x86.c revision 292588 
1///////////////////////////////////////////////////////////////////////////////
2//
3/// \file       x86.c
4/// \brief      Filter for x86 binaries (BCJ filter)
5///
6//  Authors:    Igor Pavlov
7//              Lasse Collin
8//
9//  This file has been put into the public domain.
10//  You can do whatever you want with this file.
11//
12///////////////////////////////////////////////////////////////////////////////
13
14#include "simple_private.h"
15
16
17#define Test86MSByte(b) ((b) == 0 || (b) == 0xFF)
18
19
20struct lzma_simple_s {
21	uint32_t prev_mask;
22	uint32_t prev_pos;
23};
24
25
26static size_t
27x86_code(lzma_simple *simple, uint32_t now_pos, bool is_encoder,
28		uint8_t *buffer, size_t size)
29{
30	static const bool MASK_TO_ALLOWED_STATUS[8]
31		= { true, true, true, false, true, false, false, false };
32
33	static const uint32_t MASK_TO_BIT_NUMBER[8]
34			= { 0, 1, 2, 2, 3, 3, 3, 3 };
35
36	uint32_t prev_mask = simple->prev_mask;
37	uint32_t prev_pos = simple->prev_pos;
38
39	if (size < 5)
40		return 0;
41
42	if (now_pos - prev_pos > 5)
43		prev_pos = now_pos - 5;
44
45	const size_t limit = size - 5;
46	size_t buffer_pos = 0;
47
48	while (buffer_pos <= limit) {
49		uint8_t b = buffer[buffer_pos];
50		if (b != 0xE8 && b != 0xE9) {
51			++buffer_pos;
52			continue;
53		}
54
55		const uint32_t offset = now_pos + (uint32_t)(buffer_pos)
56				- prev_pos;
57		prev_pos = now_pos + (uint32_t)(buffer_pos);
58
59		if (offset > 5) {
60			prev_mask = 0;
61		} else {
62			for (uint32_t i = 0; i < offset; ++i) {
63				prev_mask &= 0x77;
64				prev_mask <<= 1;
65			}
66		}
67
68		b = buffer[buffer_pos + 4];
69
70		if (Test86MSByte(b)
71			&& MASK_TO_ALLOWED_STATUS[(prev_mask >> 1) & 0x7]
72				&& (prev_mask >> 1) < 0x10) {
73
74			uint32_t src = ((uint32_t)(b) << 24)
75				| ((uint32_t)(buffer[buffer_pos + 3]) << 16)
76				| ((uint32_t)(buffer[buffer_pos + 2]) << 8)
77				| (buffer[buffer_pos + 1]);
78
79			uint32_t dest;
80			while (true) {
81				if (is_encoder)
82					dest = src + (now_pos + (uint32_t)(
83							buffer_pos) + 5);
84				else
85					dest = src - (now_pos + (uint32_t)(
86							buffer_pos) + 5);
87
88				if (prev_mask == 0)
89					break;
90
91				const uint32_t i = MASK_TO_BIT_NUMBER[
92						prev_mask >> 1];
93
94				b = (uint8_t)(dest >> (24 - i * 8));
95
96				if (!Test86MSByte(b))
97					break;
98
99				src = dest ^ ((1 << (32 - i * 8)) - 1);
100			}
101
102			buffer[buffer_pos + 4]
103					= (uint8_t)(~(((dest >> 24) & 1) - 1));
104			buffer[buffer_pos + 3] = (uint8_t)(dest >> 16);
105			buffer[buffer_pos + 2] = (uint8_t)(dest >> 8);
106			buffer[buffer_pos + 1] = (uint8_t)(dest);
107			buffer_pos += 5;
108			prev_mask = 0;
109
110		} else {
111			++buffer_pos;
112			prev_mask |= 1;
113			if (Test86MSByte(b))
114				prev_mask |= 0x10;
115		}
116	}
117
118	simple->prev_mask = prev_mask;
119	simple->prev_pos = prev_pos;
120
121	return buffer_pos;
122}
123
124
125static lzma_ret
126x86_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
127		const lzma_filter_info *filters, bool is_encoder)
128{
129	const lzma_ret ret = lzma_simple_coder_init(next, allocator, filters,
130			&x86_code, sizeof(lzma_simple), 5, 1, is_encoder);
131
132	if (ret == LZMA_OK) {
133		next->coder->simple->prev_mask = 0;
134		next->coder->simple->prev_pos = (uint32_t)(-5);
135	}
136
137	return ret;
138}
139
140
141extern lzma_ret
142lzma_simple_x86_encoder_init(lzma_next_coder *next,
143		const lzma_allocator *allocator,
144		const lzma_filter_info *filters)
145{
146	return x86_coder_init(next, allocator, filters, true);
147}
148
149
150extern lzma_ret
151lzma_simple_x86_decoder_init(lzma_next_coder *next,
152		const lzma_allocator *allocator,
153		const lzma_filter_info *filters)
154{
155	return x86_coder_init(next, allocator, filters, false);
156}
157