/* * Mach Operating System * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University * All Rights Reserved. * * Permission to use, copy, modify and distribute this software and its * documentation is hereby granted, provided that both the copyright * notice and this permission notice appear in all copies of the * software, derivative works or modified versions, and any portions * thereof, and that both notices appear in supporting documentation. * * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. * * Carnegie Mellon requests users of this software to return to * * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU * School of Computer Science * Carnegie Mellon University * Pittsburgh PA 15213-3890 * * any improvements or extensions that they make and grant Carnegie Mellon * the rights to redistribute these changes. */ /* * $Id: queue.c,v 1.1 2001/12/13 02:09:38 jrydberg Exp $ */ /* Routines to implement queue package. */ #include "queue.h" /* Insert element at head of queue. */ void enqueue_head( register queue_t que, register queue_entry_t elt) { elt->next = que->next; elt->prev = que; elt->next->prev = elt; que->next = elt; } /* Insert element at tail of queue. */ void enqueue_tail( register queue_t que, register queue_entry_t elt) { elt->next = que; elt->prev = que->prev; elt->prev->next = elt; que->prev = elt; } /* Remove and return element at head of queue. */ queue_entry_t dequeue_head( register queue_t que) { register queue_entry_t elt; if (que->next == que) return((queue_entry_t)0); elt = que->next; elt->next->prev = que; que->next = elt->next; return (elt); } /* Remove and return element at tail of queue. */ queue_entry_t dequeue_tail( register queue_t que) { register queue_entry_t elt; if (que->prev == que) return ((queue_entry_t)0); elt = que->prev; elt->prev->next = que; que->prev = elt->prev; return (elt); } /* Remove arbitrary element from queue. Does not check whether element is on queue - the world will go haywire if it isn't. */ /*ARGSUSED*/ void remqueue( queue_t que, register queue_entry_t elt) { elt->next->prev = elt->prev; elt->prev->next = elt->next; } void insque( register struct queue_entry *entry, register struct queue_entry *pred) { entry->next = pred->next; entry->prev = pred; (pred->next)->prev = entry; pred->next = entry; } int remque( register struct queue_entry *elt) { (elt->next)->prev = elt->prev; (elt->prev)->next = elt->next; return ((int)elt); }