1 ///////////////////////////////////////////////////////////////////////////////
2 //
3 /// \file       delta_decoder.c
4 /// \brief      Delta filter decoder
5 //
6 //  Author:     Lasse Collin
7 //
8 //  This file has been put into the public domain.
9 //  You can do whatever you want with this file.
10 //
11 ///////////////////////////////////////////////////////////////////////////////
12 
13 #include "delta_decoder.h"
14 #include "delta_private.h"
15 
16 
17 static void
18 decode_buffer(lzma_delta_coder *coder, uint8_t *buffer, size_t size)
19 {
20 	const size_t distance = coder->distance;
21 
22 	for (size_t i = 0; i < size; ++i) {
23 		buffer[i] += coder->history[(distance + coder->pos) & 0xFF];
24 		coder->history[coder->pos-- & 0xFF] = buffer[i];
25 	}
26 }
27 
28 
29 static lzma_ret
30 delta_decode(void *coder_ptr, const lzma_allocator *allocator,
31 		const uint8_t *restrict in, size_t *restrict in_pos,
32 		size_t in_size, uint8_t *restrict out,
33 		size_t *restrict out_pos, size_t out_size, lzma_action action)
34 {
35 	lzma_delta_coder *coder = coder_ptr;
36 
37 	assert(coder->next.code != NULL);
38 
39 	const size_t out_start = *out_pos;
40 
41 	const lzma_ret ret = coder->next.code(coder->next.coder, allocator,
42 			in, in_pos, in_size, out, out_pos, out_size,
43 			action);
44 
45 	decode_buffer(coder, out + out_start, *out_pos - out_start);
46 
47 	return ret;
48 }
49 
50 
51 extern lzma_ret
52 lzma_delta_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
53 		const lzma_filter_info *filters)
54 {
55 	next->code = &delta_decode;
56 	return lzma_delta_coder_init(next, allocator, filters);
57 }
58 
59 
60 extern lzma_ret
61 lzma_delta_props_decode(void **options, const lzma_allocator *allocator,
62 		const uint8_t *props, size_t props_size)
63 {
64 	if (props_size != 1)
65 		return LZMA_OPTIONS_ERROR;
66 
67 	lzma_options_delta *opt
68 			= lzma_alloc(sizeof(lzma_options_delta), allocator);
69 	if (opt == NULL)
70 		return LZMA_MEM_ERROR;
71 
72 	opt->type = LZMA_DELTA_TYPE_BYTE;
73 	opt->dist = props[0] + 1;
74 
75 	*options = opt;
76 
77 	return LZMA_OK;
78 }
79