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128 lines
3.7 KiB
C++
128 lines
3.7 KiB
C++
/*
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Copyright (c) 2007-2015 Contributors as noted in the AUTHORS file
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This file is part of 0MQ.
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0MQ is free software; you can redistribute it and/or modify it under
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the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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0MQ is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef __ZMQ_YPIPE_CONFLATE_HPP_INCLUDED__
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#define __ZMQ_YPIPE_CONFLATE_HPP_INCLUDED__
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#include "platform.hpp"
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#include "dbuffer.hpp"
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#include "ypipe_base.hpp"
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namespace zmq
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{
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// Adapter for dbuffer, to plug it in instead of a queue for the sake
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// of implementing the conflate socket option, which, if set, makes
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// the receiving side to discard all incoming messages but the last one.
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//
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// reader_awake flag is needed here to mimic ypipe delicate behaviour
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// around the reader being asleep (see 'c' pointer being NULL in ypipe.hpp)
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template <typename T> class ypipe_conflate_t : public ypipe_base_t <T>
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{
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public:
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// Initialises the pipe.
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inline ypipe_conflate_t ()
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: reader_awake(false)
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{
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}
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// The destructor doesn't have to be virtual. It is mad virtual
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// just to keep ICC and code checking tools from complaining.
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inline virtual ~ypipe_conflate_t ()
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{
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}
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// Following function (write) deliberately copies uninitialised data
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// when used with zmq_msg. Initialising the VSM body for
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// non-VSM messages won't be good for performance.
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#ifdef ZMQ_HAVE_OPENVMS
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#pragma message save
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#pragma message disable(UNINIT)
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#endif
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inline void write (const T &value_, bool incomplete_)
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{
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(void)incomplete_;
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dbuffer.write (value_);
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}
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#ifdef ZMQ_HAVE_OPENVMS
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#pragma message restore
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#endif
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// There are no incomplete items for conflate ypipe
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inline bool unwrite (T *)
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{
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return false;
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}
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// Flush is no-op for conflate ypipe. Reader asleep behaviour
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// is as of the usual ypipe.
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// Returns false if the reader thread is sleeping. In that case,
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// caller is obliged to wake the reader up before using the pipe again.
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inline bool flush ()
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{
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return reader_awake;
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}
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// Check whether item is available for reading.
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inline bool check_read ()
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{
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bool res = dbuffer.check_read ();
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if (!res)
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reader_awake = false;
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return res;
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}
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// Reads an item from the pipe. Returns false if there is no value.
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// available.
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inline bool read (T *value_)
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{
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if (!check_read ())
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return false;
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return dbuffer.read (value_);
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}
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// Applies the function fn to the first elemenent in the pipe
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// and returns the value returned by the fn.
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// The pipe mustn't be empty or the function crashes.
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inline bool probe (bool (*fn)(const T &))
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{
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return dbuffer.probe (fn);
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}
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protected:
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dbuffer_t <T> dbuffer;
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bool reader_awake;
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// Disable copying of ypipe object.
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ypipe_conflate_t (const ypipe_conflate_t&);
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const ypipe_conflate_t &operator = (const ypipe_conflate_t&);
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};
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}
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#endif
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