//////////////////////////////////////////////////////////////////////
//
//                             Pixie
//
// Copyright © 1999 - 2003, Okan Arikan
//
// Contact: okan@cs.berkeley.edu
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public
// License as published by the Free Software Foundation; either
// version 2 of the License, or (at your option) any later version.
// 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
// 
// You should have received a copy of the GNU General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//
///////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////
//
//  File				:	memoryman.cpp
//  Classes				:
//  Description			:	Implements an efficient memory manager
//
////////////////////////////////////////////////////////////////////////
#include "global.h"
#include "os.h"

#ifdef USE_MEMORY_MANAGER

#define	NUM_CHUNKS	512

typedef union TMemoryHeader {
	unsigned int	index;
	TMemoryHeader	*next;
} TMemoryHeader;


#define	MEMORY_PAGE_SIZE	1 << 18

TMemoryHeader			*memoryChunks[NUM_CHUNKS];
unsigned char			*memoryPage					=	NULL;
unsigned int			memoryAvailable				=	0;
unsigned int			memoryUsage					=	0;
TMemoryHeader			*memoryAllPages				=	NULL;
static	int				memoryManagerInited			=	0;





///////////////////////////////////////////////////////////////////////
// Function				:	operator new
// Description			:	Overloaded new
// Return Value			:
// Comments				:
// Date last edited		:	11/21/2003
inline	void	*operator new(size_t size) {
	unsigned int	 index	=	size >> 3;	// Align at 8 byte boundary
	TMemoryHeader	*ptri;

	// Round up
	if (size & 7) index++;

	// Is the requested size too large ?
	if (index >= NUM_CHUNKS) {

		// Yes: Use the regular memory allocator
		ptri	=	(TMemoryHeader *) malloc(size+sizeof(TMemoryHeader));
		assert(ptri != NULL);
	} else {

		// No: Use the memory manager
		if ((ptri=memoryChunks[index]) == 0) {
			size				=  (index << 3) + sizeof(TMemoryHeader);

			if (size > memoryAvailable) {
				memoryManagerNewPage(size);
			}

			ptri				=	(TMemoryHeader *) memoryPage;
			memoryPage			+=	size;
			memoryAvailable		-=	size;
		} else {
			memoryChunks[index]	=	ptri->next;
		}
	}

	ptri->index	=	index;

	memoryUsage	+=	index;

	return ptri+1;
}

///////////////////////////////////////////////////////////////////////
// Function				:	operator delete
// Description			:	Overloaded delete
// Return Value			:
// Comments				:
// Date last edited		:	11/21/2003
inline	void	operator delete(void *ptr) {
	if (ptr != 0) {
		TMemoryHeader	*ptri	=	(TMemoryHeader *) ptr;

		ptri--;
		memoryUsage	-=	ptri->index;

		if (ptri->index >= NUM_CHUNKS) {
			free(ptri);
		} else {
			unsigned int	index	=	ptri->index;
			ptri->next				=	memoryChunks[index];
			memoryChunks[index]		=	ptri;

		}
	}
}


///////////////////////////////////////////////////////////////////////
// Function				:	memoryManagerInit
// Description			:	Init the memory manager
// Return Value			:
// Comments				:
// Date last edited		:	11/21/2003
void	memoryManagerInit() {
	if (memoryManagerInited == 0) {
		int	i;

		for (i=0;i<NUM_CHUNKS;i++)	memoryChunks[i]	=	0;

		memoryAvailable		=	0;
		memoryUsage			=	0;
		memoryPage			=	0;
		memoryAllPages		=	0;
	}

	memoryManagerInited++;
}

///////////////////////////////////////////////////////////////////////
// Function				:	memoryManagerTini
// Description			:	Shutdown the memory manager
// Return Value			:
// Comments				:
// Date last edited		:	11/21/2003
void	memoryManagerTini() {
	if (memoryManagerInited == 1) {
		TMemoryHeader	*cPage;

		while((cPage=memoryAllPages) != NULL) {
			memoryAllPages	=	cPage->next;

			free(cPage);
		}
	}

	memoryManagerInited--;
}

///////////////////////////////////////////////////////////////////////
// Function				:	memoryManagerNewPage
// Description			:	Allocate a new page of memory
// Return Value			:
// Comments				:
// Date last edited		:	11/21/2003
void	memoryManagerNewPage(unsigned int size) {
	if (memoryManagerInited == FALSE)	memoryManagerInit();

	unsigned int	asize	=	max(size,MEMORY_PAGE_SIZE);
	TMemoryHeader	*cPage	=	(TMemoryHeader *) malloc(asize+sizeof(TMemoryHeader));

	cPage->next				=	memoryAllPages;
	memoryAllPages			=	cPage;
	memoryPage				=	(unsigned char *) (cPage+1);
	memoryAvailable			=	asize;
}

#endif