
+  s->Freq = (Byte)sumFreq;
+  
+  do
+  {
+    unsigned freq = (++s)->Freq;
+    escFreq -= freq;
+    freq = (freq + adder) >> 1;
+    sumFreq += freq;
+    s->Freq = (Byte)freq;
+    if (freq > s[-1].Freq)
+    {
+      CPpmd_State tmp = *s;
+      CPpmd_State *s1 = s;
+      do
+      {
+        s1[0] = s1[-1];
+      }
+      while (--s1 != stats && freq > s1[-1].Freq);
+      *s1 = tmp;
+    }
+  }
+  while (--i);
+  
+  if (s->Freq == 0)
+  {
+    /* Remove all items with Freq == 0 */
+    CPpmd7_Context *mc;
+    unsigned numStats, numStatsNew, n0, n1;
+    
+    i = 0; do { i++; } while ((--s)->Freq == 0);
+    
+    /* We increase (escFreq) for the number of removed symbols.
+       So we will have (0.5) increase for Escape_Freq in avarage per
+       removed symbol after Escape_Freq halving */
+    escFreq += i;
+    mc = p->MinContext;
+    numStats = mc->NumStats;
+    numStatsNew = numStats - i;
+    mc->NumStats = (UInt16)(numStatsNew);
+    n0 = (numStats + 1) >> 1;
+    
+    if (numStatsNew == 1)
+    {
+      /* Create Single-Symbol context */
+      unsigned freq = stats->Freq;
+      
+      do
+      {
+        escFreq >>= 1;
+        freq = (freq + 1) >> 1;
+      }
+      while (escFreq > 1);
+
+      s = ONE_STATE(mc);
+      *s = *stats;
+      s->Freq = (Byte)freq; // (freq <= 260 / 4)
+      p->FoundState = s;
+      InsertNode(p, stats, U2I(n0));
+      return;
+    }
+    
+    n1 = (numStatsNew + 1) >> 1;
+    if (n0 != n1)
+    {
+      // p->MinContext->Union4.Stats = STATS_REF(ShrinkUnits(p, stats, n0, n1));
+      unsigned i0 = U2I(n0);
+      unsigned i1 = U2I(n1);
+      if (i0 != i1)
+      {
+        if (p->FreeList[i1] != 0)
+        {
+          void *ptr = RemoveNode(p, i1);
+          p->MinContext->Union4.Stats = STATS_REF(ptr);
+          MyMem12Cpy(ptr, (const void *)stats, n1);
+          InsertNode(p, stats, i0);
+        }
+        else
+          SplitBlock(p, stats, i0, i1);
+      }
+    }
+  }
+  {
+    CPpmd7_Context *mc = p->MinContext;
+    mc->Union2.SummFreq = (UInt16)(sumFreq + escFreq - (escFreq >> 1));
+    // Escape_Freq halving here
+    p->FoundState = STATS(mc);
+  }
+}
+
+
+CPpmd_See *Ppmd7_MakeEscFreq(CPpmd7 *p, unsigned numMasked, UInt32 *escFreq)
+{
+  CPpmd_See *see;
+  const CPpmd7_Context *mc = p->MinContext;
+  unsigned numStats = mc->NumStats;
+  if (numStats != 256)
+  {
+    unsigned nonMasked = numStats - numMasked;
+    see = p->See[(unsigned)p->NS2Indx[(size_t)nonMasked - 1]]
+        + (nonMasked < (unsigned)SUFFIX(mc)->NumStats - numStats)
+        + 2 * (unsigned)(mc->Union2.SummFreq < 11 * numStats)
+        + 4 * (unsigned)(numMasked > nonMasked) +
+        p->HiBitsFlag;
+    {
+      // if (see->Summ) field is larger than 16-bit, we need only low 16 bits of Summ
+      unsigned summ = (UInt16)see->Summ; // & 0xFFFF
+      unsigned r = (summ >> see->Shift);
+      see->Summ = (UInt16)(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 && (const Byte *)c > p->Text)
+    p->MaxContext = p->MinContext = c;
+  else
+    Ppmd7_UpdateModel(p);
+}
+
+
+void Ppmd7_Update1(CPpmd7 *p)
+{
+  CPpmd_State *s = p->FoundState;
+  unsigned freq = s->Freq;
+  freq += 4;
+  p->MinContext->Union2.SummFreq = (UInt16)(p->MinContext->Union2.SummFreq + 4);
+  s->Freq = (Byte)freq;
+  if (freq > s[-1].Freq)
+  {
+    SwapStates(s);
+    p->FoundState = --s;
+    if (freq > MAX_FREQ)
+      Rescale(p);
+  }
+  NextContext(p);
+}
+
+
+void Ppmd7_Update1_0(CPpmd7 *p)
+{
+  CPpmd_State *s = p->FoundState;
+  CPpmd7_Context *mc = p->MinContext;
+  unsigned freq = s->Freq;
+  unsigned summFreq = mc->Union2.SummFreq;
+  p->PrevSuccess = (2 * freq > summFreq);
+  p->RunLength += (int)p->PrevSuccess;
+  mc->Union2.SummFreq = (UInt16)(summFreq + 4);
+  freq += 4;
+  s->Freq = (Byte)freq;
+  if (freq > MAX_FREQ)
+    Rescale(p);
+  NextContext(p);
+}
+
+
+/*
+void Ppmd7_UpdateBin(CPpmd7 *p)
+{
+  unsigned freq = p->FoundState->Freq;
+  p->FoundState->Freq = (Byte)(freq + (freq < 128));
+  p->PrevSuccess = 1;
+  p->RunLength++;
+  NextContext(p);
+}
+*/
+
+void Ppmd7_Update2(CPpmd7 *p)
+{
+  CPpmd_State *s = p->FoundState;
+  unsigned freq = s->Freq;
+  freq += 4;
+  p->RunLength = p->InitRL;
+  p->MinContext->Union2.SummFreq = (UInt16)(p->MinContext->Union2.SummFreq + 4);
+  s->Freq = (Byte)freq;
+  if (freq > MAX_FREQ)
+    Rescale(p);
+  Ppmd7_UpdateModel(p);
+}
+
+
+
+/*
+PPMd Memory Map:
+{
+  [ 0 ]           contains subset of original raw text, that is required to create context
+                  records, Some symbols are not written, when max order context was reached
+  [ Text ]        free area
+  [ UnitsStart ]  CPpmd_State vectors and CPpmd7_Context records
+  [ LoUnit ]      free  area for CPpmd_State and CPpmd7_Context items
+[ HiUnit ]      CPpmd7_Context records
+  [ Size ]        end of array
+}
+
+These addresses don't cross at any time.
+And the following condtions is true for addresses:
+  (0  <= Text < UnitsStart <= LoUnit <= HiUnit <= Size)
+
+Raw text is BYTE--aligned.
+the data in block [ UnitsStart ... Size ] contains 12-bytes aligned UNITs.
+
+Last UNIT of array at offset (Size - 12) is root order-0 CPpmd7_Context record.
+The code can free UNITs memory blocks that were allocated to store CPpmd_State vectors.
+The code doesn't free UNITs allocated for CPpmd7_Context records.
+
+The code calls RestartModel(), when there is no free memory for allocation.
+And RestartModel() changes the state to orignal start state, with full free block.
+
+
+The code allocates UNITs with the following order:
+
+Allocation of 1 UNIT for Context record
+  - from free space (HiUnit) down to (LoUnit)
+  - from FreeList[0]
+  - AllocUnitsRare()
+
+AllocUnits() for CPpmd_State vectors:
+  - from FreeList[i]
+  - from free space (LoUnit) up to (HiUnit)
+  - AllocUnitsRare()
+
+AllocUnitsRare()
+  - if (GlueCount == 0)
+       {  Glue lists, GlueCount = 255, allocate from FreeList[i]] }
+  - loop for all higher sized FreeList[...] lists
+  - from (UnitsStart - Text), GlueCount--
+  - ERROR
+
+
+Each Record with Context contains the CPpmd_State vector, where each
+CPpmd_State contains the link to Successor.
+There are 3 types of Successor:
+  1) NULL-Successor   - NULL pointer. NULL-Successor links can be stored
+                        only in 0-order Root Context Record.
+                        We use 0 value as NULL-Successor
+  2) RAW-Successor    - the link to position in raw text,
+                        that "RAW-Successor" is being created after first
+                        occurrence of new symbol for some existing context record.
+                        (RAW-Successor > 0).
+  3) RECORD-Successor - the link to CPpmd7_Context record of (Order+1),
+                        that record is being created when we go via RAW-Successor again.
+
+For any successors at any time: the following condtions are true for Successor links:
+(NULL-Successor < RAW-Successor < UnitsStart <= RECORD-Successor)
+
+
+---------- Symbol Frequency, SummFreq and Range in Range_Coder ----------
+
+CPpmd7_Context::SummFreq = Sum(Stats[].Freq) + Escape_Freq
+
+The PPMd code tries to fulfill the condition:
+  (SummFreq <= (256 * 128 = RC::kBot))
+
+We have (Sum(Stats[].Freq) <= 256 * 124), because of (MAX_FREQ = 124)
+So (4 = 128 - 124) is average reserve for Escape_Freq for each symbol.
+If (CPpmd_State::Freq) is not aligned for 4, the reserve can be 5, 6 or 7.
+SummFreq and Escape_Freq can be changed in Rescale() and *Update*() functions.
+Rescale() can remove symbols only from max-order contexts. So Escape_Freq can increase after multiple calls of Rescale() for
+max-order context.
+
+When the PPMd code still break (Total <= RC::Range) condition in range coder,
+we have two ways to resolve that problem:
+  1) we can report error, if we want to keep compatibility with original PPMd code that has no fix for such cases.
+  2) we can reduce (Total) value to (RC::Range) by reducing (Escape_Freq) part of (Total) value.
+*/