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 #ifndef NET_DISK_CACHE_FLASH_LOG_STORE_H_ 6 #define NET_DISK_CACHE_FLASH_LOG_STORE_H_ 7 8 #include <set> 9 #include <vector> 10 11 #include "base/basictypes.h" 12 #include "base/gtest_prod_util.h" 13 #include "net/base/net_export.h" 14 #include "net/disk_cache/flash/storage.h" 15 16 namespace disk_cache { 17 18 class Segment; 19 20 // This class implements a general purpose store for storing and retrieving 21 // entries consisting of arbitrary binary data. The store has log semantics, 22 // i.e. it's not possible to overwrite data in place. In order to update an 23 // entry, a new version must be written. Only one entry can be written to at 24 // any given time, while concurrent reading of multiple entries is supported. 25 class NET_EXPORT_PRIVATE LogStore { 26 public: 27 LogStore(const base::FilePath& path, int32 size); 28 ~LogStore(); 29 30 // Performs initialization. Must be the first function called and further 31 // calls should be made only if it is successful. 32 bool Init(); 33 34 // Closes the store. Should be the last function called before destruction. 35 bool Close(); 36 37 // Creates an entry of |size| bytes. The id of the created entry is stored in 38 // |entry_id|. 39 bool CreateEntry(int32 size, int32* entry_id); 40 41 // Deletes |entry_id|; the client should keep track of |size| and provide it 42 // here. Only inactive (i.e. not currently open or being created) entries can 43 // be deleted. 44 void DeleteEntry(int32 entry_id, int32 size); 45 46 // Appends data to the end of the last created entry. 47 bool WriteData(const void* buffer, int32 size); 48 49 // Opens an entry with id |entry_id|. 50 bool OpenEntry(int32 entry_id); 51 52 // Reads |size| bytes starting from |offset| into |buffer|, where |offset| is 53 // relative to the entry's content, from an entry identified by |entry_id|. 54 bool ReadData(int32 entry_id, void* buffer, int32 size, int32 offset) const; 55 56 // Closes an entry that was either opened with OpenEntry or created with 57 // CreateEntry. 58 void CloseEntry(int32 id); 59 60 private: 61 FRIEND_TEST_ALL_PREFIXES(FlashCacheTest, LogStoreReadFromClosedSegment); 62 FRIEND_TEST_ALL_PREFIXES(FlashCacheTest, LogStoreSegmentSelectionIsFifo); 63 FRIEND_TEST_ALL_PREFIXES(FlashCacheTest, LogStoreInUseSegmentIsSkipped); 64 FRIEND_TEST_ALL_PREFIXES(FlashCacheTest, LogStoreReadFromCurrentAfterClose); 65 66 int32 GetNextSegmentIndex(); 67 bool InUse(int32 segment_index) const; 68 69 Storage storage_; 70 71 int32 num_segments_; 72 73 // Currently open segments, either for reading or writing. There can only be 74 // one segment open for writing, and multiple open for reading. 75 std::vector<Segment*> open_segments_; 76 77 // The index of the segment currently being written to. It's an index to 78 // |open_segments_| vector. 79 int32 write_index_; 80 81 // Ids of entries currently open, either CreatEntry'ed or OpenEntry'ed. 82 std::set<int32> open_entries_; 83 84 // Id of the entry that is currently being written to, -1 if there is no entry 85 // currently being written to. 86 int32 current_entry_id_; 87 88 // Number of bytes left to be written to the entry identified by 89 // |current_entry_id_|. Its value makes sense iff |current_entry_id_| is not 90 // -1. 91 int32 current_entry_num_bytes_left_to_write_; 92 93 bool init_; // Init was called. 94 bool closed_; // Close was called. 95 96 DISALLOW_COPY_AND_ASSIGN(LogStore); 97 }; 98 99 } // namespace disk_cache 100 101 #endif // NET_DISK_CACHE_FLASH_LOG_STORE_H_ 102
