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353 lines
11 KiB
C++
353 lines
11 KiB
C++
/// \file
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/// \brief \b [Internal] Passes queued data between threads using a circular buffer with read and write pointers
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///
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/// This file is part of RakNet Copyright 2003 Kevin Jenkins.
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///
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/// Usage of RakNet is subject to the appropriate license agreement.
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/// Creative Commons Licensees are subject to the
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/// license found at
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/// http://creativecommons.org/licenses/by-nc/2.5/
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/// Single application licensees are subject to the license found at
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/// http://www.jenkinssoftware.com/SingleApplicationLicense.html
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/// Custom license users are subject to the terms therein.
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/// GPL license users are subject to the GNU General Public
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/// License as published by the Free
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/// Software Foundation; either version 2 of the License, or (at your
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/// option) any later version.
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#ifndef __SINGLE_PRODUCER_CONSUMER_H
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#define __SINGLE_PRODUCER_CONSUMER_H
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#include <assert.h>
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static const int MINIMUM_LIST_SIZE=8;
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#include "RakMemoryOverride.h"
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#include "Export.h"
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/// The namespace DataStructures was only added to avoid compiler errors for commonly named data structures
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/// As these data structures are stand-alone, you can use them outside of RakNet for your own projects if you wish.
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namespace DataStructures
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{
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/// \brief A single producer consumer implementation without critical sections.
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template <class SingleProducerConsumerType>
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class RAK_DLL_EXPORT SingleProducerConsumer : public RakNet::RakMemoryOverride
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{
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public:
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/// Constructor
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SingleProducerConsumer();
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/// Destructor
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~SingleProducerConsumer();
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/// WriteLock must be immediately followed by WriteUnlock. These two functions must be called in the same thread.
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/// \return A pointer to a block of data you can write to.
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SingleProducerConsumerType* WriteLock(void);
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/// Call if you don't want to write to a block of data from WriteLock() after all.
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/// Cancelling locks cancels all locks back up to the data passed. So if you lock twice and cancel using the first lock, the second lock is ignored
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/// \param[in] cancelToLocation Which WriteLock() to cancel.
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void CancelWriteLock(SingleProducerConsumerType* cancelToLocation);
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/// Call when you are done writing to a block of memory returned by WriteLock()
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void WriteUnlock(void);
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/// ReadLock must be immediately followed by ReadUnlock. These two functions must be called in the same thread.
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/// \retval 0 No data is availble to read
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/// \retval Non-zero The data previously written to, in another thread, by WriteLock followed by WriteUnlock.
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SingleProducerConsumerType* ReadLock(void);
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// Cancelling locks cancels all locks back up to the data passed. So if you lock twice and cancel using the first lock, the second lock is ignored
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/// param[in] Which ReadLock() to cancel.
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void CancelReadLock(SingleProducerConsumerType* cancelToLocation);
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/// Signals that we are done reading the the data from the least recent call of ReadLock.
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/// At this point that pointer is no longer valid, and should no longer be read.
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void ReadUnlock(void);
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/// Clear is not thread-safe and none of the lock or unlock functions should be called while it is running.
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void Clear(void);
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/// This function will estimate how many elements are waiting to be read. It's threadsafe enough that the value returned is stable, but not threadsafe enough to give accurate results.
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/// \return An ESTIMATE of how many data elements are waiting to be read
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int Size(void) const;
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/// Make sure that the pointer we done reading for the call to ReadUnlock is the right pointer.
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/// param[in] A previous pointer returned by ReadLock()
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bool CheckReadUnlockOrder(const SingleProducerConsumerType* data) const;
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/// Returns if ReadUnlock was called before ReadLock
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/// \return If the read is locked
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bool ReadIsLocked(void) const;
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private:
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struct DataPlusPtr
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{
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DataPlusPtr () {readyToRead=false;}
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SingleProducerConsumerType object;
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// Ready to read is so we can use an equality boolean comparison, in case the writePointer var is trashed while context switching.
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volatile bool readyToRead;
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volatile DataPlusPtr *next;
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};
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volatile DataPlusPtr *readAheadPointer;
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volatile DataPlusPtr *writeAheadPointer;
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volatile DataPlusPtr *readPointer;
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volatile DataPlusPtr *writePointer;
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unsigned readCount, writeCount;
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};
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template <class SingleProducerConsumerType>
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SingleProducerConsumer<SingleProducerConsumerType>::SingleProducerConsumer()
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{
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// Preallocate
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readPointer = new DataPlusPtr;
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writePointer=readPointer;
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readPointer->next = new DataPlusPtr;
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int listSize;
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#ifdef _DEBUG
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assert(MINIMUM_LIST_SIZE>=3);
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#endif
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for (listSize=2; listSize < MINIMUM_LIST_SIZE; listSize++)
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{
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readPointer=readPointer->next;
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readPointer->next = new DataPlusPtr;
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}
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readPointer->next->next=writePointer; // last to next = start
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readPointer=writePointer;
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readAheadPointer=readPointer;
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writeAheadPointer=writePointer;
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readCount=writeCount=0;
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}
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template <class SingleProducerConsumerType>
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SingleProducerConsumer<SingleProducerConsumerType>::~SingleProducerConsumer()
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{
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volatile DataPlusPtr *next;
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readPointer=writeAheadPointer->next;
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while (readPointer!=writeAheadPointer)
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{
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next=readPointer->next;
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delete (char*) readPointer;
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readPointer=next;
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}
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delete (char*) readPointer;
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}
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template <class SingleProducerConsumerType>
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SingleProducerConsumerType* SingleProducerConsumer<SingleProducerConsumerType>::WriteLock( void )
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{
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if (writeAheadPointer->next==readPointer ||
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writeAheadPointer->next->readyToRead==true)
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{
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volatile DataPlusPtr *originalNext=writeAheadPointer->next;
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writeAheadPointer->next=new DataPlusPtr;
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assert(writeAheadPointer->next);
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writeAheadPointer->next->next=originalNext;
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}
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volatile DataPlusPtr *last;
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last=writeAheadPointer;
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writeAheadPointer=writeAheadPointer->next;
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return (SingleProducerConsumerType*) last;
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}
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template <class SingleProducerConsumerType>
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void SingleProducerConsumer<SingleProducerConsumerType>::CancelWriteLock( SingleProducerConsumerType* cancelToLocation )
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{
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writeAheadPointer=(DataPlusPtr *)cancelToLocation;
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}
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template <class SingleProducerConsumerType>
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void SingleProducerConsumer<SingleProducerConsumerType>::WriteUnlock( void )
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{
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// DataPlusPtr *dataContainer = (DataPlusPtr *)structure;
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#ifdef _DEBUG
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assert(writePointer->next!=readPointer);
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assert(writePointer!=writeAheadPointer);
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#endif
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writeCount++;
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// User is done with the data, allow send by updating the write pointer
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writePointer->readyToRead=true;
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writePointer=writePointer->next;
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}
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template <class SingleProducerConsumerType>
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SingleProducerConsumerType* SingleProducerConsumer<SingleProducerConsumerType>::ReadLock( void )
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{
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if (readAheadPointer==writePointer ||
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readAheadPointer->readyToRead==false)
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{
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return 0;
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}
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volatile DataPlusPtr *last;
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last=readAheadPointer;
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readAheadPointer=readAheadPointer->next;
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return (SingleProducerConsumerType*)last;
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}
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template <class SingleProducerConsumerType>
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void SingleProducerConsumer<SingleProducerConsumerType>::CancelReadLock( SingleProducerConsumerType* cancelToLocation )
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{
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#ifdef _DEBUG
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assert(readPointer!=writePointer);
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#endif
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readAheadPointer=(DataPlusPtr *)cancelToLocation;
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}
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template <class SingleProducerConsumerType>
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void SingleProducerConsumer<SingleProducerConsumerType>::ReadUnlock( void )
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{
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#ifdef _DEBUG
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assert(readAheadPointer!=readPointer); // If hits, then called ReadUnlock before ReadLock
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assert(readPointer!=writePointer); // If hits, then called ReadUnlock when Read returns 0
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#endif
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readCount++;
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// Allow writes to this memory block
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readPointer->readyToRead=false;
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readPointer=readPointer->next;
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}
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template <class SingleProducerConsumerType>
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void SingleProducerConsumer<SingleProducerConsumerType>::Clear( void )
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{
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// Shrink the list down to MINIMUM_LIST_SIZE elements
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volatile DataPlusPtr *next;
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writePointer=readPointer->next;
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int listSize=1;
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next=readPointer->next;
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while (next!=readPointer)
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{
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listSize++;
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next=next->next;
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}
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while (listSize-- > MINIMUM_LIST_SIZE)
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{
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next=writePointer->next;
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#ifdef _DEBUG
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assert(writePointer!=readPointer);
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#endif
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delete (char*) writePointer;
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writePointer=next;
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}
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readPointer->next=writePointer;
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writePointer=readPointer;
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readAheadPointer=readPointer;
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writeAheadPointer=writePointer;
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readCount=writeCount=0;
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}
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template <class SingleProducerConsumerType>
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int SingleProducerConsumer<SingleProducerConsumerType>::Size( void ) const
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{
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return writeCount-readCount;
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}
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template <class SingleProducerConsumerType>
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bool SingleProducerConsumer<SingleProducerConsumerType>::CheckReadUnlockOrder(const SingleProducerConsumerType* data) const
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{
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return const_cast<const SingleProducerConsumerType *>(&readPointer->object) == data;
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}
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template <class SingleProducerConsumerType>
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bool SingleProducerConsumer<SingleProducerConsumerType>::ReadIsLocked(void) const
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{
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return readAheadPointer!=readPointer;
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}
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}
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#endif
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/*
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#include "SingleProducerConsumer.h"
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#include <process.h>
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#include <assert.h>
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#include <stdio.h>
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#include <windows.h>
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#if defined(_PS3)
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#include <math.h>
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#else
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#include <cmath>
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#endif
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#include <stdlib.h>
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#define READ_COUNT_ITERATIONS 10000000
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DataStructures::SingleProducerConsumer<unsigned long> spc;
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unsigned long readCount;
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unsigned __stdcall ProducerThread( LPVOID arguments )
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{
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unsigned long producerCount;
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unsigned long *writeBlock;
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producerCount=0;
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while (readCount < READ_COUNT_ITERATIONS)
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{
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writeBlock=spc.WriteLock();
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*writeBlock=producerCount;
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spc.WriteUnlock();
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producerCount++;
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if ((producerCount%1000000)==0)
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{
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printf("WriteCount: %i. BufferSize=%i\n", producerCount, spc.Size());
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}
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}
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printf("PRODUCER THREAD ENDED!\n");
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return 0;
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}
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unsigned __stdcall ConsumerThread( LPVOID arguments )
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{
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unsigned long *readBlock;
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while (readCount < READ_COUNT_ITERATIONS)
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{
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if ((readBlock=spc.ReadLock())!=0)
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{
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if (*readBlock!=readCount)
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{
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printf("Test failed! Expected %i got %i!\n", readCount, *readBlock);
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readCount = READ_COUNT_ITERATIONS;
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assert(0);
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}
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spc.ReadUnlock();
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readCount++;
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if ((readCount%1000000)==0)
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{
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printf("ReadCount: %i. BufferSize=%i\n", readCount, spc.Size());
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}
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}
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}
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printf("CONSUMER THREAD ENDED!\n");
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return 0;
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}
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void main(void)
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{
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readCount=0;
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unsigned threadId1 = 0;
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unsigned threadId2 = 0;
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HANDLE thread1Handle, thread2Handle;
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unsigned long startTime = timeGetTime();
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thread1Handle=(HANDLE)_beginthreadex( NULL, 0, ProducerThread, 0, 0, &threadId1 );
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thread2Handle=(HANDLE)_beginthreadex( NULL, 0, ConsumerThread, 0, 0, &threadId1 );
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while (readCount < READ_COUNT_ITERATIONS)
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{
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Sleep(0);
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}
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char str[256];
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printf("Elapsed time = %i milliseconds. Press Enter to continue\n", timeGetTime() - startTime);
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fgets(str, sizeof(str), stdin);
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}
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*/
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