#ifndef __FIFO_H__
#define __FIFO_H__

#define CONCAT3(str1, str2, str3) str1 ## str2 ## str3
#define CONCAT4(str1, str2, str3, str4) str1 ## str2 ## str3 ## str4

#define FIFO_TYPE char
#define FIFO_T(type) CONCAT3(fifo_, type, _t)
#define FIFO_METHOD(type, name) CONCAT4(fifo_, type, _, name)

typedef struct {
	FIFO_TYPE *buffer;
	int size;
	FIFO_TYPE *prius;
	FIFO_TYPE *follower;
} FIFO_T(FIFO_TYPE);

/* The mechanizm of the ring buffer.
 * 1) The "follower" can no reach the "prius" more than overtake it. 
 * 2) The "prius" can reach the "follower", but can't overtake it.
 */

int FIFO_METHOD(FIFO_TYPE, write) (FIFO_T(FIFO_TYPE) *fifo, FIFO_TYPE *values, int size);
int FIFO_METHOD(FIFO_TYPE, read) (FIFO_T(FIFO_TYPE) *fifo, FIFO_TYPE *buffer, int size);
int FIFO_METHOD(FIFO_TYPE, size) (FIFO_T(FIFO_TYPE) *fifo);
FIFO_T(FIFO_TYPE) * FIFO_METHOD(FIFO_TYPE,init) (FIFO_T(FIFO_TYPE) *fifo, FIFO_TYPE *buffer, int size);

#define NULL 0

/**
 * 
 * 
 * @param fifo
 * @param buffer
 * @param size 
 * @return ( FIFO_T(FIFO_TYPE) ) 
 */
FIFO_T(FIFO_TYPE) * FIFO_METHOD(FIFO_TYPE, init) (FIFO_T(FIFO_TYPE) *fifo, FIFO_TYPE *buffer, int size){
	if(size > 0){
		fifo->buffer = buffer;
		fifo->size = size;
		fifo->prius = fifo->buffer;	
		fifo->follower = fifo->buffer + size - 1;
		return fifo;
	}else{return NULL;}
}

/**
 * 
 * 
 * @param fifo 
 * @param data 
 * @param size 
 * @return (int)
 */
int FIFO_METHOD(FIFO_TYPE, write) (FIFO_T(FIFO_TYPE) *fifo, FIFO_TYPE *values, int size){
	int _size = 0;
	if(values != NULL){
		while(_size < size){
			if(fifo->prius == fifo->buffer + fifo->size){fifo->prius = fifo->buffer;}
			if(fifo->prius == fifo->follower){break;}
			*((fifo->prius)++) = *(values + (_size++));
		}
	}
	return _size;
}

/**
 * 
 * 
 * @param fifo 
 * @param buffer 
 * @param size 
 * @return (int) 
 */
int FIFO_METHOD(FIFO_TYPE, read) (FIFO_T(FIFO_TYPE) *fifo, FIFO_TYPE *buffer, int size){
	int _size = 0;	
	if(buffer != NULL){
		while(_size < size){		
			if((fifo->follower + 1 - fifo->prius) % fifo->size == 0){break;}
			if(++fifo->follower == fifo->buffer + fifo->size){fifo->follower = fifo->buffer;}
			*(buffer + (_size++)) = *(fifo->follower);
		}
	}
	return _size;
}

/**
 * 
 * 
 * @param fifo 
 * @return int 
 */
int FIFO_METHOD(FIFO_TYPE, size) (FIFO_T(FIFO_TYPE) *fifo){
	return (fifo->prius > fifo->follower ?
		       fifo->prius - fifo->follower - 1:
		       fifo->prius + fifo->size - fifo->follower - 1);
}

#endif /* __FIFO_H__ */