Adding class to wrap small object allocator for STL containers.

git-svn-id: svn://svn.code.sf.net/p/loki-lib/code/trunk@837 7ec92016-0320-0410-acc4-a06ded1c099a

include/loki/Allocator.h

@@ -0,0 +1,147 @@
+////////////////////////////////////////////////////////////////////////////////
+// The Loki Library
+// Copyright (c) 2008 by Rich Sposato
+//
+// Permission to use, copy, modify, distribute and sell this software for any 
+//     purpose is hereby granted without fee, provided that the above copyright 
+//     notice appear in all copies and that both that copyright notice and this 
+//     permission notice appear in supporting documentation.
+// The author makes no representations about the 
+//     suitability of this software for any purpose. It is provided "as is" 
+//     without express or implied warranty.
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef LOKI_ALLOCATOR_HPP_INCLUDED
+#define LOKI_ALLOCATOR_HPP_INCLUDED
+
+// $Id$
+
+// Requires project to be compiled with loki/src/SmallObj.cpp and loki/src/Singleton.cpp
+
+#include <loki/SmallObj.h>
+
+
+namespace Loki
+{
+
+
+//-----------------------------------------------------------------------------
+
+/** @class LokiAllocator
+ Adapts Loki's Small-Object Allocator for STL container classes.
+ This class provides all the functionality required for STL allocators, but
+ uses Loki's Small-Object Allocator to perform actual memory operations.
+ Implementation comes from a post in Loki forums (by Rasmus Ekman?).
+ */
+template
+<
+    typename Type,
+    typename AllocT = Loki::AllocatorSingleton<>
+>
+class LokiAllocator
+{
+public:
+
+    typedef ::std::size_t size_type;
+    typedef ::std::ptrdiff_t difference_type;
+    typedef Type * pointer;
+    typedef const Type * const_pointer;
+    typedef Type & reference;
+    typedef const Type & const_reference;
+    typedef Type value_type;
+
+    /// Default constructor does nothing.
+    inline LokiAllocator( void ) throw() { }
+
+    /// Copy constructor does nothing.
+    inline LokiAllocator( const LokiAllocator & ) throw() { }
+
+    /// Type converting allocator constructor does nothing.
+    template < typename Type1 >
+    inline LokiAllocator( const LokiAllocator< Type1 > & ) throw() { }
+
+    /// Destructor does nothing.
+    inline ~LokiAllocator() throw() { }
+
+    /// Convert an allocator<Type> to an allocator <Type1>.
+    template < typename Type1 >
+    struct rebind
+    {
+        typedef LokiAllocator< Type1 > other;
+    };
+
+    /// Return address of reference to mutable element.
+    pointer address( reference elem ) const { return &elem; }
+
+    /// Return address of reference to const element.
+    const_pointer address( const_reference elem ) const { return &elem; }
+
+    /** Allocate an array of count elements.  Warning!  The true parameter in
+     the call to Allocate means this function can throw exceptions.
+     @param count # of elements in array.
+     @param hint Place where caller thinks allocation should occur.
+     @return Pointer to block of memory.
+     */
+    pointer allocate( size_type count, const void * hint = 0 )
+    {
+        (void)hint;  // Ignore the hint.
+        void * p = AllocT::Instance().Allocate( count * sizeof( Type ), true );
+        return reinterpret_cast< pointer >( p );
+    }
+
+    /// Ask allocator to release memory at pointer with size bytes.
+    void deallocate( pointer p, size_type size )
+    {
+        AllocT::Instance().Deallocate( p, size * sizeof( Type ) );
+    }
+
+    /// Calculate max # of elements allocator can handle.
+    size_type max_size( void ) const throw()
+    {
+        // A good optimizer will see these calculations always produce the same
+        // value and optimize this function away completely.
+        const size_type max_bytes = size_type( -1 );
+        const size_type bytes = max_bytes / sizeof( Type );
+        return bytes;
+    }
+
+    /// Construct an element at the pointer.
+    void construct( pointer p, const Type & value )
+    {
+        // A call to global placement new forces a call to copy constructor.
+        ::new( p ) Type( value );
+    }
+
+    /// Destruct the object at pointer.
+    void destroy( pointer p )
+    {
+        p->~Type();
+    }
+
+};
+
+//-----------------------------------------------------------------------------
+
+/** All equality operators return true since LokiAllocator is basically a
+ monostate design pattern, so all instances of it are identical.
+ */
+template < typename Type >
+inline bool operator == ( const LokiAllocator< Type > &, const LokiAllocator< Type > & )
+{
+    return true;
+}
+
+/** All inequality operators return false since LokiAllocator is basically a
+ monostate design pattern, so all instances of it are identical.
+ */
+template < typename Type >
+inline bool operator != ( const LokiAllocator< Type > & , const LokiAllocator< Type > & )
+{
+    return false;
+}
+
+//-----------------------------------------------------------------------------
+
+} // namespace Loki
+
+#endif // LOKI_ALLOCATOR_INCLUDED