ENH: multi-region support for foamToEnsight (#2080)

- additional finite-area support too.

applications/utilities/postProcessing/dataConversion/foamToEnsight/checkFieldAvailability.H

@@ -0,0 +1,61 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  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, distributed under GPL-3.0-or-later.
+
+Description
+    Check field availability for last time.
+    Done to avoid mapping 'undefined' when a field only exists as time 0.
+
+Requires
+    readFields.H (for the checkData function)
+
+\*---------------------------------------------------------------------------*/
+
+// Initially all possible objects that are available at the final time
+List<wordHashSet> availableRegionObjectNames(meshes.size());
+
+forAll(meshes, regioni)
+{
+    const auto& mesh = meshes[regioni];
+
+    IOobjectList objects(mesh, timeDirs.last().name());
+
+    if (!fieldPatterns.empty())
+    {
+        objects.filterObjects(fieldPatterns);
+    }
+
+    // Remove "*_0" restart fields
+    objects.prune_0();
+
+    if (!doPointValues)
+    {
+        // Prune point fields if disabled
+        objects.filterClasses
+        (
+            [](const word& clsName)
+            {
+                return fieldTypes::point.found(clsName);
+            },
+            true // prune
+        );
+    }
+
+    wordList objectNames(objects.sortedNames());
+
+    // Check availability for all times...
+    checkData(mesh, timeDirs, objectNames);
+
+    availableRegionObjectNames[regioni] = objectNames;
+}
+
+
+// ************************************************************************* //