summaryrefslogtreecommitdiffstatshomepage
path: root/src/lib/lib7z/Bra86.c
blob: d5513ead5527c102aeb3c4c43f8affb1cb9cfb7a (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
/* Bra86.c -- Converter for x86 code (BCJ)
2008-10-04 : Igor Pavlov : Public domain */

#include "Bra.h"

#define Test86MSByte(b) ((b) == 0 || (b) == 0xFF)

const Byte kMaskToAllowedStatus[8] = {1, 1, 1, 0, 1, 0, 0, 0};
const Byte kMaskToBitNumber[8] = {0, 1, 2, 2, 3, 3, 3, 3};

SizeT x86_Convert(Byte *data, SizeT size, UInt32 ip, UInt32 *state, int encoding)
{
	SizeT bufferPos = 0, prevPosT;
	UInt32 prevMask = *state & 0x7;
	if (size < 5)
	return 0;
	ip += 5;
	prevPosT = (SizeT)0 - 1;

	for (;;)
	{
	Byte *p = data + bufferPos;
	Byte *limit = data + size - 4;
	for (; p < limit; p++)
		if ((*p & 0xFE) == 0xE8)
		break;
	bufferPos = (SizeT)(p - data);
	if (p >= limit)
		break;
	prevPosT = bufferPos - prevPosT;
	if (prevPosT > 3)
		prevMask = 0;
	else
	{
		prevMask = (prevMask << ((int)prevPosT - 1)) & 0x7;
		if (prevMask != 0)
		{
		Byte b = p[4 - kMaskToBitNumber[prevMask]];
		if (!kMaskToAllowedStatus[prevMask] || Test86MSByte(b))
		{
			prevPosT = bufferPos;
			prevMask = ((prevMask << 1) & 0x7) | 1;
			bufferPos++;
			continue;
		}
		}
	}
	prevPosT = bufferPos;

	if (Test86MSByte(p[4]))
	{
		UInt32 src = ((UInt32)p[4] << 24) | ((UInt32)p[3] << 16) | ((UInt32)p[2] << 8) | ((UInt32)p[1]);
		UInt32 dest;
		for (;;)
		{
		Byte b;
		int index;
		if (encoding)
			dest = (ip + (UInt32)bufferPos) + src;
		else
			dest = src - (ip + (UInt32)bufferPos);
		if (prevMask == 0)
			break;
		index = kMaskToBitNumber[prevMask] * 8;
		b = (Byte)(dest >> (24 - index));
		if (!Test86MSByte(b))
			break;
		src = dest ^ ((1 << (32 - index)) - 1);
		}
		p[4] = (Byte)(~(((dest >> 24) & 1) - 1));
		p[3] = (Byte)(dest >> 16);
		p[2] = (Byte)(dest >> 8);
		p[1] = (Byte)dest;
		bufferPos += 5;
	}
	else
	{
		prevMask = ((prevMask << 1) & 0x7) | 1;
		bufferPos++;
	}
	}
	prevPosT = bufferPos - prevPosT;
	*state = ((prevPosT > 3) ? 0 : ((prevMask << ((int)prevPosT - 1)) & 0x7));
	return bufferPos;
}