// C Source File
// Created 03/15/2008 06:32:43 PM

/*
*  By Lardmaster,
*  Feel free to use it for any purposes... I doubt it works at this point.
*
*  Uses unsigned shorts as pointers for the linked list of free block, to save memory.  Thus the max number of blocks is 65,535
*  Simple fixed block sized memory allocator with free and allocate.
*  I hope it works :P.
*/

#include <tigcclib.h>
/*
*  The size of the header at the top of the allocated memory, an int for size, a short for first_free
*/
#define HEADER_SIZE sizeof(unsigned int)+sizeof(unsigned short)

/*
*  block size, and the short pointer to the first free block
*/

typedef struct lardbuffer {
	unsigned int size;
	unsigned short first_free;
} lardbuffer;
/*
*  converts the within buffer(unsigned short) pointer to a system wide pointer
*/
void * conv_to_ptr(const lardbuffer *b, unsigned short ptr) {
	return (void*)(b+HEADER_SIZE+ptr*b->size);
}
/*
*  converts a systemwide pointer to somewhere inside the buffer into an unsigned short which points locally
*/
unsigned short conv_to_short(const lardbuffer *b, const void * ptr) {
	return ((unsigned int)(ptr-(void *)b)-HEADER_SIZE)/b->size;
}

/*
*  allocates the buffer with a system malloc call
*/
lardbuffer * initailize_buffer(unsigned int size, unsigned int maxelements) {
	int mallocsize=HEADER_SIZE+size*maxelements;
	lardbuffer * b= (lardbuffer*)(malloc(mallocsize));
	b->size=size;
	b->first_free=0;
	for(unsigned short i=0; i<maxelements-1; i++) {
		*(unsigned short*)conv_to_ptr(b,i)=i+i;
	}
	*(unsigned shortinvalid operands to binary - *)conv_to_ptr(b,maxelements-1)=0;
	return b;
}
/*
* returns a pointer to an allocated memory block of size b->size
*/
void * allocate(lardbuffer *b) {
	void * ptr=conv_to_ptr(b,b->first_free);
	b->first_free=*((unsigned short*)ptr);
	return ptr;
}
/*
* a simple inline method to dereference the unsigned short pointers quickly.
*/
inline unsigned short deref(lardbuffer *b, unsigned short ptr) {
	return *((unsigned short *)conv_to_ptr(b,ptr));
}
/*
* frees the memory block pointer to by ptr, which must be in larbuffer b
*/

void free(lardbuffer *b, void * ptr) {
	unsigned short next=b->first_free;
	unsigned short after=deref(b,next);
	while(after!=0) {
		if(conv_to_ptr(after)>ptr) {
			*((unsigned  short *)conv_to_ptr(next))=conv_to_short(ptr);
			*((unsigned short *)ptr)=after;
			break;
		}
	}
}