net/disk_cache/addr.h

   1 // Copyright (c) 2012 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/base/net_export.h"
  12 #include "net/disk_cache/disk_format_base.h"
  13
  14 namespace disk_cache {
  15
  16 enum FileType {
  17   EXTERNAL = 0,
  18   RANKINGS = 1,
  19   BLOCK_256 = 2,
  20   BLOCK_1K = 3,
  21   BLOCK_4K = 4,
  22   BLOCK_FILES = 5,
  23   BLOCK_ENTRIES = 6,
  24   BLOCK_EVICTED = 7
  25 };
  26
  27 const int kMaxBlockSize = 4096 * 4;
  28 const int kMaxBlockFile = 255;
  29 const int kMaxNumBlocks = 4;
  30 const int kFirstAdditionalBlockFile = 4;
  31 const int kFirstAdditionalBlockFileV3 = 7;
  32
  33 // Defines a storage address for a cache record
  34 //
  35 // Header:
  36 //   1000 0000 0000 0000 0000 0000 0000 0000 : initialized bit
  37 //   0111 0000 0000 0000 0000 0000 0000 0000 : file type
  38 //
  39 // File type values:
  40 //   0 = separate file on disk
  41 //   1 = rankings block file
  42 //   2 = 256 byte block file
  43 //   3 = 1k byte block file
  44 //   4 = 4k byte block file
  45 //   5 = external files block file
  46 //   6 = active entries block file
  47 //   7 = evicted entries block file
  48 //
  49 // If separate file:
  50 //   0000 1111 1111 1111 1111 1111 1111 1111 : file#  0 - 268,435,456 (2^28)
  51 //
  52 // If block file:
  53 //   0000 1100 0000 0000 0000 0000 0000 0000 : reserved bits
  54 //   0000 0011 0000 0000 0000 0000 0000 0000 : number of contiguous blocks 1-4
  55 //   0000 0000 1111 1111 0000 0000 0000 0000 : file selector 0 - 255
  56 //   0000 0000 0000 0000 1111 1111 1111 1111 : block#  0 - 65,535 (2^16)
  57 class NET_EXPORT_PRIVATE Addr {
  58  public:
  59   Addr() : value_(0) {}
  60   explicit Addr(CacheAddr address) : value_(address) {}
  61   Addr(FileType file_type, int max_blocks, int block_file, int index) {
  62     value_ = ((file_type << kFileTypeOffset) & kFileTypeMask) |
  63              (((max_blocks - 1) << kNumBlocksOffset) & kNumBlocksMask) |
  64              ((block_file << kFileSelectorOffset) & kFileSelectorMask) |
  65              (index  & kStartBlockMask) | kInitializedMask;
  66   }
  67
  68   CacheAddr value() const { return value_; }
  69   void set_value(CacheAddr address) {
  70     value_ = address;
  71   }
  72
  73   bool is_initialized() const {
  74     return (value_ & kInitializedMask) != 0;
  75   }
  76
  77   bool is_separate_file() const {
  78     return (value_ & kFileTypeMask) == 0;
  79   }
  80
  81   bool is_block_file() const {
  82     return !is_separate_file();
  83   }
  84
  85   FileType file_type() const {
  86     return static_cast<FileType>((value_ & kFileTypeMask) >> kFileTypeOffset);
  87   }
  88
  89   int FileNumber() const {
  90     if (is_separate_file())
  91       return value_ & kFileNameMask;
  92     else
  93       return ((value_ & kFileSelectorMask) >> kFileSelectorOffset);
  94   }
  95
  96   int start_block() const;
  97   int num_blocks() const;
  98   bool SetFileNumber(int file_number);
  99   int BlockSize() const {
 100     return BlockSizeForFileType(file_type());
 101   }
 102
 103   bool operator==(Addr other) const {
 104     return value_ == other.value_;
 105   }
 106
 107   bool operator!=(Addr other) const {
 108     return value_ != other.value_;
 109   }
 110
 111   static Addr FromEntryAddress(uint32 value) {
 112     return Addr(kInitializedMask + (BLOCK_ENTRIES << kFileTypeOffset) + value);
 113   }
 114
 115   static Addr FromEvictedAddress(uint32 value) {
 116     return Addr(kInitializedMask + (BLOCK_EVICTED << kFileTypeOffset) + value);
 117   }
 118
 119   static int BlockSizeForFileType(FileType file_type) {
 120     switch (file_type) {
 121       case RANKINGS:
 122         return 36;
 123       case BLOCK_256:
 124         return 256;
 125       case BLOCK_1K:
 126         return 1024;
 127       case BLOCK_4K:
 128         return 4096;
 129       case BLOCK_FILES:
 130         return 8;
 131       case BLOCK_ENTRIES:
 132         return 104;
 133       case BLOCK_EVICTED:
 134         return 48;
 135       default:
 136         return 0;
 137     }
 138   }
 139
 140   static FileType RequiredFileType(int size) {
 141     if (size < 1024)
 142       return BLOCK_256;
 143     else if (size < 4096)
 144       return BLOCK_1K;
 145     else if (size <= 4096 * 4)
 146       return BLOCK_4K;
 147     else
 148       return EXTERNAL;
 149   }
 150
 151   static int RequiredBlocks(int size, FileType file_type) {
 152     int block_size = BlockSizeForFileType(file_type);
 153     return (size + block_size - 1) / block_size;
 154   }
 155
 156   // Returns true if this address looks like a valid one.
 157   bool SanityCheckV2() const;
 158   bool SanityCheckV3() const;
 159   bool SanityCheckForEntryV2() const;
 160   bool SanityCheckForEntryV3() const;
 161   bool SanityCheckForRankings() const;
 162
 163  private:
 164   uint32 reserved_bits() const {
 165     return value_ & kReservedBitsMask;
 166   }
 167
 168   static const uint32 kInitializedMask    = 0x80000000;
 169   static const uint32 kFileTypeMask       = 0x70000000;
 170   static const uint32 kFileTypeOffset     = 28;
 171   static const uint32 kReservedBitsMask   = 0x0c000000;
 172   static const uint32 kNumBlocksMask      = 0x03000000;
 173   static const uint32 kNumBlocksOffset    = 24;
 174   static const uint32 kFileSelectorMask   = 0x00ff0000;
 175   static const uint32 kFileSelectorOffset = 16;
 176   static const uint32 kStartBlockMask     = 0x0000FFFF;
 177   static const uint32 kFileNameMask       = 0x0FFFFFFF;
 178
 179   CacheAddr value_;
 180 };
 181
 182 }  // namespace disk_cache
 183
 184 #endif  // NET_DISK_CACHE_ADDR_H_