[ tor-browser ].git.dasho

Ppmd7.c (17656B)
      1 /* Ppmd7.c -- PPMdH codec
      2 2017-04-03 : 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 Bool 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, Bool 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 }
	tor-browser The Tor Browser
	git clone https://git.dasho.dev/tor-browser.git
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