delta_decoder.c revision 292588 
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
17static void
18decode_buffer(lzma_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
29static lzma_ret
30delta_decode(lzma_coder *coder, 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	assert(coder->next.code != NULL);
36
37	const size_t out_start = *out_pos;
38
39	const lzma_ret ret = coder->next.code(coder->next.coder, allocator,
40			in, in_pos, in_size, out, out_pos, out_size,
41			action);
42
43	decode_buffer(coder, out + out_start, *out_pos - out_start);
44
45	return ret;
46}
47
48
49extern lzma_ret
50lzma_delta_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
51		const lzma_filter_info *filters)
52{
53	next->code = &delta_decode;
54	return lzma_delta_coder_init(next, allocator, filters);
55}
56
57
58extern lzma_ret
59lzma_delta_props_decode(void **options, const lzma_allocator *allocator,
60		const uint8_t *props, size_t props_size)
61{
62	if (props_size != 1)
63		return LZMA_OPTIONS_ERROR;
64
65	lzma_options_delta *opt
66			= lzma_alloc(sizeof(lzma_options_delta), allocator);
67	if (opt == NULL)
68		return LZMA_MEM_ERROR;
69
70	opt->type = LZMA_DELTA_TYPE_BYTE;
71	opt->dist = props[0] + 1;
72
73	*options = opt;
74
75	return LZMA_OK;
76}
77