1 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 // This is an internal class that handles the address of a cache record. 6 // See net/disk_cache/disk_cache.h for the public interface of the cache. 7 8 #ifndef NET_DISK_CACHE_ADDR_H_ 9 #define NET_DISK_CACHE_ADDR_H_ 10 11 #include "net/disk_cache/disk_format.h" 12 13 namespace disk_cache { 14 15 enum FileType { 16 EXTERNAL = 0, 17 RANKINGS = 1, 18 BLOCK_256, 19 BLOCK_1K, 20 BLOCK_4K, 21 }; 22 23 const int kMaxBlockSize = 4096 * 4; 24 const int kMaxBlockFile = 255; 25 const int kMaxNumBlocks = 4; 26 const int kFirstAdditionlBlockFile = 4; 27 28 // Defines a storage address for a cache record 29 // 30 // Header: 31 // 1000 0000 0000 0000 0000 0000 0000 0000 : initialized bit 32 // 0111 0000 0000 0000 0000 0000 0000 0000 : file type 33 // 34 // File type values: 35 // 0 = separate file on disk 36 // 1 = rankings block file 37 // 2 = 256 byte block file 38 // 3 = 1k byte block file 39 // 4 = 4k byte block file 40 // 41 // If separate file: 42 // 0000 1111 1111 1111 1111 1111 1111 1111 : file# 0 - 268,435,456 (2^28) 43 // 44 // If block file: 45 // 0000 1100 0000 0000 0000 0000 0000 0000 : reserved bits 46 // 0000 0011 0000 0000 0000 0000 0000 0000 : number of contiguous blocks 1-4 47 // 0000 0000 1111 1111 0000 0000 0000 0000 : file selector 0 - 255 48 // 0000 0000 0000 0000 1111 1111 1111 1111 : block# 0 - 65,535 (2^16) 49 class Addr { 50 public: 51 Addr() : value_(0) {} 52 explicit Addr(CacheAddr address) : value_(address) {} 53 Addr(FileType file_type, int max_blocks, int block_file, int index) { 54 value_ = ((file_type << kFileTypeOffset) & kFileTypeMask) | 55 (((max_blocks - 1) << kNumBlocksOffset) & kNumBlocksMask) | 56 ((block_file << kFileSelectorOffset) & kFileSelectorMask) | 57 (index & kStartBlockMask) | kInitializedMask; 58 } 59 60 CacheAddr value() const { return value_; } 61 void set_value(CacheAddr address) { 62 value_ = address; 63 } 64 65 bool is_initialized() const { 66 return (value_ & kInitializedMask) != 0; 67 } 68 69 bool is_separate_file() const { 70 return (value_ & kFileTypeMask) == 0; 71 } 72 73 bool is_block_file() const { 74 return !is_separate_file(); 75 } 76 77 FileType file_type() const { 78 return static_cast<FileType>((value_ & kFileTypeMask) >> kFileTypeOffset); 79 } 80 81 int FileNumber() const { 82 if (is_separate_file()) 83 return value_ & kFileNameMask; 84 else 85 return ((value_ & kFileSelectorMask) >> kFileSelectorOffset); 86 } 87 88 int start_block() const; 89 int num_blocks() const; 90 bool SetFileNumber(int file_number); 91 int BlockSize() const { 92 return BlockSizeForFileType(file_type()); 93 } 94 95 static int BlockSizeForFileType(FileType file_type) { 96 switch (file_type) { 97 case RANKINGS: 98 return 36; 99 case BLOCK_256: 100 return 256; 101 case BLOCK_1K: 102 return 1024; 103 case BLOCK_4K: 104 return 4096; 105 default: 106 return 0; 107 } 108 } 109 110 static FileType RequiredFileType(int size) { 111 if (size < 1024) 112 return BLOCK_256; 113 else if (size < 4096) 114 return BLOCK_1K; 115 else if (size <= 4096 * 4) 116 return BLOCK_4K; 117 else 118 return EXTERNAL; 119 } 120 121 private: 122 static const uint32 kInitializedMask = 0x80000000; 123 static const uint32 kFileTypeMask = 0x70000000; 124 static const uint32 kFileTypeOffset = 28; 125 static const uint32 kNumBlocksMask = 0x03000000; 126 static const uint32 kNumBlocksOffset = 24; 127 static const uint32 kFileSelectorMask = 0x00ff0000; 128 static const uint32 kFileSelectorOffset = 16; 129 static const uint32 kStartBlockMask = 0x0000FFFF; 130 static const uint32 kFileNameMask = 0x0FFFFFFF; 131 132 CacheAddr value_; 133 }; 134 135 } // namespace disk_cache 136 137 #endif // NET_DISK_CACHE_ADDR_H_ 138
