1 ///////////////////////////////////////////////////////////////////////////////
3 /// \file block_header_decoder.c
4 /// \brief Decodes Block Header from .lzma 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_options_block *options, 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_BLOCK_FILTERS_MAX; ++i) {
31 lzma_free(options->filters[i].options, allocator);
32 options->filters[i].id = LZMA_VLI_VALUE_UNKNOWN;
33 options->filters[i].options = NULL;
40 extern LZMA_API lzma_ret
41 lzma_block_header_decode(lzma_options_block *options,
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 not 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_BLOCK_FILTERS_MAX; ++i) {
52 options->filters[i].id = LZMA_VLI_VALUE_UNKNOWN;
53 options->filters[i].options = NULL;
56 size_t in_size = options->header_size;
58 // Validate. The caller must have set options->header_size with
59 // lzma_block_header_size_decode() macro, so it is a programming error
60 // if these tests fail.
61 if (in_size < LZMA_BLOCK_HEADER_SIZE_MIN
62 || in_size > LZMA_BLOCK_HEADER_SIZE_MAX
64 || lzma_block_header_size_decode(in[0]) != in_size)
65 return LZMA_PROG_ERROR;
67 // Exclude the CRC32 field.
71 if (lzma_crc32(in, in_size, 0) != integer_read_32(in + in_size))
72 return LZMA_DATA_ERROR;
74 // Check for unsupported flags.
76 return LZMA_HEADER_ERROR;
78 // Start after the Block Header Size and Block Flags fields.
83 return_if_error(lzma_vli_decode(&options->compressed_size,
84 NULL, in, &in_pos, in_size));
86 if (options->compressed_size > LZMA_VLI_VALUE_MAX / 4 - 1)
87 return LZMA_DATA_ERROR;
89 options->compressed_size = (options->compressed_size + 1) * 4;
91 // Check that Total Size (that is, size of
92 // Block Header + Compressed Data + Check) is
93 // representable as a VLI.
94 if (lzma_block_total_size_get(options) == 0)
95 return LZMA_DATA_ERROR;
97 options->compressed_size = LZMA_VLI_VALUE_UNKNOWN;
102 return_if_error(lzma_vli_decode(&options->uncompressed_size,
103 NULL, in, &in_pos, in_size));
105 options->uncompressed_size = LZMA_VLI_VALUE_UNKNOWN;
108 const size_t filter_count = (in[1] & 3) + 1;
109 for (size_t i = 0; i < filter_count; ++i) {
110 const lzma_ret ret = lzma_filter_flags_decode(
111 &options->filters[i], allocator,
112 in, &in_pos, in_size);
113 if (ret != LZMA_OK) {
114 free_properties(options, allocator);
120 while (in_pos < in_size) {
121 if (in[in_pos++] != 0x00) {
122 free_properties(options, allocator);
124 // Possibly some new field present so use
125 // LZMA_HEADER_ERROR instead of LZMA_DATA_ERROR.
126 return LZMA_HEADER_ERROR;