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| 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_STRUCTURED_STORE_H_ | |
| 6 #define NET_DISK_CACHE_FLASH_LOG_STRUCTURED_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 | |
| 15 namespace disk_cache { | |
| 16 | |
| 17 class Segment; | |
| 18 class Storage; | |
| 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 LogStructuredStore { | |
| 26 public: | |
| 27 explicit LogStructuredStore(Storage* storage); | |
| 28 ~LogStructuredStore(); | |
| 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 // TODO(agayev): Add DeleteEntry. | |
| 42 | |
| 43 // Appends data to the end of the last created entry. | |
| 44 bool WriteData(const void* buffer, int32 size); | |
| 45 | |
| 46 // Opens an entry with id |entry_id|. | |
| 47 bool OpenEntry(int32 entry_id); | |
| 48 | |
| 49 // Reads |size| bytes starting from |offset| into |buffer|, where |offset| is | |
| 50 // relative to the entry's content, from an entry identified by |entry_id|. | |
| 51 bool ReadData(int32 entry_id, void* buffer, int32 size, int32 offset) const; | |
| 52 | |
| 53 // Closes an entry that was either opened with OpenEntry or created with | |
| 54 // CreateEntry. | |
| 55 void CloseEntry(int32 id); | |
| 56 | |
| 57 private: | |
| 58 FRIEND_TEST_ALL_PREFIXES(FlashCacheTest, | |
| 59 LogStructuredStoreReadFromClosedSegment); | |
| 60 FRIEND_TEST_ALL_PREFIXES(FlashCacheTest, | |
| 61 LogStructuredStoreSegmentSelectionIsFifo); | |
| 62 FRIEND_TEST_ALL_PREFIXES(FlashCacheTest, | |
| 63 LogStructuredStoreInUseSegmentIsSkipped); | |
| 64 FRIEND_TEST_ALL_PREFIXES(FlashCacheTest, | |
| 65 LogStructuredStoreReadFromCurrentAfterClose); | |
| 66 | |
| 67 int32 GetNextSegmentIndex(); | |
| 68 bool InUse(int32 segment_index) const; | |
| 69 | |
| 70 Storage* storage_; | |
| 71 | |
| 72 int32 num_segments_; | |
| 73 | |
| 74 // Currently open segments, either for reading or writing. There can only be | |
| 75 // one segment open for writing, and multiple open for reading. | |
| 76 std::vector<Segment*> open_segments_; | |
| 77 | |
| 78 // The index of the segment currently being written to. It's an index to | |
| 79 // |open_segments_| vector. | |
| 80 int32 write_index_; | |
| 81 | |
| 82 // Ids of entries currently open, either CreatEntry'ed or OpenEntry'ed. | |
| 83 std::set<int32> open_entries_; | |
| 84 | |
| 85 // Id of the entry that is currently being written to, -1 if there is no entry | |
| 86 // currently being written to. | |
| 87 int32 current_entry_id_; | |
| 88 | |
| 89 // Number of bytes left to be written to the entry identified by | |
| 90 // |current_entry_id_|. Its value makes sense iff |current_entry_id_| is not | |
| 91 // -1. | |
| 92 int32 current_entry_num_bytes_left_to_write_; | |
| 93 | |
| 94 bool init_; // Init was called. | |
| 95 bool closed_; // Close was called. | |
| 96 | |
| 97 DISALLOW_COPY_AND_ASSIGN(LogStructuredStore); | |
| 98 }; | |
| 99 | |
| 100 } // namespace disk_cache | |
| 101 | |
| 102 #endif // NET_DISK_CACHE_FLASH_LOG_STRUCTURED_STORE_H_ | |
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