Add pollable input/output streams

When interfacing with APIs that expect unix-style async I/O, it is
useful to be able to tell in advance whether a read/write is going to
block. This adds new interfaces GPollableInputStream and
GPollableOutputStream that can be implemented by a GInputStream or
GOutputStream to add _is_readable/_is_writable, _create_source, and
_read_nonblocking/_write_nonblocking methods.

Also, implement for GUnixInput/OutputStream and
GSocketInput/OutputStream

https://bugzilla.gnome.org/show_bug.cgi?id=634241

gio/tests/.gitignore

@@ -60,6 +60,7 @@ memory-input-stream
 memory-output-stream
 network-address
 org.gtk.test.enums.xml
+pollable
 proxy
 readwrite
 resolver

gio/tests/Makefile.am

@@ -43,6 +43,7 @@ TEST_PROGS +=	 		\
 	network-address		\
 	gdbus-message		\
 	socket			\
+	pollable		\
 	$(NULL)
 
 if OS_UNIX
@@ -204,6 +205,9 @@ network_address_LDADD	  = $(progs_ldadd)
 socket_SOURCE		  = socket.c
 socket_LDADD		  = $(progs_ldadd)
 
+pollable_SOURCE		  = pollable.c
+pollable_LDADD		  = $(progs_ldadd)
+
 contexts_SOURCES	  = contexts.c
 contexts_LDADD		  = $(progs_ldadd) \
 	$(top_builddir)/gthread/libgthread-2.0.la

gio/tests/pollable.c

@@ -0,0 +1,240 @@
+/* GLib testing framework examples and tests
+ *
+ * Copyright (C) 2010 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include <gio/gio.h>
+
+#ifdef G_OS_UNIX
+#include <gio/gunixinputstream.h>
+#include <gio/gunixoutputstream.h>
+#endif
+
+GMainLoop *loop;
+GPollableInputStream *in;
+GOutputStream *out;
+
+static gboolean
+poll_source_callback (GPollableInputStream *in,
+		      gpointer              user_data)
+{
+  GError *error = NULL;
+  char buf[2];
+  gssize nread;
+  gboolean *success = user_data;
+
+  nread = g_pollable_input_stream_read_nonblocking (in, buf, 2, NULL, &error);
+  g_assert_no_error (error);
+  g_assert_cmpint (nread, ==, 2);
+  g_assert_cmpstr (buf, ==, "x");
+
+  *success = TRUE;
+  return FALSE;
+}
+
+static gboolean
+check_source_readability_callback (gpointer user_data)
+{
+  gboolean expected = GPOINTER_TO_INT (user_data);
+  gboolean readable;
+
+  readable = g_pollable_input_stream_is_readable (in);
+  g_assert_cmpint (readable, ==, expected);
+  return FALSE;
+}
+
+static gboolean
+write_callback (gpointer user_data)
+{
+  char *buf = "x";
+  gssize nwrote;
+  GError *error = NULL;
+
+  nwrote = g_output_stream_write (out, buf, 2, NULL, &error);
+  g_assert_no_error (error);
+  g_assert_cmpint (nwrote, ==, 2);
+
+  check_source_readability_callback (GINT_TO_POINTER (TRUE));
+
+  return FALSE;
+}
+
+static gboolean
+check_source_and_quit_callback (gpointer user_data)
+{
+  check_source_readability_callback (user_data);
+  g_main_loop_quit (loop);
+  return FALSE;
+}
+
+static void
+test_streams (void)
+{
+  gboolean readable;
+  GError *error = NULL;
+  char buf[1];
+  gssize nread;
+  GSource *poll_source;
+  gboolean success = FALSE;
+
+  readable = g_pollable_input_stream_is_readable (in);
+  g_assert (!readable);
+
+  nread = g_pollable_input_stream_read_nonblocking (in, buf, 1, NULL, &error);
+  g_assert_cmpint (nread, ==, -1);
+  g_assert_error (error, G_IO_ERROR, G_IO_ERROR_WOULD_BLOCK);
+  g_clear_error (&error);
+
+  /* Create 4 sources, in decreasing order of priority:
+   *   1. poll source on @in
+   *   2. idle source that checks if @in is readable once
+   *      (it won't be) and then removes itself
+   *   3. idle source that writes a byte to @out, checks that
+   *      @in is now readable, and removes itself
+   *   4. idle source that checks if @in is readable once
+   *      (it won't be, since the poll source will fire before
+   *      this one does) and then quits the loop.
+   *
+   * If the poll source triggers before it should, then it will get a
+   * %G_IO_ERROR_WOULD_BLOCK, and if check() fails in either
+   * direction, we will catch it at some point.
+   */
+
+  poll_source = g_pollable_input_stream_create_source (in, NULL);
+  g_source_set_priority (poll_source, 1);
+  g_source_set_callback (poll_source, (GSourceFunc) poll_source_callback, &success, NULL);
+  g_source_attach (poll_source, NULL);
+  g_source_unref (poll_source);
+
+  g_idle_add_full (2, check_source_readability_callback, GINT_TO_POINTER (FALSE), NULL);
+  g_idle_add_full (3, write_callback, NULL, NULL);
+  g_idle_add_full (4, check_source_and_quit_callback, GINT_TO_POINTER (FALSE), NULL);
+
+  loop = g_main_loop_new (NULL, FALSE);
+  g_main_loop_run (loop);
+  g_main_loop_unref (loop);
+
+  g_assert_cmpint (success, ==, TRUE);
+}
+
+#ifdef G_OS_UNIX
+static void
+test_pollable_unix (void)
+{
+  int pipefds[2], status;
+
+  status = pipe (pipefds);
+  g_assert_cmpint (status, ==, 0);
+
+  in = G_POLLABLE_INPUT_STREAM (g_unix_input_stream_new (pipefds[0], TRUE));
+  out = g_unix_output_stream_new (pipefds[1], TRUE);
+
+  test_streams ();
+
+  g_object_unref (in);
+  g_object_unref (out);
+}
+#endif
+
+static void
+client_connected (GObject      *source,
+		  GAsyncResult *result,
+		  gpointer      user_data)
+{
+  GSocketClient *client = G_SOCKET_CLIENT (source);
+  GSocketConnection **conn = user_data;
+  GError *error = NULL;
+
+  *conn = g_socket_client_connect_finish (client, result, &error);
+  g_assert_no_error (error);
+}
+
+static void
+server_connected (GObject      *source,
+		  GAsyncResult *result,
+		  gpointer      user_data)
+{
+  GSocketListener *listener = G_SOCKET_LISTENER (source);
+  GSocketConnection **conn = user_data;
+  GError *error = NULL;
+
+  *conn = g_socket_listener_accept_finish (listener, result, NULL, &error);
+  g_assert_no_error (error);
+}
+
+static void
+test_pollable_socket (void)
+{
+  GInetAddress *iaddr;
+  GSocketAddress *saddr, *effective_address;
+  GSocketListener *listener;
+  GSocketClient *client;
+  GError *error = NULL;
+  GSocketConnection *client_conn = NULL, *server_conn = NULL;
+
+  iaddr = g_inet_address_new_loopback (G_SOCKET_FAMILY_IPV4);
+  saddr = g_inet_socket_address_new (iaddr, 0);
+  g_object_unref (iaddr);
+
+  listener = g_socket_listener_new ();
+  g_socket_listener_add_address (listener, saddr,
+				 G_SOCKET_TYPE_STREAM,
+				 G_SOCKET_PROTOCOL_TCP,
+				 NULL,
+				 &effective_address,
+				 &error);
+  g_assert_no_error (error);
+  g_object_unref (saddr);
+
+  client = g_socket_client_new ();
+
+  g_socket_client_connect_async (client,
+				 G_SOCKET_CONNECTABLE (effective_address),
+				 NULL, client_connected, &client_conn);
+  g_socket_listener_accept_async (listener, NULL,
+				  server_connected, &server_conn);
+
+  while (!client_conn || !server_conn)
+    g_main_context_iteration (NULL, TRUE);
+
+  in = G_POLLABLE_INPUT_STREAM (g_io_stream_get_input_stream (G_IO_STREAM (client_conn)));
+  out = g_io_stream_get_output_stream (G_IO_STREAM (server_conn));
+
+  test_streams ();
+
+  g_object_unref (client_conn);
+  g_object_unref (server_conn);
+  g_object_unref (client);
+  g_object_unref (listener);
+}
+
+int
+main (int   argc,
+      char *argv[])
+{
+  g_type_init ();
+  g_test_init (&argc, &argv, NULL);
+
+#ifdef G_OS_UNIX
+  g_test_add_func ("/pollable/unix", test_pollable_unix);
+#endif
+  g_test_add_func ("/pollable/socket", test_pollable_socket);
+
+  return g_test_run();
+}
+