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/*
Copyright (c) 2007-2013 Contributors as noted in the AUTHORS file
This file is part of 0MQ.
0MQ is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
0MQ 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 Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef __ZMQ_YPIPE_CONFLATE_HPP_INCLUDED__
#define __ZMQ_YPIPE_CONFLATE_HPP_INCLUDED__
#include "platform.hpp"
#include "dbuffer.hpp"
#include "ypipe_base.hpp"
namespace zmq
{
// Adapter for dbuffer, to plug it in instead of a queue for the sake
// of implementing the conflate socket option, which, if set, makes
// the receiving side to discard all incoming messages but the last one.
//
// reader_awake flag is needed here to mimic ypipe delicate behaviour
// around the reader being asleep (see 'c' pointer being NULL in ypipe.hpp)
template <typename T, int N> class ypipe_conflate_t : public ypipe_base_t<T,N>
{
public:
// Initialises the pipe.
inline ypipe_conflate_t ()
: reader_awake(false)
{
}
// The destructor doesn't have to be virtual. It is mad virtual
// just to keep ICC and code checking tools from complaining.
inline virtual ~ypipe_conflate_t ()
{
}
// Following function (write) deliberately copies uninitialised data
// when used with zmq_msg. Initialising the VSM body for
// non-VSM messages won't be good for performance.
#ifdef ZMQ_HAVE_OPENVMS
#pragma message save
#pragma message disable(UNINIT)
#endif
inline void write (const T &value_, bool incomplete_)
{
(void)incomplete_;
dbuffer.write (value_);
}
#ifdef ZMQ_HAVE_OPENVMS
#pragma message restore
#endif
// There are no incomplete items for conflate ypipe
inline bool unwrite (T *value_)
{
return false;
}
// Flush is no-op for conflate ypipe. Reader asleep behaviour
// is as of the usual ypipe.
// Returns false if the reader thread is sleeping. In that case,
// caller is obliged to wake the reader up before using the pipe again.
inline bool flush ()
{
return reader_awake;
}
// Check whether item is available for reading.
inline bool check_read ()
{
bool res = dbuffer.check_read ();
if (!res)
reader_awake = false;
return res;
}
// Reads an item from the pipe. Returns false if there is no value.
// available.
inline bool read (T *value_)
{
if (!check_read ())
return false;
return dbuffer.read (value_);
}
// Applies the function fn to the first elemenent in the pipe
// and returns the value returned by the fn.
// The pipe mustn't be empty or the function crashes.
inline bool probe (bool (*fn)(T &))
{
return dbuffer.probe (fn);
}
protected:
dbuffer_t <T> dbuffer;
bool reader_awake;
// Disable copying of ypipe object.
ypipe_conflate_t (const ypipe_conflate_t&);
const ypipe_conflate_t &operator = (const ypipe_conflate_t&);
};
}
#endif
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