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290 lines (276 loc) · 7.88 KB
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/* Bcj2.c -- BCJ2 Decoder (Converter for x86 code)
2023-03-01 : Igor Pavlov : Public domain */
#include "Precomp.h"
#include "Bcj2.h"
#include "CpuArch.h"
#define kTopValue ((UInt32)1 << 24)
#define kNumBitModelTotalBits 11
#define kBitModelTotal (1 << kNumBitModelTotalBits)
#define kNumMoveBits 5
// UInt32 bcj2_stats[256 + 2][2];
void Bcj2Dec_Init(CBcj2Dec *p)
{
unsigned i;
p->state = BCJ2_STREAM_RC; // BCJ2_DEC_STATE_OK;
p->ip = 0;
p->temp = 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)
{
UInt32 v = p->temp;
// const Byte *src;
if (p->range <= 5)
{
UInt32 code = p->code;
p->state = BCJ2_DEC_STATE_ERROR; /* for case if we return SZ_ERROR_DATA; */
for (; p->range != 5; p->range++)
{
if (p->range == 1 && 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;
}
code = (code << 8) | *(p->bufs[BCJ2_STREAM_RC])++;
p->code = code;
}
if (code == 0xffffffff)
return SZ_ERROR_DATA;
p->range = 0xffffffff;
}
// else
{
unsigned state = p->state;
// we check BCJ2_IS_32BIT_STREAM() here instead of check in the main loop
if (BCJ2_IS_32BIT_STREAM(state))
{
const Byte *cur = p->bufs[state];
if (cur == p->lims[state])
return SZ_OK;
p->bufs[state] = cur + 4;
{
const UInt32 ip = p->ip + 4;
v = GetBe32a(cur) - ip;
p->ip = ip;
}
state = BCJ2_DEC_STATE_ORIG_0;
}
if ((unsigned)(state - BCJ2_DEC_STATE_ORIG_0) < 4)
{
Byte *dest = p->dest;
for (;;)
{
if (dest == p->destLim)
{
p->state = state;
p->temp = v;
return SZ_OK;
}
*dest++ = (Byte)v;
p->dest = dest;
if (++state == BCJ2_DEC_STATE_ORIG_3 + 1)
break;
v >>= 8;
}
}
}
// src = p->bufs[BCJ2_STREAM_MAIN];
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;
p->temp = v;
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 = p->dest;
{
const SizeT rem = (SizeT)(p->lims[BCJ2_STREAM_MAIN] - src);
SizeT num = (SizeT)(p->destLim - dest);
if (num >= rem)
num = rem;
#define NUM_ITERS 4
#if (NUM_ITERS & (NUM_ITERS - 1)) == 0
num &= ~((SizeT)NUM_ITERS - 1); // if (NUM_ITERS == (1 << x))
#else
num -= num % NUM_ITERS; // if (NUM_ITERS != (1 << x))
#endif
srcLim = src + num;
}
#define NUM_SHIFT_BITS 24
#define ONE_ITER(indx) { \
const unsigned b = src[indx]; \
*dest++ = (Byte)b; \
v = (v << NUM_SHIFT_BITS) | b; \
if (((b + (0x100 - 0xe8)) & 0xfe) == 0) break; \
if (((v - (((UInt32)0x0f << (NUM_SHIFT_BITS)) + 0x80)) & \
((((UInt32)1 << (4 + NUM_SHIFT_BITS)) - 0x1) << 4)) == 0) break; \
/* ++dest */; /* v = b; */ }
if (src != srcLim)
for (;;)
{
/* The dependency chain of 2-cycle for (v) calculation is not big problem here.
But we can remove dependency chain with v = b in the end of loop. */
ONE_ITER(0)
#if (NUM_ITERS > 1)
ONE_ITER(1)
#if (NUM_ITERS > 2)
ONE_ITER(2)
#if (NUM_ITERS > 3)
ONE_ITER(3)
#if (NUM_ITERS > 4)
ONE_ITER(4)
#if (NUM_ITERS > 5)
ONE_ITER(5)
#if (NUM_ITERS > 6)
ONE_ITER(6)
#if (NUM_ITERS > 7)
ONE_ITER(7)
#endif
#endif
#endif
#endif
#endif
#endif
#endif
src += NUM_ITERS;
if (src == srcLim)
break;
}
if (src == srcLim)
#if (NUM_ITERS > 1)
for (;;)
#endif
{
#if (NUM_ITERS > 1)
if (src == p->lims[BCJ2_STREAM_MAIN] || dest == p->destLim)
#endif
{
const SizeT num = (SizeT)(src - p->bufs[BCJ2_STREAM_MAIN]);
p->bufs[BCJ2_STREAM_MAIN] = src;
p->dest = dest;
p->ip += (UInt32)num;
/* state BCJ2_STREAM_MAIN has more priority than BCJ2_STATE_ORIG */
p->state =
src == p->lims[BCJ2_STREAM_MAIN] ?
(unsigned)BCJ2_STREAM_MAIN :
(unsigned)BCJ2_DEC_STATE_ORIG;
p->temp = v;
return SZ_OK;
}
#if (NUM_ITERS > 1)
ONE_ITER(0)
src++;
#endif
}
{
const SizeT num = (SizeT)(dest - p->dest);
p->dest = dest; // p->dest += num;
p->bufs[BCJ2_STREAM_MAIN] += num; // = src;
p->ip += (UInt32)num;
}
{
UInt32 bound, ttt;
CBcj2Prob *prob; // unsigned index;
/*
prob = p->probs + (unsigned)((Byte)v == 0xe8 ?
2 + (Byte)(v >> 8) :
((v >> 5) & 1)); // ((Byte)v < 0xe8 ? 0 : 1));
*/
{
const unsigned c = ((v + 0x17) >> 6) & 1;
prob = p->probs + (unsigned)
(((0 - c) & (Byte)(v >> NUM_SHIFT_BITS)) + c + ((v >> 5) & 1));
// (Byte)
// 8x->0 : e9->1 : xxe8->xx+2
// 8x->0x100 : e9->0x101 : xxe8->xx
// (((0x100 - (e & ~v)) & (0x100 | (v >> 8))) + (e & v));
// (((0x101 + (~e | v)) & (0x100 | (v >> 8))) + (e & v));
}
ttt = *prob;
bound = (p->range >> kNumBitModelTotalBits) * ttt;
if (p->code < bound)
{
// bcj2_stats[prob - p->probs][0]++;
p->range = bound;
*prob = (CBcj2Prob)(ttt + ((kBitModelTotal - ttt) >> kNumMoveBits));
continue;
}
{
// bcj2_stats[prob - p->probs][1]++;
p->range -= bound;
p->code -= bound;
*prob = (CBcj2Prob)(ttt - (ttt >> kNumMoveBits));
}
}
}
}
{
/* (v == 0xe8 ? 0 : 1) uses setcc instruction with additional zero register usage in x64 MSVC. */
// const unsigned cj = ((Byte)v == 0xe8) ? BCJ2_STREAM_CALL : BCJ2_STREAM_JUMP;
const unsigned cj = (((v + 0x57) >> 6) & 1) + BCJ2_STREAM_CALL;
const Byte *cur = p->bufs[cj];
Byte *dest;
SizeT rem;
if (cur == p->lims[cj])
{
p->state = cj;
break;
}
v = GetBe32a(cur);
p->bufs[cj] = cur + 4;
{
const UInt32 ip = p->ip + 4;
v -= ip;
p->ip = ip;
}
dest = p->dest;
rem = (SizeT)(p->destLim - dest);
if (rem < 4)
{
if ((unsigned)rem > 0) { dest[0] = (Byte)v; v >>= 8;
if ((unsigned)rem > 1) { dest[1] = (Byte)v; v >>= 8;
if ((unsigned)rem > 2) { dest[2] = (Byte)v; v >>= 8; }}}
p->temp = v;
p->dest = dest + rem;
p->state = BCJ2_DEC_STATE_ORIG_0 + (unsigned)rem;
break;
}
SetUi32(dest, v)
v >>= 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;
}
#undef NUM_ITERS
#undef ONE_ITER
#undef NUM_SHIFT_BITS
#undef kTopValue
#undef kNumBitModelTotalBits
#undef kBitModelTotal
#undef kNumMoveBits