Qexerpt.c

typedef struct Node Node;
typedef struct FIFOQ FIFOQ;

struct Node {
    char data;				// the data for this Node
	off_t offset;			// offset of data byte in the file
	Node *next;				// next Node in the queue
};
 
struct FIFOQ {
	Node *head;				// first Node in the queue
	Node *tail;				// last Node in the queue
	int size;				// number of Nodes
};

......

/** Pops the top Node. Returns NULL if queue is empty */
Node * q_pop (FIFOQ *q) {

    if (q->size <= 0) return NULL;	// return null if empty queue

	Node * result = q->head;		// remove head Node
	q->head = q->head->next;		// set new head to the next in line
	q->size--;						// decrement size
	return result;					// return old head Node
}