Merge commit 'e988fee1679536137b87d10e939eff5c1f27c8ab' as 'libs/libzmq'

libs/libzmq/src/ypipe_conflate.hpp

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+/*
+    Copyright (c) 2007-2016 Contributors as noted in the AUTHORS file
+
+    This file is part of libzmq, the ZeroMQ core engine in C++.
+
+    libzmq is free software; you can redistribute it and/or modify it under
+    the terms of the GNU Lesser General Public License (LGPL) as published
+    by the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    As a special exception, the Contributors give you permission to link
+    this library with independent modules to produce an executable,
+    regardless of the license terms of these independent modules, and to
+    copy and distribute the resulting executable under terms of your choice,
+    provided that you also meet, for each linked independent module, the
+    terms and conditions of the license of that module. An independent
+    module is a module which is not derived from or based on this library.
+    If you modify this library, you must extend this exception to your
+    version of the library.
+
+    libzmq 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> class ypipe_conflate_t ZMQ_FINAL : public ypipe_base_t<T>
+{
+  public:
+    //  Initialises the pipe.
+    ypipe_conflate_t () : reader_awake (false) {}
+
+    //  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
+    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
+    bool unwrite (T *) { 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.
+    bool flush () { return reader_awake; }
+
+    //  Check whether item is available for reading.
+    bool check_read ()
+    {
+        const 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.
+    bool read (T *value_)
+    {
+        if (!check_read ())
+            return false;
+
+        return dbuffer.read (value_);
+    }
+
+    //  Applies the function fn to the first element in the pipe
+    //  and returns the value returned by the fn.
+    //  The pipe mustn't be empty or the function crashes.
+    bool probe (bool (*fn_) (const T &)) { return dbuffer.probe (fn_); }
+
+  protected:
+    dbuffer_t<T> dbuffer;
+    bool reader_awake;
+
+    ZMQ_NON_COPYABLE_NOR_MOVABLE (ypipe_conflate_t)
+};
+}
+
+#endif