armthumb.c revision 292588 
1///////////////////////////////////////////////////////////////////////////////
2//
3/// \file       armthumb.c
4/// \brief      Filter for ARM-Thumb binaries
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
17static size_t
18armthumb_code(lzma_simple *simple lzma_attribute((__unused__)),
19		uint32_t now_pos, bool is_encoder,
20		uint8_t *buffer, size_t size)
21{
22	size_t i;
23	for (i = 0; i + 4 <= size; i += 2) {
24		if ((buffer[i + 1] & 0xF8) == 0xF0
25				&& (buffer[i + 3] & 0xF8) == 0xF8) {
26			uint32_t src = ((buffer[i + 1] & 0x7) << 19)
27					| (buffer[i + 0] << 11)
28					| ((buffer[i + 3] & 0x7) << 8)
29					| (buffer[i + 2]);
30
31			src <<= 1;
32
33			uint32_t dest;
34			if (is_encoder)
35				dest = now_pos + (uint32_t)(i) + 4 + src;
36			else
37				dest = src - (now_pos + (uint32_t)(i) + 4);
38
39			dest >>= 1;
40			buffer[i + 1] = 0xF0 | ((dest >> 19) & 0x7);
41			buffer[i + 0] = (dest >> 11);
42			buffer[i + 3] = 0xF8 | ((dest >> 8) & 0x7);
43			buffer[i + 2] = (dest);
44			i += 2;
45		}
46	}
47
48	return i;
49}
50
51
52static lzma_ret
53armthumb_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
54		const lzma_filter_info *filters, bool is_encoder)
55{
56	return lzma_simple_coder_init(next, allocator, filters,
57			&armthumb_code, 0, 4, 2, is_encoder);
58}
59
60
61extern lzma_ret
62lzma_simple_armthumb_encoder_init(lzma_next_coder *next,
63		const lzma_allocator *allocator,
64		const lzma_filter_info *filters)
65{
66	return armthumb_coder_init(next, allocator, filters, true);
67}
68
69
70extern lzma_ret
71lzma_simple_armthumb_decoder_init(lzma_next_coder *next,
72		const lzma_allocator *allocator,
73		const lzma_filter_info *filters)
74{
75	return armthumb_coder_init(next, allocator, filters, false);
76}
77