/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999-2004 The Apache Software Foundation.  All rights 
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:  
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Xalan" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written 
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 1999, International
 * Business Machines, Inc., http://www.ibm.com.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
#if !defined(XALANARRAYALLOCATOR_HEADER_GUARD_1357924680)
#define XALANARRAYALLOCATOR_HEADER_GUARD_1357924680



#include <xalanc/PlatformSupport/PlatformSupportDefinitions.hpp>



#include <cassert>
#include <list>
#include <utility>
#include <vector>



XALAN_CPP_NAMESPACE_BEGIN



template<class Type>
class XALAN_PLATFORMSUPPORT_EXPORT XalanArrayAllocator
{
public:

#if defined(XALAN_NO_STD_NAMESPACE)
	typedef vector<Type>					VectorType;
	typedef typename VectorType::size_type	size_type;
	typedef pair<size_type, VectorType>		ListEntryType;
	typedef list<ListEntryType>				ListType;
#else
	typedef std::vector<Type>					VectorType;
	typedef typename VectorType::size_type		size_type;
	typedef std::pair<size_type, VectorType>	ListEntryType;
	typedef std::list<ListEntryType>			ListType;
#endif

	typedef Type							value_type;

	typedef typename ListType::iterator		ListIteratorType;

    // Default size for vector allocation.
	enum { eDefaultBlockSize = 500 };

	/**
	 * Constructor.
	 *
	 * @param theBlockSize The block size when allocating.
	 */
	XalanArrayAllocator(size_type	theBlockSize = eDefaultBlockSize) :
		m_list(),
		m_blockSize(theBlockSize),
		m_lastEntryFound(0)
	{
	}

	~XalanArrayAllocator()
	{
	}

	/**
	 * Clear the instance, and release all allocated memory
	 */
	void
	clear()
	{
		m_list.clear();

		m_lastEntryFound = 0;
	}

	/**
	 * Reset the instance, but keep all memory so it can be
	 * reused for allocations.  This invalidates all previous
	 * allocations.
	 */
	void
	reset()
	{
		if (m_list.empty() == true)
		{
			m_lastEntryFound = 0;
		}
		else
		{
			const ListIteratorType	theEnd = m_list.end();
			ListIteratorType		theCurrent = m_list.begin();

			do
			{
				(*theCurrent).first = (*theCurrent).second.size();

				++theCurrent;
			} while(theCurrent != theEnd);

			m_lastEntryFound = &*m_list.begin();
		}
	}

	/**
	 * Allocate slots for the given number of Types
	 * instance and return the address of the slots.
	 *
	 * @param theCount The number of slots to allocate
	 */
	Type*
	allocate(size_type	theCount)
	{
		// Handle the case of theCount being greater than the block size first...
		if (theCount >= m_blockSize)
		{
			return createEntry(theCount, theCount);
		}
		else
		{
			ListEntryType*	theEntry =
				findEntry(theCount);

			// Did we find a slot?
			if (theEntry == 0)
			{
				// Nope, create a new one...
				return createEntry(m_blockSize, theCount);
			}
			else
			{
				// The address we want is that of the first free element in the
				// vector...
				Type* const		thePointer =
					&*theEntry->second.begin() + (theEntry->second.size() - theEntry->first);

				// Resize the vector to the appropriate size...
				theEntry->first -= theCount;

				return thePointer;
			}
		}
	}

private:

	// Utility functions...
	Type*
	createEntry(
			size_type	theBlockSize,
			size_type	theCount)
	{
		assert(theBlockSize >= theCount);

		// Push on a new entry.  The entry has no open space,
		// since it's greater than our block size...
		m_list.push_back(ListEntryType(0, VectorType()));

		// Get the new entry...
		ListEntryType&	theNewEntry = m_list.back();

		// Resize the vector to the appropriate size...
		theNewEntry.second.resize(theBlockSize, VectorType::value_type(0));

		// Set the number of free spaces accordingly...
		theNewEntry.first = theBlockSize - theCount;

		if (theNewEntry.first != 0)
		{
			m_lastEntryFound = &theNewEntry;
		}

		// Return a pointer to the beginning of the allocated memory...
		return &*theNewEntry.second.begin();
	}

	ListEntryType*
	findEntry(size_type		theCount)
	{
		// Search for an entry that has some free space.

		if (m_lastEntryFound != 0 && m_lastEntryFound->first >= theCount)
		{
			return m_lastEntryFound;
		}
		else
		{
			const ListIteratorType	theEnd = m_list.end();
			ListIteratorType		theCurrent = m_list.begin();

			ListEntryType*	theEntry = 0;

			while(theCurrent != theEnd)
			{
				// We're looking for the best fit, so
				// if the free space and the count we're
				// looking for are equal, that's pretty
				// much the best we can do...
				if ((*theCurrent).first == theCount)
				{
					theEntry = &*theCurrent;

					break;
				}
				else if ((*theCurrent).first >= theCount)
				{
					// If we haven't found anything yet, the first
					// entry we find that's large enough becomes
					// our best fit.
					//
					// Otherwise, we'll assume that a smaller
					// slot is a better fit, though I may be
					// wrong about this...
					if (theEntry == 0 ||
						(*theCurrent).first < theEntry->first)
					{
						// Nope, so this becomes our best-fit so far.
						theEntry = &*theCurrent;
					}

					++theCurrent;
				}
				else
				{
					// Won't fit, so just continue...
					++theCurrent;
				}
			}

			m_lastEntryFound = theEntry;

			return theEntry;
		}
	}

	// Not implemented...
	XalanArrayAllocator(const XalanArrayAllocator<Type>&	theSource);

	XalanArrayAllocator<Type>&
	operator=(const XalanArrayAllocator<Type>&	theSource);

	bool
	operator==(const XalanArrayAllocator<Type>&	theRHS) const;


	// Data members...
	ListType			m_list;

	const size_type		m_blockSize;

	ListEntryType*		m_lastEntryFound;
};



XALAN_CPP_NAMESPACE_END



#endif	// !defined(XALANARRAYALLOCATOR_HEADER_GUARD_1357924680)
