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_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
29static lzma_ret
30delta_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
51extern lzma_ret
52lzma_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
60extern lzma_ret
61lzma_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