bufq.c

一款类linux的操作系统源码

/*
 *  Roadrunner/pk
 *    Copyright (C) 1989-2001  Cornfed Systems, Inc.
 *
 *  The Roadrunner/pk operating system is free software; you can
 *  redistribute and/or modify it under the terms of the GNU General
 *  Public License, version 2, as published by the Free Software
 *  Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public
 *  License along with this program; if not, write to the Free
 *  Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 *  MA 02111-1307 USA
 *
 *  More information about the Roadrunner/pk operating system of
 *  which this file is a part is available on the World-Wide Web
 *  at: http://www.cornfed.com.
 *
 */

#include <stdlib.h>
#include <sys/buf.h>

void
binitq(bufq_t q)
{
    if (q == NULL)
	return;

    q->len = 0;
    q->h = q->t = NULL;
}

int
blenq(bufq_t q)
{
    if (q == NULL)
	return 0;

    return q->len;
}

void
benq(buf_t b, bufq_t q)
{
    if (q == NULL)
	return;

    if (q->t == NULL)
	q->h = q->t = b;
    else {
	q->t->next = b;
	b->prev = q->t;
	q->t = b;
    }
    q->len++;
}

buf_t
bdeq(bufq_t q)
{
    buf_t b;

    if (q == NULL || q->h == NULL)
	return NULL;

    b = q->h;
    q->h = b->next;
    if (q->h == NULL)
	q->t = NULL;
    else
	q->h->prev = NULL;
    b->prev = NULL;
    b->next = NULL;
    q->len--;
    return b;
}

void
bremq(buf_t b, bufq_t q)
{
    buf_t p;

    if (q == NULL)
	return;

    /* Special case for b at the head of q */
    if (q->h == b) {
	bdeq(q);
	return;
    }
    /* b is not at the head of q */
    for (p = q->h; p->next != NULL; p = p->next)
	if (p->next == b) {
	    p->next = b->next;
	    if (p->next == NULL)
		q->t = p;
	    else
		p->next->prev = p;
	    b->prev = b->next = NULL;
	    q->len--;
	    break;
	}
}