/* Bcj2.c -- BCJ2 Decoder (Converter for x86 code)
2015-08-01 : Igor Pavlov : Public domain */
#include "Precomp.h"
#include "Bcj2.h"
#include "CpuArch.h"
#define CProb UInt16
#define kTopValue ((UInt32)1 << 24)
#define kNumModelBits 11
#define kBitModelTotal (1 << kNumModelBits)
#define kNumMoveBits 5
#define _IF_BIT_0 ttt = *prob; bound = (p->range >> kNumModelBits) * ttt; if (p->code < bound)
#define _UPDATE_0 p->range = bound; *prob = (CProb)(ttt + ((kBitModelTotal - ttt) >> kNumMoveBits));
#define _UPDATE_1 p->range -= bound; p->code -= bound; *prob = (CProb)(ttt - (ttt >> kNumMoveBits));
void Bcj2Dec_Init(CBcj2Dec *p)
{
unsigned i;
p->state = BCJ2_DEC_STATE_OK;
p->ip = 0;
p->temp[3] = 0;
p->range = 0;
p->code = 0;
for (i = 0; i < sizeof(p->probs) / sizeof(p->probs[0]); i++)
p->probs[i] = kBitModelTotal >> 1;
}
SRes Bcj2Dec_Decode(CBcj2Dec *p)
{
if (p->range <= 5)
{
p->state = BCJ2_DEC_STATE_OK;
for (; p->range != 5; p->range++)
{
if (p->range == 1 && p->code != 0)
return SZ_ERROR_DATA;
if (p->bufs[BCJ2_STREAM_RC] == p->lims[BCJ2_STREAM_RC])
{
p->state = BCJ2_STREAM_RC;
return SZ_OK;
}
p->code = (p->code << 8) | *(p->bufs[BCJ2_STREAM_RC])++;
}
if (p->code == 0xFFFFFFFF)
return SZ_ERROR_DATA;
p->range = 0xFFFFFFFF;
}
else if (p->state >= BCJ2_DEC_STATE_ORIG_0)
{
while (p->state <= BCJ2_DEC_STATE_ORIG_3)
{
Byte *dest = p->dest;
if (dest == p->destLim)
return SZ_OK;
*dest = p->temp[p->state++ - BCJ2_DEC_STATE_ORIG_0];
p->dest = dest + 1;
}
}
/*
if (BCJ2_IS_32BIT_STREAM(p->state))
{
const Byte *cur = p->bufs[p->state];
if (cur == p->lims[p->state])
return SZ_OK;
p->bufs[p->state] = cur + 4;
{
UInt32 val;
Byte *dest;
SizeT rem;
p->ip += 4;
val = GetBe32(cur) - p->ip;
dest = p->dest;
rem = p->destLim - dest;
if (rem < 4)
{
SizeT i;
SetUi32(p->temp, val);
for (i = 0; i < rem; i++)
dest[i] = p->temp[i];
p->dest = dest + rem;
p->state = BCJ2_DEC_STATE_ORIG_0 + (unsigned)rem;
return SZ_OK;
}
SetUi32(dest, val);
p->temp[3] = (Byte)(val >> 24);
p->dest = dest + 4;
p->state = BCJ2_DEC_STATE_OK;
}
}
*/
for (;;)
{
if (BCJ2_IS_32BIT_STREAM(p->state))
p->state = BCJ2_DEC_STATE_OK;
else
{
if (p->range < kTopValue)
{
if (p->bufs[BCJ2_STREAM_RC] == p->lims[BCJ2_STREAM_RC])
{
p->state = BCJ2_STREAM_RC;
return SZ_OK;
}
p->range <<= 8;
p->code = (p->code << 8) | *(p->bufs[BCJ2_STREAM_RC])++;
}
{
const Byte *src = p->bufs[BCJ2_STREAM_MAIN];
const Byte *srcLim;
Byte *dest;
SizeT num = p->lims[BCJ2_STREAM_MAIN] - src;
if (num == 0)
{
p->state = BCJ2_STREAM_MAIN;
return SZ_OK;
}
dest = p->dest;
if (num > (SizeT)(p->destLim - dest))
{
num = p->destLim - dest;
if (num == 0)
{
p->state = BCJ2_DEC_STATE_ORIG;
return SZ_OK;
}
}
srcLim = src + num;
if (p->temp[3] == 0x0F && (src[0] & 0xF0) == 0x80)
*dest = src[0];
else for (;;)
{
Byte b = *src;
*dest = b;
if (b != 0x0F)
{
if ((b & 0xFE) == 0xE8)
break;
dest++;
if (++src != srcLim)
continue;
break;
}
dest++;
if (++src == srcLim)
break;
if ((*src & 0xF0) != 0x80)
continue;
*dest = *src;
break;
}
num = src - p->bufs[BCJ2_STREAM_MAIN];
if (src == srcLim)
{
p->temp[3] = src[-1];
p->bufs[BCJ2_STREAM_MAIN] = src;
p->ip += (UInt32)num;
p->dest += num;
p->state =
p->bufs[BCJ2_STREAM_MAIN] ==
p->lims[BCJ2_STREAM_MAIN] ?
(unsigned)BCJ2_STREAM_MAIN :
(unsigned)BCJ2_DEC_STATE_ORIG;
return SZ_OK;
}
{
UInt32 bound, ttt;
CProb *prob;
Byte b = src[0];
Byte prev = (Byte)(num == 0 ? p->temp[3] : src[-1]);
p->temp[3] = b;
p->bufs[BCJ2_STREAM_MAIN] = src + 1;
num++;
p->ip += (UInt32)num;
p->dest += num;
prob = p->probs + (unsigned)(b == 0xE8 ? 2 + (unsigned)prev : (b == 0xE9 ? 1 : 0));
_IF_BIT_0
{
_UPDATE_0
continue;
}
_UPDATE_1
}
}
}
{
UInt32 val;
unsigned cj = (p->temp[3] == 0xE8) ? BCJ2_STREAM_CALL : BCJ2_STREAM_JUMP;
const Byte *cur = p->bufs[cj];
Byte *dest;
SizeT rem;
if (cur == p->lims[cj])
{
p->state = cj;
break;
}
val = GetBe32(cur);
p->bufs[cj] = cur + 4;
p->ip += 4;
val -= p->ip;
dest = p->dest;
rem = p->destLim - dest;
if (rem < 4)
{
SizeT i;
SetUi32(p->temp, val);
for (i = 0; i < rem; i++)
dest[i] = p->temp[i];
p->dest = dest + rem;
p->state = BCJ2_DEC_STATE_ORIG_0 + (unsigned)rem;
break;
}
SetUi32(dest, val);
p->temp[3] = (Byte)(val >> 24);
p->dest = dest + 4;
}
}
if (p->range < kTopValue && p->bufs[BCJ2_STREAM_RC] != p->lims[BCJ2_STREAM_RC])
{
p->range <<= 8;
p->code = (p->code << 8) | *(p->bufs[BCJ2_STREAM_RC])++;
}
return SZ_OK;
}