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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