xref: /freebsd/contrib/libarchive/libarchive/archive_ppmd8.c (revision 2e113ef82465598b8c26e0ca415fbe90677fbd47)
1 /* Ppmd8.c -- PPMdI codec
2 2016-05-21 : Igor Pavlov : Public domain
3 This code is based on PPMd var.I (2002): Dmitry Shkarin : Public domain */
4 
5 #include "archive_platform.h"
6 
7 #include <string.h>
8 
9 #include "archive_ppmd8_private.h"
10 
11 const Byte PPMD8_kExpEscape[16] = { 25, 14, 9, 7, 5, 5, 4, 4, 4, 3, 3, 3, 2, 2, 2, 2 };
12 static const UInt16 kInitBinEsc[] = { 0x3CDD, 0x1F3F, 0x59BF, 0x48F3, 0x64A1, 0x5ABC, 0x6632, 0x6051};
13 
14 #define MAX_FREQ 124
15 #define UNIT_SIZE 12
16 
17 #define U2B(nu) ((UInt32)(nu) * UNIT_SIZE)
18 #define U2I(nu) (p->Units2Indx[(nu) - 1])
19 #define I2U(indx) (p->Indx2Units[indx])
20 
21 #ifdef PPMD_32BIT
22   #define REF(ptr) (ptr)
23 #else
24   #define REF(ptr) ((UInt32)((Byte *)(ptr) - (p)->Base))
25 #endif
26 
27 #define STATS_REF(ptr) ((CPpmd_State_Ref)REF(ptr))
28 
29 #define CTX(ref) ((CPpmd8_Context *)Ppmd8_GetContext(p, ref))
30 #define STATS(ctx) Ppmd8_GetStats(p, ctx)
31 #define ONE_STATE(ctx) Ppmd8Context_OneState(ctx)
32 #define SUFFIX(ctx) CTX((ctx)->Suffix)
33 
34 #define kTop (1 << 24)
35 #define kBot (1 << 15)
36 
37 typedef CPpmd8_Context * CTX_PTR;
38 
39 struct CPpmd8_Node_;
40 
41 typedef
42   #ifdef PPMD_32BIT
43     struct CPpmd8_Node_ *
44   #else
45     UInt32
46   #endif
47   CPpmd8_Node_Ref;
48 
49 typedef struct CPpmd8_Node_
50 {
51   UInt32 Stamp;
52   CPpmd8_Node_Ref Next;
53   UInt32 NU;
54 } CPpmd8_Node;
55 
56 #ifdef PPMD_32BIT
57   #define NODE(ptr) (ptr)
58 #else
59   #define NODE(offs) ((CPpmd8_Node *)(p->Base + (offs)))
60 #endif
61 
62 #define EMPTY_NODE 0xFFFFFFFF
63 
Ppmd8_Construct(CPpmd8 * p)64 void Ppmd8_Construct(CPpmd8 *p)
65 {
66   unsigned i, k, m;
67 
68   p->Base = 0;
69 
70   for (i = 0, k = 0; i < PPMD_NUM_INDEXES; i++)
71   {
72     unsigned step = (i >= 12 ? 4 : (i >> 2) + 1);
73     do { p->Units2Indx[k++] = (Byte)i; } while (--step);
74     p->Indx2Units[i] = (Byte)k;
75   }
76 
77   p->NS2BSIndx[0] = (0 << 1);
78   p->NS2BSIndx[1] = (1 << 1);
79   memset(p->NS2BSIndx + 2, (2 << 1), 9);
80   memset(p->NS2BSIndx + 11, (3 << 1), 256 - 11);
81 
82   for (i = 0; i < 5; i++)
83     p->NS2Indx[i] = (Byte)i;
84   for (m = i, k = 1; i < 260; i++)
85   {
86     p->NS2Indx[i] = (Byte)m;
87     if (--k == 0)
88       k = (++m) - 4;
89   }
90 }
91 
Ppmd8_Free(CPpmd8 * p)92 void Ppmd8_Free(CPpmd8 *p)
93 {
94   free(p->Base);
95   p->Size = 0;
96   p->Base = 0;
97 }
98 
Ppmd8_Alloc(CPpmd8 * p,UInt32 size)99 Bool Ppmd8_Alloc(CPpmd8 *p, UInt32 size)
100 {
101   if (p->Base == 0 || p->Size != size)
102   {
103     Ppmd8_Free(p);
104     p->AlignOffset =
105       #ifdef PPMD_32BIT
106         (4 - size) & 3;
107       #else
108         4 - (size & 3);
109       #endif
110     if ((p->Base = malloc(p->AlignOffset + size)) == 0)
111       return False;
112     p->Size = size;
113   }
114   return True;
115 }
116 
InsertNode(CPpmd8 * p,void * node,unsigned indx)117 static void InsertNode(CPpmd8 *p, void *node, unsigned indx)
118 {
119   ((CPpmd8_Node *)node)->Stamp = EMPTY_NODE;
120   ((CPpmd8_Node *)node)->Next = (CPpmd8_Node_Ref)p->FreeList[indx];
121   ((CPpmd8_Node *)node)->NU = I2U(indx);
122   p->FreeList[indx] = REF(node);
123   p->Stamps[indx]++;
124 }
125 
RemoveNode(CPpmd8 * p,unsigned indx)126 static void *RemoveNode(CPpmd8 *p, unsigned indx)
127 {
128   CPpmd8_Node *node = NODE((CPpmd8_Node_Ref)p->FreeList[indx]);
129   p->FreeList[indx] = node->Next;
130   p->Stamps[indx]--;
131   return node;
132 }
133 
SplitBlock(CPpmd8 * p,void * ptr,unsigned oldIndx,unsigned newIndx)134 static void SplitBlock(CPpmd8 *p, void *ptr, unsigned oldIndx, unsigned newIndx)
135 {
136   unsigned i, nu = I2U(oldIndx) - I2U(newIndx);
137   ptr = (Byte *)ptr + U2B(I2U(newIndx));
138   if (I2U(i = U2I(nu)) != nu)
139   {
140     unsigned k = I2U(--i);
141     InsertNode(p, ((Byte *)ptr) + U2B(k), nu - k - 1);
142   }
143   InsertNode(p, ptr, i);
144 }
145 
GlueFreeBlocks(CPpmd8 * p)146 static void GlueFreeBlocks(CPpmd8 *p)
147 {
148   CPpmd8_Node_Ref head = 0;
149   CPpmd8_Node_Ref *prev = &head;
150   unsigned i;
151 
152   p->GlueCount = 1 << 13;
153   memset(p->Stamps, 0, sizeof(p->Stamps));
154 
155   /* Order-0 context is always at top UNIT, so we don't need guard NODE at the end.
156      All blocks up to p->LoUnit can be free, so we need guard NODE at LoUnit. */
157   if (p->LoUnit != p->HiUnit)
158     ((CPpmd8_Node *)p->LoUnit)->Stamp = 0;
159 
160   /* Glue free blocks */
161   for (i = 0; i < PPMD_NUM_INDEXES; i++)
162   {
163     CPpmd8_Node_Ref next = (CPpmd8_Node_Ref)p->FreeList[i];
164     p->FreeList[i] = 0;
165     while (next != 0)
166     {
167       CPpmd8_Node *node = NODE(next);
168       if (node->NU != 0)
169       {
170         CPpmd8_Node *node2;
171         *prev = next;
172         prev = &(node->Next);
173         while ((node2 = node + node->NU)->Stamp == EMPTY_NODE)
174         {
175           node->NU += node2->NU;
176           node2->NU = 0;
177         }
178       }
179       next = node->Next;
180     }
181   }
182   *prev = 0;
183 
184   /* Fill lists of free blocks */
185   while (head != 0)
186   {
187     CPpmd8_Node *node = NODE(head);
188     unsigned nu;
189     head = node->Next;
190     nu = node->NU;
191     if (nu == 0)
192       continue;
193     for (; nu > 128; nu -= 128, node += 128)
194       InsertNode(p, node, PPMD_NUM_INDEXES - 1);
195     if (I2U(i = U2I(nu)) != nu)
196     {
197       unsigned k = I2U(--i);
198       InsertNode(p, node + k, nu - k - 1);
199     }
200     InsertNode(p, node, i);
201   }
202 }
203 
AllocUnitsRare(CPpmd8 * p,unsigned indx)204 static void *AllocUnitsRare(CPpmd8 *p, unsigned indx)
205 {
206   unsigned i;
207   void *retVal;
208   if (p->GlueCount == 0)
209   {
210     GlueFreeBlocks(p);
211     if (p->FreeList[indx] != 0)
212       return RemoveNode(p, indx);
213   }
214   i = indx;
215   do
216   {
217     if (++i == PPMD_NUM_INDEXES)
218     {
219       UInt32 numBytes = U2B(I2U(indx));
220       p->GlueCount--;
221       return ((UInt32)(p->UnitsStart - p->Text) > numBytes) ? (p->UnitsStart -= numBytes) : (NULL);
222     }
223   }
224   while (p->FreeList[i] == 0);
225   retVal = RemoveNode(p, i);
226   SplitBlock(p, retVal, i, indx);
227   return retVal;
228 }
229 
AllocUnits(CPpmd8 * p,unsigned indx)230 static void *AllocUnits(CPpmd8 *p, unsigned indx)
231 {
232   UInt32 numBytes;
233   if (p->FreeList[indx] != 0)
234     return RemoveNode(p, indx);
235   numBytes = U2B(I2U(indx));
236   if (numBytes <= (UInt32)(p->HiUnit - p->LoUnit))
237   {
238     void *retVal = p->LoUnit;
239     p->LoUnit += numBytes;
240     return retVal;
241   }
242   return AllocUnitsRare(p, indx);
243 }
244 
245 #define MyMem12Cpy(dest, src, num) do {					\
246 	UInt32 *d = (UInt32 *)dest;					\
247 	const UInt32 *z = (const UInt32 *)src;				\
248 	UInt32 n = num;							\
249 	do {								\
250 		d[0] = z[0]; d[1] = z[1]; d[2] = z[2]; z += 3; d += 3;	\
251 	} while (--n);							\
252 } while (0)
253 
ShrinkUnits(CPpmd8 * p,void * oldPtr,unsigned oldNU,unsigned newNU)254 static void *ShrinkUnits(CPpmd8 *p, void *oldPtr, unsigned oldNU, unsigned newNU)
255 {
256   unsigned i0 = U2I(oldNU);
257   unsigned i1 = U2I(newNU);
258   if (i0 == i1)
259     return oldPtr;
260   if (p->FreeList[i1] != 0)
261   {
262     void *ptr = RemoveNode(p, i1);
263     MyMem12Cpy(ptr, oldPtr, newNU);
264     InsertNode(p, oldPtr, i0);
265     return ptr;
266   }
267   SplitBlock(p, oldPtr, i0, i1);
268   return oldPtr;
269 }
270 
FreeUnits(CPpmd8 * p,void * ptr,unsigned nu)271 static void FreeUnits(CPpmd8 *p, void *ptr, unsigned nu)
272 {
273   InsertNode(p, ptr, U2I(nu));
274 }
275 
SpecialFreeUnit(CPpmd8 * p,void * ptr)276 static void SpecialFreeUnit(CPpmd8 *p, void *ptr)
277 {
278   if ((Byte *)ptr != p->UnitsStart)
279     InsertNode(p, ptr, 0);
280   else
281   {
282     #ifdef PPMD8_FREEZE_SUPPORT
283     *(UInt32 *)ptr = EMPTY_NODE; /* it's used for (Flags == 0xFF) check in RemoveBinContexts */
284     #endif
285     p->UnitsStart += UNIT_SIZE;
286   }
287 }
288 
MoveUnitsUp(CPpmd8 * p,void * oldPtr,unsigned nu)289 static void *MoveUnitsUp(CPpmd8 *p, void *oldPtr, unsigned nu)
290 {
291   unsigned indx = U2I(nu);
292   void *ptr;
293   if ((Byte *)oldPtr > p->UnitsStart + 16 * 1024 || REF(oldPtr) > p->FreeList[indx])
294     return oldPtr;
295   ptr = RemoveNode(p, indx);
296   MyMem12Cpy(ptr, oldPtr, nu);
297   if ((Byte*)oldPtr != p->UnitsStart)
298     InsertNode(p, oldPtr, indx);
299   else
300     p->UnitsStart += U2B(I2U(indx));
301   return ptr;
302 }
303 
ExpandTextArea(CPpmd8 * p)304 static void ExpandTextArea(CPpmd8 *p)
305 {
306   UInt32 count[PPMD_NUM_INDEXES];
307   unsigned i;
308   memset(count, 0, sizeof(count));
309   if (p->LoUnit != p->HiUnit)
310     ((CPpmd8_Node *)p->LoUnit)->Stamp = 0;
311 
312   {
313     CPpmd8_Node *node = (CPpmd8_Node *)p->UnitsStart;
314     for (; node->Stamp == EMPTY_NODE; node += node->NU)
315     {
316       node->Stamp = 0;
317       count[U2I(node->NU)]++;
318     }
319     p->UnitsStart = (Byte *)node;
320   }
321 
322   for (i = 0; i < PPMD_NUM_INDEXES; i++)
323   {
324     CPpmd8_Node_Ref *next = (CPpmd8_Node_Ref *)&p->FreeList[i];
325     while (count[i] != 0)
326     {
327       CPpmd8_Node *node = NODE(*next);
328       while (node->Stamp == 0)
329       {
330         *next = node->Next;
331         node = NODE(*next);
332         p->Stamps[i]--;
333         if (--count[i] == 0)
334           break;
335       }
336       next = &node->Next;
337     }
338   }
339 }
340 
341 #define SUCCESSOR(p) ((CPpmd_Void_Ref)((p)->SuccessorLow | ((UInt32)(p)->SuccessorHigh << 16)))
342 
SetSuccessor(CPpmd_State * p,CPpmd_Void_Ref v)343 static void SetSuccessor(CPpmd_State *p, CPpmd_Void_Ref v)
344 {
345   (p)->SuccessorLow = (UInt16)((UInt32)(v) & 0xFFFF);
346   (p)->SuccessorHigh = (UInt16)(((UInt32)(v) >> 16) & 0xFFFF);
347 }
348 
349 #define RESET_TEXT(offs) do {						\
350 	p->Text = p->Base + p->AlignOffset + (offs);			\
351 } while (0)
352 
RestartModel(CPpmd8 * p)353 static void RestartModel(CPpmd8 *p)
354 {
355   unsigned i, k, m, r;
356 
357   memset(p->FreeList, 0, sizeof(p->FreeList));
358   memset(p->Stamps, 0, sizeof(p->Stamps));
359   RESET_TEXT(0);
360   p->HiUnit = p->Text + p->Size;
361   p->LoUnit = p->UnitsStart = p->HiUnit - p->Size / 8 / UNIT_SIZE * 7 * UNIT_SIZE;
362   p->GlueCount = 0;
363 
364   p->OrderFall = p->MaxOrder;
365   p->RunLength = p->InitRL = -(Int32)((p->MaxOrder < 12) ? p->MaxOrder : 12) - 1;
366   p->PrevSuccess = 0;
367 
368   p->MinContext = p->MaxContext = (CTX_PTR)(p->HiUnit -= UNIT_SIZE); /* AllocContext(p); */
369   p->MinContext->Suffix = 0;
370   p->MinContext->NumStats = 255;
371   p->MinContext->Flags = 0;
372   p->MinContext->SummFreq = 256 + 1;
373   p->FoundState = (CPpmd_State *)p->LoUnit; /* AllocUnits(p, PPMD_NUM_INDEXES - 1); */
374   p->LoUnit += U2B(256 / 2);
375   p->MinContext->Stats = REF(p->FoundState);
376   for (i = 0; i < 256; i++)
377   {
378     CPpmd_State *s = &p->FoundState[i];
379     s->Symbol = (Byte)i;
380     s->Freq = 1;
381     SetSuccessor(s, 0);
382   }
383 
384   for (i = m = 0; m < 25; m++)
385   {
386     while (p->NS2Indx[i] == m)
387       i++;
388     for (k = 0; k < 8; k++)
389     {
390       UInt16 val = (UInt16)(PPMD_BIN_SCALE - kInitBinEsc[k] / (i + 1));
391       UInt16 *dest = p->BinSumm[m] + k;
392       for (r = 0; r < 64; r += 8)
393         dest[r] = val;
394     }
395   }
396 
397   for (i = m = 0; m < 24; m++)
398   {
399     while (p->NS2Indx[i + 3] == m + 3)
400       i++;
401     for (k = 0; k < 32; k++)
402     {
403       CPpmd_See *s = &p->See[m][k];
404       s->Summ = (UInt16)((2 * i + 5) << (s->Shift = PPMD_PERIOD_BITS - 4));
405       s->Count = 7;
406     }
407   }
408 }
409 
Ppmd8_Init(CPpmd8 * p,unsigned maxOrder,unsigned restoreMethod)410 void Ppmd8_Init(CPpmd8 *p, unsigned maxOrder, unsigned restoreMethod)
411 {
412   p->MaxOrder = maxOrder;
413   p->RestoreMethod = restoreMethod;
414   RestartModel(p);
415   p->DummySee.Shift = PPMD_PERIOD_BITS;
416   p->DummySee.Summ = 0; /* unused */
417   p->DummySee.Count = 64; /* unused */
418 }
419 
Refresh(CPpmd8 * p,CTX_PTR ctx,unsigned oldNU,unsigned scale)420 static void Refresh(CPpmd8 *p, CTX_PTR ctx, unsigned oldNU, unsigned scale)
421 {
422   unsigned i = ctx->NumStats, escFreq, sumFreq, flags;
423   CPpmd_State *s = (CPpmd_State *)ShrinkUnits(p, STATS(ctx), oldNU, (i + 2) >> 1);
424   ctx->Stats = REF(s);
425   #ifdef PPMD8_FREEZE_SUPPORT
426   /* fixed over Shkarin's code. Fixed code is not compatible with original code for some files in FREEZE mode. */
427   scale |= (ctx->SummFreq >= ((UInt32)1 << 15));
428   #endif
429   flags = (ctx->Flags & (0x10 + 0x04 * scale)) + 0x08 * (s->Symbol >= 0x40);
430   escFreq = ctx->SummFreq - s->Freq;
431   sumFreq = (s->Freq = (Byte)((s->Freq + scale) >> scale));
432   do
433   {
434     escFreq -= (++s)->Freq;
435     sumFreq += (s->Freq = (Byte)((s->Freq + scale) >> scale));
436     flags |= 0x08 * (s->Symbol >= 0x40);
437   }
438   while (--i);
439   ctx->SummFreq = (UInt16)(sumFreq + ((escFreq + scale) >> scale));
440   ctx->Flags = (Byte)flags;
441 }
442 
SwapStates(CPpmd_State * t1,CPpmd_State * t2)443 static void SwapStates(CPpmd_State *t1, CPpmd_State *t2)
444 {
445   CPpmd_State tmp = *t1;
446   *t1 = *t2;
447   *t2 = tmp;
448 }
449 
CutOff(CPpmd8 * p,CTX_PTR ctx,unsigned order)450 static CPpmd_Void_Ref CutOff(CPpmd8 *p, CTX_PTR ctx, unsigned order)
451 {
452   int i;
453   unsigned tmp;
454   CPpmd_State *s;
455 
456   if (!ctx->NumStats)
457   {
458     s = ONE_STATE(ctx);
459     if ((Byte *)Ppmd8_GetPtr(p, SUCCESSOR(s)) >= p->UnitsStart)
460     {
461       if (order < p->MaxOrder)
462         SetSuccessor(s, CutOff(p, CTX(SUCCESSOR(s)), order + 1));
463       else
464         SetSuccessor(s, 0);
465       if (SUCCESSOR(s) || order <= 9) /* O_BOUND */
466         return REF(ctx);
467     }
468     SpecialFreeUnit(p, ctx);
469     return 0;
470   }
471 
472   ctx->Stats = STATS_REF(MoveUnitsUp(p, STATS(ctx), tmp = ((unsigned)ctx->NumStats + 2) >> 1));
473 
474   for (s = STATS(ctx) + (i = ctx->NumStats); s >= STATS(ctx); s--)
475     if ((Byte *)Ppmd8_GetPtr(p, SUCCESSOR(s)) < p->UnitsStart)
476     {
477       CPpmd_State *s2 = STATS(ctx) + (i--);
478       SetSuccessor(s, 0);
479       SwapStates(s, s2);
480     }
481     else if (order < p->MaxOrder)
482       SetSuccessor(s, CutOff(p, CTX(SUCCESSOR(s)), order + 1));
483     else
484       SetSuccessor(s, 0);
485 
486   if (i != ctx->NumStats && order)
487   {
488     ctx->NumStats = (Byte)i;
489     s = STATS(ctx);
490     if (i < 0)
491     {
492       FreeUnits(p, s, tmp);
493       SpecialFreeUnit(p, ctx);
494       return 0;
495     }
496     if (i == 0)
497     {
498       ctx->Flags = (Byte)((ctx->Flags & 0x10) + 0x08 * (s->Symbol >= 0x40));
499       *ONE_STATE(ctx) = *s;
500       FreeUnits(p, s, tmp);
501       /* 9.31: the code was fixed. It's was not BUG, if Freq <= MAX_FREQ = 124 */
502       ONE_STATE(ctx)->Freq = (Byte)(((unsigned)ONE_STATE(ctx)->Freq + 11) >> 3);
503     }
504     else
505       Refresh(p, ctx, tmp, ctx->SummFreq > 16 * i);
506   }
507   return REF(ctx);
508 }
509 
510 #ifdef PPMD8_FREEZE_SUPPORT
RemoveBinContexts(CPpmd8 * p,CTX_PTR ctx,unsigned order)511 static CPpmd_Void_Ref RemoveBinContexts(CPpmd8 *p, CTX_PTR ctx, unsigned order)
512 {
513   CPpmd_State *s;
514   if (!ctx->NumStats)
515   {
516     s = ONE_STATE(ctx);
517     if ((Byte *)Ppmd8_GetPtr(p, SUCCESSOR(s)) >= p->UnitsStart && order < p->MaxOrder)
518       SetSuccessor(s, RemoveBinContexts(p, CTX(SUCCESSOR(s)), order + 1));
519     else
520       SetSuccessor(s, 0);
521     /* Suffix context can be removed already, since different (high-order)
522        Successors may refer to same context. So we check Flags == 0xFF (Stamp == EMPTY_NODE) */
523     if (!SUCCESSOR(s) && (!SUFFIX(ctx)->NumStats || SUFFIX(ctx)->Flags == 0xFF))
524     {
525       FreeUnits(p, ctx, 1);
526       return 0;
527     }
528     else
529       return REF(ctx);
530   }
531 
532   for (s = STATS(ctx) + ctx->NumStats; s >= STATS(ctx); s--)
533     if ((Byte *)Ppmd8_GetPtr(p, SUCCESSOR(s)) >= p->UnitsStart && order < p->MaxOrder)
534       SetSuccessor(s, RemoveBinContexts(p, CTX(SUCCESSOR(s)), order + 1));
535     else
536       SetSuccessor(s, 0);
537 
538   return REF(ctx);
539 }
540 #endif
541 
GetUsedMemory(const CPpmd8 * p)542 static UInt32 GetUsedMemory(const CPpmd8 *p)
543 {
544   UInt32 v = 0;
545   unsigned i;
546   for (i = 0; i < PPMD_NUM_INDEXES; i++)
547     v += p->Stamps[i] * I2U(i);
548   return p->Size - (UInt32)(p->HiUnit - p->LoUnit) - (UInt32)(p->UnitsStart - p->Text) - U2B(v);
549 }
550 
551 #ifdef PPMD8_FREEZE_SUPPORT
552   #define RESTORE_MODEL(c1, fSuccessor) RestoreModel(p, c1, fSuccessor)
553 #else
554   #define RESTORE_MODEL(c1, fSuccessor) RestoreModel(p, c1)
555 #endif
556 
RestoreModel(CPpmd8 * p,CTX_PTR c1,CTX_PTR fSuccessor)557 static void RestoreModel(CPpmd8 *p, CTX_PTR c1
558     #ifdef PPMD8_FREEZE_SUPPORT
559     , CTX_PTR fSuccessor
560     #endif
561     )
562 {
563   CTX_PTR c;
564   CPpmd_State *s;
565   RESET_TEXT(0);
566   for (c = p->MaxContext; c != c1; c = SUFFIX(c))
567     if (--(c->NumStats) == 0)
568     {
569       s = STATS(c);
570       c->Flags = (Byte)((c->Flags & 0x10) + 0x08 * (s->Symbol >= 0x40));
571       *ONE_STATE(c) = *s;
572       SpecialFreeUnit(p, s);
573       ONE_STATE(c)->Freq = (Byte)(((unsigned)ONE_STATE(c)->Freq + 11) >> 3);
574     }
575     else
576       Refresh(p, c, (c->NumStats+3) >> 1, 0);
577 
578   for (; c != p->MinContext; c = SUFFIX(c))
579     if (!c->NumStats)
580       ONE_STATE(c)->Freq = (Byte)(ONE_STATE(c)->Freq - (ONE_STATE(c)->Freq >> 1));
581     else if ((c->SummFreq += 4) > 128 + 4 * c->NumStats)
582       Refresh(p, c, (c->NumStats + 2) >> 1, 1);
583 
584   #ifdef PPMD8_FREEZE_SUPPORT
585   if (p->RestoreMethod > PPMD8_RESTORE_METHOD_FREEZE)
586   {
587     p->MaxContext = fSuccessor;
588     p->GlueCount += !(p->Stamps[1] & 1);
589   }
590   else if (p->RestoreMethod == PPMD8_RESTORE_METHOD_FREEZE)
591   {
592     while (p->MaxContext->Suffix)
593       p->MaxContext = SUFFIX(p->MaxContext);
594     RemoveBinContexts(p, p->MaxContext, 0);
595     p->RestoreMethod++;
596     p->GlueCount = 0;
597     p->OrderFall = p->MaxOrder;
598   }
599   else
600   #endif
601   if (p->RestoreMethod == PPMD8_RESTORE_METHOD_RESTART || GetUsedMemory(p) < (p->Size >> 1))
602     RestartModel(p);
603   else
604   {
605     while (p->MaxContext->Suffix)
606       p->MaxContext = SUFFIX(p->MaxContext);
607     do
608     {
609       CutOff(p, p->MaxContext, 0);
610       ExpandTextArea(p);
611     }
612     while (GetUsedMemory(p) > 3 * (p->Size >> 2));
613     p->GlueCount = 0;
614     p->OrderFall = p->MaxOrder;
615   }
616 }
617 
CreateSuccessors(CPpmd8 * p,Bool skip,CPpmd_State * s1,CTX_PTR c)618 static CTX_PTR CreateSuccessors(CPpmd8 *p, Bool skip, CPpmd_State *s1, CTX_PTR c)
619 {
620   CPpmd_State upState;
621   Byte flags;
622   CPpmd_Byte_Ref upBranch = (CPpmd_Byte_Ref)SUCCESSOR(p->FoundState);
623   /* fixed over Shkarin's code. Maybe it could work without + 1 too. */
624   CPpmd_State *ps[PPMD8_MAX_ORDER + 1];
625   unsigned numPs = 0;
626 
627   if (!skip)
628     ps[numPs++] = p->FoundState;
629 
630   while (c->Suffix)
631   {
632     CPpmd_Void_Ref successor;
633     CPpmd_State *s;
634     c = SUFFIX(c);
635     if (s1)
636     {
637       s = s1;
638       s1 = NULL;
639     }
640     else if (c->NumStats != 0)
641     {
642       for (s = STATS(c); s->Symbol != p->FoundState->Symbol; s++);
643       if (s->Freq < MAX_FREQ - 9)
644       {
645         s->Freq++;
646         c->SummFreq++;
647       }
648     }
649     else
650     {
651       s = ONE_STATE(c);
652       s->Freq = (Byte)(s->Freq + (!SUFFIX(c)->NumStats & (s->Freq < 24)));
653     }
654     successor = SUCCESSOR(s);
655     if (successor != upBranch)
656     {
657       c = CTX(successor);
658       if (numPs == 0)
659         return c;
660       break;
661     }
662     ps[numPs++] = s;
663   }
664 
665   upState.Symbol = *(const Byte *)Ppmd8_GetPtr(p, upBranch);
666   SetSuccessor(&upState, upBranch + 1);
667   flags = (Byte)(0x10 * (p->FoundState->Symbol >= 0x40) + 0x08 * (upState.Symbol >= 0x40));
668 
669   if (c->NumStats == 0)
670     upState.Freq = ONE_STATE(c)->Freq;
671   else
672   {
673     UInt32 cf, s0;
674     CPpmd_State *s;
675     for (s = STATS(c); s->Symbol != upState.Symbol; s++);
676     cf = s->Freq - 1;
677     s0 = c->SummFreq - c->NumStats - cf;
678     upState.Freq = (Byte)(1 + ((2 * cf <= s0) ? (5 * cf > s0) : ((cf + 2 * s0 - 3) / s0)));
679   }
680 
681   while (numPs != 0)
682   {
683     /* Create Child */
684     CTX_PTR c1; /* = AllocContext(p); */
685     if (p->HiUnit != p->LoUnit)
686       c1 = (CTX_PTR)(p->HiUnit -= UNIT_SIZE);
687     else if (p->FreeList[0] != 0)
688       c1 = (CTX_PTR)RemoveNode(p, 0);
689     else
690     {
691       c1 = (CTX_PTR)AllocUnitsRare(p, 0);
692       if (!c1)
693         return NULL;
694     }
695     c1->NumStats = 0;
696     c1->Flags = flags;
697     *ONE_STATE(c1) = upState;
698     c1->Suffix = REF(c);
699     SetSuccessor(ps[--numPs], REF(c1));
700     c = c1;
701   }
702 
703   return c;
704 }
705 
ReduceOrder(CPpmd8 * p,CPpmd_State * s1,CTX_PTR c)706 static CTX_PTR ReduceOrder(CPpmd8 *p, CPpmd_State *s1, CTX_PTR c)
707 {
708   CPpmd_State *s = NULL;
709   CTX_PTR c1 = c;
710   CPpmd_Void_Ref upBranch = REF(p->Text);
711 
712   #ifdef PPMD8_FREEZE_SUPPORT
713   /* The BUG in Shkarin's code was fixed: ps could overflow in CUT_OFF mode. */
714   CPpmd_State *ps[PPMD8_MAX_ORDER + 1];
715   unsigned numPs = 0;
716   ps[numPs++] = p->FoundState;
717   #endif
718 
719   SetSuccessor(p->FoundState, upBranch);
720   p->OrderFall++;
721 
722   for (;;)
723   {
724     if (s1)
725     {
726       c = SUFFIX(c);
727       s = s1;
728       s1 = NULL;
729     }
730     else
731     {
732       if (!c->Suffix)
733       {
734         #ifdef PPMD8_FREEZE_SUPPORT
735         if (p->RestoreMethod > PPMD8_RESTORE_METHOD_FREEZE)
736         {
737           do { SetSuccessor(ps[--numPs], REF(c)); } while (numPs);
738           RESET_TEXT(1);
739           p->OrderFall = 1;
740         }
741         #endif
742         return c;
743       }
744       c = SUFFIX(c);
745       if (c->NumStats)
746       {
747         if ((s = STATS(c))->Symbol != p->FoundState->Symbol)
748           do { s++; } while (s->Symbol != p->FoundState->Symbol);
749         if (s->Freq < MAX_FREQ - 9)
750         {
751           s->Freq += 2;
752           c->SummFreq += 2;
753         }
754       }
755       else
756       {
757         s = ONE_STATE(c);
758         s->Freq = (Byte)(s->Freq + (s->Freq < 32));
759       }
760     }
761     if (SUCCESSOR(s))
762       break;
763     #ifdef PPMD8_FREEZE_SUPPORT
764     ps[numPs++] = s;
765     #endif
766     SetSuccessor(s, upBranch);
767     p->OrderFall++;
768   }
769 
770   #ifdef PPMD8_FREEZE_SUPPORT
771   if (p->RestoreMethod > PPMD8_RESTORE_METHOD_FREEZE)
772   {
773     c = CTX(SUCCESSOR(s));
774     do { SetSuccessor(ps[--numPs], REF(c)); } while (numPs);
775     RESET_TEXT(1);
776     p->OrderFall = 1;
777     return c;
778   }
779   else
780   #endif
781   if (SUCCESSOR(s) <= upBranch)
782   {
783     CTX_PTR successor;
784     CPpmd_State *s2 = p->FoundState;
785     p->FoundState = s;
786 
787     successor = CreateSuccessors(p, False, NULL, c);
788     if (successor == NULL)
789       SetSuccessor(s, 0);
790     else
791       SetSuccessor(s, REF(successor));
792     p->FoundState = s2;
793   }
794 
795   if (p->OrderFall == 1 && c1 == p->MaxContext)
796   {
797     SetSuccessor(p->FoundState, SUCCESSOR(s));
798     p->Text--;
799   }
800   if (SUCCESSOR(s) == 0)
801     return NULL;
802   return CTX(SUCCESSOR(s));
803 }
804 
UpdateModel(CPpmd8 * p)805 static void UpdateModel(CPpmd8 *p)
806 {
807   CPpmd_Void_Ref successor, fSuccessor = SUCCESSOR(p->FoundState);
808   CTX_PTR c;
809   unsigned s0, ns, fFreq = p->FoundState->Freq;
810   Byte flag, fSymbol = p->FoundState->Symbol;
811   CPpmd_State *s = NULL;
812 
813   if (p->FoundState->Freq < MAX_FREQ / 4 && p->MinContext->Suffix != 0)
814   {
815     c = SUFFIX(p->MinContext);
816 
817     if (c->NumStats == 0)
818     {
819       s = ONE_STATE(c);
820       if (s->Freq < 32)
821         s->Freq++;
822     }
823     else
824     {
825       s = STATS(c);
826       if (s->Symbol != p->FoundState->Symbol)
827       {
828         do { s++; } while (s->Symbol != p->FoundState->Symbol);
829         if (s[0].Freq >= s[-1].Freq)
830         {
831           SwapStates(&s[0], &s[-1]);
832           s--;
833         }
834       }
835       if (s->Freq < MAX_FREQ - 9)
836       {
837         s->Freq += 2;
838         c->SummFreq += 2;
839       }
840     }
841   }
842 
843   c = p->MaxContext;
844   if (p->OrderFall == 0 && fSuccessor)
845   {
846     CTX_PTR cs = CreateSuccessors(p, True, s, p->MinContext);
847     if (cs == 0)
848     {
849       SetSuccessor(p->FoundState, 0);
850       RESTORE_MODEL(c, CTX(fSuccessor));
851     }
852     else
853     {
854       SetSuccessor(p->FoundState, REF(cs));
855       p->MaxContext = cs;
856     }
857     return;
858   }
859 
860   *p->Text++ = p->FoundState->Symbol;
861   successor = REF(p->Text);
862   if (p->Text >= p->UnitsStart)
863   {
864     RESTORE_MODEL(c, CTX(fSuccessor)); /* check it */
865     return;
866   }
867 
868   if (!fSuccessor)
869   {
870     CTX_PTR cs = ReduceOrder(p, s, p->MinContext);
871     if (cs == NULL)
872     {
873       RESTORE_MODEL(c, 0);
874       return;
875     }
876     fSuccessor = REF(cs);
877   }
878   else if ((Byte *)Ppmd8_GetPtr(p, fSuccessor) < p->UnitsStart)
879   {
880     CTX_PTR cs = CreateSuccessors(p, False, s, p->MinContext);
881     if (cs == NULL)
882     {
883       RESTORE_MODEL(c, 0);
884       return;
885     }
886     fSuccessor = REF(cs);
887   }
888 
889   if (--p->OrderFall == 0)
890   {
891     successor = fSuccessor;
892     p->Text -= (p->MaxContext != p->MinContext);
893   }
894   #ifdef PPMD8_FREEZE_SUPPORT
895   else if (p->RestoreMethod > PPMD8_RESTORE_METHOD_FREEZE)
896   {
897     successor = fSuccessor;
898     RESET_TEXT(0);
899     p->OrderFall = 0;
900   }
901   #endif
902 
903   s0 = p->MinContext->SummFreq - (ns = p->MinContext->NumStats) - fFreq;
904   flag = (Byte)(0x08 * (fSymbol >= 0x40));
905 
906   for (; c != p->MinContext; c = SUFFIX(c))
907   {
908     unsigned ns1;
909     UInt32 cf, sf;
910     if ((ns1 = c->NumStats) != 0)
911     {
912       if ((ns1 & 1) != 0)
913       {
914         /* Expand for one UNIT */
915         unsigned oldNU = (ns1 + 1) >> 1;
916         unsigned i = U2I(oldNU);
917         if (i != U2I(oldNU + 1))
918         {
919           void *ptr = AllocUnits(p, i + 1);
920           void *oldPtr;
921           if (!ptr)
922           {
923             RESTORE_MODEL(c, CTX(fSuccessor));
924             return;
925           }
926           oldPtr = STATS(c);
927           MyMem12Cpy(ptr, oldPtr, oldNU);
928           InsertNode(p, oldPtr, i);
929           c->Stats = STATS_REF(ptr);
930         }
931       }
932       c->SummFreq = (UInt16)(c->SummFreq + (3 * ns1 + 1 < ns));
933     }
934     else
935     {
936       CPpmd_State *s2 = (CPpmd_State*)AllocUnits(p, 0);
937       if (!s2)
938       {
939         RESTORE_MODEL(c, CTX(fSuccessor));
940         return;
941       }
942       *s2 = *ONE_STATE(c);
943       c->Stats = REF(s2);
944       if (s2->Freq < MAX_FREQ / 4 - 1)
945         s2->Freq <<= 1;
946       else
947         s2->Freq = MAX_FREQ - 4;
948       c->SummFreq = (UInt16)(s2->Freq + p->InitEsc + (ns > 2));
949     }
950     cf = 2 * fFreq * (c->SummFreq + 6);
951     sf = (UInt32)s0 + c->SummFreq;
952     if (cf < 6 * sf)
953     {
954       cf = 1 + (cf > sf) + (cf >= 4 * sf);
955       c->SummFreq += 4;
956     }
957     else
958     {
959       cf = 4 + (cf > 9 * sf) + (cf > 12 * sf) + (cf > 15 * sf);
960       c->SummFreq = (UInt16)(c->SummFreq + cf);
961     }
962     {
963       CPpmd_State *s2 = STATS(c) + ns1 + 1;
964       SetSuccessor(s2, successor);
965       s2->Symbol = fSymbol;
966       s2->Freq = (Byte)cf;
967       c->Flags |= flag;
968       c->NumStats = (Byte)(ns1 + 1);
969     }
970   }
971   p->MaxContext = p->MinContext = CTX(fSuccessor);
972 }
973 
Rescale(CPpmd8 * p)974 static void Rescale(CPpmd8 *p)
975 {
976   unsigned i, adder, sumFreq, escFreq;
977   CPpmd_State *stats = STATS(p->MinContext);
978   CPpmd_State *s = p->FoundState;
979   {
980     CPpmd_State tmp = *s;
981     for (; s != stats; s--)
982       s[0] = s[-1];
983     *s = tmp;
984   }
985   escFreq = p->MinContext->SummFreq - s->Freq;
986   s->Freq += 4;
987   adder = (p->OrderFall != 0
988       #ifdef PPMD8_FREEZE_SUPPORT
989       || p->RestoreMethod > PPMD8_RESTORE_METHOD_FREEZE
990       #endif
991       );
992   s->Freq = (Byte)((s->Freq + adder) >> 1);
993   sumFreq = s->Freq;
994 
995   i = p->MinContext->NumStats;
996   do
997   {
998     escFreq -= (++s)->Freq;
999     s->Freq = (Byte)((s->Freq + adder) >> 1);
1000     sumFreq += s->Freq;
1001     if (s[0].Freq > s[-1].Freq)
1002     {
1003       CPpmd_State *s1 = s;
1004       CPpmd_State tmp = *s1;
1005       do
1006         s1[0] = s1[-1];
1007       while (--s1 != stats && tmp.Freq > s1[-1].Freq);
1008       *s1 = tmp;
1009     }
1010   }
1011   while (--i);
1012 
1013   if (s->Freq == 0)
1014   {
1015     unsigned numStats = p->MinContext->NumStats;
1016     unsigned n0, n1;
1017     do { i++; } while ((--s)->Freq == 0);
1018     escFreq += i;
1019     p->MinContext->NumStats = (Byte)(p->MinContext->NumStats - i);
1020     if (p->MinContext->NumStats == 0)
1021     {
1022       CPpmd_State tmp = *stats;
1023       tmp.Freq = (Byte)((2 * tmp.Freq + escFreq - 1) / escFreq);
1024       if (tmp.Freq > MAX_FREQ / 3)
1025         tmp.Freq = MAX_FREQ / 3;
1026       InsertNode(p, stats, U2I((numStats + 2) >> 1));
1027       p->MinContext->Flags = (Byte)((p->MinContext->Flags & 0x10) + 0x08 * (tmp.Symbol >= 0x40));
1028       *(p->FoundState = ONE_STATE(p->MinContext)) = tmp;
1029       return;
1030     }
1031     n0 = (numStats + 2) >> 1;
1032     n1 = (p->MinContext->NumStats + 2) >> 1;
1033     if (n0 != n1)
1034       p->MinContext->Stats = STATS_REF(ShrinkUnits(p, stats, n0, n1));
1035     p->MinContext->Flags &= ~0x08;
1036     p->MinContext->Flags |= 0x08 * ((s = STATS(p->MinContext))->Symbol >= 0x40);
1037     i = p->MinContext->NumStats;
1038     do { p->MinContext->Flags |= 0x08*((++s)->Symbol >= 0x40); } while (--i);
1039   }
1040   p->MinContext->SummFreq = (UInt16)(sumFreq + escFreq - (escFreq >> 1));
1041   p->MinContext->Flags |= 0x4;
1042   p->FoundState = STATS(p->MinContext);
1043 }
1044 
Ppmd8_MakeEscFreq(CPpmd8 * p,unsigned numMasked1,UInt32 * escFreq)1045 CPpmd_See *Ppmd8_MakeEscFreq(CPpmd8 *p, unsigned numMasked1, UInt32 *escFreq)
1046 {
1047   CPpmd_See *see;
1048   if (p->MinContext->NumStats != 0xFF)
1049   {
1050     see = p->See[(unsigned)p->NS2Indx[(unsigned)p->MinContext->NumStats + 2] - 3] +
1051         (p->MinContext->SummFreq > 11 * ((unsigned)p->MinContext->NumStats + 1)) +
1052         2 * (unsigned)(2 * (unsigned)p->MinContext->NumStats <
1053         ((unsigned)SUFFIX(p->MinContext)->NumStats + numMasked1)) +
1054         p->MinContext->Flags;
1055     {
1056       unsigned r = (see->Summ >> see->Shift);
1057       see->Summ = (UInt16)(see->Summ - r);
1058       *escFreq = r + (r == 0);
1059     }
1060   }
1061   else
1062   {
1063     see = &p->DummySee;
1064     *escFreq = 1;
1065   }
1066   return see;
1067 }
1068 
NextContext(CPpmd8 * p)1069 static void NextContext(CPpmd8 *p)
1070 {
1071   CTX_PTR c = CTX(SUCCESSOR(p->FoundState));
1072   if (p->OrderFall == 0 && (Byte *)c >= p->UnitsStart)
1073     p->MinContext = p->MaxContext = c;
1074   else
1075   {
1076     UpdateModel(p);
1077     p->MinContext = p->MaxContext;
1078   }
1079 }
1080 
Ppmd8_Update1(CPpmd8 * p)1081 void Ppmd8_Update1(CPpmd8 *p)
1082 {
1083   CPpmd_State *s = p->FoundState;
1084   s->Freq += 4;
1085   p->MinContext->SummFreq += 4;
1086   if (s[0].Freq > s[-1].Freq)
1087   {
1088     SwapStates(&s[0], &s[-1]);
1089     p->FoundState = --s;
1090     if (s->Freq > MAX_FREQ)
1091       Rescale(p);
1092   }
1093   NextContext(p);
1094 }
1095 
Ppmd8_Update1_0(CPpmd8 * p)1096 void Ppmd8_Update1_0(CPpmd8 *p)
1097 {
1098   p->PrevSuccess = (2 * p->FoundState->Freq >= p->MinContext->SummFreq);
1099   p->RunLength += p->PrevSuccess;
1100   p->MinContext->SummFreq += 4;
1101   if ((p->FoundState->Freq += 4) > MAX_FREQ)
1102     Rescale(p);
1103   NextContext(p);
1104 }
1105 
Ppmd8_UpdateBin(CPpmd8 * p)1106 void Ppmd8_UpdateBin(CPpmd8 *p)
1107 {
1108   p->FoundState->Freq = (Byte)(p->FoundState->Freq + (p->FoundState->Freq < 196));
1109   p->PrevSuccess = 1;
1110   p->RunLength++;
1111   NextContext(p);
1112 }
1113 
Ppmd8_Update2(CPpmd8 * p)1114 void Ppmd8_Update2(CPpmd8 *p)
1115 {
1116   p->MinContext->SummFreq += 4;
1117   if ((p->FoundState->Freq += 4) > MAX_FREQ)
1118     Rescale(p);
1119   p->RunLength = p->InitRL;
1120   UpdateModel(p);
1121   p->MinContext = p->MaxContext;
1122 }
1123 
1124 /* Ppmd8Dec.c -- PPMdI Decoder
1125 2010-04-16 : Igor Pavlov : Public domain
1126 This code is based on:
1127   PPMd var.I (2002): Dmitry Shkarin : Public domain
1128   Carryless rangecoder (1999): Dmitry Subbotin : Public domain */
1129 
Ppmd8_RangeDec_Init(CPpmd8 * p)1130 Bool Ppmd8_RangeDec_Init(CPpmd8 *p)
1131 {
1132   unsigned i;
1133   p->Low = 0;
1134   p->Range = 0xFFFFFFFF;
1135   p->Code = 0;
1136   for (i = 0; i < 4; i++)
1137     p->Code = (p->Code << 8) | p->Stream.In->Read(p->Stream.In);
1138   return (p->Code < 0xFFFFFFFF);
1139 }
1140 
RangeDec_GetThreshold(CPpmd8 * p,UInt32 total)1141 static UInt32 RangeDec_GetThreshold(CPpmd8 *p, UInt32 total)
1142 {
1143   return p->Code / (p->Range /= total);
1144 }
1145 
RangeDec_Decode(CPpmd8 * p,UInt32 start,UInt32 size)1146 static void RangeDec_Decode(CPpmd8 *p, UInt32 start, UInt32 size)
1147 {
1148   start *= p->Range;
1149   p->Low += start;
1150   p->Code -= start;
1151   p->Range *= size;
1152 
1153   while ((p->Low ^ (p->Low + p->Range)) < kTop ||
1154       (p->Range < kBot && ((p->Range = (0 - p->Low) & (kBot - 1)), 1)))
1155   {
1156     p->Code = (p->Code << 8) | p->Stream.In->Read(p->Stream.In);
1157     p->Range <<= 8;
1158     p->Low <<= 8;
1159   }
1160 }
1161 
1162 #define MASK(sym) ((signed char *)charMask)[sym]
1163 
Ppmd8_DecodeSymbol(CPpmd8 * p)1164 int Ppmd8_DecodeSymbol(CPpmd8 *p)
1165 {
1166   size_t charMask[256 / sizeof(size_t)];
1167   if (p->MinContext->NumStats != 0)
1168   {
1169     CPpmd_State *s = Ppmd8_GetStats(p, p->MinContext);
1170     unsigned i;
1171     UInt32 count, hiCnt;
1172     if ((count = RangeDec_GetThreshold(p, p->MinContext->SummFreq)) < (hiCnt = s->Freq))
1173     {
1174       Byte symbol;
1175       RangeDec_Decode(p, 0, s->Freq);
1176       p->FoundState = s;
1177       symbol = s->Symbol;
1178       Ppmd8_Update1_0(p);
1179       return symbol;
1180     }
1181     p->PrevSuccess = 0;
1182     i = p->MinContext->NumStats;
1183     do
1184     {
1185       if ((hiCnt += (++s)->Freq) > count)
1186       {
1187         Byte symbol;
1188         RangeDec_Decode(p, hiCnt - s->Freq, s->Freq);
1189         p->FoundState = s;
1190         symbol = s->Symbol;
1191         Ppmd8_Update1(p);
1192         return symbol;
1193       }
1194     }
1195     while (--i);
1196     if (count >= p->MinContext->SummFreq)
1197       return -2;
1198     RangeDec_Decode(p, hiCnt, p->MinContext->SummFreq - hiCnt);
1199     PPMD_SetAllBitsIn256Bytes(charMask);
1200     MASK(s->Symbol) = 0;
1201     i = p->MinContext->NumStats;
1202     do { MASK((--s)->Symbol) = 0; } while (--i);
1203   }
1204   else
1205   {
1206     UInt16 *prob = Ppmd8_GetBinSumm(p);
1207     if (((p->Code / (p->Range >>= 14)) < *prob))
1208     {
1209       Byte symbol;
1210       RangeDec_Decode(p, 0, *prob);
1211       *prob = (UInt16)PPMD_UPDATE_PROB_0(*prob);
1212       symbol = (p->FoundState = Ppmd8Context_OneState(p->MinContext))->Symbol;
1213       Ppmd8_UpdateBin(p);
1214       return symbol;
1215     }
1216     RangeDec_Decode(p, *prob, (1 << 14) - *prob);
1217     *prob = (UInt16)PPMD_UPDATE_PROB_1(*prob);
1218     p->InitEsc = PPMD8_kExpEscape[*prob >> 10];
1219     PPMD_SetAllBitsIn256Bytes(charMask);
1220     MASK(Ppmd8Context_OneState(p->MinContext)->Symbol) = 0;
1221     p->PrevSuccess = 0;
1222   }
1223   for (;;)
1224   {
1225     CPpmd_State *ps[256], *s;
1226     UInt32 freqSum, count, hiCnt;
1227     CPpmd_See *see;
1228     unsigned i, num, numMasked = p->MinContext->NumStats;
1229     do
1230     {
1231       p->OrderFall++;
1232       if (!p->MinContext->Suffix)
1233         return -1;
1234       p->MinContext = Ppmd8_GetContext(p, p->MinContext->Suffix);
1235     }
1236     while (p->MinContext->NumStats == numMasked);
1237     hiCnt = 0;
1238     s = Ppmd8_GetStats(p, p->MinContext);
1239     i = 0;
1240     num = p->MinContext->NumStats - numMasked;
1241     do
1242     {
1243       int k = (int)(MASK(s->Symbol));
1244       hiCnt += (s->Freq & k);
1245       ps[i] = s++;
1246       i -= k;
1247     }
1248     while (i != num);
1249 
1250     see = Ppmd8_MakeEscFreq(p, numMasked, &freqSum);
1251     freqSum += hiCnt;
1252     count = RangeDec_GetThreshold(p, freqSum);
1253 
1254     if (count < hiCnt)
1255     {
1256       Byte symbol;
1257       CPpmd_State **pps = ps;
1258       for (hiCnt = 0; (hiCnt += (*pps)->Freq) <= count; pps++);
1259       s = *pps;
1260       RangeDec_Decode(p, hiCnt - s->Freq, s->Freq);
1261       Ppmd_See_Update(see);
1262       p->FoundState = s;
1263       symbol = s->Symbol;
1264       Ppmd8_Update2(p);
1265       return symbol;
1266     }
1267     if (count >= freqSum)
1268       return -2;
1269     RangeDec_Decode(p, hiCnt, freqSum - hiCnt);
1270     see->Summ = (UInt16)(see->Summ + freqSum);
1271     do { MASK(ps[--i]->Symbol) = 0; } while (i != 0);
1272   }
1273 }
1274 
1275 /* H->I changes:
1276   NS2Indx
1277   GlewCount, and Glue method
1278   BinSum
1279   See / EscFreq
1280   CreateSuccessors updates more suffix contexts
1281   UpdateModel consts.
1282   PrevSuccess Update
1283 */
1284 
1285 const IPpmd8 __archive_ppmd8_functions =
1286 {
1287   &Ppmd8_Construct,
1288   &Ppmd8_Alloc,
1289   &Ppmd8_Free,
1290   &Ppmd8_Init,
1291   &Ppmd8_RangeDec_Init,
1292   &Ppmd8_DecodeSymbol,
1293 };
1294