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// -*- C++ -*-
// Copyright (C) 2010-2017, Vaclav Haisman. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modifica-
// tion, 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.
//
// THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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
// APACHE SOFTWARE FOUNDATION OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
// INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLU-
// DING, 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.
//! @file
//! This file contains implementations of reader-writer locking
//! primitive using other primitives, IOW poor man's rwlock.
//! It does not contain any include guards because it is only a fragment
//! to be included by syncprims-{pthreads,win32}.h.
#if ! defined (INSIDE_LOG4CPLUS)
# error "This header must not be be used outside log4cplus' implementation files."
#endif
// This implements algorithm described in "Concurrent Control with "Readers"
// and "Writers"; P.J. Courtois, F. Heymans, and D.L. Parnas;
// MBLE Research Laboratory; Brussels, Belgium"
inline
SharedMutex::SharedMutex ()
: m1 ()
, m2 ()
, m3 ()
, w (1, 1)
, writer_count (0)
, r (1, 1)
, reader_count (0)
{ }
inline
SharedMutex::~SharedMutex ()
{ }
inline
void
SharedMutex::rdlock () const
{
MutexGuard m3_guard (m3);
SemaphoreGuard r_guard (r);
MutexGuard m1_guard (m1);
if (reader_count + 1 == 1)
w.lock ();
reader_count += 1;
}
inline
void
SharedMutex::rdunlock () const
{
MutexGuard m1_guard (m1);
if (reader_count - 1 == 0)
w.unlock ();
reader_count -= 1;
}
inline
void
SharedMutex::wrlock () const
{
{
MutexGuard m2_guard (m2);
if (writer_count + 1 == 1)
r.lock ();
writer_count += 1;
}
try
{
w.lock ();
}
catch (...)
{
MutexGuard m2_guard (m2);
writer_count -= 1;
throw;
}
}
inline
void
SharedMutex::wrunlock () const
{
w.unlock ();
MutexGuard m2_guard (m2);
if (writer_count - 1 == 0)
r.unlock ();
writer_count -= 1;
}
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