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

1 files changed, 98 insertions, 0 deletions

diff --git a/gio/gpollableoutputstream.h b/gio/gpollableoutputstream.h
new file mode 100644
index 000000000..abef0ede6
--- /dev/null
+++ b/gio/gpollableoutputstream.h
@@ -0,0 +1,98 @@
+/* GIO - GLib Input, Output and Streaming Library
+ *
+ * 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.
+ */
+
+#ifndef __G_POLLABLE_OUTPUT_STREAM_H__
+#define __G_POLLABLE_OUTPUT_STREAM_H__
+
+#include <gio/gio.h>
+
+G_BEGIN_DECLS
+
+#define G_TYPE_POLLABLE_OUTPUT_STREAM               (g_pollable_output_stream_get_type ())
+#define G_POLLABLE_OUTPUT_STREAM(obj)               (G_TYPE_CHECK_INSTANCE_CAST ((obj), G_TYPE_POLLABLE_OUTPUT_STREAM, GPollableOutputStream))
+#define G_IS_POLLABLE_OUTPUT_STREAM(obj)            (G_TYPE_CHECK_INSTANCE_TYPE ((obj), G_TYPE_POLLABLE_OUTPUT_STREAM))
+#define G_POLLABLE_OUTPUT_STREAM_GET_INTERFACE(obj) (G_TYPE_INSTANCE_GET_INTERFACE ((obj), G_TYPE_POLLABLE_OUTPUT_STREAM, GPollableOutputStreamInterface))
+
+/**
+ * GPollableOutputStream:
+ *
+ * An interface for a #GOutputStream that can be polled for readability.
+ *
+ * Since: 2.28
+ */
+typedef struct _GPollableOutputStreamInterface GPollableOutputStreamInterface;
+
+/**
+ * GPollableOutputStreamInterface:
+ * @g_iface: The parent interface.
+ * @can_poll: Checks if the #GPollableOutputStream instance is actually pollable
+ * @is_writable: Checks if the stream is writable
+ * @create_source: Creates a #GSource to poll the stream
+ * @write_nonblocking: Does a non-blocking write or returns
+ *   %G_IO_ERROR_WOULD_BLOCK
+ *
+ * The interface for pollable output streams.
+ *
+ * The default implementation of @can_poll always returns %TRUE.
+ *
+ * The default implementation of @write_nonblocking calls
+ * g_pollable_output_stream_is_writable(), and then calls
+ * g_output_stream_write() if it returns %TRUE. This means you only
+ * need to override it if it is possible that your @is_writable
+ * implementation may return %TRUE when the stream is not actually
+ * writable.
+ *
+ * Since: 2.28
+ */
+struct _GPollableOutputStreamInterface
+{
+  GTypeInterface g_iface;
+
+  /* Virtual Table */
+  gboolean     (*can_poll)          (GPollableOutputStream  *stream);
+
+  gboolean     (*is_writable)       (GPollableOutputStream  *stream);
+  GSource *    (*create_source)     (GPollableOutputStream  *stream,
+				     GCancellable           *cancellable);
+  gssize       (*write_nonblocking) (GPollableOutputStream  *stream,
+				     const void             *buffer,
+				     gsize                   size,
+				     GError                **error);
+};
+
+GType    g_pollable_output_stream_get_type          (void) G_GNUC_CONST;
+
+gboolean g_pollable_output_stream_can_poll          (GPollableOutputStream  *stream);
+
+gboolean g_pollable_output_stream_is_writable       (GPollableOutputStream  *stream);
+GSource *g_pollable_output_stream_create_source     (GPollableOutputStream  *stream,
+						     GCancellable           *cancellable);
+
+gssize   g_pollable_output_stream_write_nonblocking (GPollableOutputStream  *stream,
+						     const void             *buffer,
+						     gsize                   size,
+						     GCancellable           *cancellable,
+						     GError                **error);
+
+G_END_DECLS
+
+
+#endif /* __G_POLLABLE_OUTPUT_STREAM_H__ */
+