delta_common.c revision 292588 
1///////////////////////////////////////////////////////////////////////////////
2//
3/// \file       delta_common.c
4/// \brief      Common stuff for Delta encoder and 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_common.h"
14#include "delta_private.h"
15
16
17static void
18delta_coder_end(lzma_coder *coder, const lzma_allocator *allocator)
19{
20	lzma_next_end(&coder->next, allocator);
21	lzma_free(coder, allocator);
22	return;
23}
24
25
26extern lzma_ret
27lzma_delta_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
28		const lzma_filter_info *filters)
29{
30	// Allocate memory for the decoder if needed.
31	if (next->coder == NULL) {
32		next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
33		if (next->coder == NULL)
34			return LZMA_MEM_ERROR;
35
36		// End function is the same for encoder and decoder.
37		next->end = &delta_coder_end;
38		next->coder->next = LZMA_NEXT_CODER_INIT;
39	}
40
41	// Validate the options.
42	if (lzma_delta_coder_memusage(filters[0].options) == UINT64_MAX)
43		return LZMA_OPTIONS_ERROR;
44
45	// Set the delta distance.
46	const lzma_options_delta *opt = filters[0].options;
47	next->coder->distance = opt->dist;
48
49	// Initialize the rest of the variables.
50	next->coder->pos = 0;
51	memzero(next->coder->history, LZMA_DELTA_DIST_MAX);
52
53	// Initialize the next decoder in the chain, if any.
54	return lzma_next_filter_init(&next->coder->next,
55			allocator, filters + 1);
56}
57
58
59extern uint64_t
60lzma_delta_coder_memusage(const void *options)
61{
62	const lzma_options_delta *opt = options;
63
64	if (opt == NULL || opt->type != LZMA_DELTA_TYPE_BYTE
65			|| opt->dist < LZMA_DELTA_DIST_MIN
66			|| opt->dist > LZMA_DELTA_DIST_MAX)
67		return UINT64_MAX;
68
69	return sizeof(lzma_coder);
70}
71