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SPSCQueue.h
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SPSCQueue.h
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/*
Pharmer: Efficient and Exact 3D Pharmacophore Search
Copyright (C) 2011 David Ryan Koes and the University of Pittsburgh
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; either version 2
of the License, or (at your option) any later version.
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.
*/
/*
* SPSCQueue.h
*
* Created on: Feb 11, 2010
* Author: dkoes
*
* A single producer/single consumer thread-safe non-blocking queue
*/
#ifndef SPSCQUEUE_H_
#define SPSCQUEUE_H_
using namespace std;
template < typename T, unsigned N>
class SPSCQueue
{
T* buffer[N];
//buffering is to avoid false sharing
volatile unsigned pread;
unsigned padding[15];
volatile unsigned pwrite;
unsigned padding2[15];
bool done;
public:
SPSCQueue(): pread(0), pwrite(0), done(false)
{
memset(buffer, 0, sizeof(buffer));
}
virtual ~SPSCQueue() {}
//removes all data, calling delete on the pointers and resets done
//NOT THREAD SAFE
void clearAndDestroy()
{
for(unsigned i = 0; i < N; i++)
{
if(buffer[i])
{
delete buffer[i];
buffer[i] = NULL;
}
}
done = false;
pread = pwrite = 0;
}
//return true if succesful (queue not blocked, val not null)
bool push(T* val)
{
if (val == NULL) return false;
if (buffer[pwrite] == NULL) {
//memory barrier necessary here if stores become visible out of order
__sync_synchronize();
buffer[pwrite] = val;
pwrite = (pwrite+1)%N;
return true;
}
return false;
}
//return true if successful (data currently available)
bool pop(T*& val)
{
if(buffer[pread] == NULL)
return false;
val = buffer[pread];
buffer[pread] = NULL;
pread = (pread+1)%N;
return true;
}
//empty and will continue to be empty
bool empty()
{
return buffer[pread] == NULL && done;
}
//producer has no more data
void setDone() { done =true; }
};
//stores data, not pointers
template < typename T, unsigned N>
class SPSCDataQueue
{
struct Node {
T val;
bool isEmpty;
Node(): isEmpty(true) {}
};
Node buffer[N];
//buffering is to avoid false sharing
volatile unsigned pread;
unsigned padding[15];
volatile unsigned pwrite;
unsigned padding2[15];
bool done;
public:
SPSCDataQueue(): pread(0), pwrite(0), done(false)
{
}
virtual ~SPSCDataQueue() {}
//rblocks on full queue
void push(const T& val)
{
while(true)
{
if (buffer[pwrite].isEmpty)
{
//memory barrier necessary here if stores become visible out of order
__sync_synchronize();
buffer[pwrite].val = val;
buffer[pwrite].isEmpty = false;
if (pwrite >= N - 1)
pwrite = 0;
else
pwrite++;
return;
}
this_thread::yield();
this_thread::interruption_point();
}
}
//return true if successful (data currently available)
bool pop(T& val)
{
if(buffer[pread].isEmpty)
return false;
swap(val,buffer[pread].val);
buffer[pread].isEmpty = true;;
if(pread >= N-1)
pread = 0;
else
pread++;
return true;
}
T* top()
{
if(buffer[pread].isEmpty)
return NULL;
return &buffer[pread].val;
}
//empty and will continue to be empty
bool empty()
{
return buffer[pread].isEmpty && done;
}
//producer has no more data
void setDone() { done =true; }
};
#endif /* SPSCQUEUE_H_ */