add front demo in this project

LFtid1056/cloudfront/code/log4cplus/thread/impl/syncprims-pmsm.h

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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;
+}