[PATCH] filesystem: added cancellation support

[Guillaume Emont <gemont igalia com>]

For search, this is done easily by passing a GCancellable to GIO calls.
Since browse does not use GIO's async API, the only useful thing to do
(assuming an operation cannot be cancelled from another thread), is to check if
the operation has been cancelled at the start of browse_emit_idle(), which is
when the browse operation continues execution in the only cases where it had
delayed some of its execution.
---
 src/filesystem/grl-filesystem.c |   90 +++++++++++++++++++++++++++++++++++---
 1 files changed, 82 insertions(+), 8 deletions(-)

diff --git a/src/filesystem/grl-filesystem.c b/src/filesystem/grl-filesystem.c
index 2fca9c7..a256e82 100644
--- a/src/filesystem/grl-filesystem.c
+++ b/src/filesystem/grl-filesystem.c
@@ -77,6 +77,8 @@ GRL_LOG_DOMAIN_STATIC(filesystem_log_domain);
 struct _GrlFilesystemSourcePrivate {
   GList *chosen_paths;
   guint max_search_depth;
+  /* a mapping operation_id -> GCancellable to cancel this operation */
+  GHashTable *cancellables;
 };
 
 /* --- Data types --- */
@@ -87,6 +89,8 @@ typedef struct {
   GList *current;
   const gchar *path;
   guint remaining;
+  GCancellable *cancellable;
+  guint id;
 }  BrowseIdleData;
 
 /* probably not thread-safe */
@@ -97,6 +101,8 @@ typedef struct {
   guint skipped;
   guint max_depth;
   GQueue *trees;
+  GCancellable *cancellable;
+  guint id;
 } SearchOperation;
 
 typedef struct {
@@ -131,6 +137,9 @@ static gboolean grl_filesystem_test_media_from_uri (GrlMediaSource *source,
 static void grl_filesystem_get_media_from_uri (GrlMediaSource *source,
                                                GrlMediaSourceMediaFromUriSpec *mfus);
 
+static void grl_filesystem_source_cancel (GrlMediaSource *source,
+                                          guint operation_id);
+
 /* =================== Filesystem Plugin  =============== */
 
 gboolean
@@ -198,6 +207,7 @@ grl_filesystem_source_class_init (GrlFilesystemSourceClass * klass)
   GrlMetadataSourceClass *metadata_class = GRL_METADATA_SOURCE_CLASS (klass);
   source_class->browse = grl_filesystem_source_browse;
   source_class->search = grl_filesystem_source_search;
+  source_class->cancel = grl_filesystem_source_cancel;
   source_class->metadata = grl_filesystem_source_metadata;
   source_class->test_media_from_uri = grl_filesystem_test_media_from_uri;
   source_class->media_from_uri = grl_filesystem_get_media_from_uri;
@@ -210,6 +220,7 @@ static void
 grl_filesystem_source_init (GrlFilesystemSource *source)
 {
   source->priv = GRL_FILESYSTEM_SOURCE_GET_PRIVATE (source);
+  source->priv->cancellables = g_hash_table_new (NULL, NULL);
 }
 
 static void
@@ -218,6 +229,7 @@ grl_filesystem_source_finalize (GObject *object)
   GrlFilesystemSource *filesystem_source = GRL_FILESYSTEM_SOURCE (object);
   g_list_foreach (filesystem_source->priv->chosen_paths, (GFunc) g_free, NULL);
   g_list_free (filesystem_source->priv->chosen_paths);
+  g_hash_table_unref (filesystem_source->priv->cancellables);
   G_OBJECT_CLASS (grl_filesystem_source_parent_class)->finalize (object);
 }
 
@@ -467,10 +479,21 @@ browse_emit_idle (gpointer user_data)
 {
   BrowseIdleData *idle_data;
   guint count;
+  GrlFilesystemSource *fs_source;
 
   GRL_DEBUG ("browse_emit_idle");
 
   idle_data = (BrowseIdleData *) user_data;
+  fs_source = GRL_FILESYSTEM_SOURCE (idle_data->spec->source);
+
+  if (g_cancellable_is_cancelled (idle_data->cancellable)) {
+    GRL_DEBUG ("Browse operation %d (\"%s\") has been cancelled",
+               idle_data->id, idle_data->path);
+    idle_data->spec->callback(idle_data->spec->source,
+                              idle_data->id, NULL, 0,
+                              idle_data->spec->user_data, NULL);
+    goto finish;
+  }
 
   count = 0;
   do {
@@ -495,13 +518,18 @@ browse_emit_idle (gpointer user_data)
     count++;
   } while (count < BROWSE_IDLE_CHUNK_SIZE && idle_data->current);
 
-  if (!idle_data->current) {
+  if (!idle_data->current)
+    goto finish;
+
+  return TRUE;
+
+finish:
     g_list_free (idle_data->entries);
+    g_hash_table_remove (fs_source->priv->cancellables,
+                         GUINT_TO_POINTER (idle_data->id));
+    g_object_unref (idle_data->cancellable);
     g_slice_free (BrowseIdleData, idle_data);
     return FALSE;
-  } else {
-    return TRUE;
-  }
 }
 
 static void
@@ -572,6 +600,12 @@ produce_from_path (GrlMediaSourceBrowseSpec *bs, const gchar *path)
     idle_data->path = path;
     idle_data->entries = entries;
     idle_data->current = entries;
+    idle_data->cancellable = g_cancellable_new ();
+    idle_data->id = bs->browse_id;
+    g_hash_table_insert (GRL_FILESYSTEM_SOURCE (bs->source)->priv->cancellables,
+                         GUINT_TO_POINTER (bs->browse_id),
+                         idle_data->cancellable);
+
     g_idle_add (browse_emit_idle, idle_data);
   } else {
     /* No results */
@@ -615,11 +649,17 @@ search_operation_new (GrlMediaSource *source, GrlMediaSourceSearchSpec *ss, guin
 
   operation = g_new (SearchOperation, 1);
   operation->source = source;
+  operation->id = ss->search_id;
   operation->ss = ss;
   operation->found_count = 0;
   operation->skipped = 0;
   operation->max_depth = max_depth;
   operation->trees = g_queue_new ();
+  operation->cancellable = g_cancellable_new ();
+
+  g_hash_table_insert (GRL_FILESYSTEM_SOURCE (source)->priv->cancellables,
+                       GUINT_TO_POINTER (operation->id),
+                       operation->cancellable);
 
   return operation;
 }
@@ -627,8 +667,14 @@ search_operation_new (GrlMediaSource *source, GrlMediaSourceSearchSpec *ss, guin
 static void
 search_operation_free (SearchOperation *operation)
 {
+  GrlFilesystemSource *source;
+  source = GRL_FILESYSTEM_SOURCE (operation->source);
+
   g_queue_foreach (operation->trees, (GFunc)search_tree_free, NULL);
   g_queue_free (operation->trees);
+  g_hash_table_remove (source->priv->cancellables,
+                       GUINT_TO_POINTER (operation->id));
+  g_object_unref (operation->cancellable);
   g_free (operation);
 }
 
@@ -702,7 +748,8 @@ got_file (GFileEnumerator *enumerator, GAsyncResult *res, SearchTree *tree)
 
   files = g_file_enumerator_next_files_finish (enumerator, res, &error);
   if (error) {
-    GRL_WARNING ("Got error while searching: %s", error->message);
+    if (!g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED))
+      GRL_WARNING ("Got error while searching: %s", error->message);
     g_error_free (error);
     goto finished;
   }
@@ -746,7 +793,8 @@ got_file (GFileEnumerator *enumerator, GAsyncResult *res, SearchTree *tree)
     goto finished;
   }
 
-  g_file_enumerator_next_files_async (enumerator, 1, G_PRIORITY_DEFAULT, NULL,
+  g_file_enumerator_next_files_async (enumerator, 1, G_PRIORITY_DEFAULT,
+                                      tree->operation->cancellable,
                                      (GAsyncReadyCallback)got_file, tree);
 
   return;
@@ -778,7 +826,8 @@ got_children (GFile *directory, GAsyncResult *res, SearchTree *tree)
     return;
   }
 
-  g_file_enumerator_next_files_async (enumerator, 1, G_PRIORITY_DEFAULT, NULL,
+  g_file_enumerator_next_files_async (enumerator, 1, G_PRIORITY_DEFAULT,
+                                      tree->operation->cancellable,
                                      (GAsyncReadyCallback)got_file, tree);
 }
 
@@ -794,6 +843,16 @@ search_next_directory (SearchOperation *operation)
     goto finished;
   }
 
+  if (g_cancellable_is_cancelled (operation->cancellable)) {
+    /* We've been cancelled! */
+    /* FIXME: set here a cancelled error when we have one */
+    GRL_DEBUG ("Search operation %d (\"%s\") has been cancelled",
+               operation->id, ss->text);
+    ss->callback (ss->source, ss->search_id, NULL, 0, ss->user_data, NULL);
+    operation->ss = NULL;
+    goto finished;
+  }
+
   tree = g_queue_pop_head (operation->trees);
   if (!tree) { /* We've crawled everything, before reaching count */
     ss->callback (ss->source, ss->search_id, NULL, 0, ss->user_data, NULL);
@@ -806,7 +865,7 @@ search_next_directory (SearchOperation *operation)
                                    G_FILE_ATTRIBUTE_STANDARD_DISPLAY_NAME,
                                    G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS,
                                    G_PRIORITY_DEFAULT,
-                                   NULL,
+                                   operation->cancellable,
                                    (GAsyncReadyCallback)got_children,
                                    tree);
 
@@ -1008,3 +1067,18 @@ beach:
   g_free (path);
 }
 
+static void
+grl_filesystem_source_cancel (GrlMediaSource *source, guint operation_id)
+{
+  GCancellable *cancellable;
+  GrlFilesystemSourcePrivate *priv;
+
+  priv = GRL_FILESYSTEM_SOURCE (source)->priv;
+
+  /* TODO ensure we add/remove stuff to priv->cancellables at the right places */
+  cancellable =
+      G_CANCELLABLE (g_hash_table_lookup (priv->cancellables,
+                                          GUINT_TO_POINTER (operation_id)));
+  if (cancellable)
+    g_cancellable_cancel (cancellable);
+}
-- 
1.7.1