1 ///////////////////////////////////////////////////////////////////////////////
3 /// \file block_header_encoder.c
4 /// \brief Encodes Block Header for .xz files
6 // Author: Lasse Collin
8 // This file has been put into the public domain.
9 // You can do whatever you want with this file.
11 ///////////////////////////////////////////////////////////////////////////////
17 extern LZMA_API(lzma_ret)
18 lzma_block_header_size(lzma_block *block)
20 if (block->version != 0)
21 return LZMA_OPTIONS_ERROR;
23 // Block Header Size + Block Flags + CRC32.
24 uint32_t size = 1 + 1 + 4;
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;
36 if (block->uncompressed_size != LZMA_VLI_UNKNOWN) {
37 const uint32_t add = lzma_vli_size(block->uncompressed_size);
39 return LZMA_PROG_ERROR;
44 // List of Filter Flags
45 if (block->filters == NULL || block->filters[0].id == LZMA_VLI_UNKNOWN)
46 return LZMA_PROG_ERROR;
49 for (i = 0; block->filters[i].id != LZMA_VLI_UNKNOWN; ++i) {
50 // Don't allow too many filters.
51 if (i == LZMA_FILTERS_MAX)
52 return LZMA_PROG_ERROR;
55 return_if_error(lzma_filter_flags_size(&add,
61 // Pad to a multiple of four bytes.
62 block->header_size = (size + 3) & ~UINT32_C(3);
64 // NOTE: We don't verify that the encoded size of the Block stays
65 // within limits. This is because it is possible that we are called
66 // with exaggerated Compressed Size (e.g. LZMA_VLI_MAX) to reserve
67 // space for Block Header, and later called again with lower,
74 extern LZMA_API(lzma_ret)
75 lzma_block_header_encode(const lzma_block *block, uint8_t *out)
77 // Validate everything but filters.
78 if (lzma_block_unpadded_size(block) == 0
79 || !lzma_vli_is_valid(block->uncompressed_size))
80 return LZMA_PROG_ERROR;
82 // Indicate the size of the buffer _excluding_ the CRC32 field.
83 const size_t out_size = block->header_size - 4;
85 // Store the Block Header Size.
86 out[0] = out_size / 4;
88 // We write Block Flags in pieces.
93 if (block->compressed_size != LZMA_VLI_UNKNOWN) {
94 return_if_error(lzma_vli_encode(block->compressed_size, NULL,
95 out, &out_pos, out_size));
101 if (block->uncompressed_size != LZMA_VLI_UNKNOWN) {
102 return_if_error(lzma_vli_encode(block->uncompressed_size, NULL,
103 out, &out_pos, out_size));
109 if (block->filters == NULL || block->filters[0].id == LZMA_VLI_UNKNOWN)
110 return LZMA_PROG_ERROR;
112 size_t filter_count = 0;
114 // There can be a maximum of four filters.
115 if (filter_count == LZMA_FILTERS_MAX)
116 return LZMA_PROG_ERROR;
118 return_if_error(lzma_filter_flags_encode(
119 block->filters + filter_count,
120 out, &out_pos, out_size));
122 } while (block->filters[++filter_count].id != LZMA_VLI_UNKNOWN);
124 out[1] |= filter_count - 1;
127 memzero(out + out_pos, out_size - out_pos);
130 unaligned_write32le(out + out_size, lzma_crc32(out, out_size, 0));