1 ///////////////////////////////////////////////////////////////////////////////
3 /// \file block_header_decoder.c
4 /// \brief Decodes Block Header from .xz files
6 // Copyright (C) 2007 Lasse Collin
8 // This library is free software; you can redistribute it and/or
9 // modify it under the terms of the GNU Lesser General Public
10 // License as published by the Free Software Foundation; either
11 // version 2.1 of the License, or (at your option) any later version.
13 // This library is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 // Lesser General Public License for more details.
18 ///////////////////////////////////////////////////////////////////////////////
25 free_properties(lzma_block *block, lzma_allocator *allocator)
27 // Free allocated filter options. The last array member is not
28 // touched after the initialization in the beginning of
29 // lzma_block_header_decode(), so we don't need to touch that here.
30 for (size_t i = 0; i < LZMA_FILTERS_MAX; ++i) {
31 lzma_free(block->filters[i].options, allocator);
32 block->filters[i].id = LZMA_VLI_UNKNOWN;
33 block->filters[i].options = NULL;
40 extern LZMA_API(lzma_ret)
41 lzma_block_header_decode(lzma_block *block,
42 lzma_allocator *allocator, const uint8_t *in)
44 // NOTE: We consider the header to be corrupt not only when the
45 // CRC32 doesn't match, but also when variable-length integers
46 // are invalid or over 63 bits, or if the header is too small
47 // to contain the claimed information.
49 // Initialize the filter options array. This way the caller can
50 // safely free() the options even if an error occurs in this function.
51 for (size_t i = 0; i <= LZMA_FILTERS_MAX; ++i) {
52 block->filters[i].id = LZMA_VLI_UNKNOWN;
53 block->filters[i].options = NULL;
56 // Always zero for now.
59 // Validate Block Header Size and Check type. The caller must have
60 // already set these, so it is a programming error if this test fails.
61 if (lzma_block_header_size_decode(in[0]) != block->header_size
62 || (unsigned int)(block->check) > LZMA_CHECK_ID_MAX)
63 return LZMA_PROG_ERROR;
65 // Exclude the CRC32 field.
66 const size_t in_size = block->header_size - 4;
69 if (lzma_crc32(in, in_size, 0) != integer_read_32(in + in_size))
70 return LZMA_DATA_ERROR;
72 // Check for unsupported flags.
74 return LZMA_OPTIONS_ERROR;
76 // Start after the Block Header Size and Block Flags fields.
81 return_if_error(lzma_vli_decode(&block->compressed_size,
82 NULL, in, &in_pos, in_size));
84 // Validate Compressed Size. This checks that it isn't zero
85 // and that the total size of the Block is a valid VLI.
86 if (lzma_block_unpadded_size(block) == 0)
87 return LZMA_DATA_ERROR;
89 block->compressed_size = LZMA_VLI_UNKNOWN;
94 return_if_error(lzma_vli_decode(&block->uncompressed_size,
95 NULL, in, &in_pos, in_size));
97 block->uncompressed_size = LZMA_VLI_UNKNOWN;
100 const size_t filter_count = (in[1] & 3) + 1;
101 for (size_t i = 0; i < filter_count; ++i) {
102 const lzma_ret ret = lzma_filter_flags_decode(
103 &block->filters[i], allocator,
104 in, &in_pos, in_size);
105 if (ret != LZMA_OK) {
106 free_properties(block, allocator);
112 while (in_pos < in_size) {
113 if (in[in_pos++] != 0x00) {
114 free_properties(block, allocator);
116 // Possibly some new field present so use
117 // LZMA_OPTIONS_ERROR instead of LZMA_DATA_ERROR.
118 return LZMA_OPTIONS_ERROR;