1// SPDX-License-Identifier: 0BSD
2
3///////////////////////////////////////////////////////////////////////////////
4//
5/// \file       delta_decoder.c
6/// \brief      Delta filter decoder
7//
8//  Author:     Lasse Collin
9//
10///////////////////////////////////////////////////////////////////////////////
11
12#include "delta_decoder.h"
13#include "delta_private.h"
14
15
16static void
17decode_buffer(lzma_delta_coder *coder, uint8_t *buffer, size_t size)
18{
19	const size_t distance = coder->distance;
20
21	for (size_t i = 0; i < size; ++i) {
22		buffer[i] += coder->history[(distance + coder->pos) & 0xFF];
23		coder->history[coder->pos-- & 0xFF] = buffer[i];
24	}
25}
26
27
28// For an unknown reason NVIDIA HPC Compiler needs this pragma
29// to produce working code.
30#ifdef __NVCOMPILER
31#	pragma routine novector
32#endif
33static lzma_ret
34delta_decode(void *coder_ptr, const lzma_allocator *allocator,
35		const uint8_t *restrict in, size_t *restrict in_pos,
36		size_t in_size, uint8_t *restrict out,
37		size_t *restrict out_pos, size_t out_size, lzma_action action)
38{
39	lzma_delta_coder *coder = coder_ptr;
40
41	assert(coder->next.code != NULL);
42
43	const size_t out_start = *out_pos;
44
45	const lzma_ret ret = coder->next.code(coder->next.coder, allocator,
46			in, in_pos, in_size, out, out_pos, out_size,
47			action);
48
49	// out might be NULL. In that case size == 0. Null pointer + 0 is
50	// undefined behavior so skip the call in that case as it would
51	// do nothing anyway.
52	const size_t size = *out_pos - out_start;
53	if (size > 0)
54		decode_buffer(coder, out + out_start, size);
55
56	return ret;
57}
58
59
60extern lzma_ret
61lzma_delta_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
62		const lzma_filter_info *filters)
63{
64	next->code = &delta_decode;
65	return lzma_delta_coder_init(next, allocator, filters);
66}
67
68
69extern lzma_ret
70lzma_delta_props_decode(void **options, const lzma_allocator *allocator,
71		const uint8_t *props, size_t props_size)
72{
73	if (props_size != 1)
74		return LZMA_OPTIONS_ERROR;
75
76	lzma_options_delta *opt
77			= lzma_alloc(sizeof(lzma_options_delta), allocator);
78	if (opt == NULL)
79		return LZMA_MEM_ERROR;
80
81	opt->type = LZMA_DELTA_TYPE_BYTE;
82	opt->dist = props[0] + 1U;
83
84	*options = opt;
85
86	return LZMA_OK;
87}
88