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/*
* libjingle
* Copyright 2004--2005, Google Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef TALK_BASE_DISKCACHE_H__
#define TALK_BASE_DISKCACHE_H__
#include <map>
#include <string>
#ifdef WIN32
#undef UnlockResource
#endif // WIN32
namespace talk_base {
class StreamInterface;
///////////////////////////////////////////////////////////////////////////////
// DiskCache - An LRU cache of streams, stored on disk.
//
// Streams are identified by a unique resource id. Multiple streams can be
// associated with each resource id, distinguished by an index. When old
// resources are flushed from the cache, all streams associated with those
// resources are removed together.
// DiskCache is designed to persist across executions of the program. It is
// safe for use from an arbitrary number of users on a single thread, but not
// from multiple threads or other processes.
///////////////////////////////////////////////////////////////////////////////
class DiskCache {
public:
DiskCache();
~DiskCache();
bool Initialize(const std::string& folder, size_t size);
bool Purge();
bool LockResource(const std::string& id);
StreamInterface* WriteResource(const std::string& id, size_t index);
bool UnlockResource(const std::string& id);
StreamInterface* ReadResource(const std::string& id, size_t index) const;
bool HasResource(const std::string& id) const;
bool HasResourceStream(const std::string& id, size_t index) const;
bool DeleteResource(const std::string& id);
protected:
virtual bool InitializeEntries() = 0;
virtual bool PurgeFiles() = 0;
virtual bool FileExists(const std::string& filename) const = 0;
virtual bool DeleteFile(const std::string& filename) const = 0;
enum LockState { LS_UNLOCKED, LS_LOCKED, LS_UNLOCKING };
struct Entry {
LockState lock_state;
mutable size_t accessors;
size_t size;
size_t streams;
time_t last_modified;
};
typedef std::map<std::string, Entry> EntryMap;
friend class DiskCacheAdapter;
bool CheckLimit();
std::string IdToFilename(const std::string& id, size_t index) const;
bool FilenameToId(const std::string& filename, std::string* id,
size_t* index) const;
const Entry* GetEntry(const std::string& id) const {
return const_cast<DiskCache*>(this)->GetOrCreateEntry(id, false);
}
Entry* GetOrCreateEntry(const std::string& id, bool create);
void ReleaseResource(const std::string& id, size_t index) const;
std::string folder_;
size_t max_cache_, total_size_;
EntryMap map_;
mutable size_t total_accessors_;
};
///////////////////////////////////////////////////////////////////////////////
// CacheLock - Automatically manage locking and unlocking, with optional
// rollback semantics
///////////////////////////////////////////////////////////////////////////////
class CacheLock {
public:
CacheLock(DiskCache* cache, const std::string& id, bool rollback = false)
: cache_(cache), id_(id), rollback_(rollback)
{
locked_ = cache_->LockResource(id_);
}
~CacheLock() {
if (locked_) {
cache_->UnlockResource(id_);
if (rollback_) {
cache_->DeleteResource(id_);
}
}
}
bool IsLocked() const { return locked_; }
void Commit() { rollback_ = false; }
private:
DiskCache* cache_;
std::string id_;
bool rollback_, locked_;
};
///////////////////////////////////////////////////////////////////////////////
} // namespace talk_base
#endif // TALK_BASE_DISKCACHE_H__
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