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, 89 insertions, 18 deletions

diff --git a/daemon/gvfsjobopenforwrite.c b/daemon/gvfsjobopenforwrite.c
index 429e2679..1388dabf 100644
--- a/daemon/gvfsjobopenforwrite.c
+++ b/daemon/gvfsjobopenforwrite.c
@@ -81,28 +81,29 @@ g_vfs_job_open_for_write_init (GVfsJobOpenForWrite *job)
 {
 }
 
-gboolean
-g_vfs_job_open_for_write_new_handle (GVfsDBusMount *object,
-                                     GDBusMethodInvocation *invocation,
-                                     GUnixFDList *fd_list,
-                                     const gchar *arg_path_data,
-                                     guint16 arg_mode,
-                                     const gchar *arg_etag,
-                                     gboolean arg_make_backup,
-                                     guint arg_flags,
-                                     guint arg_pid,
-                                     GVfsBackend *backend)
+static gboolean
+open_for_write_new_handle_common (GVfsDBusMount *object,
+                                  GDBusMethodInvocation *invocation,
+                                  GUnixFDList *fd_list,
+                                  const gchar *arg_path_data,
+                                  guint16 arg_mode,
+                                  const gchar *arg_etag,
+                                  gboolean arg_make_backup,
+                                  guint arg_flags,
+                                  guint arg_pid,
+                                  GVfsBackend *backend,
+                                  GVfsJobOpenForWriteVersion version)
 {
   GVfsJobOpenForWrite *job;
-  
+
   if (g_vfs_backend_invocation_first_handler (object, invocation, backend))
     return TRUE;
-  
+
   job = g_object_new (G_VFS_TYPE_JOB_OPEN_FOR_WRITE,
                       "object", object,
                       "invocation", invocation,
                       NULL);
-  
+
   job->filename = g_strdup (arg_path_data);
   job->mode = arg_mode;
   if (*arg_etag != 0)
@@ -111,6 +112,7 @@ g_vfs_job_open_for_write_new_handle (GVfsDBusMount *object,
   job->flags = arg_flags;
   job->backend = backend;
   job->pid = arg_pid;
+  job->version = version;
 
   g_vfs_job_source_new_job (G_VFS_JOB_SOURCE (backend), G_VFS_JOB (job));
   g_object_unref (job);
@@ -118,6 +120,56 @@ g_vfs_job_open_for_write_new_handle (GVfsDBusMount *object,
   return TRUE;
 }
 
+gboolean
+g_vfs_job_open_for_write_new_handle (GVfsDBusMount *object,
+                                     GDBusMethodInvocation *invocation,
+                                     GUnixFDList *fd_list,
+                                     const gchar *arg_path_data,
+                                     guint16 arg_mode,
+                                     const gchar *arg_etag,
+                                     gboolean arg_make_backup,
+                                     guint arg_flags,
+                                     guint arg_pid,
+                                     GVfsBackend *backend)
+{
+  return open_for_write_new_handle_common(object,
+                                          invocation,
+                                          fd_list,
+                                          arg_path_data,
+                                          arg_mode,
+                                          arg_etag,
+                                          arg_make_backup,
+                                          arg_flags,
+                                          arg_pid,
+                                          backend,
+                                          OPEN_FOR_WRITE_VERSION_ORIGINAL);
+}
+
+gboolean
+g_vfs_job_open_for_write_new_handle_with_flags (GVfsDBusMount *object,
+                                                GDBusMethodInvocation *invocation,
+                                                GUnixFDList *fd_list,
+                                                const gchar *arg_path_data,
+                                                guint16 arg_mode,
+                                                const gchar *arg_etag,
+                                                gboolean arg_make_backup,
+                                                guint arg_flags,
+                                                guint arg_pid,
+                                                GVfsBackend *backend)
+{
+  return open_for_write_new_handle_common(object,
+                                          invocation,
+                                          fd_list,
+                                          arg_path_data,
+                                          arg_mode,
+                                          arg_etag,
+                                          arg_make_backup,
+                                          arg_flags,
+                                          arg_pid,
+                                          backend,
+                                          OPEN_FOR_WRITE_VERSION_WITH_FLAGS);
+}
+
 static void
 run (GVfsJob *job)
 {
@@ -233,6 +285,13 @@ g_vfs_job_open_for_write_set_can_seek (GVfsJobOpenForWrite *job,
 }
 
 void
+g_vfs_job_open_for_write_set_can_truncate (GVfsJobOpenForWrite *job,
+                                           gboolean can_truncate)
+{
+  job->can_truncate = can_truncate;
+}
+
+void
 g_vfs_job_open_for_write_set_initial_offset (GVfsJobOpenForWrite *job,
 					     goffset              initial_offset)
 {
@@ -284,10 +343,22 @@ create_reply (GVfsJob *job,
 
   g_signal_emit_by_name (job, "new-source", open_job->write_channel);
 
-  gvfs_dbus_mount_complete_open_for_write (object, invocation,
-                                           fd_list, g_variant_new_handle (fd_id),
-                                           open_job->can_seek,
-                                           open_job->initial_offset);
+  switch (open_job->version)
+    {
+      case OPEN_FOR_WRITE_VERSION_ORIGINAL:
+        gvfs_dbus_mount_complete_open_for_write (object, invocation,
+                                                 fd_list, g_variant_new_handle (fd_id),
+                                                 open_job->can_seek ? OPEN_FOR_WRITE_FLAG_CAN_SEEK : 0,
+                                                 open_job->initial_offset);
+        break;
+      case OPEN_FOR_WRITE_VERSION_WITH_FLAGS:
+        gvfs_dbus_mount_complete_open_for_write_flags (object, invocation,
+                                                 fd_list, g_variant_new_handle (fd_id),
+                                                 (open_job->can_seek ? OPEN_FOR_WRITE_FLAG_CAN_SEEK : 0) |
+                                                 (open_job->can_truncate ? OPEN_FOR_WRITE_FLAG_CAN_TRUNCATE : 0),
+                                                 open_job->initial_offset);
+        break;
+    }
   
   close (remote_fd);
   g_object_unref (fd_list);