Line data    Source code

       1             : /*
       2             :     Copyright (c) 2007-2016 Contributors as noted in the AUTHORS file
       3             : 
       4             :     This file is part of libzmq, the ZeroMQ core engine in C++.
       5             : 
       6             :     libzmq is free software; you can redistribute it and/or modify it under
       7             :     the terms of the GNU Lesser General Public License (LGPL) as published
       8             :     by the Free Software Foundation; either version 3 of the License, or
       9             :     (at your option) any later version.
      10             : 
      11             :     As a special exception, the Contributors give you permission to link
      12             :     this library with independent modules to produce an executable,
      13             :     regardless of the license terms of these independent modules, and to
      14             :     copy and distribute the resulting executable under terms of your choice,
      15             :     provided that you also meet, for each linked independent module, the
      16             :     terms and conditions of the license of that module. An independent
      17             :     module is a module which is not derived from or based on this library.
      18             :     If you modify this library, you must extend this exception to your
      19             :     version of the library.
      20             : 
      21             :     libzmq is distributed in the hope that it will be useful, but WITHOUT
      22             :     ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
      23             :     FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
      24             :     License for more details.
      25             : 
      26             :     You should have received a copy of the GNU Lesser General Public License
      27             :     along with this program.  If not, see <http://www.gnu.org/licenses/>.
      28             : */
      29             : 
      30             : #ifndef __ZMQ_YPIPE_CONFLATE_HPP_INCLUDED__
      31             : #define __ZMQ_YPIPE_CONFLATE_HPP_INCLUDED__
      32             : 
      33             : #include "platform.hpp"
      34             : #include "dbuffer.hpp"
      35             : #include "ypipe_base.hpp"
      36             : 
      37             : namespace zmq
      38             : {
      39             : 
      40             :     //  Adapter for dbuffer, to plug it in instead of a queue for the sake
      41             :     //  of implementing the conflate socket option, which, if set, makes
      42             :     //  the receiving side to discard all incoming messages but the last one.
      43             :     //
      44             :     //  reader_awake flag is needed here to mimic ypipe delicate behaviour
      45             :     //  around the reader being asleep (see 'c' pointer being NULL in ypipe.hpp)
      46             : 
      47             :     template <typename T> class ypipe_conflate_t : public ypipe_base_t <T>
      48             :     {
      49             :     public:
      50             : 
      51             :         //  Initialises the pipe.
      52             :         inline ypipe_conflate_t ()
      53          12 :             : reader_awake(false)
      54             :         {
      55             :         }
      56             : 
      57             :         //  The destructor doesn't have to be virtual. It is made virtual
      58             :         //  just to keep ICC and code checking tools from complaining.
      59           6 :         inline virtual ~ypipe_conflate_t ()
      60             :         {
      61          12 :         }
      62             : 
      63             :         //  Following function (write) deliberately copies uninitialised data
      64             :         //  when used with zmq_msg. Initialising the VSM body for
      65             :         //  non-VSM messages won't be good for performance.
      66             : 
      67             : #ifdef ZMQ_HAVE_OPENVMS
      68             : #pragma message save
      69             : #pragma message disable(UNINIT)
      70             : #endif
      71          63 :         inline void write (const T &value_, bool incomplete_)
      72             :         {
      73             :             (void)incomplete_;
      74             : 
      75          63 :             dbuffer.write (value_);
      76          63 :         }
      77             : 
      78             : #ifdef ZMQ_HAVE_OPENVMS
      79             : #pragma message restore
      80             : #endif
      81             : 
      82             :         // There are no incomplete items for conflate ypipe
      83           3 :         inline bool unwrite (T *)
      84             :         {
      85           3 :             return false;
      86             :         }
      87             : 
      88             :         //  Flush is no-op for conflate ypipe. Reader asleep behaviour
      89             :         //  is as of the usual ypipe.
      90             :         //  Returns false if the reader thread is sleeping. In that case,
      91             :         //  caller is obliged to wake the reader up before using the pipe again.
      92           9 :         inline bool flush ()
      93             :         {
      94           9 :             return reader_awake;
      95             :         }
      96             : 
      97             :         //  Check whether item is available for reading.
      98           9 :         inline bool check_read ()
      99             :         {
     100          18 :             bool res = dbuffer.check_read ();
     101           9 :             if (!res)
     102           3 :                 reader_awake = false;
     103             : 
     104           9 :             return res;
     105             :         }
     106             : 
     107             :         //  Reads an item from the pipe. Returns false if there is no value.
     108             :         //  available.
     109           9 :         inline bool read (T *value_)
     110             :         {
     111           9 :             if (!check_read ())
     112             :                 return false;
     113             : 
     114           6 :             return dbuffer.read (value_);
     115             :         }
     116             : 
     117             :         //  Applies the function fn to the first elemenent in the pipe
     118             :         //  and returns the value returned by the fn.
     119             :         //  The pipe mustn't be empty or the function crashes.
     120           0 :         inline bool probe (bool (*fn)(const T &))
     121             :         {
     122           0 :             return dbuffer.probe (fn);
     123             :         }
     124             : 
     125             :     protected:
     126             : 
     127             :         dbuffer_t <T> dbuffer;
     128             :         bool reader_awake;
     129             : 
     130             :         //  Disable copying of ypipe object.
     131             :         ypipe_conflate_t (const ypipe_conflate_t&);
     132             :         const ypipe_conflate_t &operator = (const ypipe_conflate_t&);
     133             :     };
     134             : 
     135             : }
     136             : 
     137             : #endif