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Annotation of OSKit-Mach/kern/queue.c, revision 1.1

1.1     ! root        1: /* 
        !             2:  * Mach Operating System
        !             3:  * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
        !             4:  * All Rights Reserved.
        !             5:  * 
        !             6:  * Permission to use, copy, modify and distribute this software and its
        !             7:  * documentation is hereby granted, provided that both the copyright
        !             8:  * notice and this permission notice appear in all copies of the
        !             9:  * software, derivative works or modified versions, and any portions
        !            10:  * thereof, and that both notices appear in supporting documentation.
        !            11:  * 
        !            12:  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
        !            13:  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
        !            14:  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
        !            15:  * 
        !            16:  * Carnegie Mellon requests users of this software to return to
        !            17:  * 
        !            18:  *  Software Distribution Coordinator  or  [email protected]
        !            19:  *  School of Computer Science
        !            20:  *  Carnegie Mellon University
        !            21:  *  Pittsburgh PA 15213-3890
        !            22:  * 
        !            23:  * any improvements or extensions that they make and grant Carnegie Mellon
        !            24:  * the rights to redistribute these changes.
        !            25:  */
        !            26: /*
        !            27:  *     Routines to implement queue package.
        !            28:  */
        !            29: 
        !            30: #include <kern/queue.h>
        !            31: 
        !            32: 
        !            33: 
        !            34: /*
        !            35:  *     Insert element at head of queue.
        !            36:  */
        !            37: void enqueue_head(
        !            38:        register queue_t        que,
        !            39:        register queue_entry_t  elt)
        !            40: {
        !            41:        elt->next = que->next;
        !            42:        elt->prev = que;
        !            43:        elt->next->prev = elt;
        !            44:        que->next = elt;
        !            45: }
        !            46: 
        !            47: /*
        !            48:  *     Insert element at tail of queue.
        !            49:  */
        !            50: void enqueue_tail(
        !            51:        register queue_t        que,
        !            52:        register queue_entry_t  elt)
        !            53: {
        !            54:        elt->next = que;
        !            55:        elt->prev = que->prev;
        !            56:        elt->prev->next = elt;
        !            57:        que->prev = elt;
        !            58: }
        !            59: 
        !            60: /*
        !            61:  *     Remove and return element at head of queue.
        !            62:  */
        !            63: queue_entry_t dequeue_head(
        !            64:        register queue_t        que)
        !            65: {
        !            66:        register queue_entry_t  elt;
        !            67: 
        !            68:        if (que->next == que)
        !            69:                return((queue_entry_t)0);
        !            70: 
        !            71:        elt = que->next;
        !            72:        elt->next->prev = que;
        !            73:        que->next = elt->next;
        !            74:        return(elt);
        !            75: }
        !            76: 
        !            77: /*
        !            78:  *     Remove and return element at tail of queue.
        !            79:  */
        !            80: queue_entry_t dequeue_tail(
        !            81:        register queue_t        que)
        !            82: {
        !            83:        register queue_entry_t  elt;
        !            84: 
        !            85:        if (que->prev == que)
        !            86:                return((queue_entry_t)0);
        !            87: 
        !            88:        elt = que->prev;
        !            89:        elt->prev->next = que;
        !            90:        que->prev = elt->prev;
        !            91:        return(elt);
        !            92: }
        !            93: 
        !            94: /*
        !            95:  *     Remove arbitrary element from queue.
        !            96:  *     Does not check whether element is on queue - the world
        !            97:  *     will go haywire if it isn't.
        !            98:  */
        !            99: 
        !           100: /*ARGSUSED*/
        !           101: void remqueue(
        !           102:        queue_t                 que,
        !           103:        register queue_entry_t  elt)
        !           104: {
        !           105:        elt->next->prev = elt->prev;
        !           106:        elt->prev->next = elt->next;
        !           107: }
        !           108: 
        !           109: /*
        !           110:  *     Routines to directly imitate the VAX hardware queue
        !           111:  *     package.
        !           112:  */
        !           113: void insque(
        !           114:        register struct queue_entry *entry,
        !           115:        register struct queue_entry *pred)
        !           116: {
        !           117:        entry->next = pred->next;
        !           118:        entry->prev = pred;
        !           119:        (pred->next)->prev = entry;
        !           120:        pred->next = entry;
        !           121: }
        !           122: 
        !           123: struct queue_entry
        !           124: *remque(
        !           125:        register struct queue_entry *elt)
        !           126: {
        !           127:        (elt->next)->prev = elt->prev;
        !           128:        (elt->prev)->next = elt->next;
        !           129:        return(elt);
        !           130: }
        !           131: 

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