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119 lines
3.1 KiB
119 lines
3.1 KiB
// -*- C++ -*-
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// Copyright (C) 2010, Vaclav Haisman. All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without modifica-
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// tion, are permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice,
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// this list of conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright notice,
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// this list of conditions and the following disclaimer in the documentation
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// and/or other materials provided with the distribution.
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//
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// THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
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// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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// FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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// APACHE SOFTWARE FOUNDATION OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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// INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLU-
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// DING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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// OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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// ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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// THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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//! @file
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//! This file contains implementations of reader-writer locking
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//! primitive using other primitives, IOW poor man's rwlock.
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//! It does not contain any include guards because it is only a fragment
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//! to be included by syncprims-{pthreads,win32}.h.
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#if ! defined (INSIDE_LOG4CPLUS)
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# error "This header must not be be used outside log4cplus' implementation files."
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#endif
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// This implements algorithm described in "Concurrent Control with "Readers"
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// and "Writers"; P.J. Courtois, F. Heymans, and D.L. Parnas;
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// MBLE Research Laboratory; Brussels, Belgium"
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inline
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SharedMutex::SharedMutex ()
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: m1 (log4cplus::thread::Mutex::DEFAULT)
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, m2 (log4cplus::thread::Mutex::DEFAULT)
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, m3 (log4cplus::thread::Mutex::DEFAULT)
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, w (1, 1)
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, writer_count (0)
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, r (1, 1)
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, reader_count (0)
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{ }
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inline
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SharedMutex::~SharedMutex ()
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{ }
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inline
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void
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SharedMutex::rdlock () const
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{
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MutexGuard m3_guard (m3);
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SemaphoreGuard r_guard (r);
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MutexGuard m1_guard (m1);
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if (reader_count + 1 == 1)
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w.lock ();
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reader_count += 1;
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}
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inline
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void
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SharedMutex::rdunlock () const
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{
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MutexGuard m1_guard (m1);
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if (reader_count - 1 == 0)
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w.unlock ();
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reader_count -= 1;
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}
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inline
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void
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SharedMutex::wrlock () const
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{
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{
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MutexGuard m2_guard (m2);
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if (writer_count + 1 == 1)
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r.lock ();
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writer_count += 1;
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}
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try
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{
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w.lock ();
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}
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catch (...)
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{
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MutexGuard m2_guard (m2);
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writer_count -= 1;
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throw;
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}
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}
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inline
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void
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SharedMutex::wrunlock () const
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{
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w.unlock ();
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MutexGuard m2_guard (m2);
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if (writer_count - 1 == 0)
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r.unlock ();
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writer_count -= 1;
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}
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