shared/shmdr/shmdr-getlq.c

0001 /* SPDX-License-Identifier: BSD-2-Clause */
0002
0003 /*  Shm_Envelope_control *Shm_Locked_queue_Get( lq_cb )
0004  *
0005  *  This routine returns an envelope control block from a shared
0006  *  memory queue.
0007  *
0008  *  Input parameters:
0009  *    lq_cb - pointer to a locked queue control block
0010  *
0011  *  Output parameters:
0012  *    returns - pointer to an envelope control block
0013  *            - NULL if no envelopes on specified queue
0014  *
0015  *  COPYRIGHT (c) 1989-1999.
0016  *  On-Line Applications Research Corporation (OAR).
0017  *
0018  * Redistribution and use in source and binary forms, with or without
0019  * modification, are permitted provided that the following conditions
0020  * are met:
0021  * 1. Redistributions of source code must retain the above copyright
0022  *    notice, this list of conditions and the following disclaimer.
0023  * 2. Redistributions in binary form must reproduce the above copyright
0024  *    notice, this list of conditions and the following disclaimer in the
0025  *    documentation and/or other materials provided with the distribution.
0026  *
0027  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
0028  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
0029  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
0030  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
0031  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
0032  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
0033  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
0034  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
0035  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
0036  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
0037  * POSSIBILITY OF SUCH DAMAGE.
0038  */
0039
0040 #include <rtems.h>
0041 #include <shm_driver.h>
0042
0043 Shm_Envelope_control *Shm_Locked_queue_Get(
0044   Shm_Locked_queue_Control *lq_cb
0045 )
0046 {
0047   Shm_Envelope_control *tmp_ecb;
0048   uint32_t   tmpfront;
0049
0050   tmp_ecb = NULL;
0051   Shm_Lock( lq_cb );
0052
0053     tmpfront = Shm_Convert(lq_cb->front);
0054     if ( tmpfront != Shm_Locked_queue_End_of_list ) {
0055       tmp_ecb = &Shm_Envelopes[ tmpfront ];
0056       lq_cb->front = tmp_ecb->next;
0057       if ( tmp_ecb->next == Shm_Locked_queue_End_of_list )
0058         lq_cb->rear = Shm_Locked_queue_End_of_list;
0059       tmp_ecb->next = Shm_Locked_queue_Not_on_list;
0060     }
0061
0062   Shm_Unlock( lq_cb );
0063   return( tmp_ecb );
0064 }