1/* Bcj2.c -- BCJ2 Decoder (Converter for x86 code)
  22018-04-28 : Igor Pavlov : Public domain */
  3
  4#include "Precomp.h"
  5
  6#include "Bcj2.h"
  7#include "CpuArch.h"
  8
  9#define CProb UInt16
 10
 11#define kTopValue ((UInt32)1 << 24)
 12#define kNumModelBits 11
 13#define kBitModelTotal (1 << kNumModelBits)
 14#define kNumMoveBits 5
 15
 16#define _IF_BIT_0 ttt = *prob; bound = (p->range >> kNumModelBits) * ttt; if (p->code < bound)
 17#define _UPDATE_0 p->range = bound; *prob = (CProb)(ttt + ((kBitModelTotal - ttt) >> kNumMoveBits));
 18#define _UPDATE_1 p->range -= bound; p->code -= bound; *prob = (CProb)(ttt - (ttt >> kNumMoveBits));
 19
 20void Bcj2Dec_Init(CBcj2Dec *p)
 21{
 22  unsigned i;
 23
 24  p->state = BCJ2_DEC_STATE_OK;
 25  p->ip = 0;
 26  p->temp[3] = 0;
 27  p->range = 0;
 28  p->code = 0;
 29  for (i = 0; i < sizeof(p->probs) / sizeof(p->probs[0]); i++)
 30    p->probs[i] = kBitModelTotal >> 1;
 31}
 32
 33SRes Bcj2Dec_Decode(CBcj2Dec *p)
 34{
 35  if (p->range <= 5)
 36  {
 37    p->state = BCJ2_DEC_STATE_OK;
 38    for (; p->range != 5; p->range++)
 39    {
 40      if (p->range == 1 && p->code != 0)
 41        return SZ_ERROR_DATA;
 42      
 43      if (p->bufs[BCJ2_STREAM_RC] == p->lims[BCJ2_STREAM_RC])
 44      {
 45        p->state = BCJ2_STREAM_RC;
 46        return SZ_OK;
 47      }
 48
 49      p->code = (p->code << 8) | *(p->bufs[BCJ2_STREAM_RC])++;
 50    }
 51    
 52    if (p->code == 0xFFFFFFFF)
 53      return SZ_ERROR_DATA;
 54    
 55    p->range = 0xFFFFFFFF;
 56  }
 57  else if (p->state >= BCJ2_DEC_STATE_ORIG_0)
 58  {
 59    while (p->state <= BCJ2_DEC_STATE_ORIG_3)
 60    {
 61      Byte *dest = p->dest;
 62      if (dest == p->destLim)
 63        return SZ_OK;
 64      *dest = p->temp[(size_t)p->state - BCJ2_DEC_STATE_ORIG_0];
 65      p->state++;
 66      p->dest = dest + 1;
 67    }
 68  }
 69
 70  /*
 71  if (BCJ2_IS_32BIT_STREAM(p->state))
 72  {
 73    const Byte *cur = p->bufs[p->state];
 74    if (cur == p->lims[p->state])
 75      return SZ_OK;
 76    p->bufs[p->state] = cur + 4;
 77    
 78    {
 79      UInt32 val;
 80      Byte *dest;
 81      SizeT rem;
 82      
 83      p->ip += 4;
 84      val = GetBe32(cur) - p->ip;
 85      dest = p->dest;
 86      rem = p->destLim - dest;
 87      if (rem < 4)
 88      {
 89        SizeT i;
 90        SetUi32(p->temp, val);
 91        for (i = 0; i < rem; i++)
 92          dest[i] = p->temp[i];
 93        p->dest = dest + rem;
 94        p->state = BCJ2_DEC_STATE_ORIG_0 + (unsigned)rem;
 95        return SZ_OK;
 96      }
 97      SetUi32(dest, val);
 98      p->temp[3] = (Byte)(val >> 24);
 99      p->dest = dest + 4;
100      p->state = BCJ2_DEC_STATE_OK;
101    }
102  }
103  */
104
105  for (;;)
106  {
107    if (BCJ2_IS_32BIT_STREAM(p->state))
108      p->state = BCJ2_DEC_STATE_OK;
109    else
110    {
111      if (p->range < kTopValue)
112      {
113        if (p->bufs[BCJ2_STREAM_RC] == p->lims[BCJ2_STREAM_RC])
114        {
115          p->state = BCJ2_STREAM_RC;
116          return SZ_OK;
117        }
118        p->range <<= 8;
119        p->code = (p->code << 8) | *(p->bufs[BCJ2_STREAM_RC])++;
120      }
121
122      {
123        const Byte *src = p->bufs[BCJ2_STREAM_MAIN];
124        const Byte *srcLim;
125        Byte *dest;
126        SizeT num = p->lims[BCJ2_STREAM_MAIN] - src;
127        
128        if (num == 0)
129        {
130          p->state = BCJ2_STREAM_MAIN;
131          return SZ_OK;
132        }
133        
134        dest = p->dest;
135        if (num > (SizeT)(p->destLim - dest))
136        {
137          num = p->destLim - dest;
138          if (num == 0)
139          {
140            p->state = BCJ2_DEC_STATE_ORIG;
141            return SZ_OK;
142          }
143        }
144       
145        srcLim = src + num;
146
147        if (p->temp[3] == 0x0F && (src[0] & 0xF0) == 0x80)
148          *dest = src[0];
149        else for (;;)
150        {
151          Byte b = *src;
152          *dest = b;
153          if (b != 0x0F)
154          {
155            if ((b & 0xFE) == 0xE8)
156              break;
157            dest++;
158            if (++src != srcLim)
159              continue;
160            break;
161          }
162          dest++;
163          if (++src == srcLim)
164            break;
165          if ((*src & 0xF0) != 0x80)
166            continue;
167          *dest = *src;
168          break;
169        }
170        
171        num = src - p->bufs[BCJ2_STREAM_MAIN];
172        
173        if (src == srcLim)
174        {
175          p->temp[3] = src[-1];
176          p->bufs[BCJ2_STREAM_MAIN] = src;
177          p->ip += (UInt32)num;
178          p->dest += num;
179          p->state =
180            p->bufs[BCJ2_STREAM_MAIN] ==
181            p->lims[BCJ2_STREAM_MAIN] ?
182              (unsigned)BCJ2_STREAM_MAIN :
183              (unsigned)BCJ2_DEC_STATE_ORIG;
184          return SZ_OK;
185        }
186        
187        {
188          UInt32 bound, ttt;
189          CProb *prob;
190          Byte b = src[0];
191          Byte prev = (Byte)(num == 0 ? p->temp[3] : src[-1]);
192          
193          p->temp[3] = b;
194          p->bufs[BCJ2_STREAM_MAIN] = src + 1;
195          num++;
196          p->ip += (UInt32)num;
197          p->dest += num;
198          
199          prob = p->probs + (unsigned)(b == 0xE8 ? 2 + (unsigned)prev : (b == 0xE9 ? 1 : 0));
200          
201          _IF_BIT_0
202          {
203            _UPDATE_0
204            continue;
205          }
206          _UPDATE_1
207            
208        }
209      }
210    }
211
212    {
213      UInt32 val;
214      unsigned cj = (p->temp[3] == 0xE8) ? BCJ2_STREAM_CALL : BCJ2_STREAM_JUMP;
215      const Byte *cur = p->bufs[cj];
216      Byte *dest;
217      SizeT rem;
218      
219      if (cur == p->lims[cj])
220      {
221        p->state = cj;
222        break;
223      }
224      
225      val = GetBe32(cur);
226      p->bufs[cj] = cur + 4;
227
228      p->ip += 4;
229      val -= p->ip;
230      dest = p->dest;
231      rem = p->destLim - dest;
232      
233      if (rem < 4)
234      {
235        p->temp[0] = (Byte)val; if (rem > 0) dest[0] = (Byte)val; val >>= 8;
236        p->temp[1] = (Byte)val; if (rem > 1) dest[1] = (Byte)val; val >>= 8;
237        p->temp[2] = (Byte)val; if (rem > 2) dest[2] = (Byte)val; val >>= 8;
238        p->temp[3] = (Byte)val;
239        p->dest = dest + rem;
240        p->state = BCJ2_DEC_STATE_ORIG_0 + (unsigned)rem;
241        break;
242      }
243      
244      SetUi32(dest, val);
245      p->temp[3] = (Byte)(val >> 24);
246      p->dest = dest + 4;
247    }
248  }
249
250  if (p->range < kTopValue && p->bufs[BCJ2_STREAM_RC] != p->lims[BCJ2_STREAM_RC])
251  {
252    p->range <<= 8;
253    p->code = (p->code << 8) | *(p->bufs[BCJ2_STREAM_RC])++;
254  }
255
256  return SZ_OK;
257}