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/* Copyright (c) 2003-2007 MySQL AB
Use is subject to license terms
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */
#ifndef MemoryChannel_H
#define MemoryChannel_H
//===========================================================================
//
// .DESCRIPTION
// Pointer based communication channel for communication between two
// thread. It does not copy any data in or out the channel so the
// item that is put in can not be used untill the other thread has
// given it back. There is no support for detecting the return of a
// item. The channel is half-duplex.
// For comminication between 1 writer and 1 reader use the MemoryChannel
// class, for comminication between multiple writer and 1 reader use the
// MemoryChannelMultipleWriter. There is no support for multiple readers.
//
// .TYPICAL USE:
// to communicate between threads.
//
// .EXAMPLE:
// See AsyncFile.C
//===========================================================================
//
//
// MemoryChannel( int size= 256);
// Constuctor
// Parameters:
// size : amount of pointer it can hold
//
// void operator ++ ();
// increments the index with one, if size is reached it is set to zero
//
// virtual void write( T *t);
// Puts the item in the channel if the channel is full an error is reported.
// Parameters:
// t: pointer to item to put in the channel, after this the item
// is shared with the other thread.
// errors
// AFS_ERROR_CHANNALFULL, channel is full
//
// T* read();
// Reads a itemn from the channel, if channel is empty it blocks untill
// an item can be read.
// return
// T : item from the channel
//
// T* tryRead();
// Reads a item from the channel, if channel is empty it returns zero.
// return
// T : item from the channel or zero if channel is empty.
//
#include "ErrorHandlingMacros.hpp"
#include "CircularIndex.hpp"
#include "NdbMutex.h"
#include "NdbCondition.h"
#include <NdbOut.hpp>
template <class T>
class MemoryChannel
{
public:
MemoryChannel( int size= 512);
virtual ~MemoryChannel( );
void writeChannel( T *t);
void writeChannelNoSignal( T *t);
T* readChannel();
T* tryReadChannel();
private:
int theSize;
T **theChannel;
CircularIndex theWriteIndex;
CircularIndex theReadIndex;
NdbMutex* theMutexPtr;
NdbCondition* theConditionPtr;
template<class U>
friend NdbOut& operator<<(NdbOut& out, const MemoryChannel<U> & chn);
};
template <class T>
NdbOut& operator<<(NdbOut& out, const MemoryChannel<T> & chn)
{
NdbMutex_Lock(chn.theMutexPtr);
out << "[ theSize: " << chn.theSize
<< " theReadIndex: " << (int)chn.theReadIndex
<< " theWriteIndex: " << (int)chn.theWriteIndex << " ]";
NdbMutex_Unlock(chn.theMutexPtr);
return out;
}
template <class T> MemoryChannel<T>::MemoryChannel( int size):
theSize(size),
theChannel(new T*[size] ),
theWriteIndex(0, size),
theReadIndex(0, size)
{
theMutexPtr = NdbMutex_Create();
theConditionPtr = NdbCondition_Create();
}
template <class T> MemoryChannel<T>::~MemoryChannel( )
{
NdbMutex_Destroy(theMutexPtr);
NdbCondition_Destroy(theConditionPtr);
delete [] theChannel;
}
template <class T> void MemoryChannel<T>::writeChannel( T *t)
{
NdbMutex_Lock(theMutexPtr);
if(full(theWriteIndex, theReadIndex) || theChannel == NULL) abort();
theChannel[theWriteIndex]= t;
++theWriteIndex;
NdbMutex_Unlock(theMutexPtr);
NdbCondition_Signal(theConditionPtr);
}
template <class T> void MemoryChannel<T>::writeChannelNoSignal( T *t)
{
NdbMutex_Lock(theMutexPtr);
if(full(theWriteIndex, theReadIndex) || theChannel == NULL) abort();
theChannel[theWriteIndex]= t;
++theWriteIndex;
NdbMutex_Unlock(theMutexPtr);
}
template <class T> T* MemoryChannel<T>::readChannel()
{
T* tmp;
NdbMutex_Lock(theMutexPtr);
while ( empty(theWriteIndex, theReadIndex) )
{
NdbCondition_Wait(theConditionPtr,
theMutexPtr);
}
tmp= theChannel[theReadIndex];
++theReadIndex;
NdbMutex_Unlock(theMutexPtr);
return tmp;
}
template <class T> T* MemoryChannel<T>::tryReadChannel()
{
T* tmp= 0;
NdbMutex_Lock(theMutexPtr);
if ( !empty(theWriteIndex, theReadIndex) )
{
tmp= theChannel[theReadIndex];
++theReadIndex;
}
NdbMutex_Unlock(theMutexPtr);
return tmp;
}
#endif // MemoryChannel_H
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