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// $Id: bounded_buffer.cpp 91671 2010-09-08 18:39:23Z johnnyw $
// This short program copies stdin to stdout via the use of an ASX
// Message_Queue. It illustrates an implementation of the classic
// "bounded buffer" program.
#include "ace/Message_Queue.h"
#include "ace/Thread_Manager.h"
#include "ace/Truncate.h"
#include "ace/OS_NS_time.h"
#include "ace/OS_NS_unistd.h"
#if defined (ACE_HAS_THREADS)
// The producer reads data from the stdin stream, creates a message,
// and then queues the message in the message list, where it is
// removed by the consumer thread. A 0-sized message is enqueued when
// there is no more data to read. The consumer uses this as a flag to
// know when to exit.
static void *
producer (ACE_Message_Queue<ACE_MT_SYNCH> *msg_queue)
{
// Keep reading stdin, until we reach EOF.
for (int n; ; )
{
// Allocate a new message.
ACE_Message_Block *mb = 0;
ACE_NEW_RETURN (mb, ACE_Message_Block (BUFSIZ), 0);
n = ACE_OS::read (ACE_STDIN, mb->wr_ptr (), mb->size ());
if (n <= 0)
{
// Send a shutdown message to the other thread and exit.
mb->length (0);
if (msg_queue->enqueue_tail (mb) == -1)
ACE_ERROR ((LM_ERROR,
"(%t) %p\n",
"put_next"));
break;
}
// Send the message to the other thread.
else
{
mb->msg_priority (n);
mb->wr_ptr (n);
if (msg_queue->enqueue_tail (mb) == -1)
ACE_ERROR ((LM_ERROR,
"(%t) %p\n",
"put_next"));
}
}
return 0;
}
// The consumer dequeues a message from the ACE_Message_Queue, writes
// the message to the stderr stream, and deletes the message. The
// producer sends a 0-sized message to inform the consumer to stop
// reading and exit.
static void *consumer (ACE_Message_Queue<ACE_MT_SYNCH> *msg_queue)
{
int result = 0;
// Keep looping, reading a message out of the queue, until we timeout
// or get a message with a length == 0, which signals us to quit.
for (;;)
{
ACE_Message_Block *mb = 0;
ACE_Time_Value timeout (ACE_OS::time (0) + 4, 0); // Wait for upto 4 seconds
result = msg_queue->dequeue_head (mb, &timeout);
if (result == -1)
break;
int length = ACE_Utils::truncate_cast<int> (mb->length ());
if (length > 0)
ACE_OS::write (ACE_STDOUT, mb->rd_ptr (), length);
mb->release ();
if (length == 0)
break;
}
if (result == -1 && errno == EWOULDBLOCK)
ACE_ERROR ((LM_ERROR,
"(%t) %p\n%a",
"timed out waiting for message",
1));
return 0;
}
// Spawn off two threads that copy stdin to stdout.
int
ACE_TMAIN (int, ACE_TCHAR *[])
{
// Message list.
ACE_Message_Queue<ACE_MT_SYNCH> msg_queue;
if (ACE_Thread_Manager::instance ()->spawn
(ACE_THR_FUNC (producer),
(void *) &msg_queue,
THR_NEW_LWP | THR_DETACHED) == -1)
ACE_ERROR_RETURN ((LM_ERROR,
"%p\n",
"spawn"),
1);
else if (ACE_Thread_Manager::instance ()->spawn
(ACE_THR_FUNC (consumer),
(void *) &msg_queue,
THR_NEW_LWP | THR_DETACHED) == -1)
ACE_ERROR_RETURN ((LM_ERROR,
"%p\n",
"spawn"),
1);
// Wait for producer and consumer threads to exit.
ACE_Thread_Manager::instance ()->wait ();
return 0;
}
#else
int
ACE_TMAIN (int, ACE_TCHAR *[])
{
ACE_ERROR ((LM_ERROR, "threads not supported on this platform\n"));
return 0;
}
#endif /* ACE_HAS_THREADS */
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