1 /* 2 * libjingle 3 * Copyright 2004--2005, Google Inc. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions are met: 7 * 8 * 1. Redistributions of source code must retain the above copyright notice, 9 * this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright notice, 11 * this list of conditions and the following disclaimer in the documentation 12 * and/or other materials provided with the distribution. 13 * 3. The name of the author may not be used to endorse or promote products 14 * derived from this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED 17 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 18 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO 19 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 20 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 21 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 22 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 23 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR 24 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 25 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 */ 27 28 #ifndef TALK_BASE_DISKCACHE_H__ 29 #define TALK_BASE_DISKCACHE_H__ 30 31 #include <map> 32 #include <string> 33 34 #ifdef WIN32 35 #undef UnlockResource 36 #endif // WIN32 37 38 namespace talk_base { 39 40 class StreamInterface; 41 42 /////////////////////////////////////////////////////////////////////////////// 43 // DiskCache - An LRU cache of streams, stored on disk. 44 // 45 // Streams are identified by a unique resource id. Multiple streams can be 46 // associated with each resource id, distinguished by an index. When old 47 // resources are flushed from the cache, all streams associated with those 48 // resources are removed together. 49 // DiskCache is designed to persist across executions of the program. It is 50 // safe for use from an arbitrary number of users on a single thread, but not 51 // from multiple threads or other processes. 52 /////////////////////////////////////////////////////////////////////////////// 53 54 class DiskCache { 55 public: 56 DiskCache(); 57 virtual ~DiskCache(); 58 59 bool Initialize(const std::string& folder, size_t size); 60 bool Purge(); 61 62 bool LockResource(const std::string& id); 63 StreamInterface* WriteResource(const std::string& id, size_t index); 64 bool UnlockResource(const std::string& id); 65 66 StreamInterface* ReadResource(const std::string& id, size_t index) const; 67 68 bool HasResource(const std::string& id) const; 69 bool HasResourceStream(const std::string& id, size_t index) const; 70 bool DeleteResource(const std::string& id); 71 72 protected: 73 virtual bool InitializeEntries() = 0; 74 virtual bool PurgeFiles() = 0; 75 76 virtual bool FileExists(const std::string& filename) const = 0; 77 virtual bool DeleteFile(const std::string& filename) const = 0; 78 79 enum LockState { LS_UNLOCKED, LS_LOCKED, LS_UNLOCKING }; 80 struct Entry { 81 LockState lock_state; 82 mutable size_t accessors; 83 size_t size; 84 size_t streams; 85 time_t last_modified; 86 }; 87 typedef std::map<std::string, Entry> EntryMap; 88 friend class DiskCacheAdapter; 89 90 bool CheckLimit(); 91 92 std::string IdToFilename(const std::string& id, size_t index) const; 93 bool FilenameToId(const std::string& filename, std::string* id, 94 size_t* index) const; 95 GetEntry(const std::string & id)96 const Entry* GetEntry(const std::string& id) const { 97 return const_cast<DiskCache*>(this)->GetOrCreateEntry(id, false); 98 } 99 Entry* GetOrCreateEntry(const std::string& id, bool create); 100 101 void ReleaseResource(const std::string& id, size_t index) const; 102 103 std::string folder_; 104 size_t max_cache_, total_size_; 105 EntryMap map_; 106 mutable size_t total_accessors_; 107 }; 108 109 /////////////////////////////////////////////////////////////////////////////// 110 // CacheLock - Automatically manage locking and unlocking, with optional 111 // rollback semantics 112 /////////////////////////////////////////////////////////////////////////////// 113 114 class CacheLock { 115 public: 116 CacheLock(DiskCache* cache, const std::string& id, bool rollback = false) cache_(cache)117 : cache_(cache), id_(id), rollback_(rollback) 118 { 119 locked_ = cache_->LockResource(id_); 120 } ~CacheLock()121 ~CacheLock() { 122 if (locked_) { 123 cache_->UnlockResource(id_); 124 if (rollback_) { 125 cache_->DeleteResource(id_); 126 } 127 } 128 } IsLocked()129 bool IsLocked() const { return locked_; } Commit()130 void Commit() { rollback_ = false; } 131 132 private: 133 DiskCache* cache_; 134 std::string id_; 135 bool rollback_, locked_; 136 }; 137 138 /////////////////////////////////////////////////////////////////////////////// 139 140 } // namespace talk_base 141 142 #endif // TALK_BASE_DISKCACHE_H__ 143