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version 1.1, 2006/07/30 22:51:07
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version 1.1.2.2, 2006/07/30 23:11:55
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//%2006//////////////////////////////////////////////////////////////////////// |
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// |
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// Copyright (c) 2000, 2001, 2002 BMC Software; Hewlett-Packard Development |
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// Company, L.P.; IBM Corp.; The Open Group; Tivoli Systems. |
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// Copyright (c) 2003 BMC Software; Hewlett-Packard Development Company, L.P.; |
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// IBM Corp.; EMC Corporation, The Open Group. |
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// Copyright (c) 2004 BMC Software; Hewlett-Packard Development Company, L.P.; |
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// IBM Corp.; EMC Corporation; VERITAS Software Corporation; The Open Group. |
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// Copyright (c) 2005 Hewlett-Packard Development Company, L.P.; IBM Corp.; |
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// EMC Corporation; VERITAS Software Corporation; The Open Group. |
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// Copyright (c) 2006 Hewlett-Packard Development Company, L.P.; IBM Corp.; |
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// EMC Corporation; Symantec Corporation; The Open Group. |
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// |
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// Permission is hereby granted, free of charge, to any person obtaining a copy |
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// of this software and associated documentation files (the "Software"), to |
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// deal in the Software without restriction, including without limitation the |
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// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or |
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// sell copies of the Software, and to permit persons to whom the Software is |
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// furnished to do so, subject to the following conditions: |
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// |
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// THE ABOVE COPYRIGHT NOTICE AND THIS PERMISSION NOTICE SHALL BE INCLUDED IN |
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// ALL COPIES OR SUBSTANTIAL PORTIONS OF THE SOFTWARE. THE SOFTWARE IS PROVIDED |
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// "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT |
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// LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR |
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// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT |
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// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN |
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// ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION |
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// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
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// |
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//============================================================================== |
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// |
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// Author: Mike Brasher (m.brasher@inovadevelopment.com) |
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// |
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//%///////////////////////////////////////////////////////////////////////////// |
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#ifndef Pegasus_Once_h |
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#define Pegasus_Once_h |
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#include <Pegasus/Common/Config.h> |
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#include <Pegasus/Common/Linkage.h> |
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#include <Pegasus/Common/Mutex.h> |
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#define PEGASUS_ONCE_INITIALIZER { PEGASUS_MUTEX_INITIALIZER, 0 } |
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PEGASUS_NAMESPACE_BEGIN |
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/** Once implements the "once" concept as introduced by POSIX threads. |
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That is, it arranges for a function to be called just once in a thread |
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safe manner. The following example shows how to constuct an object of |
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type X the first time any thread reaches the line that calls once(). |
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static Once _once = PEGASUS_ONCE_INITIALIZER; |
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static static X* _ptr; |
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static void _create_X() |
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{ |
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ptr = new X; |
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} |
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... |
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once(&_once, _create_X()); |
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The _create_X() function is called exactly once no matter how many times |
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once() is called on it. Also, once() may be called safely from multiple |
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threads. |
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CAUTION: Once instances must always be defined statically. |
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*/ |
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struct Once |
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{ |
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MutexType mutex; |
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int initialized; |
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}; |
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void PEGASUS_COMMON_LINKAGE __once(Once* once, void (*function)()); |
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inline void once(Once* once, void (*function)()) |
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{ |
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if (once->initialized == 0) |
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__once(once, function); |
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} |
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PEGASUS_NAMESPACE_END |
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#endif /* Pegasus_Once_h */ |
Return to
Once.h
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