/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program 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 program 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 program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * Contributor(s): Tao Ju
 *
 * ***** END GPL LICENSE BLOCK *****
 */

#ifndef MEMORYALLOCATOR_H
#define MEMORYALLOCATOR_H

#include <stdio.h>
#include <stdlib.h>

#define HEAP_BASE 16
#define UCHAR unsigned char

/**
 * Customized memory allocators that allocates/deallocates memory in chunks
 *
 * @author Tao Ju
 */



/**
 * Base class of memory allocators
 */
class VirtualMemoryAllocator
{
public:
virtual ~VirtualMemoryAllocator() {}

virtual void *allocate( ) = 0;
virtual void deallocate(void *obj) = 0;
virtual void destroy( ) = 0;
virtual void printInfo( ) = 0;

virtual int getAllocated( ) = 0;
virtual int getAll( ) = 0;
virtual int getBytes( ) = 0;
};

/**
 * Dynamic memory allocator - allows allocation/deallocation
 *
 * Note: there are 4 bytes overhead for each allocated yet unused object.
 */
template < int N >
class MemoryAllocator : public VirtualMemoryAllocator
{
private:

/// Constants
int HEAP_UNIT, HEAP_MASK;

/// Data array
UCHAR **data;

/// Allocation stack
UCHAR ***stack;

/// Number of data blocks
int datablocknum;

/// Number of stack blocks
int stackblocknum;

/// Size of stack
int stacksize;

/// Number of available objects on stack
int available;

/**
 * Allocate a memory block
 */
void allocateDataBlock( )
{
	// Allocate a data block
	datablocknum += 1;
	data = ( UCHAR ** )realloc(data, sizeof (UCHAR *) * datablocknum);
	data[datablocknum - 1] = ( UCHAR * )malloc(HEAP_UNIT * N);

	// Update allocation stack
	for (int i = 0; i < HEAP_UNIT; i++)
	{
		stack[0][i] = (data[datablocknum - 1] + i * N);
	}
	available = HEAP_UNIT;
}

/**
 * Allocate a stack block, to store more deallocated objects
 */
void allocateStackBlock( )
{
	// Allocate a stack block
	stackblocknum += 1;
	stacksize += HEAP_UNIT;
	stack = ( UCHAR *** )realloc(stack, sizeof (UCHAR * *) * stackblocknum);
	stack[stackblocknum - 1] = ( UCHAR ** )malloc(HEAP_UNIT * sizeof (UCHAR *) );
}


public:
/**
 * Constructor
 */
MemoryAllocator( )
{
	HEAP_UNIT = 1 << HEAP_BASE;
	HEAP_MASK = (1 << HEAP_BASE) - 1;

	data = ( UCHAR ** )malloc(sizeof(UCHAR *) );
	data[0] = ( UCHAR * )malloc(HEAP_UNIT * N);
	datablocknum = 1;

	stack = ( UCHAR *** )malloc(sizeof (UCHAR * *) );
	stack[0] = ( UCHAR ** )malloc(HEAP_UNIT * sizeof (UCHAR *) );
	stackblocknum = 1;
	stacksize = HEAP_UNIT;
	available = HEAP_UNIT;

	for (int i = 0; i < HEAP_UNIT; i++)
	{
		stack[0][i] = (data[0] + i * N);
	}
}

/**
 * Destructor
 */
void destroy( )
{
	int i;
	for (i = 0; i < datablocknum; i++)
	{
		free(data[i]);
	}
	for (i = 0; i < stackblocknum; i++)
	{
		free(stack[i]);
	}
	free(data);
	free(stack);
}

/**
 * Allocation method
 */
void *allocate( )
{
	if (available == 0)
	{
		allocateDataBlock( );
	}

	// printf("Allocating %d\n", header[ allocated ]) ;
	available--;
	return (void *)stack[available >> HEAP_BASE][available & HEAP_MASK];
}

/**
 * De-allocation method
 */
void deallocate(void *obj)
{
	if (available == stacksize)
	{
		allocateStackBlock( );
	}

	// printf("De-allocating %d\n", ( obj - data ) / N ) ;
	stack[available >> HEAP_BASE][available & HEAP_MASK] = (UCHAR *)obj;
	available++;
	// printf("%d %d\n", allocated, header[ allocated ]) ;
}

/**
 * Print information
 */
void printInfo( )
{
	printf("Bytes: %d Used: %d Allocated: %d Maxfree: %d\n", getBytes(), getAllocated(), getAll(), stacksize);
}

/**
 * Query methods
 */
int getAllocated( )
{
	return HEAP_UNIT * datablocknum - available;
};

int getAll( )
{
	return HEAP_UNIT * datablocknum;
};

int getBytes( )
{
	return N;
};
};

#endif
