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source: webrtc/talk/base/diskcache.h @ 0:4bda6873e34c

pub_scrub_3792 tip
Last change on this file since 0:4bda6873e34c was 0:4bda6873e34c, checked in by Michael Prittie <mprittie@…>, 6 years ago

Scrubbed password for publication.

File size: 4.8 KB
Line 
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
38namespace talk_base {
39
40class 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
54class DiskCache {
55public:
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
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
114class CacheLock {
115public:
116  CacheLock(DiskCache* cache, const std::string& id, bool rollback = false)
117  : cache_(cache), id_(id), rollback_(rollback)
118  {
119    locked_ = cache_->LockResource(id_);
120  }
121  ~CacheLock() {
122    if (locked_) {
123      cache_->UnlockResource(id_);
124      if (rollback_) {
125        cache_->DeleteResource(id_);
126      }
127    }
128  }
129  bool IsLocked() const { return locked_; }
130  void Commit() { rollback_ = false; }
131
132private:
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__
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