ENH: improved infrastructure for writing VTK content

Note: classes are prefixed with 'foamVtk' instead of 'vtk' to avoid potential
conflicts with VTK itself.

foamVtkCore
~~~~~~~~~~~
- General very low-level functionality.

foamVtkPTraits
~~~~~~~~~~~~~~
- Traits type of functionality for VTK

foamVtkOutputOptions
~~~~~~~~~~~~~~~~~~~~
- The various format output options as a class that can be passed to
  formatters etc.

foamVtkCells
~~~~~~~~~~~~
- Intended for unifying vtkTopo and PV-Reader code in the future.
- Handles polyhedron decompose internally etc

foamVtkOutput, foamVtkFormatter
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- Output helpers.
- Selector for individual formatters.
  Currently write all scalar data a 'float' (not 'double'). Can
  revisit this in the future.

src/fileFormats/vtk/format/foamVtkLegacyFormatter.C

@@ -0,0 +1,139 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 2016 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 3 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, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "foamVtkLegacyFormatter.H"
+#include "endian.H"
+
+// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
+
+const char* Foam::foamVtkLegacyFormatter::name_ = "BINARY";
+
+
+// * * * * * * * * * * * * Protected Member Functions  * * * * * * * * * * * //
+
+void Foam::foamVtkLegacyFormatter::write
+(
+    const char* s,
+    std::streamsize n
+)
+{
+    os().write(s, n);
+}
+
+
+// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
+
+Foam::foamVtkLegacyFormatter::foamVtkLegacyFormatter(std::ostream& os)
+:
+    foamVtkFormatter(os)
+{}
+
+
+// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
+
+Foam::foamVtkLegacyFormatter::~foamVtkLegacyFormatter()
+{}
+
+
+// * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * * //
+
+const char* Foam::foamVtkLegacyFormatter::name() const
+{
+    return name_;
+}
+
+
+const char* Foam::foamVtkLegacyFormatter::encoding() const
+{
+    return name_;
+}
+
+
+void Foam::foamVtkLegacyFormatter::writeSize(const uint64_t)
+{}
+
+
+void Foam::foamVtkLegacyFormatter::write(const uint8_t val)
+{
+    // Can only handle integers
+    int copy(val);
+    write(copy);
+}
+
+
+void Foam::foamVtkLegacyFormatter::write(const label val)
+{
+    // std::cerr<<"label is:" << sizeof(val) << '\n';
+
+    // Not entirely correct: the legacy format only supports 32-bit integers.
+    // Either limit size for 64-bit label, or simply do not support for 64-bit.
+#ifdef WM_LITTLE_ENDIAN
+# if WM_LABEL_SIZE == 32
+    uint32_t swapped = endian::swap32(val);
+    write(reinterpret_cast<const char*>(&swapped), sizeof(uint32_t));
+# elif WM_LABEL_SIZE == 64
+    uint64_t swapped = endian::swap64(val);
+    write(reinterpret_cast<const char*>(&swapped), sizeof(uint64_t));
+#endif
+#else
+    write(reinterpret_cast<const char*>(&val), sizeof(label));
+#endif
+}
+
+
+void Foam::foamVtkLegacyFormatter::write(const float val)
+{
+    // std::cerr<<"float is:" << sizeof(val) << '\n';
+
+#ifdef WM_LITTLE_ENDIAN
+    // De-reference in two stages to avoid the warning
+    //     dereferencing type-punned pointer will break strict-aliasing rules
+    //     [-Wstrict-aliasing]
+
+    const uint32_t* ptr = reinterpret_cast<const uint32_t*>(&val);
+    uint32_t swapped = endian::swap32(*ptr);
+    write(reinterpret_cast<const char*>(&swapped), sizeof(uint32_t));
+#else
+    write(reinterpret_cast<const char*>(&val), sizeof(float));
+#endif
+}
+
+
+void Foam::foamVtkLegacyFormatter::write(const double val)
+{
+    // Legacy cannot support Float64 anyhow.
+    // std::cerr<<"write double as float:" << val << '\n';
+    float copy(val);
+    write(copy);
+}
+
+
+void Foam::foamVtkLegacyFormatter::flush()
+{
+    os()<< '\n';
+}
+
+
+// ************************************************************************* //