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123 lines
3.8 KiB
C++
123 lines
3.8 KiB
C++
/*
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Copyright (c) 2007-2016 Contributors as noted in the AUTHORS file
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This file is part of libzmq, the ZeroMQ core engine in C++.
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libzmq 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 (LGPL) as published
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by 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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As a special exception, the Contributors give you permission to link
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this library with independent modules to produce an executable,
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regardless of the license terms of these independent modules, and to
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copy and distribute the resulting executable under terms of your choice,
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provided that you also meet, for each linked independent module, the
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terms and conditions of the license of that module. An independent
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module is a module which is not derived from or based on this library.
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If you modify this library, you must extend this exception to your
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version of the library.
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libzmq is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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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 ZMQ_FINAL : 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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ypipe_conflate_t () : reader_awake (false) {}
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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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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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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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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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bool check_read ()
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{
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const 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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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 element 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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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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ZMQ_NON_COPYABLE_NOR_MOVABLE (ypipe_conflate_t)
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};
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}
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#endif
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