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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 // For a general description of the files used by the cache see file_format.h. | 5 // For a general description of the files used by the cache see file_format.h. |
6 // | 6 // |
7 // A block file is a file designed to store blocks of data of a given size. It | 7 // A block file is a file designed to store blocks of data of a given size. It |
8 // is able to store data that spans from one to four consecutive "blocks", and | 8 // is able to store data that spans from one to four consecutive "blocks", and |
9 // it grows as needed to store up to approximately 65000 blocks. It has a fixed | 9 // it grows as needed to store up to approximately 65000 blocks. It has a fixed |
10 // size header used for book keeping such as tracking free of blocks on the | 10 // size header used for book keeping such as tracking free of blocks on the |
11 // file. For example, a block-file for 1KB blocks will grow from 8KB when | 11 // file. For example, a block-file for 1KB blocks will grow from 8KB when |
12 // totally empty to about 64MB when completely full. At that point, data blocks | 12 // totally empty to about 64MB when completely full. At that point, data blocks |
13 // of 1KB will be stored on a second block file that will store the next set of | 13 // of 1KB will be stored on a second block file that will store the next set of |
14 // 65000 blocks. The first file contains the number of the second file, and the | 14 // 65000 blocks. The first file contains the number of the second file, and the |
15 // second file contains the number of a third file, created when the second file | 15 // second file contains the number of a third file, created when the second file |
16 // reaches its limit. It is important to remember that no matter how long the | 16 // reaches its limit. It is important to remember that no matter how long the |
17 // chain of files is, any given block can be located directly by its address, | 17 // chain of files is, any given block can be located directly by its address, |
18 // which contains the file number and starting block inside the file. | 18 // which contains the file number and starting block inside the file. |
19 | 19 |
20 #ifndef NET_DISK_CACHE_BLOCKFILE_DISK_FORMAT_BASE_H_ | 20 #ifndef NET_DISK_CACHE_BLOCKFILE_DISK_FORMAT_BASE_H_ |
21 #define NET_DISK_CACHE_BLOCKFILE_DISK_FORMAT_BASE_H_ | 21 #define NET_DISK_CACHE_BLOCKFILE_DISK_FORMAT_BASE_H_ |
22 | 22 |
23 #include <stdint.h> | 23 #include <stdint.h> |
24 | 24 |
25 #include "net/base/net_export.h" | |
26 | |
27 namespace disk_cache { | 25 namespace disk_cache { |
28 | 26 |
29 typedef uint32_t CacheAddr; | 27 typedef uint32_t CacheAddr; |
30 | 28 |
31 const uint32_t kBlockVersion2 = 0x20000; // Version 2.0. | 29 const uint32_t kBlockVersion2 = 0x20000; // Version 2.0. |
32 const uint32_t kBlockCurrentVersion = 0x30000; // Version 3.0. | 30 const uint32_t kBlockCurrentVersion = 0x30000; // Version 3.0. |
33 | 31 |
34 const uint32_t kBlockMagic = 0xC104CAC3; | 32 const uint32_t kBlockMagic = 0xC104CAC3; |
35 const int kBlockHeaderSize = 8192; // Two pages: almost 64k entries | 33 const int kBlockHeaderSize = 8192; // Two pages: almost 64k entries |
36 const int kMaxBlocks = (kBlockHeaderSize - 80) * 8; | 34 const int kMaxBlocks = (kBlockHeaderSize - 80) * 8; |
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124 }; | 122 }; |
125 | 123 |
126 // The number of blocks stored by a child entry. | 124 // The number of blocks stored by a child entry. |
127 const int kNumSparseBits = 1024; | 125 const int kNumSparseBits = 1024; |
128 static_assert(sizeof(SparseData) == sizeof(SparseHeader) + kNumSparseBits / 8, | 126 static_assert(sizeof(SparseData) == sizeof(SparseHeader) + kNumSparseBits / 8, |
129 "invalid SparseData bitmap"); | 127 "invalid SparseData bitmap"); |
130 | 128 |
131 } // namespace disk_cache | 129 } // namespace disk_cache |
132 | 130 |
133 #endif // NET_DISK_CACHE_BLOCKFILE_DISK_FORMAT_BASE_H_ | 131 #endif // NET_DISK_CACHE_BLOCKFILE_DISK_FORMAT_BASE_H_ |
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