90 lines
3.0 KiB
C
90 lines
3.0 KiB
C
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/*
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----
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This file is part of SECONDO.
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Copyright (C) 2017, Faculty of Mathematics and Computer Science, Database
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Systems for New Applications.
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SECONDO is free software; you can redistribute it and/or modify it under the
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terms of the GNU General Public License as published by the Free Software
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Foundation; either version 2 of the License, or (at your option) any later
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version.
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SECONDO is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
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PARTICULAR PURPOSE. See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along with
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SECONDO; if not, write to the Free Software Foundation, Inc., 59 Temple Place,
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Suite 330, Boston, MA 02111-1307 USA
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----
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//paragraph [10] title: [{\Large \bf] [}]
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//characters [1] tt: [\texttt{] [}]
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//[secondo] [{\sc Secondo}]
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[10] Definition of Class ManagedMutex
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2017-10-24: Sebastian J. Bronner $<$sebastian@bronner.name$>$
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\tableofcontents
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1 About this Class
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This class uses "named\_sharable\_mutex"[1] from the "boost"[1] library and
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adds the property that the corresponding shared memory segment is removed when
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it is no longer used. The implementation is specific to Linux and requires
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careful checks in both the constructor and the destructor.
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By default an instance of "ManagedMutex"[1] will unlock any lock held when it
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is destroyed. This protects against unexpected out-of-scope situations that
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might arise in the face of exceptions. And it also simplifies code. When the
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mutex should remain locked past the lifetime of the object, the automatic
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unlocking can be disabled by calling "noautounlock()".
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*/
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#ifndef ALGEBRAS_DISTRIBUTED4_MANAGEDMUTEX_H
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#define ALGEBRAS_DISTRIBUTED4_MANAGEDMUTEX_H
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#include <boost/interprocess/sync/named_sharable_mutex.hpp>
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#include <boost/filesystem.hpp>
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namespace distributed4 {
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class ManagedMutex {
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protected:
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/*
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2 Member Variables
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*/
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const boost::filesystem::path shm_target;
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std::unique_ptr<boost::interprocess::named_sharable_mutex> mutex;
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bool owned{false};
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bool exclusive;
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bool autounlock{true};
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/*
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"shm\_target"[1] is initialized with the path to the shared memory segment in
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the file system. It is used when checking what processes have mapped the shared
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memory segment when creating and removing the shared memory segment.
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"mutex"[1] is a pointer to the mutex that provides the actual locking.
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"owned"[1] tracks whether the current instance owns (holds a lock on) the
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"mutex"[1]. "exclusive"[1] tracks the type of lock held. And "autounlock"[1]
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tells the destructor whether to unlock the mutex when the object is destroyed.
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3 Member Functions
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*/
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public:
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ManagedMutex(const std::string&, bool, bool = true);
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ManagedMutex(const std::string&);
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~ManagedMutex();
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void noautounlock();
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void lock(bool, bool = true);
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void unlock();
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protected:
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static std::string getSHMPath(const std::string&);
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};
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}
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#endif
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