2012-05-29 13:31:11 +00:00
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/* BranchX86.c */
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#include "BranchX86.h"
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/*
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static int inline Test86MSByte(Byte b)
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{
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return (b == 0 || b == 0xFF);
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}
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*/
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#define Test86MSByte(b) ((b) == 0 || (b) == 0xFF)
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const int kMaskToAllowedStatus[8] = {1, 1, 1, 0, 1, 0, 0, 0};
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const Byte kMaskToBitNumber[8] = {0, 1, 2, 2, 3, 3, 3, 3};
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/*
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void x86_Convert_Init(UInt32 *prevMask, UInt32 *prevPos)
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{
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*prevMask = 0;
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*prevPos = (UInt32)(-5);
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}
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*/
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UInt32 x86_Convert(Byte *buffer, UInt32 endPos, UInt32 nowPos,
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UInt32 *prevMask, UInt32 *prevPos, int encoding)
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{
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UInt32 bufferPos = 0;
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UInt32 limit;
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if (endPos < 5)
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return 0;
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if (nowPos - *prevPos > 5)
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*prevPos = nowPos - 5;
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limit = endPos - 5;
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while(bufferPos <= limit)
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{
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Byte b = buffer[bufferPos];
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UInt32 offset;
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if (b != 0xE8 && b != 0xE9)
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{
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bufferPos++;
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continue;
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}
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offset = (nowPos + bufferPos - *prevPos);
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*prevPos = (nowPos + bufferPos);
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if (offset > 5)
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*prevMask = 0;
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else
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{
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UInt32 i;
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for (i = 0; i < offset; i++)
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{
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*prevMask &= 0x77;
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*prevMask <<= 1;
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}
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}
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b = buffer[bufferPos + 4];
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if (Test86MSByte(b) && kMaskToAllowedStatus[(*prevMask >> 1) & 0x7] &&
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(*prevMask >> 1) < 0x10)
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{
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UInt32 src =
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((UInt32)(b) << 24) |
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((UInt32)(buffer[bufferPos + 3]) << 16) |
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((UInt32)(buffer[bufferPos + 2]) << 8) |
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(buffer[bufferPos + 1]);
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UInt32 dest;
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for(;;)
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{
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UInt32 index;
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if (encoding)
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dest = (nowPos + bufferPos + 5) + src;
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else
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dest = src - (nowPos + bufferPos + 5);
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if (*prevMask == 0)
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break;
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index = kMaskToBitNumber[*prevMask >> 1];
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b = (Byte)(dest >> (24 - index * 8));
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if (!Test86MSByte(b))
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break;
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src = dest ^ ((1 << (32 - index * 8)) - 1);
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}
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buffer[bufferPos + 4] = (Byte)(~(((dest >> 24) & 1) - 1));
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buffer[bufferPos + 3] = (Byte)(dest >> 16);
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buffer[bufferPos + 2] = (Byte)(dest >> 8);
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buffer[bufferPos + 1] = (Byte)dest;
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bufferPos += 5;
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*prevMask = 0;
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}
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else
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{
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bufferPos++;
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*prevMask |= 1;
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if (Test86MSByte(b))
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*prevMask |= 0x10;
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}
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}
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return bufferPos;
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}
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