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/* Licensed under BSD-MIT - see LICENSE file for details */
#ifndef CCAN_LQUEUE_H
#define CCAN_LQUEUE_H
#include <stdbool.h>
#include <stdio.h>
#include <assert.h>
#include <ccan/container_of/container_of.h>
/**
* struct lqueue_link - a queue link
* @next: next entry, or front of queue, if this is the back
*
* This is used as a link within a queue entry.
*
* Example:
* struct waiter {
* char *name;
* struct lqueue_link ql;
* };
*/
struct lqueue_link {
struct lqueue_link *next;
};
/**
* struct lqueue - the head of a queue
* @b: the back of the queue (NULL if empty)
*/
struct lqueue {
struct lqueue_link *back;
};
/**
* LQUEUE - define and initialize an empty queue
* @name: the name of the lqueue.
*
* The LQUEUE macro defines an lqueue and initializes it to an empty
* queue. It can be prepended by "static" to define a static lqueue.
*
* See also:
* lqueue_init()
*
* Example:
* LQUEUE(my_queue);
*
* assert(lqueue_empty(&my_queue));
*/
#define LQUEUE(name) \
struct lqueue name = { NULL, }
/**
* lqueue_init_from_back - initialize a queue with a specific back element
* @s: the lqueue to initialize
* @e: pointer to the back element of the new queue
* @member: member of the element containing the lqueue_link
*
* USE WITH CAUTION: This is for handling unusual cases where you have
* a pointer to an element in a previously constructed queue but can't
* conveniently pass around a normal struct lqueue. Usually you
* should use lqueue_init().
*
* Example:
* LQUEUE(queue1);
* struct lqueue queue2;
* struct element {
* int value;
* struct lqueue_link link;
* } el;
*
* lqueue_enqueue(&queue1, &el, link);
*
* lqueue_init_from_back(&queue2,
* lqueue_back(&queue1, struct element, link), link);
*/
#define lqueue_init_from_back(s, e, member) \
(lqueue_init_((s), &(e)->member))
/**
* lqueue_init - initialize a queue
* @h: the lqueue to set to an empty queue
*
* Example:
* struct lqueue *qp = malloc(sizeof(*qp));
* lqueue_init(qp);
*/
#define lqueue_init(s) \
(lqueue_init_((s), NULL))
static inline void lqueue_init_(struct lqueue *q, struct lqueue_link *back)
{
q->back = back;
}
/**
* lqueue_empty - is a queue empty?
* @q: the queue
*
* If the queue is empty, returns true.
*
* Example:
* assert(lqueue_empty(qp));
*/
static inline bool lqueue_empty(const struct lqueue *q)
{
return (q->back == NULL);
}
/**
* lqueue_entry - convert an lqueue_link back into the structure containing it.
* @e: the lqueue_link
* @type: the type of the entry
* @member: the lqueue_link member of the type
*
* Example:
* struct waiter {
* char *name;
* struct lqueue_link ql;
* } w;
* assert(lqueue_entry(&w.ql, struct waiter, ql) == &w);
*/
#define lqueue_entry(n, type, member) container_of_or_null(n, type, member)
/**
* lqueue_front - get front entry in a queue
* @q: the queue
* @type: the type of queue entries
* @member: the lqueue_link entry
*
* If the queue is empty, returns NULL.
*
* Example:
* struct waiter *f;
*
* f = lqueue_front(qp, struct waiter, ql);
* assert(lqueue_dequeue(qp, struct waiter, ql) == f);
*/
#define lqueue_front(q, type, member) \
lqueue_entry(lqueue_front_((q)), type, member)
static inline struct lqueue_link *lqueue_front_(const struct lqueue *q)
{
if (!q->back)
return NULL;
else
return q->back->next;
}
/**
* lqueue_back - get back entry in a queue
* @q: the queue
* @type: the type of queue entries
* @member: the lqueue_link entry
*
* If the queue is empty, returns NULL.
*
* Example:
* struct waiter b;
*
* lqueue_enqueue(qp, &b, ql);
* assert(lqueue_back(qp, struct waiter, ql) == &b);
*/
#define lqueue_back(q, type, member) \
lqueue_entry(lqueue_back_((q)), type, member)
static inline struct lqueue_link *lqueue_back_(const struct lqueue *q)
{
return q->back;
}
/**
* lqueue_enqueue - add an entry to the back of a queue
* @q: the queue to add the node to
* @e: the item to enqueue
* @member: the lqueue_link field of *e
*
* The lqueue_link does not need to be initialized; it will be overwritten.
*/
#define lqueue_enqueue(q, e, member) \
lqueue_enqueue_((q), &((e)->member))
static inline void lqueue_enqueue_(struct lqueue *q, struct lqueue_link *e)
{
if (lqueue_empty(q)) {
/* New entry will be both front and back of queue */
e->next = e;
q->back = e;
} else {
e->next = lqueue_front_(q);
q->back->next = e;
q->back = e;
}
}
/**
* lqueue_dequeue - remove and return the entry from the front of the queue
* @q: the queue
* @type: the type of queue entries
* @member: the lqueue_link field of @type
*
* Note that this leaves the returned entry's link in an undefined
* state; it can be added to another queue, but not deleted again.
*/
#define lqueue_dequeue(q, type, member) \
lqueue_entry(lqueue_dequeue_((q)), type, member)
static inline struct lqueue_link *lqueue_dequeue_(struct lqueue *q)
{
struct lqueue_link *front;
if (lqueue_empty(q))
return NULL;
front = lqueue_front_(q);
if (front == lqueue_back_(q)) {
assert(front->next == front);
q->back = NULL;
} else {
q->back->next = front->next;
}
return front;
}
#endif /* CCAN_LQUEUE_H */
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