3
* Copyright 2004--2005, Google Inc.
5
* Redistribution and use in source and binary forms, with or without
6
* modification, are permitted provided that the following conditions are met:
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.
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.
28
#ifndef TALK_BASE_DISKCACHE_H__
29
#define TALK_BASE_DISKCACHE_H__
40
class StreamInterface;
42
///////////////////////////////////////////////////////////////////////////////
43
// DiskCache - An LRU cache of streams, stored on disk.
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
///////////////////////////////////////////////////////////////////////////////
59
bool Initialize(const std::string& folder, size_t size);
62
bool LockResource(const std::string& id);
63
StreamInterface* WriteResource(const std::string& id, size_t index);
64
bool UnlockResource(const std::string& id);
66
StreamInterface* ReadResource(const std::string& id, size_t index) const;
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);
73
virtual bool InitializeEntries() = 0;
74
virtual bool PurgeFiles() = 0;
76
virtual bool FileExists(const std::string& filename) const = 0;
77
virtual bool DeleteFile(const std::string& filename) const = 0;
79
enum LockState { LS_UNLOCKED, LS_LOCKED, LS_UNLOCKING };
82
mutable size_t accessors;
87
typedef std::map<std::string, Entry> EntryMap;
88
friend class DiskCacheAdapter;
92
std::string IdToFilename(const std::string& id, size_t index) const;
93
bool FilenameToId(const std::string& filename, std::string* id,
96
const Entry* GetEntry(const std::string& id) const {
97
return const_cast<DiskCache*>(this)->GetOrCreateEntry(id, false);
99
Entry* GetOrCreateEntry(const std::string& id, bool create);
101
void ReleaseResource(const std::string& id, size_t index) const;
104
size_t max_cache_, total_size_;
106
mutable size_t total_accessors_;
109
///////////////////////////////////////////////////////////////////////////////
110
// CacheLock - Automatically manage locking and unlocking, with optional
111
// rollback semantics
112
///////////////////////////////////////////////////////////////////////////////
116
CacheLock(DiskCache* cache, const std::string& id, bool rollback = false)
117
: cache_(cache), id_(id), rollback_(rollback)
119
locked_ = cache_->LockResource(id_);
123
cache_->UnlockResource(id_);
125
cache_->DeleteResource(id_);
129
bool IsLocked() const { return locked_; }
130
void Commit() { rollback_ = false; }
135
bool rollback_, locked_;
138
///////////////////////////////////////////////////////////////////////////////
140
} // namespace talk_base
142
#endif // TALK_BASE_DISKCACHE_H__