block_header_encoder.c revision 292588 
1///////////////////////////////////////////////////////////////////////////////
2//
3/// \file       block_header_encoder.c
4/// \brief      Encodes Block Header for .xz files
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 "common.h"
14#include "check.h"
15
16
17extern LZMA_API(lzma_ret)
18lzma_block_header_size(lzma_block *block)
19{
20	if (block->version > 1)
21		return LZMA_OPTIONS_ERROR;
22
23	// Block Header Size + Block Flags + CRC32.
24	uint32_t size = 1 + 1 + 4;
25
26	// Compressed Size
27	if (block->compressed_size != LZMA_VLI_UNKNOWN) {
28		const uint32_t add = lzma_vli_size(block->compressed_size);
29		if (add == 0 || block->compressed_size == 0)
30			return LZMA_PROG_ERROR;
31
32		size += add;
33	}
34
35	// Uncompressed Size
36	if (block->uncompressed_size != LZMA_VLI_UNKNOWN) {
37		const uint32_t add = lzma_vli_size(block->uncompressed_size);
38		if (add == 0)
39			return LZMA_PROG_ERROR;
40
41		size += add;
42	}
43
44	// List of Filter Flags
45	if (block->filters == NULL || block->filters[0].id == LZMA_VLI_UNKNOWN)
46		return LZMA_PROG_ERROR;
47
48	for (size_t i = 0; block->filters[i].id != LZMA_VLI_UNKNOWN; ++i) {
49		// Don't allow too many filters.
50		if (i == LZMA_FILTERS_MAX)
51			return LZMA_PROG_ERROR;
52
53		uint32_t add;
54		return_if_error(lzma_filter_flags_size(&add,
55				block->filters + i));
56
57		size += add;
58	}
59
60	// Pad to a multiple of four bytes.
61	block->header_size = (size + 3) & ~UINT32_C(3);
62
63	// NOTE: We don't verify that the encoded size of the Block stays
64	// within limits. This is because it is possible that we are called
65	// with exaggerated Compressed Size (e.g. LZMA_VLI_MAX) to reserve
66	// space for Block Header, and later called again with lower,
67	// real values.
68
69	return LZMA_OK;
70}
71
72
73extern LZMA_API(lzma_ret)
74lzma_block_header_encode(const lzma_block *block, uint8_t *out)
75{
76	// Validate everything but filters.
77	if (lzma_block_unpadded_size(block) == 0
78			|| !lzma_vli_is_valid(block->uncompressed_size))
79		return LZMA_PROG_ERROR;
80
81	// Indicate the size of the buffer _excluding_ the CRC32 field.
82	const size_t out_size = block->header_size - 4;
83
84	// Store the Block Header Size.
85	out[0] = out_size / 4;
86
87	// We write Block Flags in pieces.
88	out[1] = 0x00;
89	size_t out_pos = 2;
90
91	// Compressed Size
92	if (block->compressed_size != LZMA_VLI_UNKNOWN) {
93		return_if_error(lzma_vli_encode(block->compressed_size, NULL,
94				out, &out_pos, out_size));
95
96		out[1] |= 0x40;
97	}
98
99	// Uncompressed Size
100	if (block->uncompressed_size != LZMA_VLI_UNKNOWN) {
101		return_if_error(lzma_vli_encode(block->uncompressed_size, NULL,
102				out, &out_pos, out_size));
103
104		out[1] |= 0x80;
105	}
106
107	// Filter Flags
108	if (block->filters == NULL || block->filters[0].id == LZMA_VLI_UNKNOWN)
109		return LZMA_PROG_ERROR;
110
111	size_t filter_count = 0;
112	do {
113		// There can be a maximum of four filters.
114		if (filter_count == LZMA_FILTERS_MAX)
115			return LZMA_PROG_ERROR;
116
117		return_if_error(lzma_filter_flags_encode(
118				block->filters + filter_count,
119				out, &out_pos, out_size));
120
121	} while (block->filters[++filter_count].id != LZMA_VLI_UNKNOWN);
122
123	out[1] |= filter_count - 1;
124
125	// Padding
126	memzero(out + out_pos, out_size - out_pos);
127
128	// CRC32
129	unaligned_write32le(out + out_size, lzma_crc32(out, out_size, 0));
130
131	return LZMA_OK;
132}
133