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/*  Shm_Envelope_control *Shm_Locked_queue_Get( lq_cb )

 *

 *  This routine returns an envelope control block from a shared

 *  memory queue.

 *

 *  Input parameters:

 *    lq_cb - pointer to a locked queue control block

 *

 *  Output parameters:

 *    returns - pointer to an envelope control block

 *            - NULL if no envelopes on specified queue

 *

 *  COPYRIGHT (c) 1989-1999.

 *  On-Line Applications Research Corporation (OAR).

 *

 *  The license and distribution terms for this file may be

 *  found in the file LICENSE in this distribution or at

 *  http://www.OARcorp.com/rtems/license.html.

 *

 *  getlq.c,v 1.10 1999/11/30 19:57:58 joel Exp

 */

#include <rtems.h>

#include <shm_driver.h>

Shm_Envelope_control *Shm_Locked_queue_Get(

  Shm_Locked_queue_Control *lq_cb

)

{

  Shm_Envelope_control *tmp_ecb;

  rtems_unsigned32 tmpfront;

  tmp_ecb = NULL;

  Shm_Lock( lq_cb );

    tmpfront = Shm_Convert(lq_cb->front);

    if ( tmpfront != Shm_Locked_queue_End_of_list ) {

      tmp_ecb = &Shm_Envelopes[ tmpfront ];

      lq_cb->front = tmp_ecb->next;

      if ( tmp_ecb->next == Shm_Locked_queue_End_of_list )

        lq_cb->rear = Shm_Locked_queue_End_of_list;

      tmp_ecb->next = Shm_Locked_queue_Not_on_list;

    }

  Shm_Unlock( lq_cb );

  return( tmp_ecb );

}