ENH: add bitSet::null() and clarify some documentation

- the NullObject singleton can also be cast to a bitSet
  (sufficient size and bit-pattern). Useful for places that
  need to hold a reference on construction

applications/test/bitSet2/Test-bitSet2.C

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2018 OpenCFD Ltd.
+    Copyright (C) 2018-2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -164,6 +164,23 @@ inline bool compare
 
 int main(int argc, char *argv[])
 {
+    Info<< "bitSet::null()" << nl
+        << "sizeof : " << sizeof(bitSet::null()) << " bytes" << nl;
+
+    info(bitSet::null());
+
+    {
+        bitSet emptySet;
+        info(emptySet);
+        extent(emptySet);
+
+        emptySet.resize(10);
+        info(emptySet);
+        extent(emptySet);
+    }
+
+    Info<< nl << "Tests" << nl;
+
     bitSet list1(22);
     // Set every third one on
     forAll(list1, i)

applications/test/boolList/Test-boolList.C

@@ -36,6 +36,7 @@ Description
 #include "bitSet.H"
 #include "BitOps.H"
 #include "FlatOutput.H"
+#include "bitSetOrBoolList.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -153,6 +154,24 @@ int main(int argc, char *argv[])
     Info<< "\nafter set [13,5]\n";
     compare(list1, "1..1..1..1..111111....");
 
+    {
+        boolList list2(5, true);
+        list2.unset(2);
+
+        Info<< "Test wrapper idea" << nl;
+
+        bitSetOrBoolList wrapper(list2);
+
+        if (wrapper.test(1))
+        {
+            Info<< "1 is on" << nl;
+        }
+        if (!wrapper.test(2))
+        {
+            Info<< "2 is off" << nl;
+        }
+    }
+
     Info<< "\nDone" << nl << endl;
     return 0;
 }

applications/test/boolList/bitSetOrBoolList.H

@@ -0,0 +1,102 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2020 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/>.
+
+Class
+    Foam::bitSetOrBoolList
+
+Description
+    Simple wrapper for handling test() on bitSet or boolList
+    without a templating layer or lambda expresssion.
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef bitSetOrBoolList_H
+#define bitSetOrBoolList_H
+
+#include "bitSet.H"
+#include "boolList.H"
+
+/*---------------------------------------------------------------------------*\
+                      Class bitSetOrBoolList Declaration
+\*---------------------------------------------------------------------------*/
+
+namespace Foam
+{
+
+class bitSetOrBoolList
+{
+    const bitSet& bits_;
+    const boolList& bools_;
+
+public:
+
+    // Constructors
+
+        //- Construct with a bitSet reference
+        explicit bitSetOrBoolList(const bitSet& select)
+        :
+            bits_(select),
+            bools_(boolList::null())
+        {}
+
+        //- Construct with a boolList reference
+        explicit bitSetOrBoolList(const boolList& select)
+        :
+            bits_(bitSet::null()),
+            bools_(select)
+        {}
+
+
+    // Member Functions
+
+        //- Is empty
+        bool empty() const
+        {
+            return bits_.empty() && bools_.empty();
+        }
+
+        //- Size
+        label size() const
+        {
+            return bits_.size() + bools_.size();
+        }
+
+        //- Test function
+        bool test(const label i) const
+        {
+            return bits_.test(i) || bools_.test(i);
+        }
+};
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+} // End namespace Foam
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //

applications/test/boolList/disabledBoolList.H

@@ -0,0 +1,73 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2020 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/>.
+
+Class
+    Foam::disabledBoolList
+
+Description
+    A trivial structure to use as a boolList replacement when testing
+    compilation without using the [] accessors.
+
+    Example,
+    \code
+    const disableBoolList blockedFace;
+    ...
+
+    if (blockedFace.test(facei)) ...    // Good
+    if (blockedFace[facei]) ...         // Compile error
+    \endcode
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef disabledBoolList_H
+#define disabledBoolList_H
+
+/*---------------------------------------------------------------------------*\
+                      Class disabledBoolList Declaration
+\*---------------------------------------------------------------------------*/
+
+namespace Foam
+{
+
+struct disabledBoolList
+{
+    bool empty() const { return true; }
+
+    int size() const { return 0; }
+
+    bool test(int) const { return true; }
+
+    void set(bool) {}
+};
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+} // End namespace Foam
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //

src/OpenFOAM/containers/Bits/bitSet/bitSet.H

@@ -128,6 +128,11 @@ public:
         class const_iterator;
         typedef unsigned int const_reference;
 
+    // Static Member Functions
+
+        //- Return a null bitSet reference
+        inline static const bitSet& null();
+
 
     //- Declare type-name (with debug switch)
     ClassName("bitSet");
@@ -214,7 +219,9 @@ public:
 
     // Query
 
-        //- True if all bits in this bitset are set or if the set is empty.
+        //- True if all bits in this bitset are set or if the set is \b empty.
+        //  Returning true for an empty set may not seem intuitive, but
+        //  conforms to how boost has defined things.
         //  \note Method name compatibility with boost::dynamic_bitset
         inline bool all() const;
 

src/OpenFOAM/containers/Bits/bitSet/bitSetI.H

@@ -451,8 +451,16 @@ inline Foam::label Foam::bitSet::find_next(label pos) const
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
+inline const Foam::bitSet& Foam::bitSet::null()
+{
+    return NullObjectRef<bitSet>();
+}
+
+
 inline bool Foam::bitSet::all() const
 {
+    if (empty()) return true;  // SIC. boost convention
+
     return -1 == first_not_block();
 }