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/* osgEarth - Dynamic map generation toolkit for OpenSceneGraph
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* Copyright 2008-2010 Pelican Mapping
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* osgEarth is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>
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#ifndef OSGEARTH_THREADING_UTILS_H
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#define OSGEARTH_THREADING_UTILS_H 1
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#include <osgEarth/Common>
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#include <OpenThreads/Condition>
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#include <OpenThreads/Mutex>
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#define USE_CUSTOM_READ_WRITE_LOCK 1
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//# define TRACE_THREADS 1
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namespace osgEarth { namespace Threading
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typedef OpenThreads::Mutex Mutex;
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typedef OpenThreads::ScopedLock<OpenThreads::Mutex> ScopedMutexLock;
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#ifdef USE_CUSTOM_READ_WRITE_LOCK
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* Event with a toggled signal state.
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Event() : _set( false ) { }
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for( int i=0; i<255; ++i ) // workaround buggy broadcast
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OpenThreads::ScopedLock<OpenThreads::Mutex> lock( _m );
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return _set ? true : (_cond.wait( &_m ) == 0);
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OpenThreads::ScopedLock<OpenThreads::Mutex> lock( _m );
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_cond.broadcast(); // possible deadlock before OSG r10457 on windows
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OpenThreads::ScopedLock<OpenThreads::Mutex> lock( _m );
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inline bool isSet() const {
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OpenThreads::Mutex _m;
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OpenThreads::Condition _cond;
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* Custom read/write lock. The read/write lock in OSG can unlock mutexes from a different
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* thread than the one that locked them - this can hang the thread in Windows.
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* http://www.codeproject.com/KB/threads/ReadWriteLock.aspx
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typedef std::set<OpenThreads::Thread*> TracedThreads;
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OpenThreads::Mutex _traceMutex;
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_noWriterEvent.set();
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_noReadersEvent.set();
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OpenThreads::ScopedLock<OpenThreads::Mutex> ttLock(_traceMutex);
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if( _trace.find(OpenThreads::Thread::CurrentThread()) != _trace.end() )
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OE_WARN << "TRACE: tried to double-lock" << std::endl;
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_noWriterEvent.wait(); // wait for a writer to quit if there is one
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incrementReaderCount(); // register this reader
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if ( !_noWriterEvent.isSet() ) // double lock check, in case a writer snuck in while inrementing
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decrementReaderCount(); // if it did, undo the registration and try again
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break; // otherwise, we're in
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OpenThreads::ScopedLock<OpenThreads::Mutex> ttLock(_traceMutex);
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_trace.insert(OpenThreads::Thread::CurrentThread());
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decrementReaderCount(); // unregister this reader
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OpenThreads::ScopedLock<OpenThreads::Mutex> ttLock(_traceMutex);
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_trace.erase(OpenThreads::Thread::CurrentThread());
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OpenThreads::ScopedLock<OpenThreads::Mutex> ttLock(_traceMutex);
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if( _trace.find(OpenThreads::Thread::CurrentThread()) != _trace.end() )
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OE_WARN << "TRACE: tried to double-lock" << std::endl;
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OpenThreads::ScopedLock<OpenThreads::Mutex> lock( _lockWriterMutex ); // one at a time please
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_noWriterEvent.wait(); // wait for a writer to quit if there is one
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_noWriterEvent.reset(); // prevent further writers from joining
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_noReadersEvent.wait(); // wait for all readers to quit
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OpenThreads::ScopedLock<OpenThreads::Mutex> ttLock(_traceMutex);
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_trace.insert(OpenThreads::Thread::CurrentThread());
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_noWriterEvent.set();
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OpenThreads::ScopedLock<OpenThreads::Mutex> ttLock(_traceMutex);
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_trace.erase(OpenThreads::Thread::CurrentThread());
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void incrementReaderCount()
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OpenThreads::ScopedLock<OpenThreads::Mutex> lock( _readerCountMutex );
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_readerCount++; // add a reader
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_noReadersEvent.reset(); // there's at least one reader now so clear the flag
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void decrementReaderCount()
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OpenThreads::ScopedLock<OpenThreads::Mutex> lock( _readerCountMutex );
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_readerCount--; // remove a reader
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if ( _readerCount <= 0 ) // if that was the last one, signal that writers are now allowed
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_noReadersEvent.set();
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OpenThreads::Mutex _lockWriterMutex;
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OpenThreads::Mutex _readerCountMutex;
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Event _noWriterEvent;
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Event _noReadersEvent;
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struct ScopedWriteLock
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ScopedWriteLock( ReadWriteMutex& lock ) : _lock(lock) { _lock.writeLock(); }
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~ScopedWriteLock() { _lock.writeUnlock(); }
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ReadWriteMutex& _lock;
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struct ScopedReadLock
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ScopedReadLock( ReadWriteMutex& lock ) : _lock(lock) { _lock.readLock(); }
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~ScopedReadLock() { _lock.readUnlock(); }
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ReadWriteMutex& _lock;
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typedef OpenThreads::ReadWriteMutex ReadWriteMutex;
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typedef OpenThreads::ScopedWriteLock ScopedWriteLock;
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typedef OpenThreads::ScopedReadLock ScopedReadLock;
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} } // namepsace osgEarth::Threading
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#endif // OSGEARTH_THREADING_UTILS_H
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src/osgEarth/ThreadingUtils
