1/* Bcj2.c -- BCJ2 Decoder (Converter for x86 code)
  22015-08-01 : 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[p->state++ - BCJ2_DEC_STATE_ORIG_0];
 65      p->dest = dest + 1;
 66    }
 67  }
 68
 69  /*
 70  if (BCJ2_IS_32BIT_STREAM(p->state))
 71  {
 72    const Byte *cur = p->bufs[p->state];
 73    if (cur == p->lims[p->state])
 74      return SZ_OK;
 75    p->bufs[p->state] = cur + 4;
 76    
 77    {
 78      UInt32 val;
 79      Byte *dest;
 80      SizeT rem;
 81      
 82      p->ip += 4;
 83      val = GetBe32(cur) - p->ip;
 84      dest = p->dest;
 85      rem = p->destLim - dest;
 86      if (rem < 4)
 87      {
 88        SizeT i;
 89        SetUi32(p->temp, val);
 90        for (i = 0; i < rem; i++)
 91          dest[i] = p->temp[i];
 92        p->dest = dest + rem;
 93        p->state = BCJ2_DEC_STATE_ORIG_0 + (unsigned)rem;
 94        return SZ_OK;
 95      }
 96      SetUi32(dest, val);
 97      p->temp[3] = (Byte)(val >> 24);
 98      p->dest = dest + 4;
 99      p->state = BCJ2_DEC_STATE_OK;
100    }
101  }
102  */
103
104  for (;;)
105  {
106    if (BCJ2_IS_32BIT_STREAM(p->state))
107      p->state = BCJ2_DEC_STATE_OK;
108    else
109    {
110      if (p->range < kTopValue)
111      {
112        if (p->bufs[BCJ2_STREAM_RC] == p->lims[BCJ2_STREAM_RC])
113        {
114          p->state = BCJ2_STREAM_RC;
115          return SZ_OK;
116        }
117        p->range <<= 8;
118        p->code = (p->code << 8) | *(p->bufs[BCJ2_STREAM_RC])++;
119      }
120
121      {
122        const Byte *src = p->bufs[BCJ2_STREAM_MAIN];
123        const Byte *srcLim;
124        Byte *dest;
125        SizeT num = p->lims[BCJ2_STREAM_MAIN] - src;
126        
127        if (num == 0)
128        {
129          p->state = BCJ2_STREAM_MAIN;
130          return SZ_OK;
131        }
132        
133        dest = p->dest;
134        if (num > (SizeT)(p->destLim - dest))
135        {
136          num = p->destLim - dest;
137          if (num == 0)
138          {
139            p->state = BCJ2_DEC_STATE_ORIG;
140            return SZ_OK;
141          }
142        }
143       
144        srcLim = src + num;
145
146        if (p->temp[3] == 0x0F && (src[0] & 0xF0) == 0x80)
147          *dest = src[0];
148        else for (;;)
149        {
150          Byte b = *src;
151          *dest = b;
152          if (b != 0x0F)
153          {
154            if ((b & 0xFE) == 0xE8)
155              break;
156            dest++;
157            if (++src != srcLim)
158              continue;
159            break;
160          }
161          dest++;
162          if (++src == srcLim)
163            break;
164          if ((*src & 0xF0) != 0x80)
165            continue;
166          *dest = *src;
167          break;
168        }
169        
170        num = src - p->bufs[BCJ2_STREAM_MAIN];
171        
172        if (src == srcLim)
173        {
174          p->temp[3] = src[-1];
175          p->bufs[BCJ2_STREAM_MAIN] = src;
176          p->ip += (UInt32)num;
177          p->dest += num;
178          p->state =
179            p->bufs[BCJ2_STREAM_MAIN] ==
180            p->lims[BCJ2_STREAM_MAIN] ?
181              (unsigned)BCJ2_STREAM_MAIN :
182              (unsigned)BCJ2_DEC_STATE_ORIG;
183          return SZ_OK;
184        }
185        
186        {
187          UInt32 bound, ttt;
188          CProb *prob;
189          Byte b = src[0];
190          Byte prev = (Byte)(num == 0 ? p->temp[3] : src[-1]);
191          
192          p->temp[3] = b;
193          p->bufs[BCJ2_STREAM_MAIN] = src + 1;
194          num++;
195          p->ip += (UInt32)num;
196          p->dest += num;
197          
198          prob = p->probs + (unsigned)(b == 0xE8 ? 2 + (unsigned)prev : (b == 0xE9 ? 1 : 0));
199          
200          _IF_BIT_0
201          {
202            _UPDATE_0
203            continue;
204          }
205          _UPDATE_1
206            
207        }
208      }
209    }
210
211    {
212      UInt32 val;
213      unsigned cj = (p->temp[3] == 0xE8) ? BCJ2_STREAM_CALL : BCJ2_STREAM_JUMP;
214      const Byte *cur = p->bufs[cj];
215      Byte *dest;
216      SizeT rem;
217      
218      if (cur == p->lims[cj])
219      {
220        p->state = cj;
221        break;
222      }
223      
224      val = GetBe32(cur);
225      p->bufs[cj] = cur + 4;
226
227      p->ip += 4;
228      val -= p->ip;
229      dest = p->dest;
230      rem = p->destLim - dest;
231      
232      if (rem < 4)
233      {
234        SizeT i;
235        SetUi32(p->temp, val);
236        for (i = 0; i < rem; i++)
237          dest[i] = p->temp[i];
238        p->dest = dest + rem;
239        p->state = BCJ2_DEC_STATE_ORIG_0 + (unsigned)rem;
240        break;
241      }
242      
243      SetUi32(dest, val);
244      p->temp[3] = (Byte)(val >> 24);
245      p->dest = dest + 4;
246    }
247  }
248
249  if (p->range < kTopValue && p->bufs[BCJ2_STREAM_RC] != p->lims[BCJ2_STREAM_RC])
250  {
251    p->range <<= 8;
252    p->code = (p->code << 8) | *(p->bufs[BCJ2_STREAM_RC])++;
253  }
254
255  return SZ_OK;
256}