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// $Id: priority_buffer.cpp 91671 2010-09-08 18:39:23Z johnnyw $
// This short program prints the contents of stdin to stdout sorted by
// the length of each line via the use of an ASX Message_Queue. It
// illustrates how priorities can be used for ACE Message_Queues.
#include "ace/OS_NS_stdio.h"
#include "ace/Malloc_Base.h" // To get ACE_Allocator
#include "ace/Message_Queue.h"
#include "ace/Read_Buffer.h"
#include "ace/Thread_Manager.h"
#include "ace/Service_Config.h"
#include "ace/Truncate.h"
#if defined (ACE_HAS_THREADS)
// Global thread manager.
static ACE_Thread_Manager thr_mgr;
// Make the queue be capable of being *very* large.
static const long max_queue = LONG_MAX;
// 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)
{
// 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;
if (msg_queue->dequeue_head (mb) == -1)
break;
int length = ACE_Utils::truncate_cast<int> (mb->length ());
if (length > 0)
ACE_OS::puts (mb->rd_ptr ());
// Free up the buffer memory and the Message_Block.
ACE_Allocator::instance ()->free (mb->rd_ptr ());
mb->release ();
if (length == 0)
break;
}
return 0;
}
// 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)
{
ACE_Read_Buffer rb (ACE_STDIN);
// Keep reading stdin, until we reach EOF.
for (;;)
{
// Allocate a new buffer.
char *buffer = rb.read ('\n');
ACE_Message_Block *mb = 0;
if (buffer == 0)
{
// Send a 0-sized shutdown message to the other thread and
// exit.
ACE_NEW_RETURN (mb, ACE_Message_Block ((size_t) 0), 0);
if (msg_queue->enqueue_tail (mb) == -1)
ACE_ERROR ((LM_ERROR, "(%t) %p\n", "put_next"));
break;
}
// Enqueue the message in priority order.
else
{
// Allocate a new message, but have it "borrow" its memory
// from the buffer.
ACE_NEW_RETURN (mb,
ACE_Message_Block (rb.size (),
ACE_Message_Block::MB_DATA,
0,
buffer),
0);
mb->msg_priority (ACE_Utils::truncate_cast<unsigned long> (rb.size ()));
mb->wr_ptr (rb.size ());
ACE_DEBUG ((LM_DEBUG,
"enqueueing message of size %d\n",
mb->msg_priority ()));
// Enqueue in priority order.
if (msg_queue->enqueue_prio (mb) == -1)
ACE_ERROR ((LM_ERROR, "(%t) %p\n", "put_next"));
}
}
// Now read all the items out in priority order (i.e., ordered by
// the size of the lines!).
consumer (msg_queue);
return 0;
}
// Spawn off one thread that copies stdin to stdout in order of the
// size of each line.
int
ACE_TMAIN (int, ACE_TCHAR *[])
{
// Message queue.
ACE_Message_Queue<ACE_MT_SYNCH> msg_queue (max_queue);
if (thr_mgr.spawn (ACE_THR_FUNC (producer), (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.
thr_mgr.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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