nel/3rdparty/seven_zip/Ppmd7.c

   1 /* Ppmd7.c -- PPMdH codec
   2 2018-07-04 : Igor Pavlov : Public domain
   3 This code is based on PPMd var.H (2001): Dmitry Shkarin : Public domain */
   4
   5 #include "Precomp.h"
   6
   7 #include <string.h>
   8
   9 #include "Ppmd7.h"
  10
  11 const Byte PPMD7_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[(size_t)(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) ((CPpmd7_Context *)Ppmd7_GetContext(p, ref))
  30 #define STATS(ctx) Ppmd7_GetStats(p, ctx)
  31 #define ONE_STATE(ctx) Ppmd7Context_OneState(ctx)
  32 #define SUFFIX(ctx) CTX((ctx)->Suffix)
  33
  34 typedef CPpmd7_Context * CTX_PTR;
  35
  36 struct CPpmd7_Node_;
  37
  38 typedef
  39   #ifdef PPMD_32BIT
  40     struct CPpmd7_Node_ *
  41   #else
  42     UInt32
  43   #endif
  44   CPpmd7_Node_Ref;
  45
  46 typedef struct CPpmd7_Node_
  47 {
  48   UInt16 Stamp; /* must be at offset 0 as CPpmd7_Context::NumStats. Stamp=0 means free */
  49   UInt16 NU;
  50   CPpmd7_Node_Ref Next; /* must be at offset >= 4 */
  51   CPpmd7_Node_Ref Prev;
  52 } CPpmd7_Node;
  53
  54 #ifdef PPMD_32BIT
  55   #define NODE(ptr) (ptr)
  56 #else
  57   #define NODE(offs) ((CPpmd7_Node *)(p->Base + (offs)))
  58 #endif
  59
  60 void Ppmd7_Construct(CPpmd7 *p)
  61 {
  62   unsigned i, k, m;
  63
  64   p->Base = 0;
  65
  66   for (i = 0, k = 0; i < PPMD_NUM_INDEXES; i++)
  67   {
  68     unsigned step = (i >= 12 ? 4 : (i >> 2) + 1);
  69     do { p->Units2Indx[k++] = (Byte)i; } while (--step);
  70     p->Indx2Units[i] = (Byte)k;
  71   }
  72
  73   p->NS2BSIndx[0] = (0 << 1);
  74   p->NS2BSIndx[1] = (1 << 1);
  75   memset(p->NS2BSIndx + 2, (2 << 1), 9);
  76   memset(p->NS2BSIndx + 11, (3 << 1), 256 - 11);
  77
  78   for (i = 0; i < 3; i++)
  79     p->NS2Indx[i] = (Byte)i;
  80   for (m = i, k = 1; i < 256; i++)
  81   {
  82     p->NS2Indx[i] = (Byte)m;
  83     if (--k == 0)
  84       k = (++m) - 2;
  85   }
  86
  87   memset(p->HB2Flag, 0, 0x40);
  88   memset(p->HB2Flag + 0x40, 8, 0x100 - 0x40);
  89 }
  90
  91 void Ppmd7_Free(CPpmd7 *p, ISzAllocPtr alloc)
  92 {
  93   ISzAlloc_Free(alloc, p->Base);
  94   p->Size = 0;
  95   p->Base = 0;
  96 }
  97
  98 BoolInt Ppmd7_Alloc(CPpmd7 *p, UInt32 size, ISzAllocPtr alloc)
  99 {
 100   if (!p->Base || p->Size != size)
 101   {
 102     size_t size2;
 103     Ppmd7_Free(p, alloc);
 104     size2 = 0
 105       #ifndef PPMD_32BIT
 106       + UNIT_SIZE
 107       #endif
 108       ;
 109     p->AlignOffset =
 110       #ifdef PPMD_32BIT
 111         (4 - size) & 3;
 112       #else
 113         4 - (size & 3);
 114       #endif
 115     if ((p->Base = (Byte *)ISzAlloc_Alloc(alloc, p->AlignOffset + size + size2)) == 0)
 116       return False;
 117     p->Size = size;
 118   }
 119   return True;
 120 }
 121
 122 static void InsertNode(CPpmd7 *p, void *node, unsigned indx)
 123 {
 124   *((CPpmd_Void_Ref *)node) = p->FreeList[indx];
 125   p->FreeList[indx] = REF(node);
 126 }
 127
 128 static void *RemoveNode(CPpmd7 *p, unsigned indx)
 129 {
 130   CPpmd_Void_Ref *node = (CPpmd_Void_Ref *)Ppmd7_GetPtr(p, p->FreeList[indx]);
 131   p->FreeList[indx] = *node;
 132   return node;
 133 }
 134
 135 static void SplitBlock(CPpmd7 *p, void *ptr, unsigned oldIndx, unsigned newIndx)
 136 {
 137   unsigned i, nu = I2U(oldIndx) - I2U(newIndx);
 138   ptr = (Byte *)ptr + U2B(I2U(newIndx));
 139   if (I2U(i = U2I(nu)) != nu)
 140   {
 141     unsigned k = I2U(--i);
 142     InsertNode(p, ((Byte *)ptr) + U2B(k), nu - k - 1);
 143   }
 144   InsertNode(p, ptr, i);
 145 }
 146
 147 static void GlueFreeBlocks(CPpmd7 *p)
 148 {
 149   #ifdef PPMD_32BIT
 150   CPpmd7_Node headItem;
 151   CPpmd7_Node_Ref head = &headItem;
 152   #else
 153   CPpmd7_Node_Ref head = p->AlignOffset + p->Size;
 154   #endif
 155
 156   CPpmd7_Node_Ref n = head;
 157   unsigned i;
 158
 159   p->GlueCount = 255;
 160
 161   /* create doubly-linked list of free blocks */
 162   for (i = 0; i < PPMD_NUM_INDEXES; i++)
 163   {
 164     UInt16 nu = I2U(i);
 165     CPpmd7_Node_Ref next = (CPpmd7_Node_Ref)p->FreeList[i];
 166     p->FreeList[i] = 0;
 167     while (next != 0)
 168     {
 169       CPpmd7_Node *node = NODE(next);
 170       node->Next = n;
 171       n = NODE(n)->Prev = next;
 172       next = *(const CPpmd7_Node_Ref *)node;
 173       node->Stamp = 0;
 174       node->NU = (UInt16)nu;
 175     }
 176   }
 177   NODE(head)->Stamp = 1;
 178   NODE(head)->Next = n;
 179   NODE(n)->Prev = head;
 180   if (p->LoUnit != p->HiUnit)
 181     ((CPpmd7_Node *)p->LoUnit)->Stamp = 1;
 182
 183   /* Glue free blocks */
 184   while (n != head)
 185   {
 186     CPpmd7_Node *node = NODE(n);
 187     UInt32 nu = (UInt32)node->NU;
 188     for (;;)
 189     {
 190       CPpmd7_Node *node2 = NODE(n) + nu;
 191       nu += node2->NU;
 192       if (node2->Stamp != 0 || nu >= 0x10000)
 193         break;
 194       NODE(node2->Prev)->Next = node2->Next;
 195       NODE(node2->Next)->Prev = node2->Prev;
 196       node->NU = (UInt16)nu;
 197     }
 198     n = node->Next;
 199   }
 200
 201   /* Fill lists of free blocks */
 202   for (n = NODE(head)->Next; n != head;)
 203   {
 204     CPpmd7_Node *node = NODE(n);
 205     unsigned nu;
 206     CPpmd7_Node_Ref next = node->Next;
 207     for (nu = node->NU; nu > 128; nu -= 128, node += 128)
 208       InsertNode(p, node, PPMD_NUM_INDEXES - 1);
 209     if (I2U(i = U2I(nu)) != nu)
 210     {
 211       unsigned k = I2U(--i);
 212       InsertNode(p, node + k, nu - k - 1);
 213     }
 214     InsertNode(p, node, i);
 215     n = next;
 216   }
 217 }
 218
 219 static void *AllocUnitsRare(CPpmd7 *p, unsigned indx)
 220 {
 221   unsigned i;
 222   void *retVal;
 223   if (p->GlueCount == 0)
 224   {
 225     GlueFreeBlocks(p);
 226     if (p->FreeList[indx] != 0)
 227       return RemoveNode(p, indx);
 228   }
 229   i = indx;
 230   do
 231   {
 232     if (++i == PPMD_NUM_INDEXES)
 233     {
 234       UInt32 numBytes = U2B(I2U(indx));
 235       p->GlueCount--;
 236       return ((UInt32)(p->UnitsStart - p->Text) > numBytes) ? (p->UnitsStart -= numBytes) : (NULL);
 237     }
 238   }
 239   while (p->FreeList[i] == 0);
 240   retVal = RemoveNode(p, i);
 241   SplitBlock(p, retVal, i, indx);
 242   return retVal;
 243 }
 244
 245 static void *AllocUnits(CPpmd7 *p, unsigned indx)
 246 {
 247   UInt32 numBytes;
 248   if (p->FreeList[indx] != 0)
 249     return RemoveNode(p, indx);
 250   numBytes = U2B(I2U(indx));
 251   if (numBytes <= (UInt32)(p->HiUnit - p->LoUnit))
 252   {
 253     void *retVal = p->LoUnit;
 254     p->LoUnit += numBytes;
 255     return retVal;
 256   }
 257   return AllocUnitsRare(p, indx);
 258 }
 259
 260 #define MyMem12Cpy(dest, src, num) \
 261   { UInt32 *d = (UInt32 *)dest; const UInt32 *s = (const UInt32 *)src; UInt32 n = num; \
 262     do { d[0] = s[0]; d[1] = s[1]; d[2] = s[2]; s += 3; d += 3; } while (--n); }
 263
 264 static void *ShrinkUnits(CPpmd7 *p, void *oldPtr, unsigned oldNU, unsigned newNU)
 265 {
 266   unsigned i0 = U2I(oldNU);
 267   unsigned i1 = U2I(newNU);
 268   if (i0 == i1)
 269     return oldPtr;
 270   if (p->FreeList[i1] != 0)
 271   {
 272     void *ptr = RemoveNode(p, i1);
 273     MyMem12Cpy(ptr, oldPtr, newNU);
 274     InsertNode(p, oldPtr, i0);
 275     return ptr;
 276   }
 277   SplitBlock(p, oldPtr, i0, i1);
 278   return oldPtr;
 279 }
 280
 281 #define SUCCESSOR(p) ((CPpmd_Void_Ref)((p)->SuccessorLow | ((UInt32)(p)->SuccessorHigh << 16)))
 282
 283 static void SetSuccessor(CPpmd_State *p, CPpmd_Void_Ref v)
 284 {
 285   (p)->SuccessorLow = (UInt16)((UInt32)(v) & 0xFFFF);
 286   (p)->SuccessorHigh = (UInt16)(((UInt32)(v) >> 16) & 0xFFFF);
 287 }
 288
 289 static void RestartModel(CPpmd7 *p)
 290 {
 291   unsigned i, k, m;
 292
 293   memset(p->FreeList, 0, sizeof(p->FreeList));
 294   p->Text = p->Base + p->AlignOffset;
 295   p->HiUnit = p->Text + p->Size;
 296   p->LoUnit = p->UnitsStart = p->HiUnit - p->Size / 8 / UNIT_SIZE * 7 * UNIT_SIZE;
 297   p->GlueCount = 0;
 298
 299   p->OrderFall = p->MaxOrder;
 300   p->RunLength = p->InitRL = -(Int32)((p->MaxOrder < 12) ? p->MaxOrder : 12) - 1;
 301   p->PrevSuccess = 0;
 302
 303   p->MinContext = p->MaxContext = (CTX_PTR)(p->HiUnit -= UNIT_SIZE); /* AllocContext(p); */
 304   p->MinContext->Suffix = 0;
 305   p->MinContext->NumStats = 256;
 306   p->MinContext->SummFreq = 256 + 1;
 307   p->FoundState = (CPpmd_State *)p->LoUnit; /* AllocUnits(p, PPMD_NUM_INDEXES - 1); */
 308   p->LoUnit += U2B(256 / 2);
 309   p->MinContext->Stats = REF(p->FoundState);
 310   for (i = 0; i < 256; i++)
 311   {
 312     CPpmd_State *s = &p->FoundState[i];
 313     s->Symbol = (Byte)i;
 314     s->Freq = 1;
 315     SetSuccessor(s, 0);
 316   }
 317
 318   for (i = 0; i < 128; i++)
 319     for (k = 0; k < 8; k++)
 320     {
 321       UInt16 *dest = p->BinSumm[i] + k;
 322       UInt16 val = (UInt16)(PPMD_BIN_SCALE - kInitBinEsc[k] / (i + 2));
 323       for (m = 0; m < 64; m += 8)
 324         dest[m] = val;
 325     }
 326
 327   for (i = 0; i < 25; i++)
 328     for (k = 0; k < 16; k++)
 329     {
 330       CPpmd_See *s = &p->See[i][k];
 331       s->Summ = (UInt16)((5 * i + 10) << (s->Shift = PPMD_PERIOD_BITS - 4));
 332       s->Count = 4;
 333     }
 334 }
 335
 336 void Ppmd7_Init(CPpmd7 *p, unsigned maxOrder)
 337 {
 338   p->MaxOrder = maxOrder;
 339   RestartModel(p);
 340   p->DummySee.Shift = PPMD_PERIOD_BITS;
 341   p->DummySee.Summ = 0; /* unused */
 342   p->DummySee.Count = 64; /* unused */
 343 }
 344
 345 static CTX_PTR CreateSuccessors(CPpmd7 *p, BoolInt skip)
 346 {
 347   CPpmd_State upState;
 348   CTX_PTR c = p->MinContext;
 349   CPpmd_Byte_Ref upBranch = (CPpmd_Byte_Ref)SUCCESSOR(p->FoundState);
 350   CPpmd_State *ps[PPMD7_MAX_ORDER];
 351   unsigned numPs = 0;
 352
 353   if (!skip)
 354     ps[numPs++] = p->FoundState;
 355
 356   while (c->Suffix)
 357   {
 358     CPpmd_Void_Ref successor;
 359     CPpmd_State *s;
 360     c = SUFFIX(c);
 361     if (c->NumStats != 1)
 362     {
 363       for (s = STATS(c); s->Symbol != p->FoundState->Symbol; s++);
 364     }
 365     else
 366       s = ONE_STATE(c);
 367     successor = SUCCESSOR(s);
 368     if (successor != upBranch)
 369     {
 370       c = CTX(successor);
 371       if (numPs == 0)
 372         return c;
 373       break;
 374     }
 375     ps[numPs++] = s;
 376   }
 377
 378   upState.Symbol = *(const Byte *)Ppmd7_GetPtr(p, upBranch);
 379   SetSuccessor(&upState, upBranch + 1);
 380
 381   if (c->NumStats == 1)
 382     upState.Freq = ONE_STATE(c)->Freq;
 383   else
 384   {
 385     UInt32 cf, s0;
 386     CPpmd_State *s;
 387     for (s = STATS(c); s->Symbol != upState.Symbol; s++);
 388     cf = s->Freq - 1;
 389     s0 = c->SummFreq - c->NumStats - cf;
 390     upState.Freq = (Byte)(1 + ((2 * cf <= s0) ? (5 * cf > s0) : ((2 * cf + 3 * s0 - 1) / (2 * s0))));
 391   }
 392
 393   do
 394   {
 395     /* Create Child */
 396     CTX_PTR c1; /* = AllocContext(p); */
 397     if (p->HiUnit != p->LoUnit)
 398       c1 = (CTX_PTR)(p->HiUnit -= UNIT_SIZE);
 399     else if (p->FreeList[0] != 0)
 400       c1 = (CTX_PTR)RemoveNode(p, 0);
 401     else
 402     {
 403       c1 = (CTX_PTR)AllocUnitsRare(p, 0);
 404       if (!c1)
 405         return NULL;
 406     }
 407     c1->NumStats = 1;
 408     *ONE_STATE(c1) = upState;
 409     c1->Suffix = REF(c);
 410     SetSuccessor(ps[--numPs], REF(c1));
 411     c = c1;
 412   }
 413   while (numPs != 0);
 414
 415   return c;
 416 }
 417
 418 static void SwapStates(CPpmd_State *t1, CPpmd_State *t2)
 419 {
 420   CPpmd_State tmp = *t1;
 421   *t1 = *t2;
 422   *t2 = tmp;
 423 }
 424
 425 static void UpdateModel(CPpmd7 *p)
 426 {
 427   CPpmd_Void_Ref successor, fSuccessor = SUCCESSOR(p->FoundState);
 428   CTX_PTR c;
 429   unsigned s0, ns;
 430
 431   if (p->FoundState->Freq < MAX_FREQ / 4 && p->MinContext->Suffix != 0)
 432   {
 433     c = SUFFIX(p->MinContext);
 434
 435     if (c->NumStats == 1)
 436     {
 437       CPpmd_State *s = ONE_STATE(c);
 438       if (s->Freq < 32)
 439         s->Freq++;
 440     }
 441     else
 442     {
 443       CPpmd_State *s = STATS(c);
 444       if (s->Symbol != p->FoundState->Symbol)
 445       {
 446         do { s++; } while (s->Symbol != p->FoundState->Symbol);
 447         if (s[0].Freq >= s[-1].Freq)
 448         {
 449           SwapStates(&s[0], &s[-1]);
 450           s--;
 451         }
 452       }
 453       if (s->Freq < MAX_FREQ - 9)
 454       {
 455         s->Freq += 2;
 456         c->SummFreq += 2;
 457       }
 458     }
 459   }
 460
 461   if (p->OrderFall == 0)
 462   {
 463     p->MinContext = p->MaxContext = CreateSuccessors(p, True);
 464     if (p->MinContext == 0)
 465     {
 466       RestartModel(p);
 467       return;
 468     }
 469     SetSuccessor(p->FoundState, REF(p->MinContext));
 470     return;
 471   }
 472
 473   *p->Text++ = p->FoundState->Symbol;
 474   successor = REF(p->Text);
 475   if (p->Text >= p->UnitsStart)
 476   {
 477     RestartModel(p);
 478     return;
 479   }
 480
 481   if (fSuccessor)
 482   {
 483     if (fSuccessor <= successor)
 484     {
 485       CTX_PTR cs = CreateSuccessors(p, False);
 486       if (cs == NULL)
 487       {
 488         RestartModel(p);
 489         return;
 490       }
 491       fSuccessor = REF(cs);
 492     }
 493     if (--p->OrderFall == 0)
 494     {
 495       successor = fSuccessor;
 496       p->Text -= (p->MaxContext != p->MinContext);
 497     }
 498   }
 499   else
 500   {
 501     SetSuccessor(p->FoundState, successor);
 502     fSuccessor = REF(p->MinContext);
 503   }
 504
 505   s0 = p->MinContext->SummFreq - (ns = p->MinContext->NumStats) - (p->FoundState->Freq - 1);
 506
 507   for (c = p->MaxContext; c != p->MinContext; c = SUFFIX(c))
 508   {
 509     unsigned ns1;
 510     UInt32 cf, sf;
 511     if ((ns1 = c->NumStats) != 1)
 512     {
 513       if ((ns1 & 1) == 0)
 514       {
 515         /* Expand for one UNIT */
 516         unsigned oldNU = ns1 >> 1;
 517         unsigned i = U2I(oldNU);
 518         if (i != U2I((size_t)oldNU + 1))
 519         {
 520           void *ptr = AllocUnits(p, i + 1);
 521           void *oldPtr;
 522           if (!ptr)
 523           {
 524             RestartModel(p);
 525             return;
 526           }
 527           oldPtr = STATS(c);
 528           MyMem12Cpy(ptr, oldPtr, oldNU);
 529           InsertNode(p, oldPtr, i);
 530           c->Stats = STATS_REF(ptr);
 531         }
 532       }
 533       c->SummFreq = (UInt16)(c->SummFreq + (2 * ns1 < ns) + 2 * ((4 * ns1 <= ns) & (c->SummFreq <= 8 * ns1)));
 534     }
 535     else
 536     {
 537       CPpmd_State *s = (CPpmd_State*)AllocUnits(p, 0);
 538       if (!s)
 539       {
 540         RestartModel(p);
 541         return;
 542       }
 543       *s = *ONE_STATE(c);
 544       c->Stats = REF(s);
 545       if (s->Freq < MAX_FREQ / 4 - 1)
 546         s->Freq <<= 1;
 547       else
 548         s->Freq = MAX_FREQ - 4;
 549       c->SummFreq = (UInt16)(s->Freq + p->InitEsc + (ns > 3));
 550     }
 551     cf = 2 * (UInt32)p->FoundState->Freq * (c->SummFreq + 6);
 552     sf = (UInt32)s0 + c->SummFreq;
 553     if (cf < 6 * sf)
 554     {
 555       cf = 1 + (cf > sf) + (cf >= 4 * sf);
 556       c->SummFreq += 3;
 557     }
 558     else
 559     {
 560       cf = 4 + (cf >= 9 * sf) + (cf >= 12 * sf) + (cf >= 15 * sf);
 561       c->SummFreq = (UInt16)(c->SummFreq + cf);
 562     }
 563     {
 564       CPpmd_State *s = STATS(c) + ns1;
 565       SetSuccessor(s, successor);
 566       s->Symbol = p->FoundState->Symbol;
 567       s->Freq = (Byte)cf;
 568       c->NumStats = (UInt16)(ns1 + 1);
 569     }
 570   }
 571   p->MaxContext = p->MinContext = CTX(fSuccessor);
 572 }
 573
 574 static void Rescale(CPpmd7 *p)
 575 {
 576   unsigned i, adder, sumFreq, escFreq;
 577   CPpmd_State *stats = STATS(p->MinContext);
 578   CPpmd_State *s = p->FoundState;
 579   {
 580     CPpmd_State tmp = *s;
 581     for (; s != stats; s--)
 582       s[0] = s[-1];
 583     *s = tmp;
 584   }
 585   escFreq = p->MinContext->SummFreq - s->Freq;
 586   s->Freq += 4;
 587   adder = (p->OrderFall != 0);
 588   s->Freq = (Byte)((s->Freq + adder) >> 1);
 589   sumFreq = s->Freq;
 590
 591   i = p->MinContext->NumStats - 1;
 592   do
 593   {
 594     escFreq -= (++s)->Freq;
 595     s->Freq = (Byte)((s->Freq + adder) >> 1);
 596     sumFreq += s->Freq;
 597     if (s[0].Freq > s[-1].Freq)
 598     {
 599       CPpmd_State *s1 = s;
 600       CPpmd_State tmp = *s1;
 601       do
 602         s1[0] = s1[-1];
 603       while (--s1 != stats && tmp.Freq > s1[-1].Freq);
 604       *s1 = tmp;
 605     }
 606   }
 607   while (--i);
 608
 609   if (s->Freq == 0)
 610   {
 611     unsigned numStats = p->MinContext->NumStats;
 612     unsigned n0, n1;
 613     do { i++; } while ((--s)->Freq == 0);
 614     escFreq += i;
 615     p->MinContext->NumStats = (UInt16)(p->MinContext->NumStats - i);
 616     if (p->MinContext->NumStats == 1)
 617     {
 618       CPpmd_State tmp = *stats;
 619       do
 620       {
 621         tmp.Freq = (Byte)(tmp.Freq - (tmp.Freq >> 1));
 622         escFreq >>= 1;
 623       }
 624       while (escFreq > 1);
 625       InsertNode(p, stats, U2I(((numStats + 1) >> 1)));
 626       *(p->FoundState = ONE_STATE(p->MinContext)) = tmp;
 627       return;
 628     }
 629     n0 = (numStats + 1) >> 1;
 630     n1 = (p->MinContext->NumStats + 1) >> 1;
 631     if (n0 != n1)
 632       p->MinContext->Stats = STATS_REF(ShrinkUnits(p, stats, n0, n1));
 633   }
 634   p->MinContext->SummFreq = (UInt16)(sumFreq + escFreq - (escFreq >> 1));
 635   p->FoundState = STATS(p->MinContext);
 636 }
 637
 638 CPpmd_See *Ppmd7_MakeEscFreq(CPpmd7 *p, unsigned numMasked, UInt32 *escFreq)
 639 {
 640   CPpmd_See *see;
 641   unsigned nonMasked = p->MinContext->NumStats - numMasked;
 642   if (p->MinContext->NumStats != 256)
 643   {
 644     see = p->See[(unsigned)p->NS2Indx[(size_t)nonMasked - 1]] +
 645         (nonMasked < (unsigned)SUFFIX(p->MinContext)->NumStats - p->MinContext->NumStats) +
 646         2 * (unsigned)(p->MinContext->SummFreq < 11 * p->MinContext->NumStats) +
 647         4 * (unsigned)(numMasked > nonMasked) +
 648         p->HiBitsFlag;
 649     {
 650       unsigned r = (see->Summ >> see->Shift);
 651       see->Summ = (UInt16)(see->Summ - r);
 652       *escFreq = r + (r == 0);
 653     }
 654   }
 655   else
 656   {
 657     see = &p->DummySee;
 658     *escFreq = 1;
 659   }
 660   return see;
 661 }
 662
 663 static void NextContext(CPpmd7 *p)
 664 {
 665   CTX_PTR c = CTX(SUCCESSOR(p->FoundState));
 666   if (p->OrderFall == 0 && (Byte *)c > p->Text)
 667     p->MinContext = p->MaxContext = c;
 668   else
 669     UpdateModel(p);
 670 }
 671
 672 void Ppmd7_Update1(CPpmd7 *p)
 673 {
 674   CPpmd_State *s = p->FoundState;
 675   s->Freq += 4;
 676   p->MinContext->SummFreq += 4;
 677   if (s[0].Freq > s[-1].Freq)
 678   {
 679     SwapStates(&s[0], &s[-1]);
 680     p->FoundState = --s;
 681     if (s->Freq > MAX_FREQ)
 682       Rescale(p);
 683   }
 684   NextContext(p);
 685 }
 686
 687 void Ppmd7_Update1_0(CPpmd7 *p)
 688 {
 689   p->PrevSuccess = (2 * p->FoundState->Freq > p->MinContext->SummFreq);
 690   p->RunLength += p->PrevSuccess;
 691   p->MinContext->SummFreq += 4;
 692   if ((p->FoundState->Freq += 4) > MAX_FREQ)
 693     Rescale(p);
 694   NextContext(p);
 695 }
 696
 697 void Ppmd7_UpdateBin(CPpmd7 *p)
 698 {
 699   p->FoundState->Freq = (Byte)(p->FoundState->Freq + (p->FoundState->Freq < 128 ? 1: 0));
 700   p->PrevSuccess = 1;
 701   p->RunLength++;
 702   NextContext(p);
 703 }
 704
 705 void Ppmd7_Update2(CPpmd7 *p)
 706 {
 707   p->MinContext->SummFreq += 4;
 708   if ((p->FoundState->Freq += 4) > MAX_FREQ)
 709     Rescale(p);
 710   p->RunLength = p->InitRL;
 711   UpdateModel(p);
 712 }