Finally, a new and improved IO Channel and condition watch implementation

2000-07-30  Tor Lillqvist  <tml@iki.fi>

	Finally, a new and improved IO Channel and condition watch
	implementation for Win32. Based on code provided by Craig Setera.

	When watching file descriptors, for which there is no select()
	like functionality on Win32 that would work on all Win32 platforms
	for all types of file descriptors (including anonymous pipes), we
	start a new thread that blocks while trying to read from the file
	descriptor. When the read returns, a Win32 Event is signalled that
	the polling routine eventually notices. Meanwhile, the data being
	read is stored in a circular buffer, from where the IO channel's
	read() method picks it up.

	If the buffer fills up the reading thread has to wait for space
	becoming available. For this another Win32 Event is used. The IO
	Channel's read() method signals this when it has read some data
	out of the buffer.

	The separate reader thread(s), and the circular buffer(s) with
	associated events mean lots of possibilities for fun parallellism
	errors. But it seems to work OK, i.e. GIMP runs.

	* gmain.c: Small changes to the Win32 polling function.
	(g_main_win32_get_poll_func): New function. Perhaps it would be a
	good idea to provide this on all platforms.

	* giowin32.c: The bulk of the new implementation.
	(g_io_channel_win32_wait_for_condition): New function. To be used
	where on Unix one does a select() on the channel's fd, like
	libgimp's gimp_extension_process(). Could be provided on all
	platforms.

	* glib.h: Update documentation for IO Channels on Win32. Remove
	the declarations for the as of now obsolete old functions related
	to IO Channels for pipes with "wakeup" messages.

	* glib.def: Some new functions.

	* tests/gio-test.c: New file, to test GIOChannel and main loop.

	* tests/Makefile.am
	* tests/makefile.mingw.in: Add it.

1 files changed, 72 insertions, 32 deletions

diff --git a/gmain.c b/gmain.c
index 23a0c30d2..a3404a6e9 100644
--- a/gmain.c
+++ b/gmain.c
@@ -36,8 +36,6 @@
 /* uncomment the next line to get poll() debugging info */
 /* #define G_MAIN_POLL_DEBUG */
 
-
-
 #include "glib.h"
 #include <sys/types.h>
 #include <time.h>
@@ -192,34 +190,39 @@ static GPollFunc poll_func = (GPollFunc) poll;
 #ifdef G_OS_WIN32
 
 static gint
-g_poll (GPollFD *fds, guint nfds, gint timeout)
+g_poll (GPollFD *fds,
+	guint    nfds,
+	gint     timeout)
 {
   HANDLE handles[MAXIMUM_WAIT_OBJECTS];
+  gboolean poll_msgs = FALSE;
   GPollFD *f;
   DWORD ready;
   MSG msg;
   UINT timer;
-  LONG prevcnt;
-  gint poll_msgs = -1;
   gint nhandles = 0;
 
   for (f = fds; f < &fds[nfds]; ++f)
     if (f->fd >= 0)
       {
 	if (f->events & G_IO_IN)
-	  if (f->fd == G_WIN32_MSG_HANDLE)
-	    poll_msgs = f - fds;
-	  else
-	    {
-	      /* g_print ("g_poll: waiting for handle %#x\n", f->fd); */
-	      handles[nhandles++] = (HANDLE) f->fd;
-	    }
+	  {
+	    if (f->fd == G_WIN32_MSG_HANDLE)
+	      poll_msgs = TRUE;
+	    else
+	      {
+#ifdef G_MAIN_POLL_DEBUG
+		g_print ("g_poll: waiting for %#x\n", f->fd);
+#endif
+		handles[nhandles++] = (HANDLE) f->fd;
+	      }
+	  }
       }
 
   if (timeout == -1)
     timeout = INFINITE;
 
-  if (poll_msgs >= 0)
+  if (poll_msgs)
     {
       /* Waiting for messages, and maybe events */
       if (nhandles == 0)
@@ -229,7 +232,9 @@ g_poll (GPollFD *fds, guint nfds, gint timeout)
 	      /* Waiting just for messages, infinite timeout
 	       * -> Use PeekMessage, then WaitMessage
 	       */
-	      /* g_print ("WaitMessage, PeekMessage\n"); */
+#ifdef G_MAIN_POLL_DEBUG
+	      g_print ("PeekMessage, then WaitMessage\n");
+#endif
 	      if (PeekMessage (&msg, NULL, 0, 0, PM_NOREMOVE))
 		ready = WAIT_OBJECT_0;
 	      else if (!WaitMessage ())
@@ -241,7 +246,9 @@ g_poll (GPollFD *fds, guint nfds, gint timeout)
 	      /* Waiting just for messages, zero timeout
 	       * -> Use PeekMessage
 	       */
-	      /* g_print ("PeekMessage\n"); */
+#ifdef G_MAIN_POLL_DEBUG
+	      g_print ("PeekMessage\n");
+#endif
 	      if (PeekMessage (&msg, NULL, 0, 0, PM_NOREMOVE))
 		ready = WAIT_OBJECT_0;
 	      else
@@ -253,17 +260,22 @@ g_poll (GPollFD *fds, guint nfds, gint timeout)
 	       * -> First try PeekMessage, then set a timer, wait for message,
 	       * kill timer, use PeekMessage
 	       */
-	      /* g_print ("PeekMessage\n"); */
+#ifdef G_MAIN_POLL_DEBUG
+	      g_print ("PeekMessage\n");
+#endif
 	      if (PeekMessage (&msg, NULL, 0, 0, PM_NOREMOVE))
 		ready = WAIT_OBJECT_0;
 	      else if ((timer = SetTimer (NULL, 0, timeout, NULL)) == 0)
 		g_warning ("g_poll: SetTimer failed");
 	      else
 		{
-		  /* g_print ("WaitMessage\n"); */
+#ifdef G_MAIN_POLL_DEBUG
+		  g_print ("WaitMessage\n");
+#endif
 		  WaitMessage ();
 		  KillTimer (NULL, timer);
-		  if (PeekMessage (&msg, NULL, 0, 0, PM_NOREMOVE))
+		  if (PeekMessage (&msg, NULL, 0, 0, PM_NOREMOVE)
+		      && msg.message != WM_TIMER)
 		    ready = WAIT_OBJECT_0;
 		  else
 		    ready = WAIT_TIMEOUT;
@@ -275,10 +287,12 @@ g_poll (GPollFD *fds, guint nfds, gint timeout)
 	  /* Wait for either message or event
 	   * -> Use MsgWaitForMultipleObjects
 	   */
-	  /* g_print ("MsgWaitForMultipleObjects(%d, %d)\n", nhandles, timeout); */
+#ifdef G_MAIN_POLL_DEBUG
+	  g_print ("MsgWaitForMultipleObjects(%d, %d)\n", nhandles, timeout);
+#endif
 	  ready = MsgWaitForMultipleObjects (nhandles, handles, FALSE,
 					     timeout, QS_ALLINPUT);
-	  /* g_print("=%d\n", ready); */
+
 	  if (ready == WAIT_FAILED)
 	    g_warning ("g_poll: MsgWaitForMultipleObjects failed");
 	}
@@ -293,9 +307,10 @@ g_poll (GPollFD *fds, guint nfds, gint timeout)
       /* Wait for just events
        * -> Use WaitForMultipleObjects
        */
-      /* g_print ("WaitForMultipleObjects(%d, %d)\n", nhandles, timeout); */
+#ifdef G_MAIN_POLL_DEBUG
+      g_print ("WaitForMultipleObjects(%d, %d)\n", nhandles, timeout);
+#endif
       ready = WaitForMultipleObjects (nhandles, handles, FALSE, timeout);
-      /* g_print("=%d\n", ready); */
       if (ready == WAIT_FAILED)
 	g_warning ("g_poll: WaitForMultipleObjects failed");
     }
@@ -305,9 +320,17 @@ g_poll (GPollFD *fds, guint nfds, gint timeout)
 
   if (ready == WAIT_FAILED)
     return -1;
-  else if (poll_msgs >= 0 && ready == WAIT_OBJECT_0 + nhandles)
+  else if (ready == WAIT_TIMEOUT)
+    return 0;
+  else if (poll_msgs && ready == WAIT_OBJECT_0 + nhandles)
     {
-      fds[poll_msgs].revents |= G_IO_IN;
+      for (f = fds; f < &fds[nfds]; ++f)
+	if (f->fd >= 0)
+	  {
+	    if (f->events & G_IO_IN)
+	      if (f->fd == G_WIN32_MSG_HANDLE)
+		f->revents |= G_IO_IN;
+	  }
     }
   else if (ready >= WAIT_OBJECT_0 && ready < WAIT_OBJECT_0 + nhandles)
     for (f = fds; f < &fds[nfds]; ++f)
@@ -316,15 +339,19 @@ g_poll (GPollFD *fds, guint nfds, gint timeout)
 	    && f->fd == (gint) handles[ready - WAIT_OBJECT_0])
 	  {
 	    f->revents |= G_IO_IN;
-	    /* g_print ("event %#x\n", f->fd); */
+#ifdef G_MAIN_POLL_DEBUG
+	    g_print ("g_poll: got event %#x\n", f->fd);
+#endif
+#if 0
 	    ResetEvent ((HANDLE) f->fd);
+#endif
 	  }
       }
     
-  if (ready == WAIT_TIMEOUT)
-    return 0;
+  if (ready >= WAIT_OBJECT_0 && ready < WAIT_OBJECT_0 + nhandles)
+    return ready - WAIT_OBJECT_0 + 1;
   else
-    return 1;
+    return 0;
 }
 
 #else  /* !G_OS_WIN32 */
@@ -592,7 +619,6 @@ void
 g_get_current_time (GTimeVal *result)
 {
 #ifndef G_OS_WIN32
-  struct timeval r;
   g_return_if_fail (result != NULL);
 
   /*this is required on alpha, there the timeval structs are int's
@@ -608,7 +634,6 @@ g_get_current_time (GTimeVal *result)
   static DWORD start_tick = 0;
   static time_t start_time;
   DWORD tick;
-  time_t t;
 
   g_return_if_fail (result != NULL);
  
@@ -992,9 +1017,12 @@ g_main_poll (gint     timeout,
   if (wake_up_semaphore == NULL)
     {
       if ((wake_up_semaphore = CreateSemaphore (NULL, 0, 100, NULL)) == NULL)
-	g_error ("Cannot create wake-up semaphore: %d", GetLastError ());
+	g_error ("Cannot create wake-up semaphore: %s", g_win32_error_message (GetLastError ()));
       wake_up_rec.fd = (gint) wake_up_semaphore;
       wake_up_rec.events = G_IO_IN;
+#ifdef G_MAIN_POLL_DEBUG
+      g_print ("wake-up semaphore: %#x\n", (guint) wake_up_semaphore);
+#endif
       g_main_add_poll_unlocked (0, &wake_up_rec);
     }
 #endif
@@ -1029,7 +1057,7 @@ g_main_poll (gint     timeout,
   if (npoll || timeout != 0)
     {
 #ifdef	G_MAIN_POLL_DEBUG
-      g_print ("g_main_poll(%d) timeout: %d\r", npoll, timeout);
+      g_print ("g_main_poll(%d) timeout: %d\n", npoll, timeout);
       poll_timer = g_timer_new ();
 #endif
       
@@ -1223,6 +1251,18 @@ g_main_set_poll_func (GPollFunc func)
 #endif
 }
 
+#ifdef G_OS_WIN32
+
+/* Useful on other platforms, too? */
+
+GPollFunc
+g_main_win32_get_poll_func (void)
+{
+  return poll_func;
+}
+
+#endif
+
 /* Wake the main loop up from a poll() */
 static void
 g_main_wakeup (void)