ENH: additional routines for reading/writing/parsing IOObject headers

- support selective enable/disable of the file banner.

ENH: improve code isolation for decomposedBlockData

- use readBlockEntry/writeBlockEntry to encapsulate the IO handling,
  which ensures more consistency

- new decomposedBlockData::readHeader for chaining into the
  block header information.

- remove unused constructors for decomposedBlockData

ENH: minor cleanup of collated fileOperations

src/OpenFOAM/db/IOobjects/decomposedBlockData/decomposedBlockDataHeader.C

@@ -0,0 +1,217 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2021 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+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 "decomposedBlockData.H"
+#include "dictionary.H"
+#include "foamVersion.H"
+#include "objectRegistry.H"
+#include "ListStream.H"
+
+// * * * * * * * * * * * * * * * Local Functions * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+
+inline void writeSpaces(Ostream& os, label nSpaces)
+{
+    if (nSpaces < 1)
+    {
+        nSpaces = 1;
+    }
+    while (nSpaces--)
+    {
+        os.write(char(token::SPACE));
+    }
+}
+
+// Similar to writeEntry, but with fewer spaces
+template<class T>
+inline void writeHeaderEntry(Ostream& os, const word& key, const T& value)
+{
+    os << indent << key;
+    writeSpaces(os, 12 - label(key.size()));
+    os << value << char(token::END_STATEMENT) << nl;
+}
+
+} // End namespace Foam
+
+
+// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
+
+void Foam::decomposedBlockData::writeHeaderContent
+(
+    Ostream& os,
+    IOstreamOption streamOptContainer,
+    const word& objectType,
+    const string& note,
+    const fileName& location,
+    const word& objectName
+)
+{
+    // Standard header entries
+    writeHeaderEntry(os, "version", streamOptContainer.version());
+    writeHeaderEntry(os, "format", streamOptContainer.format());
+    writeHeaderEntry(os, "arch", foamVersion::buildArch);
+
+    if (!note.empty())
+    {
+        writeHeaderEntry(os, "note", note);
+    }
+
+    if (objectType.empty())
+    {
+        // Empty type not allowed - use 'dictionary' fallback
+        writeHeaderEntry(os, "class", word("dictionary"));
+    }
+    else
+    {
+        writeHeaderEntry(os, "class", objectType);
+    }
+
+    if (!location.empty())
+    {
+        writeHeaderEntry(os, "location", location);
+    }
+    writeHeaderEntry(os, "object", objectName);
+}
+
+
+// * * * * * * * * * * * * * * * Members Functions * * * * * * * * * * * * * //
+
+bool Foam::decomposedBlockData::readHeader(IOobject& io, Istream& is)
+{
+    dictionary headerDict;
+
+    // Read the regular "FoamFile" header
+    bool ok = io.readHeader(headerDict, is);
+
+    if (decomposedBlockData::isCollatedType(io))
+    {
+        // Quick information - extract from "data.class"
+        if (headerDict.readIfPresent("data.class", io.headerClassName()))
+        {
+            return ok;
+        }
+
+        {
+            // Master-only reading of header
+            List<char> charData;
+            decomposedBlockData::readBlockEntry(is, charData);
+
+            UIListStream headerStream(charData);
+            headerStream.name() = is.name();
+
+            ok = io.readHeader(headerStream);
+        }
+    }
+
+    return ok;
+}
+
+
+void Foam::decomposedBlockData::writeHeader
+(
+    Ostream& os,
+    IOstreamOption streamOptContainer,
+    const word& objectType,
+    const string& note,
+    const fileName& location,
+    const word& objectName
+)
+{
+    if (IOobject::bannerEnabled())
+    {
+        IOobject::writeBanner(os);
+    }
+
+    os.beginBlock("FoamFile");
+
+    decomposedBlockData::writeHeaderContent
+    (
+        os,
+        streamOptContainer,
+        objectType,
+        note,
+        location,
+        objectName
+    );
+
+    os.endBlock();
+
+    if (IOobject::bannerEnabled())
+    {
+        IOobject::writeDivider(os) << nl;
+    }
+}
+
+
+void Foam::decomposedBlockData::writeHeader
+(
+    Ostream& os,
+    IOstreamOption streamOptData,
+    const IOobject& io
+)
+{
+    if (IOobject::bannerEnabled())
+    {
+        IOobject::writeBanner(os);
+    }
+
+    os.beginBlock("FoamFile");
+
+    decomposedBlockData::writeHeaderContent
+    (
+        os,
+        static_cast<IOstreamOption>(os),    // streamOpt container
+        decomposedBlockData::typeName,      // class
+        io.note(),
+        (io.instance()/io.db().dbDir()/io.local()),  // location
+        io.name()
+    );
+
+    {
+        writeHeaderEntry(os, "data.format", streamOptData.format());
+        writeHeaderEntry(os, "data.class", io.type());
+    }
+
+    // Meta-data (if any)
+    const dictionary* metaDataDict = io.findMetaData();
+    if (metaDataDict && !metaDataDict->empty())
+    {
+        metaDataDict->writeEntry("meta", os);
+    }
+
+    os.endBlock();
+
+    if (IOobject::bannerEnabled())
+    {
+        IOobject::writeDivider(os) << nl;
+    }
+}
+
+
+// ************************************************************************* //