source: rtems/cpukit/score/src/coremsgseize.c @ b094233

/*
 *  CORE Message Queue Handler
 *
 *  DESCRIPTION:
 *
 *  This package is the implementation of the CORE Message Queue Handler.
 *  This core object provides task synchronization and communication functions
 *  via messages passed to queue objects.
 *
 *  COPYRIGHT (c) 1989-2007.
 *  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.rtems.com/license/LICENSE.
 *
 *  $Id$
 */

#if HAVE_CONFIG_H
#include "config.h"
#endif

#include <rtems/system.h>
#include <rtems/score/chain.h>
#include <rtems/score/isr.h>
#include <rtems/score/object.h>
#include <rtems/score/coremsg.h>
#include <rtems/score/states.h>
#include <rtems/score/thread.h>
#include <rtems/score/wkspace.h>

/*PAGE
 *
 *  _CORE_message_queue_Seize
 *
 *  This kernel routine dequeues a message, copies the message buffer to
 *  a given destination buffer, and frees the message buffer to the
 *  inactive message pool.  The thread will be blocked if wait is true,
 *  otherwise an error will be given to the thread if no messages are available.
 *
 *  Input parameters:
 *    the_message_queue - pointer to message queue
 *    id                - id of object we are waitig on
 *    buffer            - pointer to message buffer to be filled
 *    size_p            - pointer to the size of buffer to be filled
 *    wait              - true if wait is allowed, false otherwise
 *    timeout           - time to wait for a message
 *
 *  Output parameters:  NONE
 *
 *  NOTE: Dependent on BUFFER_LENGTH
 *
 *  INTERRUPT LATENCY:
 *    available
 *    wait
 */

void _CORE_message_queue_Seize(
  CORE_message_queue_Control      *the_message_queue,
  Objects_Id                       id,
  void                            *buffer,
  size_t                          *size_p,
  bool                             wait,
  Watchdog_Interval                timeout
)
{
  ISR_Level                          level;
  CORE_message_queue_Buffer_control *the_message;
  Thread_Control                    *executing;
  Thread_Control                    *the_thread;

  executing = _Thread_Executing;
  executing->Wait.return_code = CORE_MESSAGE_QUEUE_STATUS_SUCCESSFUL;
  _ISR_Disable( level );
  the_message = _CORE_message_queue_Get_pending_message( the_message_queue );
  if ( the_message != NULL ) {
    the_message_queue->number_of_pending_messages -= 1;
    _ISR_Enable( level );

    *size_p = the_message->Contents.size;
    _Thread_Executing->Wait.count = the_message->priority;
    _CORE_message_queue_Copy_buffer(the_message->Contents.buffer,buffer,*size_p);

    /*
     *  There could be a thread waiting to send a message.  If there
     *  is not, then we can go ahead and free the buffer.
     *
     *  NOTE: If we note that the queue was not full before this receive,
     *  then we can avoid this dequeue.
     */

    the_thread = _Thread_queue_Dequeue( &the_message_queue->Wait_queue );
    if ( !the_thread ) {
      _CORE_message_queue_Free_message_buffer( the_message_queue, the_message );
      return;
    }

    /*
     *  There was a thread waiting to send a message.  This code
     *  puts the messages in the message queue on behalf of the
     *  waiting task.
     */

    the_message->priority  = the_thread->Wait.count;
    the_message->Contents.size = (size_t) the_thread->Wait.option;
    _CORE_message_queue_Copy_buffer(
      the_thread->Wait.return_argument_second.immutable_object,
      the_message->Contents.buffer,
      the_message->Contents.size
    );

    _CORE_message_queue_Insert_message(
       the_message_queue,
       the_message,
       the_message->priority
    );
    return;
  }

  if ( !wait ) {
    _ISR_Enable( level );
    executing->Wait.return_code = CORE_MESSAGE_QUEUE_STATUS_UNSATISFIED_NOWAIT;
    return;
  }

  _Thread_queue_Enter_critical_section( &the_message_queue->Wait_queue );
  executing->Wait.queue = &the_message_queue->Wait_queue;
  executing->Wait.id = id;
  executing->Wait.return_argument_second.mutable_object = buffer;
  executing->Wait.return_argument = size_p;
  /* Wait.count will be filled in with the message priority */
  _ISR_Enable( level );

  _Thread_queue_Enqueue( &the_message_queue->Wait_queue, timeout );
}