ENH: allow early completion in PackedBoolList::used()

- can stop producing content when the target number of entries has
  been reached.

- change return type to labelList instead an Xfer container.
  This allows return-value-optimization and avoids a surrounding
  allocation. This potentially breaks existing code.

- make PackedList and PackedBoolList moveable. Drop xfer wrappers.

applications/test/PackedList4/Test-PackedList4.C

@@ -144,18 +144,18 @@ int main(int argc, char *argv[])
     Info<< "\ntest Istream constructor\n";
 
     list4.printInfo(Info, true);
-    Info<< list4 << " indices: " << list4.used()() << nl;
+    Info<< list4 << " indices: " << list4.used() << nl;
 
     Info<< "\nassign from labelList\n";
     list4 = labelList{0, 1, 2, 3, 12, 13, 14, 19, 20, 21};
 
     list4.printInfo(Info, true);
-    Info<< list4 << " indices: " << list4.used()() << nl;
+    Info<< list4 << " indices: " << list4.used() << nl;
 
     // Not yet:
     // PackedBoolList list5{0, 1, 2, 3, 12, 13, 14, 19, 20, 21};
     // list5.printInfo(Info, true);
-    // Info<< list5 << " indices: " << list5.used()() << nl;
+    // Info<< list5 << " indices: " << list5.used() << nl;
 
     Info<< "\nassign from indices\n";
     list4.read
@@ -168,7 +168,7 @@ int main(int argc, char *argv[])
 
 
     list4.printInfo(Info, true);
-    Info<< list4 << " indices: " << list4.used()() << nl;
+    Info<< list4 << " indices: " << list4.used() << nl;
 
     boolList bools(list4.size());
     forAll(list4, i)

src/OpenFOAM/containers/Lists/PackedList/PackedBoolList.C

@@ -265,26 +265,28 @@ Foam::label Foam::PackedBoolList::subset(const labelUIndList& indices)
 }
 
 
-Foam::Xfer<Foam::labelList> Foam::PackedBoolList::used() const
+Foam::labelList Foam::PackedBoolList::used() const
 {
-    labelList lst(this->count());
+    // Number of used (set) entries
+    const label cnt = this->count();
 
-    if (lst.size())
+    labelList lst(cnt);
+
+    if (cnt)
     {
-        label nElem = 0;
+        // The length of the input list
+        const label len = this->size();
 
-        forAll(*this, elemI)
+        for (label i=0, usedi=0; (i < len && usedi < cnt); ++i)
         {
-            if (get(elemI))
+            if (get(i))
             {
-                lst[nElem++] = elemI;
+                lst[usedi++] = i;
             }
         }
-
-        lst.setSize(nElem);
     }
 
-    return lst.xfer();
+    return lst;
 }
 
 

src/OpenFOAM/containers/Lists/PackedList/PackedBoolList.H

@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-     \\/     M anipulation  | Copyright (C) 2017 OpenCFD Ltd.
+     \\/     M anipulation  | Copyright (C) 2017-2018 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -91,7 +91,7 @@ public:
     // Constructors
 
         //- Construct null
-        inline PackedBoolList();
+        PackedBoolList() = default;
 
         //- Construct from Istream
         PackedBoolList(Istream& is);
@@ -102,17 +102,17 @@ public:
         //- Construct with given size and value for all elements
         inline PackedBoolList(const label size, const bool val);
 
-        //- Copy constructor
+        //- Copy construct
         inline PackedBoolList(const PackedBoolList& lst);
 
-        //- Copy constructor
+        //- Copy construct
         explicit inline PackedBoolList(const PackedList<1>& lst);
 
-        //- Construct by transferring the parameter contents
-        inline PackedBoolList(const Xfer<PackedBoolList>& lst);
+        //- Move construct
+        inline PackedBoolList(PackedBoolList&& lst);
 
-        //- Construct by transferring the parameter contents
-        inline PackedBoolList(const Xfer<PackedList<1>>& lst);
+        //- Move construct
+        inline PackedBoolList(PackedList<1>&& lst);
 
         //- Construct with given size and list of labels to set as true.
         inline PackedBoolList(const label size, const labelUList& indices);
@@ -137,7 +137,7 @@ public:
 
     // Member Functions
 
-      // Access
+    // Access
 
         using PackedList<1>::set;
         using PackedList<1>::unset;
@@ -175,12 +175,11 @@ public:
         //  Return number of elements subsetted.
         label subset(const labelUIndList& indices);
 
-
         //- Return indices of the used (true) elements as a list of labels
-        Xfer<labelList> used() const;
+        labelList used() const;
 
 
-      // Edit
+    // Edit
 
         //- Transfer the contents of the argument list into this list
         //- and annul the argument list.
@@ -190,21 +189,24 @@ public:
         //- and annul the argument list.
         inline void transfer(PackedList<1>& lst);
 
-        //- Transfer contents to the Xfer container
-        inline Xfer<PackedBoolList> xfer();
-
 
     // Member Operators
 
         //- Assignment of all entries to the given value.
         inline void operator=(const bool val);
 
-        //- Assignment operator.
+        //- Copy assignment
         inline void operator=(const PackedBoolList& lst);
 
-        //- Assignment operator.
+        //- Copy assignment
         inline void operator=(const PackedList<1>& lst);
 
+        //- Move assignment
+        inline void operator=(PackedBoolList&& lst);
+
+        //- Move assignment
+        inline void operator=(PackedList<1>&& lst);
+
         //- Assignment operator.
         void operator=(const UList<bool>& lst);
 

src/OpenFOAM/containers/Lists/PackedList/PackedBoolListI.H

@@ -25,12 +25,6 @@ License
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
-inline Foam::PackedBoolList::PackedBoolList()
-:
-    PackedList<1>()
-{}
-
-
 inline Foam::PackedBoolList::PackedBoolList(const label size)
 :
     PackedList<1>(size)
@@ -59,18 +53,20 @@ inline Foam::PackedBoolList::PackedBoolList(const PackedList<1>& lst)
 {}
 
 
-inline Foam::PackedBoolList::PackedBoolList(const Xfer<PackedBoolList>& lst)
+inline Foam::PackedBoolList::PackedBoolList(PackedBoolList&& lst)
 :
     PackedList<1>()
 {
-    transfer(lst());
+    transfer(lst);
 }
 
 
-inline Foam::PackedBoolList::PackedBoolList(const Xfer<PackedList<1>>& lst)
+inline Foam::PackedBoolList::PackedBoolList(PackedList<1>&& lst)
 :
-    PackedList<1>(lst)
-{}
+    PackedList<1>()
+{
+    transfer(lst);
+}
 
 
 inline Foam::PackedBoolList::PackedBoolList(const UList<bool>& lst)
@@ -147,12 +143,6 @@ inline void Foam::PackedBoolList::transfer(PackedList<1>& lst)
 }
 
 
-inline Foam::Xfer<Foam::PackedBoolList> Foam::PackedBoolList::xfer()
-{
-    return xferMove(*this);
-}
-
-
 // * * * * * * * * * * * * * * * Member Operators  * * * * * * * * * * * * * //
 
 inline void Foam::PackedBoolList::operator=(const bool val)
@@ -173,6 +163,18 @@ inline void Foam::PackedBoolList::operator=(const PackedList<1>& lst)
 }
 
 
+inline void Foam::PackedBoolList::operator=(PackedBoolList&& lst)
+{
+    transfer(lst);
+}
+
+
+inline void Foam::PackedBoolList::operator=(PackedList<1>&& lst)
+{
+    transfer(lst);
+}
+
+
 inline void Foam::PackedBoolList::operator=(const labelUList& indices)
 {
     clear();

src/OpenFOAM/containers/Lists/PackedList/PackedList.C

@@ -141,16 +141,16 @@ void Foam::PackedList<nBits>::flip()
 
 
 template<unsigned nBits>
-Foam::Xfer<Foam::labelList> Foam::PackedList<nBits>::values() const
+Foam::labelList Foam::PackedList<nBits>::values() const
 {
     labelList elems(size_);
 
-    forAll(*this, i)
+    for (label i=0; i < size_; ++i)
     {
         elems[i] = get(i);
     }
 
-    return elems.xfer();
+    return elems;
 }
 
 
@@ -522,6 +522,13 @@ void Foam::PackedList<nBits>::operator=(const PackedList<nBits>& lst)
 }
 
 
+template<unsigned nBits>
+void Foam::PackedList<nBits>::operator=(PackedList<nBits>&& lst)
+{
+    transfer(lst);
+}
+
+
 template<unsigned nBits>
 void Foam::PackedList<nBits>::operator=(const labelUList& lst)
 {

src/OpenFOAM/containers/Lists/PackedList/PackedList.H

@@ -235,11 +235,11 @@ public:
         //- Construct from Istream
         inline PackedList(Istream& is);
 
-        //- Copy constructor
+        //- Copy construct
         inline PackedList(const PackedList<nBits>& lst);
 
-        //- Construct by transferring the parameter contents
-        inline PackedList(const Xfer<PackedList<nBits>>& lst);
+        //- Move construct
+        inline PackedList(PackedList<nBits>&& lst);
 
         //- Construct from a list of labels
         explicit inline PackedList(const labelUList& lst);
@@ -297,7 +297,7 @@ public:
         unsigned int count() const;
 
         //- Return the values as a list of labels
-        Xfer<labelList> values() const;
+        labelList values() const;
 
         //- Print bit patterns, optionally output unused elements
         //
@@ -356,9 +356,6 @@ public:
         //  and annul the argument list.
         inline void transfer(PackedList<nBits>& lst);
 
-        //- Transfer contents to the Xfer container
-        inline Xfer<PackedList<nBits>> xfer();
-
 
       // IO
 
@@ -407,9 +404,12 @@ public:
         //- Assignment of all entries to the given value. Takes linear time.
         inline void operator=(const unsigned int val);
 
-        //- Assignment operator.
+        //- Copy assignment.
         void operator=(const PackedList<nBits>& lst);
 
+        //- Move assignment.
+        void operator=(PackedList<nBits>&& lst);
+
         //- Assignment operator.
         void operator=(const labelUList& lst);
 

src/OpenFOAM/containers/Lists/PackedList/PackedListI.H

@@ -223,9 +223,13 @@ inline Foam::PackedList<nBits>::PackedList(const PackedList<nBits>& lst)
 
 
 template<unsigned nBits>
-inline Foam::PackedList<nBits>::PackedList(const Xfer<PackedList<nBits>>& lst)
+inline Foam::PackedList<nBits>::PackedList(PackedList<nBits>&& lst)
+:
+    PackedListCore(),
+    StorageList(),
+    size_(0)
 {
-    transfer(lst());
+    transfer(lst);
 }
 
 
@@ -956,13 +960,6 @@ inline void Foam::PackedList<nBits>::transfer(PackedList<nBits>& lst)
 }
 
 
-template<unsigned nBits>
-inline Foam::Xfer<Foam::PackedList<nBits>> Foam::PackedList<nBits>::xfer()
-{
-    return xferMove(*this);
-}
-
-
 template<unsigned nBits>
 inline unsigned int Foam::PackedList<nBits>::get(const label i) const
 {