1 files changed, 106 insertions, 0 deletions
diff --git a/cpukit/score/src/coremsgflushsupp.c b/cpukit/score/src/coremsgflushsupp.c
new file mode 100644
index 0000000000..4e15e1a495
--- /dev/null
+++ b/cpukit/score/src/coremsgflushsupp.c
@@ -0,0 +1,106 @@
+/*
+ *  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) 1989-1999.
+ *  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.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_Flush_support
+ *
+ *  This message handler routine removes all messages from a message queue
+ *  and returns them to the inactive message pool.  The number of messages
+ *  flushed from the queue is returned
+ *
+ *  Input parameters:
+ *    the_message_queue - pointer to message queue
+ *
+ *  Output parameters:
+ *    returns - number of messages placed on inactive chain
+ *
+ *  INTERRUPT LATENCY:
+ *    only case
+ */
+
+uint32_t   _CORE_message_queue_Flush_support(
+  CORE_message_queue_Control *the_message_queue
+)
+{
+  ISR_Level   level;
+  Chain_Node *inactive_head;
+  Chain_Node *inactive_first;
+  Chain_Node *message_queue_first;
+  Chain_Node *message_queue_last;
+  uint32_t    count;
+
+  /*
+   *  Currently, RTEMS supports no API that has both flush and blocking
+   *  sends.  Thus, this routine assumes that there are no senders
+   *  blocked waiting to send messages.  In the event, that an API is
+   *  added that can flush a message queue when threads are blocked
+   *  waiting to send, there are two basic behaviors envisioned:
+   *
+   *  (1) The thread queue of pending senders is a logical extension
+   *  of the pending message queue.  In this case, it should be
+   *  flushed using the _Thread_queue_Flush() service with a status
+   *  such as CORE_MESSAGE_QUEUE_SENDER_FLUSHED (which currently does
+   *  not exist).  This can be implemented without changing the "big-O"
+   *  of the message flushing part of the routine.
+   *
+   *  (2) Only the actual messages queued should be purged.  In this case,
+   *  the blocked sender threads must be allowed to send their messages.
+   *  In this case, the implementation will be forced to individually
+   *  dequeue the senders and queue their messages.  This will force
+   *  this routine to have "big O(n)" where n is the number of blocked
+   *  senders.  If there are more messages pending than senders blocked,
+   *  then the existing flush code can be used to dispose of the remaining
+   *  pending messages.
+   *
+   *  For now, though, we are very happy to have a small routine with
+   *  fixed execution time that only deals with pending messages.
+   */
+
+  _ISR_Disable( level );
+    inactive_head = _Chain_Head( &the_message_queue->Inactive_messages );
+    inactive_first = inactive_head->next;;
+    message_queue_first = _Chain_First( &the_message_queue->Pending_messages );
+    message_queue_last = _Chain_Last( &the_message_queue->Pending_messages );
+
+    inactive_head->next = message_queue_first;
+    message_queue_last->next = inactive_first;
+    inactive_first->previous = message_queue_last;
+    message_queue_first->previous = inactive_head;
+
+    _Chain_Initialize_empty( &the_message_queue->Pending_messages );
+
+    count = the_message_queue->number_of_pending_messages;
+    the_message_queue->number_of_pending_messages = 0;
+  _ISR_Enable( level );
+  return count;
+}