Implement truncate support for output streams

Backends receive a TRUNCATE message which contains a size parameter.
Truncation is signaled with a TRUNCATED message (which contains no other
useful information).

In more detail:
Add a new dbus method, OpenForWriteFlags, which has a flags parameter to
implement can_seek and can_truncate.  These flags are used in
GDaemonFileOutputStream.  Compatability with old clients is maintained.
Implement the can_truncate and truncate_fn GDaemonFileOutputStream
methods.
Add two new message types to the daemon socket protocol:
    G_VFS_DAEMON_SOCKET_PROTOCOL_REQUEST_TRUNCATE
    G_VFS_DAEMON_SOCKET_PROTOCOL_REPLY_TRUNCATED
Add a new job type, GVfsJobTruncate.
Add two new methods to GVfsBackend which backend classes can implement:
truncate and try_truncate

https://bugzilla.gnome.org/show_bug.cgi?id=573837

1 files changed, 128 insertions, 0 deletions

diff --git a/daemon/gvfsjobtruncate.c b/daemon/gvfsjobtruncate.c
new file mode 100644
index 00000000..bac32483
--- /dev/null
+++ b/daemon/gvfsjobtruncate.c
@@ -0,0 +1,128 @@
+/* GIO - GLib Input, Output and Streaming Library
+ * 
+ * Copyright (C) 2013 Ross Lagerwall
+ *
+ * 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., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include <config.h>
+
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include <glib.h>
+#include <glib/gi18n.h>
+#include "gvfswritechannel.h"
+#include "gvfsjobtruncate.h"
+#include "gvfsdaemonutils.h"
+
+G_DEFINE_TYPE (GVfsJobTruncate, g_vfs_job_truncate, G_VFS_TYPE_JOB)
+
+static void     run        (GVfsJob *job);
+static gboolean try        (GVfsJob *job);
+static void     send_reply (GVfsJob *job);
+
+static void
+g_vfs_job_truncate_finalize (GObject *object)
+{
+  GVfsJobTruncate *job;
+
+  job = G_VFS_JOB_TRUNCATE (object);
+  g_object_unref (job->channel);
+
+  if (G_OBJECT_CLASS (g_vfs_job_truncate_parent_class)->finalize)
+    (*G_OBJECT_CLASS (g_vfs_job_truncate_parent_class)->finalize) (object);
+}
+
+static void
+g_vfs_job_truncate_class_init (GVfsJobTruncateClass *klass)
+{
+  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
+  GVfsJobClass *job_class = G_VFS_JOB_CLASS (klass);
+
+  gobject_class->finalize = g_vfs_job_truncate_finalize;
+
+  job_class->run = run;
+  job_class->try = try;
+  job_class->send_reply = send_reply;
+}
+
+static void
+g_vfs_job_truncate_init (GVfsJobTruncate *job)
+{
+}
+
+GVfsJob *
+g_vfs_job_truncate_new (GVfsWriteChannel *channel,
+                        GVfsBackendHandle handle,
+                        goffset size,
+                        GVfsBackend *backend)
+{
+  GVfsJobTruncate *job;
+
+  job = g_object_new (G_VFS_TYPE_JOB_TRUNCATE, NULL);
+
+  job->backend = backend;
+  job->channel = g_object_ref (channel);
+  job->handle = handle;
+  job->size = size;
+
+  return G_VFS_JOB (job);
+}
+
+/* Might be called on an i/o thread */
+static void
+send_reply (GVfsJob *job)
+{
+  GVfsJobTruncate *op_job = G_VFS_JOB_TRUNCATE (job);
+
+  g_debug ("job_truncate send reply\n");
+
+  if (job->failed)
+    g_vfs_channel_send_error (G_VFS_CHANNEL (op_job->channel), job->error);
+  else
+    g_vfs_write_channel_send_truncated (op_job->channel);
+}
+
+static void
+run (GVfsJob *job)
+{
+  GVfsJobTruncate *op_job = G_VFS_JOB_TRUNCATE (job);
+  GVfsBackendClass *class = G_VFS_BACKEND_GET_CLASS (op_job->backend);
+
+  if (class->truncate)
+    class->truncate (op_job->backend, op_job, op_job->handle, op_job->size);
+  else
+    g_vfs_job_failed (job, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
+                      _("Operation not supported by backend"));
+}
+
+static gboolean
+try (GVfsJob *job)
+{
+  GVfsJobTruncate *op_job = G_VFS_JOB_TRUNCATE (job);
+  GVfsBackendClass *class = G_VFS_BACKEND_GET_CLASS (op_job->backend);
+
+  if (class->try_truncate)
+    return class->try_truncate (op_job->backend,
+                                op_job,
+                                op_job->handle,
+                                op_job->size);
+  else
+    return FALSE;
+}