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