pkt_queue.c

/*
 * Copyright (C) 2014 Yuzhong Wen<supermartian@gmail.com>
 *
 * Distributed under terms of the MIT license.
 */

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

#include "pkt_queue.h"

void init_queue(struct queue_root **root)
{
	*root = (struct queue_root*) malloc(sizeof(struct queue_root));
    if (root == NULL) {
        printf("malloc failed");
        exit(1);
    }
	(*root)->head = (struct queue_node*) malloc(sizeof(struct queue_node)); /* Sentinel node */
	(*root)->tail = (*root)->head;
	(*root)->head->n = NULL;
	(*root)->head->next = NULL;
}

int queue_add(struct queue_root *root, void *val)
{
	struct queue_node *n;
	struct queue_node *node = (struct queue_node *)malloc(sizeof(struct queue_node));
	node->n = val; 
	node->next = NULL;
	while (1) {
		n = root->tail;
		if (__sync_bool_compare_and_swap(&(n->next), NULL, node)) {
			break;
		} else {
			__sync_bool_compare_and_swap(&(root->tail), n, n->next);
		}
	}
	__sync_bool_compare_and_swap(&(root->tail), n, node);

	return 1;
}

void *queue_get(struct queue_root *root)
{
	struct queue_node *n;
	void *val;
	while (1) {
		n = root->head;
		if (n->next == NULL) {
            return NULL;
		}

		if (__sync_bool_compare_and_swap(&(root->head), n, n->next)) {
			break;
		}
	}
	val = (void *) n->next->n;
	free(n);
	return val;
}