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// Copyright (C) 2012-2015 Internet Systems Consortium, Inc. ("ISC")
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
#ifndef INTERPROCESS_SYNC_FILE_H
#define INTERPROCESS_SYNC_FILE_H
#include <log/interprocess/interprocess_sync.h>
#include <exceptions/exceptions.h>
namespace isc {
namespace log {
namespace interprocess {
/// \brief InterprocessSyncFileError
///
/// Exception that is thrown if it's not possible to open the
/// lock file.
class InterprocessSyncFileError : public Exception {
public:
InterprocessSyncFileError(const char* file, size_t line,
const char* what) :
isc::Exception(file, line, what) {}
};
/// \brief File-based Interprocess Sync Class
///
/// This class specifies a concrete implementation for a file-based
/// interprocess synchronization mechanism. Please see the
/// InterprocessSync class documentation for usage.
///
/// An InterprocessSyncFileError exception may be thrown if there is an
/// issue opening the lock file.
///
/// Lock files are created typically in the local state directory
/// (var). They are typically named like "<task_name>_lockfile".
/// This implementation opens lock files lazily (only when
/// necessary). It also leaves the lock files lying around as multiple
/// processes may have locks on them.
class InterprocessSyncFile : public InterprocessSync {
public:
/// \brief Constructor
///
/// Creates a file-based interprocess synchronization object
///
/// \param task_name Name of the synchronization task. This has to be
/// identical among the various processes that need to be
/// synchronized for the same task.
InterprocessSyncFile(const std::string& task_name) :
InterprocessSync(task_name), fd_(-1)
{}
/// \brief Destructor
virtual ~InterprocessSyncFile();
protected:
/// \brief Acquire the lock (blocks if something else has acquired a
/// lock on the same task name)
///
/// \return Returns true if the lock was acquired, false otherwise.
bool lock();
/// \brief Try to acquire a lock (doesn't block)
///
/// \return Returns true if the lock was acquired, false otherwise.
bool tryLock();
/// \brief Release the lock
///
/// \return Returns true if the lock was released, false otherwise.
bool unlock();
private:
bool do_lock(int cmd, short l_type);
int fd_; ///< The descriptor for the open file
};
} // namespace interprocess
} // namespace log
} // namespace isc
#endif // INTERPROCESS_SYNC_FILE_H
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