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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)
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)
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         unaligned_write32le(out + out_size, lzma_crc32(out, out_size, 0));
130
131         return LZMA_OK;
132 }