[tracker/extractor-dbus-fd] libtracker-common: Add "send and splice"

[Adrien Bustany <abustany src gnome org>]

commit 6b7fad4608db319b9dd988167cdcd917d1638cfa
Author: Adrien Bustany <abustany gnome org>
Date:   Fri Jul 2 12:12:22 2010 +0200

    libtracker-common: Add "send and splice"
    
    The tracker_dbus_send_and_splice function sends a DBusMessage, splices
    from a file descriptor and then blocks on the reply of the message.

 src/libtracker-common/tracker-dbus.c |   99 ++++++++++++++++++++++++++++++++++
 src/libtracker-common/tracker-dbus.h |   22 +++++++-
 2 files changed, 119 insertions(+), 2 deletions(-)
---
diff --git a/src/libtracker-common/tracker-dbus.c b/src/libtracker-common/tracker-dbus.c
index ffdbc07..8915cc8 100644
--- a/src/libtracker-common/tracker-dbus.c
+++ b/src/libtracker-common/tracker-dbus.c
@@ -20,6 +20,8 @@
 #include "config.h"
 
 #include <gio/gio.h>
+#include <gio/gunixinputstream.h>
+#include <gio/gunixoutputstream.h>
 
 #include <dbus/dbus-glib-bindings.h>
 
@@ -696,3 +698,100 @@ tracker_dbus_enable_client_lookup (gboolean enabled)
 
 	client_lookup_enabled = enabled;
 }
+
+/*
+ * /!\ BIG FAT WARNING /!\
+ * The message must be destroyed for this function to succeed, so pass a
+ * message with a refcount of 1 (and say goodbye to it, 'cause you'll never
+ * see it again
+ */
+gboolean
+tracker_dbus_send_and_splice (DBusConnection  *connection,
+                              DBusMessage     *message,
+                              int              fd,
+                              GCancellable    *cancellable,
+                              void           **dest_buffer,
+                              gssize          *dest_buffer_size,
+                              GError         **error)
+{
+	DBusPendingCall *call;
+	DBusMessage *reply = NULL;
+	GInputStream *unix_input_stream;
+	GInputStream *buffered_input_stream;
+	GOutputStream *output_stream;
+	GError *inner_error = NULL;
+	gboolean ret_value = FALSE;
+
+	g_return_val_if_fail (connection, FALSE);
+	g_return_val_if_fail (message, FALSE);
+	g_return_val_if_fail (dest_buffer, FALSE);
+
+	dbus_connection_send_with_reply (connection,
+	                                 message,
+	                                 &call,
+	                                 -1);
+	dbus_message_unref (message);
+
+	if (!call) {
+		g_set_error (error,
+		             TRACKER_DBUS_ERROR,
+		             TRACKER_DBUS_ERROR_UNSUPPORTED,
+		             "FD passing unsupported or connection disconnected");
+		return FALSE;
+	}
+
+	unix_input_stream = g_unix_input_stream_new (fd, TRUE);
+	buffered_input_stream = g_buffered_input_stream_new_sized (unix_input_stream,
+	                                                           TRACKER_DBUS_PIPE_BUFFER_SIZE);
+	output_stream = g_memory_output_stream_new (NULL, 0, g_realloc, NULL);
+
+	g_output_stream_splice (output_stream,
+	                        buffered_input_stream,
+	                        G_OUTPUT_STREAM_SPLICE_CLOSE_SOURCE |
+	                        G_OUTPUT_STREAM_SPLICE_CLOSE_TARGET,
+	                        NULL,
+	                        &inner_error);
+
+	if (G_LIKELY (!inner_error)) {
+		/* Wait for any current d-bus call to finish */
+		dbus_pending_call_block (call);
+
+		/* Check we didn't get an error */
+		reply = dbus_pending_call_steal_reply (call);
+
+		if (G_UNLIKELY (dbus_message_get_type (reply) == DBUS_MESSAGE_TYPE_ERROR)) {
+			DBusError dbus_error;
+
+			dbus_error_init (&dbus_error);
+			dbus_set_error_from_message (&dbus_error, reply);
+			dbus_set_g_error (error, &dbus_error);
+			dbus_error_free (&dbus_error);
+		} else {
+			*dest_buffer = g_memory_output_stream_get_data (G_MEMORY_OUTPUT_STREAM (output_stream));
+
+			if (dest_buffer_size) {
+				*dest_buffer_size = g_memory_output_stream_get_data_size (G_MEMORY_OUTPUT_STREAM (output_stream));
+			}
+
+			ret_value = TRUE;
+		}
+	} else {
+		g_set_error (error,
+		             TRACKER_DBUS_ERROR,
+		             TRACKER_DBUS_ERROR_BROKEN_PIPE,
+		             "Couldn't get results from server");
+		g_error_free (inner_error);
+	}
+
+	g_object_unref (output_stream);
+	g_object_unref (buffered_input_stream);
+	g_object_unref (unix_input_stream);
+
+	if (reply) {
+		dbus_message_unref (reply);
+	}
+
+	dbus_pending_call_unref (call);
+
+	return ret_value;
+}
diff --git a/src/libtracker-common/tracker-dbus.h b/src/libtracker-common/tracker-dbus.h
index 09b5419..4b66e21 100644
--- a/src/libtracker-common/tracker-dbus.h
+++ b/src/libtracker-common/tracker-dbus.h
@@ -22,6 +22,8 @@
 
 #include <glib/gi18n.h>
 
+#include <gio/gio.h>
+
 #include <dbus/dbus.h>
 #include <dbus/dbus-glib-lowlevel.h>
 #include <dbus/dbus-glib.h>
@@ -54,7 +56,7 @@ G_BEGIN_DECLS
 	  \
 			g_set_error (&assert_error, \
 			             TRACKER_DBUS_ERROR, \
-			             0, \
+			             TRACKER_DBUS_ERROR_ASSERTION_FAILED, \
 			             _("Assertion `%s' failed"), \
 			             #expr); \
 	  \
@@ -70,7 +72,7 @@ G_BEGIN_DECLS
 		if G_LIKELY(expr) { } else { \
 			g_set_error (error, \
 			             TRACKER_DBUS_ERROR, \
-			             0, \
+			             TRACKER_DBUS_ERROR_ASSERTION_FAILED, \
 			             _("Assertion `%s' failed"), \
 			             #expr); \
 	  \
@@ -78,6 +80,9 @@ G_BEGIN_DECLS
 		}; \
 	} G_STMT_END
 
+/* Size of buffers used when sending data over a pipe, using DBus FD passing */
+#define TRACKER_DBUS_PIPE_BUFFER_SIZE 65536
+
 #define TRACKER_DBUS_SERVICE_EXTRACT   "org.freedesktop.Tracker1.Extract"
 #define TRACKER_DBUS_PATH_EXTRACT      "/org/freedesktop/Tracker1/Extract"
 #define TRACKER_DBUS_INTERFACE_EXTRACT "org.freedesktop.Tracker1.Extract"
@@ -99,6 +104,12 @@ typedef enum {
 	TRACKER_DBUS_EVENTS_TYPE_DELETE
 } TrackerDBusEventsType;
 
+typedef enum {
+	TRACKER_DBUS_ERROR_ASSERTION_FAILED,
+	TRACKER_DBUS_ERROR_UNSUPPORTED,
+	TRACKER_DBUS_ERROR_BROKEN_PIPE
+} TrackerDBusError;
+
 GQuark           tracker_dbus_error_quark            (void);
 TrackerDBusData *tracker_dbus_data_new               (const gpointer              arg1,
                                                       const gpointer              arg2);
@@ -150,6 +161,13 @@ void             tracker_dbus_request_block_hooks    (void);
 void             tracker_dbus_request_unblock_hooks  (void);
 
 void             tracker_dbus_enable_client_lookup   (gboolean                    enable);
+gboolean         tracker_dbus_send_and_splice        (DBusConnection             *connection,
+                                                      DBusMessage                *message,
+                                                      int                         fd,
+                                                      GCancellable               *cancellable,
+                                                      void                      **dest_buffer,
+                                                      gssize                     *dest_buffer_size,
+                                                      GError                    **error);
 
 G_END_DECLS