Support for zero length arrays

[SVN r34156]

include/boost/array.hpp

@@ -52,7 +52,7 @@ namespace boost {
         typedef const T&       const_reference;
         typedef std::size_t    size_type;
         typedef std::ptrdiff_t difference_type;
-    
+
         // iterator support
         iterator begin() { return elems; }
         const_iterator begin() const { return elems; }
@@ -135,6 +135,7 @@ namespace boost {
 
         // direct access to data (read-only)
         const T* data() const { return elems; }
+        T* data() { return elems; }
 
         // use array as C array (direct read/write access to data)
         T* c_array() { return elems; }
@@ -154,13 +155,127 @@ namespace boost {
 
         // check range (may be private because it is static)
         static void rangecheck (size_type i) {
-            if (i >= size()) { 
+            if (i >= size()) {
                 throw std::range_error("array<>: index out of range");
             }
         }
 
     };
 
+    template< class T >
+    class array< T, 0 > {
+
+      public:
+        // type definitions
+        typedef T              value_type;
+        typedef T*             iterator;
+        typedef const T*       const_iterator;
+        typedef T&             reference;
+        typedef const T&       const_reference;
+        typedef std::size_t    size_type;
+        typedef std::ptrdiff_t difference_type;
+
+        // iterator support
+        iterator begin() { return iterator( reinterpret_cast< T * >( this ) ); }
+        const_iterator begin() const { return const_iterator(  reinterpret_cast< const T * >( this ) ); }
+        iterator end() { return begin(); }
+        const_iterator end() const { return begin(); }
+
+        // reverse iterator support
+#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) && !defined(BOOST_MSVC_STD_ITERATOR) && !defined(BOOST_NO_STD_ITERATOR_TRAITS)
+        typedef std::reverse_iterator<iterator> reverse_iterator;
+        typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
+#elif defined(_MSC_VER) && (_MSC_VER == 1300) && defined(BOOST_DINKUMWARE_STDLIB) && (BOOST_DINKUMWARE_STDLIB == 310)
+        // workaround for broken reverse_iterator in VC7
+        typedef std::reverse_iterator<std::_Ptrit<value_type, difference_type, iterator,
+                                      reference, iterator, reference> > reverse_iterator;
+        typedef std::reverse_iterator<std::_Ptrit<value_type, difference_type, const_iterator,
+                                      const_reference, iterator, reference> > const_reverse_iterator;
+#else
+        // workaround for broken reverse_iterator implementations
+        typedef std::reverse_iterator<iterator,T> reverse_iterator;
+        typedef std::reverse_iterator<const_iterator,T> const_reverse_iterator;
+#endif
+
+        reverse_iterator rbegin() { return reverse_iterator(end()); }
+        const_reverse_iterator rbegin() const {
+            return const_reverse_iterator(end());
+        }
+        reverse_iterator rend() { return reverse_iterator(begin()); }
+        const_reverse_iterator rend() const {
+            return const_reverse_iterator(begin());
+        }
+
+        // operator[]
+        reference operator[](size_type i)
+        {
+            BOOST_ASSERT( "out of range" );
+            failed_rangecheck();
+        }
+
+        const_reference operator[](size_type i) const
+        {
+            BOOST_ASSERT( "out of range" );
+            failed_rangecheck();
+        }
+
+        // at() with range check
+        reference at(size_type i)               {   failed_rangecheck();  }
+        const_reference at(size_type i) const   {   failed_rangecheck();  }
+
+        // front() and back()
+        reference front()
+        {
+            failed_rangecheck();
+        }
+
+        const_reference front() const
+        {
+            failed_rangecheck();
+        }
+
+        reference back()
+        {
+            failed_rangecheck();
+        }
+
+        const_reference back() const
+        {
+            failed_rangecheck();
+        }
+
+        // size is constant
+        static size_type size() { return 0; }
+        static bool empty() { return true; }
+        static size_type max_size() { return 0; }
+        enum { static_size = 0 };
+
+        void swap (array<T,0>& y) {
+        }
+
+        // direct access to data (read-only)
+        const T* data() const { return 0; }
+        T* data() { return 0; }
+
+        // use array as C array (direct read/write access to data)
+        T* c_array() { return 0; }
+
+        // assignment with type conversion
+        template <typename T2>
+        array<T,0>& operator= (const array<T2,0>& ) {
+            return *this;
+        }
+
+        // assign one value to all elements
+        void assign (const T& ) {   }
+
+        // check range (may be private because it is static)
+        static void failed_rangecheck () {
+                throw std::range_error("attempt to access element of an empty array");
+            }
+
+    };
+
     // comparisons
     template<class T, std::size_t N>
     bool operator== (const array<T,N>& x, const array<T,N>& y) {