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connection.h

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00001 /* -*- c++ -*- */
00002 /**************************************************************************
00003  Copyright (c) 2000-2001, Tony Garnock-Jones
00004  All rights reserved.
00005 
00006  Redistribution and use in source and binary forms, with or without
00007  modification, are permitted provided that the following conditions are
00008  met:
00009 
00010      * Redistributions of source code must retain the above copyright
00011        notice, this list of conditions and the following disclaimer.
00012 
00013      * Redistributions in binary form must reproduce the above
00014        copyright notice, this list of conditions and the following
00015        disclaimer in the documentation and/or other materials provided
00016        with the distribution.
00017 
00018      * Neither the names of the copyright holders nor the names of this
00019        software's contributors may be used to endorse or promote
00020        products derived from this software without specific prior
00021        written permission.
00022 
00023  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
00024  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00025  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
00026  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR
00027  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
00028  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
00029  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
00030  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
00031  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
00032  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
00033  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00034 **************************************************************************/
00035 
00036 #ifndef MPS_Connection_H
00037 #define MPS_Connection_H
00038 
00039 namespace MPS {
00040 
00041 /**
00042  * Manages a connection over a Transport to an MPS server. Allows
00043  * message reception and transmission. */
00044 class Connection: public Referenceable {
00045 public:
00046   /// A callback - subclass, and use with setCallback.
00047   class Callback: public Referenceable {
00048   public:
00049     typedef void (Callback::*Method)(InputStream &input);
00050   };
00051 
00052 private:
00053   Address address;              ///< the address of the remote object
00054   ref<Callback> callback;               ///< currently-registered callback.
00055   Callback::Method callbackMethod;      ///< method to invoke on registered callback.
00056 
00057 protected:
00058   /// Constructor for subclasses.
00059   Connection(Address const &a)
00060     : address(a),
00061       callback(0),
00062       callbackMethod(0)
00063   {}
00064 
00065 public:
00066   virtual ~Connection() {}
00067 
00068   /// Extract the address of the object we're connected to.
00069   Address const &getRemoteAddress() const { return address; }
00070 
00071   /**
00072    * Obtain an OutputStream to use to send a message to the remote
00073    * object. The caller must call releaseOutputStream() when it's
00074    * finished with the stream.
00075    *
00076    * @return an OutputStream which, when flushed, will send a message
00077    * to the remote object. */
00078   virtual OutputStream *getOutputStream() = 0;
00079 
00080   /**
00081    * Signals that the caller is finished with an OutputStream obtained
00082    * via the getOutputStream() method.
00083    *
00084    * @param stream the stream to release */
00085   virtual void releaseOutputStream(OutputStream *stream) = 0;
00086 
00087   /**
00088    * Obtain an InputStream to use to receive a message from the remote
00089    * object. The caller must call releaseInputStream() when it's
00090    * finished with the stream.
00091    *
00092    * @return an InputStream which allows reading of the most recent
00093    * message sent back from the remote object. */
00094   virtual InputStream *getInputStream() = 0;
00095 
00096   /**
00097    * Signals that the caller is finished with an InputStream obtained
00098    * via the getInputStream() method.
00099    *
00100    * @param stream the stream to release */
00101   virtual void releaseInputStream(InputStream *stream) = 0;
00102 
00103   /**
00104    * Registers a callback.  Override this if you need to do special
00105    * processing on callback registration (unlikely).
00106    *
00107    * @see Proxy::_setCallback */
00108   virtual void setCallback(ref<Callback> _callback, Callback::Method _method) {
00109     callback = _callback;
00110     callbackMethod = _method;
00111   }
00112 
00113   /**
00114    * If a callback is registered, deregisters it, and calls it. Note
00115    * that callbacks should be called when it's safe to read a complete
00116    * message from this connection (ie. it won't block to do so). This
00117    * method should be called from somewhere within Transports' main loops.
00118    *
00119    * @see Proxy::_setCallback */
00120   void fireCallback(InputStream &input) {
00121     if (callback.valid()) {
00122       // Save the existing callback...
00123       ref<Callback> cb = callback;
00124       Callback::Method meth = callbackMethod;
00125 
00126       // Clear it out, so there's no registered callback anymore...
00127       callback = 0;
00128       callbackMethod = 0;
00129 
00130       // ... and finally call our saved callback.
00131       (cb->*meth)(input);
00132     } else {
00133       // Do nothing if no callback is registered.
00134     }
00135   }
00136 };
00137 
00138 }
00139 
00140 #endif

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