1 // Copyright 2013 The Chromium Authors 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef NET_DISK_CACHE_SIMPLE_SIMPLE_ENTRY_FORMAT_H_ 6 #define NET_DISK_CACHE_SIMPLE_SIMPLE_ENTRY_FORMAT_H_ 7 8 #include <stdint.h> 9 10 #include "net/base/net_export.h" 11 12 namespace disk_cache { 13 14 const uint64_t kSimpleInitialMagicNumber = UINT64_C(0xfcfb6d1ba7725c30); 15 const uint64_t kSimpleFinalMagicNumber = UINT64_C(0xf4fa6f45970d41d8); 16 const uint64_t kSimpleSparseRangeMagicNumber = UINT64_C(0xeb97bf016553676b); 17 18 // A file containing stream 0 and stream 1 in the Simple cache consists of: 19 // - a SimpleFileHeader. 20 // - the key. 21 // - the data from stream 1. 22 // - a SimpleFileEOF record for stream 1. 23 // - the data from stream 0. 24 // - (optionally) the SHA256 of the key. 25 // - a SimpleFileEOF record for stream 0. 26 // 27 // Because stream 0 data (typically HTTP headers) is on the critical path of 28 // requests, on open, the cache reads the end of the record and does not 29 // read the SimpleFileHeader. If the key can be validated with a SHA256, then 30 // the stream 0 data can be returned to the caller without reading the 31 // SimpleFileHeader. If the key SHA256 is not present, then the cache must 32 // read the SimpleFileHeader to confirm key equality. 33 34 // A file containing stream 2 in the Simple cache consists of: 35 // - a SimpleFileHeader. 36 // - the key. 37 // - the data. 38 // - at the end, a SimpleFileEOF record. 39 40 // This is the number of files we can use for representing normal/dense streams. 41 static const int kSimpleEntryNormalFileCount = 2; 42 static const int kSimpleEntryStreamCount = 3; 43 44 // Total # of files name we can potentially use; this includes both normal 45 // API and sparse streams. 46 static const int kSimpleEntryTotalFileCount = kSimpleEntryNormalFileCount + 1; 47 48 // Note that stream 0/stream 1 files rely on the footer to verify the entry, 49 // so if the format changes, it's insufficient to change the version here; 50 // likely the EOF magic should be updated as well. 51 struct NET_EXPORT_PRIVATE SimpleFileHeader { 52 SimpleFileHeader(); 53 54 uint64_t initial_magic_number; 55 uint32_t version; 56 uint32_t key_length; 57 uint32_t key_hash; 58 }; 59 60 struct NET_EXPORT_PRIVATE SimpleFileEOF { 61 enum Flags { 62 FLAG_HAS_CRC32 = (1U << 0), 63 FLAG_HAS_KEY_SHA256 = (1U << 1), // Preceding the record if present. 64 }; 65 66 SimpleFileEOF(); 67 68 uint64_t final_magic_number; 69 uint32_t flags; 70 uint32_t data_crc32; 71 // |stream_size| is only used in the EOF record for stream 0. 72 uint32_t stream_size; 73 }; 74 75 struct SimpleFileSparseRangeHeader { 76 SimpleFileSparseRangeHeader(); 77 78 uint64_t sparse_range_magic_number; 79 int64_t offset; 80 int64_t length; 81 uint32_t data_crc32; 82 }; 83 84 } // namespace disk_cache 85 86 #endif // NET_DISK_CACHE_SIMPLE_SIMPLE_ENTRY_FORMAT_H_ 87