PackedList: encapsulate calculations in an iterator

- eliminated previous PackedBitRef class, the iterator does all of that and
  can also be used to (forward) traverse the list
- no const_iterator yet

- Note that PackedList is also a bit like DynamicList in terms of storage
  management and the append() method. Since the underlying storage in
  integer, any auto-vivified elements will also flood-fill the gaps with
  zero.

applications/test/PackedList/PackedListTest.C

@@ -28,112 +28,144 @@ Description
 
 \*---------------------------------------------------------------------------*/
 
-#include "OSspecific.H"
-
 #include "IOstreams.H"
-#include "IStringStream.H"
-#include "scalar.H"
-#include "vector.H"
-#include "ListOps.H"
-#include "List.H"
 #include "PackedBoolList.H"
-#include <bitset>
 
 using namespace Foam;
 
-template <int nBits>
-void printPackedList(const PackedList<nBits>& L)
-{
-    const List<unsigned int>& stor = L.storage();
-
-    cout<< "PackedList<" << nBits << ">"
-        << " max_bits:"  << L.max_bits()
-        << " max_value:" << L.max_value()
-        << " packing:"   << L.packing() << nl;
-
-    cout<< "values:  " << L.size() << "/" << L.capacity() << " ( ";
-    forAll(L, i)
-    {
-        cout<< L[i] << ' ';
-    }
-    cout<< ")\n";
-
-    // using std:bitset for output works, but annoys valgrind
-    cout<< "storage: " << stor.size() << "( ";
-    forAll(stor, i)
-    {
-        cout<< std::bitset<32>(stor[i]) << ' ';
-    }
-    cout<< ")\n" << nl;
-}
-
-
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 //  Main program:
 
 int main(int argc, char *argv[])
 {
-    cout<< "PackedList::max_bits() = " << PackedList<0>::max_bits() << nl;
+    bool changed;
+    Info<< "PackedList max_bits() = " << PackedList<0>::max_bits() << nl;
 
+    Info<< "\ntest allocation with value\n";
     PackedList<3> list1(5,1);
+    list1.print(Info);
 
-    printPackedList(list1);
+    Info<< "\ntest assign uniform value\n";
-
     list1 = 2;
-    printPackedList(list1);
+    list1.print(Info);
 
+    Info<< "\ntest resize with value (without reallocation)\n";
     list1.resize(6, 3);
-    printPackedList(list1);
+    list1.print(Info);
 
+    Info<< "\ntest set() function\n";
+    list1.set(1, 5);
+    list1.print(Info);
+
+    Info<< "\ntest assign bool\n";
     list1 = false;
-    printPackedList(list1);
+    list1.print(Info);
 
+    Info<< "\ntest assign bool\n";
     list1 = true;
-    printPackedList(list1);
+    list1.print(Info);
 
+    Info<< "\ntest resize without value (with reallocation)\n";
     list1.resize(12);
-    printPackedList(list1);
+    list1.print(Info);
 
+    Info<< "\ntest resize with value (with reallocation)\n";
     list1.resize(25, list1.max_value());
-    printPackedList(list1);
+    list1.print(Info);
 
+    Info<< "\ntest resize smaller (should not touch allocation)\n";
     list1.resize(8);
-    printPackedList(list1);
+    list1.print(Info);
 
+    Info<< "\ntest append() operation\n";
     list1.append(2);
     list1.append(3);
     list1.append(4);
-    printPackedList(list1);
+    list1.print(Info);
 
+    Info<< "\ntest reserve() operation\n";
     list1.reserve(32);
-    printPackedList(list1);
+    list1.print(Info);
 
+    Info<< "\ntest shrink() operation\n";
     list1.shrink();
-    printPackedList(list1);
+    list1.print(Info);
 
-    list1.setSize(15);
+    Info<< "\ntest setCapacity() operation\n";
-    printPackedList(list1);
+    list1.setCapacity(15);
+    list1.print(Info);
 
-    list1.setSize(32);
+    Info<< "\ntest setCapacity() operation\n";
-    printPackedList(list1);
+    list1.setCapacity(30);
+    list1.print(Info);
 
-    // test assignment
+    Info<< "\ntest operator[] assignment\n";
     list1[16] = 5;
-    printPackedList(list1);
+    list1.print(Info);
 
-    // auto-vivify
+    Info<< "\ntest operator[] assignment with auto-vivify\n";
     list1[36] = list1.max_value();
-    printPackedList(list1);
+    list1.print(Info);
 
-    list1.setSize(4);
+    Info<< "\ntest setCapacity smaller\n";
-    printPackedList(list1);
+    list1.setCapacity(32);
+    list1.print(Info);
 
+    // add in some misc values
+    list1[31] = 1;
+    list1[32] = 2;
+    list1[33] = 3;
+
+    Info<< "\ntest iterator\n";
+    PackedList<3>::iterator iter = list1.begin();
+    Info<< "iterator:" << iter() << "\n";
+    iter.print(Info) << "\n";
+
+    Info<< "\ntest iterator operator=\n";
+    changed = (iter = 5);
+
+    Info<< "iterator:" << iter() << "\n";
+    Info<< "changed:" << changed << "\n";
+    changed = (iter = 5);
+    Info<< "changed:" << changed << "\n";
+    list1.print(Info);
+
+    Info<< "\ntest get() method\n";
+    Info<< "get(10):" << list1.get(10)
+        << " and list[10]:" << unsigned(list1[10]) << "\n";
+    list1.print(Info);
+
+    Info<< "\ntest iterator indexing\n";
+    Info<< "end() ";
+    list1.end().print(Info) << "\n";
+
+    for (iter = list1[31]; iter != list1.end(); ++iter)
+    {
+        iter.print(Info);
+    }
+
+    Info<< "\ntest operator[] auto-vivify\n";
+    const unsigned int val = list1[45];
+
+    Info<< "list[45]:" << val << "\n";
+    list1.print(Info);
+
+
+    Info<< "\ntest copy constructor + append\n";
     PackedList<3> list2(list1);
     list2.append(4);
+    Info<< "source list:\n";
+    list1.print(Info);
+    Info<< "destination list:\n";
+    list2.print(Info);
 
-    cout << "after copy + append\n";
+    Info<< "\ntest pattern that fills all bits\n";
-    printPackedList(list1);
+    PackedList<4> list3(8, 8);
-    printPackedList(list2);
+    list3[list3.size()-2] = 0;
+    list3[list3.size()-1] = list3.max_value();
+    list3.print(Info);
+
+    Info<< "\n\nDone.\n";
 
     return 0;
 }

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

@@ -31,7 +31,7 @@ License
 template<int nBits>
 Foam::PackedList<nBits>::PackedList(const label size, const unsigned int val)
 :
-    List<unsigned int>(storageSize(size)),
+    List<PackedStorage>(packedLength(size), 0u),
     size_(size)
 {
     operator=(val);
@@ -41,7 +41,7 @@ Foam::PackedList<nBits>::PackedList(const label size, const unsigned int val)
 template<int nBits>
 Foam::PackedList<nBits>::PackedList(const UList<label>& lst)
 :
-    List<unsigned int>(storageSize(lst.size()), 0),
+    List<PackedStorage>(packedLength(lst.size()), 0u),
     size_(lst.size())
 {
     forAll(lst, i)
@@ -51,7 +51,6 @@ Foam::PackedList<nBits>::PackedList(const UList<label>& lst)
 }
 
 
-
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
 template<int nBits>
@@ -67,13 +66,81 @@ Foam::labelList Foam::PackedList<nBits>::values() const
 }
 
 
+template<int nBits>
+Foam::Ostream& Foam::PackedList<nBits>::iterator::print(Ostream& os) const
+{
+    os  << "iterator<" << nBits << "> [" << position() << "]"
+        << " elem:" << elem_ << " offset:" << offset_
+        << " value:" << unsigned(*this)
+        << nl;
+
+    return os;
+}
+
+
+template<int nBits>
+Foam::Ostream& Foam::PackedList<nBits>::print(Ostream& os) const
+{
+    os  << "PackedList<" << nBits << ">"
+        << " max_value:" << max_value()
+        << " packing:"   << packing() << nl
+        << "values: " << size() << "/" << capacity() << "( ";
+    forAll(*this, i)
+    {
+        os << get(i) << ' ';
+    }
+
+    os  << ")\n"
+        << "storage: " << storage().size() << "( ";
+
+    label count = size();
+
+    forAll(storage(), i)
+    {
+        const PackedStorage& rawBits = storage()[i];
+
+        // create mask for unaddressed bits
+        unsigned int addressed = 0;
+
+        for (unsigned packI = 0; count && packI < packing(); packI++, count--)
+        {
+            addressed <<= nBits;
+            addressed |= max_value();
+        }
+
+        for (unsigned int testBit = 0x1 << max_bits(); testBit; testBit >>= 1)
+        {
+            if (testBit & addressed)
+            {
+                if (rawBits & testBit)
+                {
+                    os << '1';
+                }
+                else
+                {
+                    os << '0';
+                }
+            }
+            else
+            {
+                os << '_';
+            }
+        }
+        cout << ' ';
+    }
+    os << ")\n";
+
+    return os;
+}
+
+
 // * * * * * * * * * * * * * * * Member Operators  * * * * * * * * * * * * * //
 
 template<int nBits>
 void Foam::PackedList<nBits>::operator=(const PackedList<nBits>& lst)
 {
     setCapacity(lst.size());
-    List<unsigned int>::operator=(lst);
+    List<PackedStorage>::operator=(lst);
 }
 
 

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

@@ -40,7 +40,7 @@ SeeAlso
 
 ToDo
     Add checks for bad template parameters (ie, nBits=0, nBits too large).
-    Could make PackedBitRef an iterator and use for traversing as well.
+    The missing const_iterator might eventually still be needed.
 
 SourceFiles
     PackedListI.H
@@ -52,7 +52,6 @@ SourceFiles
 #define PackedList_H
 
 #include "labelList.H"
-#include "List.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -72,84 +71,6 @@ template<int nBits> class PackedList;
 
 TemplateName(PackedList);
 
-
-/*---------------------------------------------------------------------------*\
-                        Class PackedBitRef Declaration
-\*---------------------------------------------------------------------------*/
-
-//- The PackedBitRef is used for PackedList
-template <int nBits>
-class PackedBitRef
-{
-private:
-
-    // private data
-    // const mutable List<unsigned int>& list_;
-
-    unsigned int& elem_;
-
-    const label startBit_;
-
-public:
-
-    // Static Public Members
-
-        //- The max. number of bits that can be templated.
-        //  Might someday be useful for a template assert.
-        inline static unsigned int max_bits();
-
-        //- The max. value for an entry, can also be used as the mask
-        //  eg, ((1 << 2) - 1) yields 0b0011
-        inline static unsigned int max_value();
-
-        //- The number of entries per storage entry
-        inline static unsigned int packing();
-
-
-    // Constructors
-    inline PackedBitRef
-    (
-        // const List<unsigned int>& lst
-        const unsigned int& elem, label startBit)
-    :
-        // list_(lst),
-        elem_(const_cast<unsigned int&>(elem)),
-        startBit_(startBit)
-    {}
-
-
-    // Members
-
-    // Assign value
-    inline void operator=(const unsigned int val)
-    {
-        unsigned int shiftedMask = max_value() << startBit_;
-        unsigned int shiftedVal  = (val & max_value()) << startBit_;
-
-        elem_ = (elem_ & ~shiftedMask) | shiftedVal;
-    }
-
-    // return value
-    inline unsigned int operator()() const
-    {
-        return ((elem_ >> startBit_) & max_value());
-    }
-
-    //- Conversion operator
-    inline operator unsigned int () const
-    {
-        return ((elem_ >> startBit_) & max_value());
-    }
-
-    //- Conversion operator
-    inline operator bool() const
-    {
-        return !!((elem_ >> startBit_) & max_value());
-    }
-
-};
-
-
 /*---------------------------------------------------------------------------*\
                          Class PackedList Declaration
 \*---------------------------------------------------------------------------*/
@@ -159,6 +80,8 @@ class PackedList
 :
     private List<unsigned int>
 {
+    typedef unsigned int PackedStorage;
+
     // Private data
 
         //- Number of nBits entries
@@ -166,16 +89,10 @@ class PackedList
 
     // Private Member Functions
 
-        //- Calculate underlying list size
+        //- Calculate the list length when packed
-        inline static label storageSize(const label);
+        inline static label packedLength(const label);
 
-        //- Calculate element index and offset (start) bit within storage
+        //- Check index I is within valid range [ 0 .. max_value() ]
-        inline static label location(const label, label& offset);
-
-        //- Check if value is representable in nBits
-        inline static void checkValue(const unsigned int);
-
-        //- Check index i is within valid range (0 ... size-1).
         inline void checkIndex(const label) const;
 
 public:
@@ -184,23 +101,18 @@ public:
 
         //- The max. number of bits that can be templated.
         //  Might someday be useful for a template assert.
-        inline static unsigned int max_bits()
+        inline static unsigned int max_bits();
-        {
-            return PackedBitRef<nBits>::max_bits();
-        }
 
-        //- The max. value for an entry, can also be used as the mask
+        //- The max. value for an entry, which simultaneously the bit-mask
         //  eg, ((1 << 2) - 1) yields 0b0011
-        inline static unsigned int max_value()
+        inline static unsigned int max_value();
-        {
-            return PackedBitRef<nBits>::max_value();
-        }
 
-        //- The number of entries per storage entry
+        //- The number of entries per packed storage element
-        inline static unsigned int packing()
+        inline static unsigned int packing();
-        {
+
-            return PackedBitRef<nBits>::packing();
+    // Forward declaration of iterator
-        }
+        class iterator;
+        friend class iterator;
 
 
     // Constructors
@@ -208,7 +120,7 @@ public:
         //- Null constructor
         inline PackedList();
 
-        //- Construct with given size. Note: initializes list to 0.
+        //- Construct with given size, initializes list to 0.
         inline PackedList(const label size);
 
         //- Construct with given size and value for all elements.
@@ -233,38 +145,41 @@ public:
         //- The number of elements that can be stored before resizing
         inline label capacity() const;
 
-        //- Number of packed elements.
+        //- Number of entries.
         inline label size() const;
 
         //- Return true if the list is empty (i.e., if size() == 0).
         inline bool empty() const;
 
         //- Get value at index I.
-        //  Does not auto-vivifies elements.
+        //  Does not auto-vivifies entries.
-        inline unsigned int get(const label i) const;
+        inline unsigned int get(const label) const;
 
         //- Set value at index I. Return true if value changed.
-        //  Does not auto-vivifies elements.
+        //  Does not auto-vivifies entries.
-        inline bool set(const label i, const unsigned int val);
+        inline bool set(const label, const unsigned int val);
 
-        //- Underlying storage
+        //- Return the underlying packed storage
         inline const List<unsigned int>& storage() const;
 
-        //- Return as labelList
+        //- Return the values as a labelList
         labelList values() const;
 
+        //- Print values and information
+        Ostream& print(Ostream&) const;
+
         // Edit
 
         //- Alter the size of the underlying storage.
         //  The addressed size will be truncated if needed to fit, but will
         //  remain otherwise untouched.
-        //  Use this or reserve() in combination with append().
         inline void setCapacity(const label);
 
-        //- Reset size of List, optionally specify a value for new elements.
+        //- Reset addressable list size, does not shrink the allocated size.
+        //  Optionally specify a value for new elements.
         inline void resize(const label, const unsigned int& val = 0);
 
-        //- Reset size of List, optionally specify a value for new elements.
+        //- Alias for resize()
         inline void setSize(const label, const unsigned int& val = 0);
 
         //- Reserve allocation space for at least this size.
@@ -272,8 +187,8 @@ public:
         //  Optionally provide an initialization value for new elements.
         inline void reserve(const label, const unsigned int& val = 0);
 
-        //- Clear the list, i.e. set size to zero.
+        //- Clear the list, i.e. set addressable size to zero.
-        //- Does not adjust the underlying storage
+        //  Does not adjust the underlying storage
         inline void clear();
 
         //- Clear the list and delete storage.
@@ -282,7 +197,7 @@ public:
         //- Shrink the allocated space to what is used.
         inline void shrink();
 
-        //- Transfer the contents of the argument List into this List
+        //- Transfer the contents of the argument list into this list
         //  and annull the argument list.
         inline void transfer(PackedList<nBits>&);
 
@@ -291,17 +206,17 @@ public:
 
     // Member operators
 
-        //- Append a value at the end of the list. Return true if value changed.
+        //- Append a value at the end of the list
-        inline bool append(const unsigned int val);
+        inline void append(const unsigned int val);
 
         //- Get value at index I
-        //  Does not auto-vivifies elements.
+        //  Auto-vivifies any new values to zero.
-        inline unsigned int operator[](const label i) const;
+        inline unsigned int operator[](const label) const;
 
         //- Set value at index I.
         //  Returns proxy to perform the actual operation.
         //  Auto-vivifies any new values to zero.
-        inline ::Foam::PackedBitRef<nBits> operator[](const label i);
+        inline iterator operator[](const label);
 
         //- Assignment of all entries to the given value.
         //  Does set on all elements.
@@ -318,6 +233,71 @@ public:
     //  // Write PackedList to Ostream.
     //  friend Ostream& operator<< <nBits> (Ostream&, const PackedList<nBits>&);
 
+
+    //- The iterator-like class used for PackedList
+    class iterator
+    {
+        friend class PackedList;
+
+        // Private Data
+
+        //- Reference to original list
+        PackedList& list_;
+
+        //- Element index within storage
+        unsigned elem_;
+
+        //- Offset within storage element
+        unsigned offset_;
+
+        //- Return the raw storage element
+        inline PackedStorage& chunk() const;
+
+        //- Return the position in the PackedList
+        inline label position() const;
+
+    public:
+
+        // Constructors
+
+        //- Construct from base list and position index
+        inline iterator(const PackedList&, const label i);
+
+        // Members
+
+        //- Assign value, returns true if the value changed
+        inline bool operator=(const unsigned int val);
+
+        //- Conversion operator
+        inline operator unsigned int () const;
+
+        //- Conversion operator
+        inline operator bool() const;
+
+        // Member operators
+
+        inline void operator=(const iterator&);
+        inline bool operator==(const iterator&) const;
+        inline bool operator!=(const iterator&) const;
+
+        //- Return referenced value
+        inline unsigned int operator()() const;
+
+        inline iterator& operator++();
+        inline iterator operator++(int);
+
+        //- Print value and information
+        Ostream& print(Ostream&) const;
+
+    };
+
+
+    //- iterator set to the begining of the PackedList
+    inline iterator begin();
+
+    //- iterator set to beyond the end of the HashTable
+    inline iterator end();
+
 };
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

@@ -25,71 +25,38 @@ License
 
 \*---------------------------------------------------------------------------*/
 
-#ifndef PackedListI_H
+#include "error.H"
-#define PackedListI_H
-
-#include "IOstreams.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 template<int nBits>
-inline unsigned int Foam::PackedBitRef<nBits>::max_bits()
+inline unsigned int Foam::PackedList<nBits>::max_bits()
 {
-    return sizeof(unsigned int)*8 - 1;
+    return sizeof(PackedStorage)*8 - 1;
 }
 
 
 template<int nBits>
-inline unsigned int Foam::PackedBitRef<nBits>::max_value()
+inline unsigned int Foam::PackedList<nBits>::max_value()
 {
     return ((1u << nBits) - 1);
 }
 
 
 template<int nBits>
-inline unsigned int Foam::PackedBitRef<nBits>::packing()
+inline unsigned int Foam::PackedList<nBits>::packing()
 {
-    return sizeof(unsigned int)*8 / nBits;
+    return sizeof(PackedStorage)*8 / nBits;
-}
-
-
-// Calculate underlying list size
-template<int nBits>
-inline Foam::label Foam::PackedList<nBits>::storageSize(const label sz)
-{
-    return (sz + packing() - 1) / packing();
 }
 
 
 template<int nBits>
-inline Foam::label Foam::PackedList<nBits>::location
+inline Foam::label Foam::PackedList<nBits>::packedLength(const label nElem)
-(
-    const label i,
-    label& offset
-)
 {
-    // the offset is the start bit within the storage element
+    return (nElem + packing() - 1) / packing();
-    offset = nBits * (i % packing());
-    return i / packing();
 }
 
 
-// Check value is representable in nBits
-template<int nBits>
-inline void Foam::PackedList<nBits>::checkValue(const unsigned int val)
-{
-    if (val > max_value())
-    {
-        FatalErrorIn("PackedList<T>::checkValue(const unsigned int)")
-            << "value " << label(val) << " out of range 0 ... "
-            << label(max_value())
-            << " representable by " << nBits << " bits"
-            << abort(FatalError);
-    }
-}
-
-
-// Check index i is within valid range (0 ... size-1).
 template<int nBits>
 inline void Foam::PackedList<nBits>::checkIndex(const label i) const
 {
@@ -110,20 +77,18 @@ inline void Foam::PackedList<nBits>::checkIndex(const label i) const
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
-// Null constructor
 template<int nBits>
 inline Foam::PackedList<nBits>::PackedList()
 :
-    List<unsigned int>(),
+    List<PackedStorage>(),
     size_(0)
 {}
 
 
-// Construct with given size.
 template<int nBits>
 inline Foam::PackedList<nBits>::PackedList(const label size)
 :
-    List<unsigned int>(storageSize(size), 0u),
+    List<PackedStorage>(packedLength(size), 0u),
     size_(size)
 {}
 
@@ -131,7 +96,7 @@ inline Foam::PackedList<nBits>::PackedList(const label size)
 template<int nBits>
 inline Foam::PackedList<nBits>::PackedList(const PackedList<nBits>& lst)
 :
-    List<unsigned int>(lst),
+    List<PackedStorage>(lst),
     size_(lst.size())
 {}
 
@@ -143,14 +108,161 @@ inline Foam::PackedList<nBits>::PackedList(const Xfer<PackedList<nBits> >& lst)
 }
 
 
-
 template<int nBits>
-inline Foam::autoPtr<Foam::PackedList<nBits> > Foam::PackedList<nBits>::clone() const
+inline Foam::autoPtr<Foam::PackedList<nBits> >
+Foam::PackedList<nBits>::clone() const
 {
     return autoPtr<PackedList<nBits> >(new PackedList<nBits>(*this));
 }
 
 
+// * * * * * * * * * * * * * * * * Iterators * * * * * * * * * * * * * * * * //
+
+template<int nBits>
+inline Foam::PackedList<nBits>::iterator::iterator
+(
+    const PackedList<nBits>& lst,
+    const label i
+)
+:
+    list_(const_cast<PackedList<nBits>&>(lst)),
+    elem_(i / packing()),
+    offset_(i % packing())
+{}
+
+
+template<int nBits>
+inline void Foam::PackedList<nBits>::iterator::operator=
+(
+    const iterator& iter
+)
+{
+    elem_ = iter.elem_;
+    offset_ = iter.offset_;
+}
+
+
+template<int nBits>
+inline bool Foam::PackedList<nBits>::iterator::operator==
+(
+    const iterator& iter
+) const
+{
+    return elem_ == iter.elem_ && offset_ == iter.offset_;
+}
+
+
+template<int nBits>
+inline bool Foam::PackedList<nBits>::iterator::operator!=
+(
+    const iterator& iter
+) const
+{
+    return !(operator==(iter));
+}
+
+
+template<int nBits>
+inline bool Foam::PackedList<nBits>::iterator::operator=
+(
+    const unsigned int val
+)
+{
+    const unsigned int startBit = nBits * offset_;
+    const unsigned int mask = max_value() << startBit;
+
+    unsigned int& stored = chunk();
+    const unsigned int old = stored;
+
+    stored &= ~mask;
+    stored |= (val << startBit) & mask;
+
+    return (old != stored);
+}
+
+
+template<int nBits>
+inline Foam::label Foam::PackedList<nBits>::iterator::position() const
+{
+    return (elem_ * packing() + offset_);
+}
+
+
+template<int nBits>
+inline unsigned int& Foam::PackedList<nBits>::iterator::chunk() const
+{
+    return list_.List<PackedStorage>::operator[](elem_);
+}
+
+
+template<int nBits>
+inline typename Foam::PackedList<nBits>::iterator&
+Foam::PackedList<nBits>::iterator::operator++()
+{
+    if (position() < list_.size())
+    {
+        offset_++;
+        if (offset_ >= packing())
+        {
+            elem_++;
+            offset_ = 0;
+        }
+    }
+
+    return *this;
+}
+
+
+template<int nBits>
+inline typename Foam::PackedList<nBits>::iterator
+Foam::PackedList<nBits>::iterator::operator++(int)
+{
+    iterator old = *this;
+    ++*this;
+    return old;
+}
+
+
+template<int nBits>
+inline unsigned int
+Foam::PackedList<nBits>::iterator::operator()() const
+{
+    return (chunk() >> (nBits * offset_)) & max_value();
+}
+
+
+template<int nBits>
+inline Foam::PackedList<nBits>::iterator::operator
+unsigned int () const
+{
+    return (chunk() >> (nBits * offset_)) & max_value();
+}
+
+
+template<int nBits>
+inline Foam::PackedList<nBits>::iterator::operator
+bool() const
+{
+    return !!(chunk() >> (nBits * offset_)) & max_value();
+}
+
+
+template<int nBits>
+inline typename Foam::PackedList<nBits>::iterator
+Foam::PackedList<nBits>::begin()
+{
+    return iterator(*this, 0);
+}
+
+
+template<int nBits>
+inline typename Foam::PackedList<nBits>::iterator
+Foam::PackedList<nBits>::end()
+{
+    return iterator(*this, size());
+}
+
+
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
 template<int nBits>
@@ -170,12 +282,12 @@ inline bool Foam::PackedList<nBits>::empty() const
 template<int nBits>
 inline void Foam::PackedList<nBits>::resize
 (
-    const label newSize,
+    const label nElem,
     const unsigned int& val
 )
 {
-    reserve(newSize, val);
+    reserve(nElem, val);
-    size_ = newSize;
+    size_ = nElem;
 }
 
 
@@ -194,21 +306,35 @@ inline void Foam::PackedList<nBits>::setSize
 template<int nBits>
 inline Foam::label Foam::PackedList<nBits>::capacity() const
 {
-    return packing() * List<unsigned int>::size();
+    return packing() * List<PackedStorage>::size();
 }
 
 
 template<int nBits>
 inline void Foam::PackedList<nBits>::setCapacity(const label nElem)
 {
-    List<unsigned int>::setSize(storageSize(nElem), 0);
+    List<PackedStorage>::setSize(packedLength(nElem), 0u);
 
-    for (label i = size_; i < nElem; i++)
+    // truncates addressable section too
+    if (size_ > nElem)
     {
-        set(i, 0);
+#       ifdef DEBUGList
+        // clear old values (purely cosmetics for string output)
+        for (label i = nElem; i < size_; i++)
+        {
+            set(i, 0);
+        }
+#       endif
+        size_ = nElem;
+    }
+    else
+    {
+        // fill new elements
+        for (label i = size_; i < nElem; i++)
+        {
+            set(i, 0);
+        }
     }
-
-    size_ = nElem;
 }
 
 
@@ -219,15 +345,15 @@ inline void Foam::PackedList<nBits>::reserve
     const unsigned int& val
 )
 {
-    label rawSize = storageSize(nElem);
+    label len = packedLength(nElem);
 
     // need more capacity?
-    if (rawSize > List<unsigned int>::size())
+    if (len > List<PackedStorage>::size())
     {
-        List<unsigned int>::setSize(rawSize, 0);
+        List<PackedStorage>::setSize(len, 0);
     }
 
-    // fill new elements, don't rely on List::setSize
+    // fill new elements
     for (label i = size_; i < nElem; i++)
     {
         set(i, val);
@@ -245,7 +371,7 @@ inline void Foam::PackedList<nBits>::clear()
 template<int nBits>
 inline void Foam::PackedList<nBits>::clearStorage()
 {
-    List<unsigned int>::clear();
+    List<PackedStorage>::clear();
     size_ = 0;
 }
 
@@ -253,86 +379,20 @@ inline void Foam::PackedList<nBits>::clearStorage()
 template<int nBits>
 inline void Foam::PackedList<nBits>::shrink()
 {
-    label rawSize = storageSize(size_);
+    label len = packedLength(size_);
 
     // we have unused space?
-    if (rawSize < List<unsigned int>::size())
+    if (len < List<PackedStorage>::size())
     {
-        List<unsigned int>::setSize(rawSize);
+        List<PackedStorage>::setSize(len);
     }
 }
 
-
-// Get value at i
 template<int nBits>
-inline unsigned int Foam::PackedList<nBits>::get(const label i) const
+inline const Foam::List<unsigned int>&
+Foam::PackedList<nBits>::storage() const
 {
-#   ifdef DEBUGList
+    return static_cast<const List<PackedStorage>&>(*this);
-    checkIndex(i);
-#   endif
-
-    label startBit;
-    const unsigned int& elem = List<unsigned int>::operator[]
-    (
-        location(i, startBit)
-    );
-
-    // PackedBitRef<nBits> iter(*this, elem, startBit);
-
-    // return PackedBitRef<nBits>(*this, elem, startBit)();
-
-    return (elem >> startBit) & max_value();
-}
-
-
-template<int nBits>
-inline unsigned int Foam::PackedList<nBits>::operator[](const label i) const
-{
-    return get(i);
-}
-
-
-// Set value at i
-template<int nBits>
-inline bool Foam::PackedList<nBits>::set(const label i, const unsigned int val)
-{
-#   ifdef DEBUGList
-    checkIndex(i);
-    checkValue(val);
-#   endif
-
-    label startBit;
-    unsigned int& elem = List<unsigned int>::operator[]
-    (
-        location(i, startBit)
-    );
-
-    unsigned int oldElem = elem;
-
-    unsigned int shiftedMask = max_value() << startBit;
-    unsigned int shiftedVal  = (val & max_value()) << startBit;
-
-    elem = (elem & ~shiftedMask) | shiftedVal;
-
-    return elem != oldElem;
-}
-
-
-template<int nBits>
-inline bool Foam::PackedList<nBits>::append(const unsigned int val)
-{
-    label elemI = size_;
-    reserve(elemI + 1);
-    size_++;
-
-    return set(elemI, val);
-}
-
-
-template<int nBits>
-inline const Foam::List<unsigned int>& Foam::PackedList<nBits>::storage() const
-{
-    return static_cast<const List<unsigned int>&>(*this);
 }
 
 
@@ -342,11 +402,10 @@ inline void Foam::PackedList<nBits>::transfer(PackedList<nBits>& lst)
     size_ = lst.size_;
     lst.size_ = 0;
 
-    List<unsigned int>::transfer(lst);
+    List<PackedStorage>::transfer(lst);
 }
 
 
-
 template<int nBits>
 inline Foam::Xfer<Foam::PackedList<nBits> >
 Foam::PackedList<nBits>::xfer()
@@ -355,9 +414,69 @@ Foam::PackedList<nBits>::xfer()
 }
 
 
+template<int nBits>
+inline unsigned int Foam::PackedList<nBits>::get(const label i) const
+{
+#   ifdef DEBUGList
+    checkIndex(i);
+#   endif
+
+    return iterator(*this, i)();
+}
+
 
 template<int nBits>
-inline typename Foam::PackedBitRef<nBits>
+inline unsigned int Foam::PackedList<nBits>::operator[](const label i) const
+{
+    if (i >= size_)
+    {
+        setSize(i + 1);
+        return 0;
+    }
+    else
+    {
+        return iterator(*this, i)();
+    }
+}
+
+
+template<int nBits>
+inline bool Foam::PackedList<nBits>::set
+(
+    const label i,
+    const unsigned int val
+)
+{
+#   ifdef DEBUGList
+    checkIndex(i);
+
+    if (val & ~max_value())
+    {
+        FatalErrorIn("PackedList<T>::set(const label, const unsigned int)")
+            << "value " << label(val)
+            << " out-of-range 0 ... " << label(max_value())
+            << " representable by " << nBits << " bits"
+            << abort(FatalError);
+    }
+#   endif
+
+    return (iterator(*this, i) = val);
+}
+
+
+template<int nBits>
+inline void Foam::PackedList<nBits>::append(const unsigned int val)
+{
+    label elemI = size_;
+    reserve(elemI + 1);
+    size_++;
+
+    iterator(*this, elemI) = val;
+}
+
+
+template<int nBits>
+inline typename Foam::PackedList<nBits>::iterator
 Foam::PackedList<nBits>::operator[](const label i)
 {
     if (i >= size_)
@@ -365,45 +484,25 @@ Foam::PackedList<nBits>::operator[](const label i)
         setSize(i + 1);
     }
 
-    label startBit;
+    return iterator(*this, i);
-    unsigned int& elem = List<unsigned int>::operator[]
-    (
-        location(i, startBit)
-    );
-
-    return ::Foam::PackedBitRef<nBits>
-    (
-        // *this,
-        elem, 
-        startBit
-    );
 }
 
 
-// Set all to val
 template<int nBits>
 inline void Foam::PackedList<nBits>::operator=(const unsigned int val)
 {
-#   ifdef DEBUGList
-    checkValue(val);
-#   endif
-
     if (val)
     {
-        forAll(*this, i)
+        forAll(*this, elemI)
         {
-            set(i, val);
+            set(elemI, val);
         }
     }
     else
     {
-        List<unsigned int>::operator=(val);
+        List<PackedStorage>::operator=(val);
     }
 }
 
 
-// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
-
-#endif
-
 // ************************************************************************* //