ENH: adjust header management for foamVtk output

- provide headerType typedef in foamVtkFormatter, foamVtkOutput

- remove byteOrder and headerType constants from foamVtkFormatter
  since the same strings can also be obtained from foamVtkPTraits

- additional convenience methods in foamVtkFormatter

src/conversion/vtk/output/foamVtkOutput.C

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2016 OpenCFD Ltd.
+    \\  /    A nd           | Copyright (C) 2016-2017 OpenCFD Ltd.
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -62,14 +62,7 @@ Foam::label Foam::foamVtkOutput::writeVtmFile
 
     vtmFile
         .xmlHeader()
-        .openTag("VTKFile")
+        .beginVTKFile(content, "1.0");
-        ( "type",        content )
-        ( "version",     "1.0" )
-        ( "byte_order",  foamVtkFormatter::byteOrder )
-        ( "header_type", foamVtkFormatter::headerType )
-        .closeTag();
-
-    vtmFile.tag(content);
 
     forAll(files, i)
     {
@@ -80,7 +73,7 @@ Foam::label Foam::foamVtkOutput::writeVtmFile
             .closeTag(true);
     }
 
-    vtmFile.endTag(content).endTag("VTKFile");
+    vtmFile.endTag(content).endVTKFile();
 
     return files.size();
 }

src/conversion/vtk/output/foamVtkOutput.H

@@ -58,6 +58,12 @@ class foamVtkOutput
 
 public:
 
+    // Public typedefs
+
+        //- Use UInt64 for header data
+        typedef foamVtkFormatter::headerType headerType;
+
+
     // Forward declarations
     class legacy;
 

src/fileFormats/vtk/format/foamVtkFormatter.C

@@ -23,16 +23,6 @@ License
 \*---------------------------------------------------------------------------*/
 
 #include "foamVtkFormatter.H"
-#include "foamVtkPTraits.H"
-
-// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
-
-const char* const Foam::foamVtkFormatter::byteOrder
-    = Foam::foamVtkPTraits<endian>::typeName;
-
-const char* const Foam::foamVtkFormatter::headerType =
-    Foam::foamVtkPTraits<uint64_t>::typeName;
-
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
@@ -145,16 +135,6 @@ Foam::foamVtkFormatter::closeTag(const bool isEmpty)
 }
 
 
-Foam::foamVtkFormatter&
-Foam::foamVtkFormatter::tag(const word& tag)
-{
-    openTag(tag);
-    closeTag();
-
-    return *this;
-}
-
-
 Foam::foamVtkFormatter&
 Foam::foamVtkFormatter::endTag(const word& tag)
 {
@@ -186,6 +166,53 @@ Foam::foamVtkFormatter::endTag(const word& tag)
 }
 
 
+Foam::foamVtkFormatter&
+Foam::foamVtkFormatter::tag(const word& tag)
+{
+    openTag(tag);
+    closeTag();
+
+    return *this;
+}
+
+
+Foam::foamVtkFormatter&
+Foam::foamVtkFormatter::beginVTKFile
+(
+    const word& contentType,
+    const word& contentVersion,
+    const bool leaveOpen
+)
+{
+    openTag("VTKFile");
+    xmlAttr("type",        contentType);
+    xmlAttr("version",     contentVersion);
+    xmlAttr("byte_order",  foamVtkPTraits<Foam::endian>::typeName);
+    xmlAttr("header_type", foamVtkPTraits<headerType>::typeName);
+    closeTag();
+
+    openTag(contentType);
+    if (!leaveOpen)
+    {
+        closeTag();
+    }
+
+    return *this;
+}
+
+
+Foam::foamVtkFormatter&
+Foam::foamVtkFormatter::beginAppendedData()
+{
+    openTag("AppendedData");
+    xmlAttr("encoding", encoding());
+    closeTag();
+    os_ << '_';
+
+    return *this;
+}
+
+
 Foam::foamVtkFormatter&
 Foam::foamVtkFormatter::xmlAttr
 (
@@ -258,55 +285,35 @@ Foam::foamVtkFormatter::xmlAttr
 // * * * * * * * * * * * * * * Member Operators * * * * * * * * * * * * * * //
 
 Foam::foamVtkFormatter&
-Foam::foamVtkFormatter::operator()
+Foam::foamVtkFormatter::operator()(const word& k, const std::string& v)
-(
-    const word& k,
-    const std::string& v
-)
 {
     return xmlAttr(k, v);
 }
 
 
 Foam::foamVtkFormatter&
-Foam::foamVtkFormatter::operator()
+Foam::foamVtkFormatter::operator()(const word& k, const int32_t v)
-(
-    const word& k,
-    const int32_t v
-)
 {
     return xmlAttr(k, v);
 }
 
 
 Foam::foamVtkFormatter&
-Foam::foamVtkFormatter::operator()
+Foam::foamVtkFormatter::operator()(const word& k, const int64_t v)
-(
-    const word& k,
-    const int64_t v
-)
 {
     return xmlAttr(k, v);
 }
 
 
 Foam::foamVtkFormatter&
-Foam::foamVtkFormatter::operator()
+Foam::foamVtkFormatter::operator()(const word& k, const uint64_t v)
-(
-    const word& k,
-    const uint64_t v
-)
 {
     return xmlAttr(k, v);
 }
 
 
 Foam::foamVtkFormatter&
-Foam::foamVtkFormatter::operator()
+Foam::foamVtkFormatter::operator()(const word& k, const scalar v)
-(
-    const word& k,
-    const scalar v
-)
 {
     return xmlAttr(k, v);
 }

src/fileFormats/vtk/format/foamVtkFormatter.H

@@ -89,13 +89,10 @@ protected:
 
 public:
 
-    // Static Data
+    // Public typedefs
 
-        //- VTK name for the 'byte_order' attribute
+        //- Use UInt64 for header data
-        static const char* const byteOrder;
+        typedef uint64_t headerType;
-
-        //- VTK name for the 'header_type' attribute (UInt64)
-        static const char* const headerType;
 
 
     //- Destructor
@@ -161,6 +158,20 @@ public:
         //- Write XML tag without any attributes. Combines openTag/closeTag.
         foamVtkFormatter& tag(const word& tag);
 
+        //- Add a "VTKFile" XML tag for contentType, followed by a tag for
+        //  the contentType itself. Optionally leave the contentType tag
+        //  open for adding additional attributes.
+        foamVtkFormatter& beginVTKFile
+        (
+            const word& contentType,
+            const word& contentVersion,
+            const bool leaveOpen = false
+        );
+
+        //- Add a "AppendedData" XML tag with the current encoding and  output
+        //  the requisite '_' prefix.
+        foamVtkFormatter& beginAppendedData();
+
 
         //- Open "DataArray" XML tag
         template<class Type, int nComp=0>
@@ -174,11 +185,25 @@ public:
 
 
         //- End "DataArray" XML tag
-        foamVtkFormatter& endDataArray()
+        inline foamVtkFormatter& endDataArray()
         {
             return endTag("DataArray");
         }
 
+        //- End "AppendedData" XML tag
+        inline foamVtkFormatter& endAppendedData()
+        {
+            flush();     // flush any pending encoded content
+            os_ << '\n'; // clear separation from content.
+            return endTag("AppendedData");
+        }
+
+        //- End "VTKFile" XML tag
+        inline foamVtkFormatter& endVTKFile()
+        {
+            return endTag("VTKFile");
+        }
+
 
         //- Write XML attribute
         foamVtkFormatter& xmlAttr