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
17 extern LZMA_API(lzma_ret)
lzma_block_header_size(lzma_block * block)18 lzma_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
73 extern LZMA_API(lzma_ret)
lzma_block_header_encode(const lzma_block * block,uint8_t * out)74 lzma_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 write32le(out + out_size, lzma_crc32(out, out_size, 0));
130
131 return LZMA_OK;
132 }
133