added draft of xfer<T> class

  - A simple container for objects of type \<T\> that can be used for
    transferring the contents rather than copying them.
  - The wrapped object of type \<T\> must implement a transfer() method.

src/OpenFOAM/containers/misc/xfer.H

+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 1991-2008 OpenCFD Ltd.
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software; you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by the
+    Free Software Foundation; either version 2 of the License, or (at your
+    option) any later version.
+
+    OpenFOAM 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 General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM; if not, write to the Free Software Foundation,
+    Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+
+Class
+    Foam::xfer
+
+Description
+    A simple container for objects of type \<T\> that can be used for
+    transferring the contents rather than copying them.
+
+    The wrapped object of type \<T\> must implement a transfer() method.
+
+SourceFiles
+    xferI.H
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef xfer_H
+#define xfer_H
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+
+class Istream;
+class Ostream;
+
+// Forward declaration of friend functions and operators
+template<class T> class xfer;
+
+template<class T> Istream& operator>>(Istream&, xfer<T>&);
+template<class T> Ostream& operator<<(Ostream&, const xfer<T>&);
+
+
+/*---------------------------------------------------------------------------*\
+                         Class xfer Declaration
+\*---------------------------------------------------------------------------*/
+
+template<class T>
+class xfer
+{
+    // Private data
+
+        //- Reference to the underlying datatype
+        T& ref_;
+
+    // Private Member Functions
+
+        //- Disallow default bitwise copy construct
+        xfer(const xfer<T>&);
+
+        //- Disallow default bitwise assignment
+        void operator=(const xfer<T>&);
+
+public:
+
+    // Constructors
+
+        //- Construct null, delaying the transfer to later
+        inline xfer();
+
+        //- Construct by transferring the parameter into this object
+        inline xfer(T&);
+
+        //- Construct by transferring the parameter into this object
+        inline xfer(xfer<T>&);
+
+    // Destructor
+
+        inline ~xfer();
+
+    // Member Functions
+
+        //- Access to the underlying datatype
+        inline T& ref();
+
+        //- Transfer the contents of the parameter into this object
+        inline void transfer(T&);
+
+        //- Transfer the contents of the parameter into this object
+        inline void transfer(xfer<T>&);
+
+        //- Transfer the contents from this object to the parameter
+        inline void yield(T&);
+
+        //- Transfer the contents from this object to the parameter
+        inline void yield(xfer<T>&);
+
+    // Member Operators
+
+        //- Transfer the contents into this object
+        inline void operator=(T&);
+
+        //- Transfer the contents into this object
+        inline void operator=(xfer<T>&);
+
+        //- Return a non-const reference to const object
+        //  Useful for read-constructors where the argument is temporary
+        inline xfer<T>& operator()() const;
+
+
+    // Istream operator
+
+        //- Read from Istream, discarding current contents
+        friend Istream& operator>>
+        #ifndef __CINT__
+        <T>
+        #endif
+        (Istream&, xfer<T>&);
+
+    // Ostream operator
+
+        //- Write to Ostream
+        friend Ostream& operator<<
+        #ifndef __CINT__
+        <T>
+        #endif
+        (Ostream&, const xfer<T>&);
+
+};
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+} // End namespace Foam
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#include "xferI.H"
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //

src/OpenFOAM/containers/misc/xferI.H

+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 1991-2008 OpenCFD Ltd.
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software; you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by the
+    Free Software Foundation; either version 2 of the License, or (at your
+    option) any later version.
+
+    OpenFOAM 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 General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM; if not, write to the Free Software Foundation,
+    Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+
+\*---------------------------------------------------------------------------*/
+
+// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
+
+template<class T>
+Foam::xfer<T>::xfer()
+:
+    ref_()
+{}
+
+
+template<class T>
+Foam::xfer<T>::xfer(T& t)
+:
+    ref_()
+{
+    transfer(t);
+}
+
+
+template<class T>
+Foam::xfer<T>::xfer(xfer<T>& t)
+:
+    ref_()
+{
+    transfer(t);
+}
+
+
+
+// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
+
+template<class T>
+Foam::xfer<T>::~xfer()
+{}
+
+
+// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
+
+template<class T>
+T& Foam::xfer<T>::ref()
+{
+    return ref_;
+}
+
+
+template<class T>
+void Foam::xfer<T>::transfer(T& t)
+{
+    ref_.transfer(t);
+}
+
+
+template<class T>
+void Foam::xfer<T>::transfer(xfer<T>& t)
+{
+    ref_.transfer(t.ref_);
+}
+
+
+template<class T>
+void Foam::xfer<T>::yield(T& t)
+{
+    t.transfer(ref_);
+}
+
+
+template<class T>
+void Foam::xfer<T>::yield(xfer<T>& t)
+{
+    t.ref_.transfer(ref_);
+}
+
+
+// * * * * * * * * * * * * * * * Member Operators  * * * * * * * * * * * * * //
+
+
+template<class T>
+void Foam::xfer<T>::operator=(T& t)
+{
+    transfer(t);
+}
+
+
+template<class T>
+void Foam::xfer<T>::operator=(xfer<T>& t)
+{
+    if (this == &t)
+    {
+        FatalErrorIn
+        (
+            "Foam::xfer<T>::operator="
+            "(const Foam::xfer<T>&)"
+        )   << "Attempted assignment to self"
+            << abort(FatalError);
+    }
+
+    transfer(t);
+}
+
+
+template<class T>
+Foam::xfer<T>& Foam::xfer<T>::operator()() const
+{
+    return const_cast<xfer<T>&>(*this);
+}
+
+
+
+// * * * * * * * * * * * * * * * Friend Operators  * * * * * * * * * * * * * //
+
+template<class T>
+Foam::Istream& Foam::operator>>(Istream& is, xfer<T>& t)
+{
+    is >> t.ref_;
+    return is;
+}
+
+
+template<class T>
+Foam::Ostream& Foam::operator<<(Ostream& os, const xfer<T>& t)
+{
+    os << t.ref_;
+    return os;
+}
+
+// ************************************************************************* //