filesink: Adds rb+ file mode

Adds rb+ file mode to filesink so that files can be pre-allocated. This
can be use to keep reduce fragmentation over time with splitmuxsink.

Fixes  #955

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1532>

.vscode/settings.json

@@ -0,0 +1,6 @@
+{
+    "files.associations": {
+        "fstream": "c",
+        "xlocmes": "c"
+    }
+}

subprojects/gstreamer/docs/plugins/gst_plugins_cache.json

@@ -906,6 +906,18 @@
                         "type": "guint",
                         "writable": true
                     },
+                    "file-mode": {
+                        "blurb": "Specify file mode used to open file",
+                        "conditionally-available": false,
+                        "construct": false,
+                        "construct-only": false,
+                        "controllable": false,
+                        "default": "truncate (1)",
+                        "mutable": "null",
+                        "readable": true,
+                        "type": "GstFileSinkFileMode",
+                        "writable": true
+                    },
                     "location": {
                         "blurb": "Location of the file to write",
                         "conditionally-available": false,
@@ -2646,6 +2658,26 @@
                     }
                 ]
             },
+            "GstFileSinkFileMode": {
+                "kind": "enum",
+                "values": [
+                    {
+                        "desc": "Truncate file (mode wb)",
+                        "name": "truncate",
+                        "value": "1"
+                    },
+                    {
+                        "desc": "Append file (mode ab)",
+                        "name": "output",
+                        "value": "2"
+                    },
+                    {
+                        "desc": "Overwrite file without truncating (mode rb+)",
+                        "name": "overwrite",
+                        "value": "3"
+                    }
+                ]
+            },
             "GstInputSelectorSyncMode": {
                 "kind": "enum",
                 "values": [

subprojects/gstreamer/plugins/elements/gstfilesink.c

@@ -81,6 +81,29 @@ static GstStaticPadTemplate sinktemplate = GST_STATIC_PAD_TEMPLATE ("sink",
     GST_PAD_ALWAYS,
     GST_STATIC_CAPS_ANY);
 
+#define GST_TYPE_FILE_SINK_FILE_MODE (gst_file_sink_file_mode_get_type())
+static GType
+gst_file_sink_file_mode_get_type (void)
+{
+  static GType file_mode_type = 0;
+
+  if (g_once_init_enter (&file_mode_type)) {
+    static const GEnumValue file_mode[] = {
+      {GST_FILE_SINK_FILE_MODE_TRUNC, "Truncate file (mode wb)", "truncate"},
+      {GST_FILE_SINK_FILE_MODE_APPEND, "Append file (mode ab)", "output"},
+      {GST_FILE_SINK_FILE_MODE_OVERWRITE,
+          "Overwrite file without truncating (mode rb+)", "overwrite"},
+      {0, NULL, NULL}
+    };
+
+    GType new_file_mode_type =
+        g_enum_register_static ("GstFileSinkFileMode", file_mode);
+
+    g_once_init_leave (&file_mode_type, new_file_mode_type);
+  }
+  return file_mode_type;
+}
+
 #define GST_TYPE_FILE_SINK_BUFFER_MODE (gst_file_sink_buffer_mode_get_type ())
 static GType
 gst_file_sink_buffer_mode_get_type (void)
@@ -111,6 +134,7 @@ GST_DEBUG_CATEGORY_STATIC (gst_file_sink_debug);
 #define DEFAULT_APPEND		FALSE
 #define DEFAULT_O_SYNC		FALSE
 #define DEFAULT_MAX_TRANSIENT_ERROR_TIMEOUT	0
+#define DEFAULT_FILE_MODE      GST_FILE_SINK_FILE_MODE_TRUNC
 
 enum
 {
@@ -121,6 +145,7 @@ enum
   PROP_APPEND,
   PROP_O_SYNC,
   PROP_MAX_TRANSIENT_ERROR_TIMEOUT,
+  PROP_FILE_MODE,
   PROP_LAST
 };
 
@@ -145,6 +170,8 @@ gst_fopen (const gchar * filename, const gchar * mode, gboolean o_sync)
     flags |= O_TRUNC;
   else if (strcmp (mode, "ab") == 0)
     flags |= O_APPEND;
+  else if (strcmp (mode, "rb+") == 0)
+    flags |= O_RDWR;
   else
     g_assert_not_reached ();
 
@@ -230,6 +257,18 @@ gst_file_sink_class_init (GstFileSinkClass * klass)
           G_MAXUINT, DEFAULT_BUFFER_SIZE,
           G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
 
+  /**
+   * GstFileSink:file-mode
+   *
+   * Ability to specify file mode.
+   *
+   * Since: 1.24
+   */
+  g_object_class_install_property (gobject_class, PROP_FILE_MODE,
+      g_param_spec_enum ("file-mode", "File Mode",
+          "Specify file mode used to open file", GST_TYPE_FILE_SINK_FILE_MODE,
+          DEFAULT_FILE_MODE, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
   /**
    * GstFileSink:append
    *
@@ -238,7 +277,7 @@ gst_file_sink_class_init (GstFileSinkClass * klass)
   g_object_class_install_property (gobject_class, PROP_APPEND,
       g_param_spec_boolean ("append", "Append",
           "Append to an already existing file", DEFAULT_APPEND,
-          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS | G_PARAM_DEPRECATED));
 
   g_object_class_install_property (gobject_class, PROP_O_SYNC,
       g_param_spec_boolean ("o-sync", "Synchronous IO",
@@ -276,6 +315,7 @@ gst_file_sink_class_init (GstFileSinkClass * klass)
   }
 
   gst_type_mark_as_plugin_api (GST_TYPE_FILE_SINK_BUFFER_MODE, 0);
+  gst_type_mark_as_plugin_api (GST_TYPE_FILE_SINK_FILE_MODE, 0);
 }
 
 static void
@@ -287,6 +327,7 @@ gst_file_sink_init (GstFileSink * filesink)
   filesink->buffer_mode = DEFAULT_BUFFER_MODE;
   filesink->buffer_size = DEFAULT_BUFFER_SIZE;
   filesink->append = FALSE;
+  filesink->file_mode = DEFAULT_FILE_MODE;
 
   gst_base_sink_set_sync (GST_BASE_SINK (filesink), FALSE);
 }
@@ -358,6 +399,9 @@ gst_file_sink_set_property (GObject * object, guint prop_id,
     case PROP_APPEND:
       sink->append = g_value_get_boolean (value);
       break;
+    case PROP_FILE_MODE:
+      sink->file_mode = g_value_get_enum (value);
+      break;
     case PROP_O_SYNC:
       sink->o_sync = g_value_get_boolean (value);
       break;
@@ -389,6 +433,9 @@ gst_file_sink_get_property (GObject * object, guint prop_id, GValue * value,
     case PROP_APPEND:
       g_value_set_boolean (value, sink->append);
       break;
+    case PROP_FILE_MODE:
+      g_value_set_enum (value, sink->file_mode);
+      break;
     case PROP_O_SYNC:
       g_value_set_boolean (value, sink->o_sync);
       break;
@@ -408,8 +455,10 @@ gst_file_sink_open_file (GstFileSink * sink)
   if (sink->filename == NULL || sink->filename[0] == '\0')
     goto no_filename;
 
-  if (sink->append)
+  if (sink->append || sink->file_mode == GST_FILE_SINK_FILE_MODE_APPEND)
     sink->file = gst_fopen (sink->filename, "ab", sink->o_sync);
+  else if (sink->file_mode == GST_FILE_SINK_FILE_MODE_OVERWRITE)
+    sink->file = gst_fopen (sink->filename, "rb+", sink->o_sync);
   else
     sink->file = gst_fopen (sink->filename, "wb", sink->o_sync);
   if (sink->file == NULL)

subprojects/gstreamer/plugins/elements/gstfilesink.h

@@ -30,7 +30,6 @@
 #include <gst/base/gstbasesink.h>
 
 G_BEGIN_DECLS
-
 #define GST_TYPE_FILE_SINK \
   (gst_file_sink_get_type())
 #define GST_FILE_SINK(obj) \
@@ -62,6 +61,22 @@ typedef enum {
   GST_FILE_SINK_BUFFER_MODE_UNBUFFERED = _IONBF
 } GstFileSinkBufferMode;
 
+/**
+ * GstFileSinkFileMode:
+ * @FILESINK_FILE_MODE_TRUNC: Default file mode (wb)
+ * @FILESINK_FILE_MODE_APPEND: Append file mode (ab)
+ * @FILESINK_FILE_MODE_OVERWRITE: Overwrite file mode (rb+)
+ *
+ * File write mode.
+ *
+ * Since: 1.24
+ */
+typedef enum {
+  GST_FILE_SINK_FILE_MODE_TRUNC     = 1,
+  GST_FILE_SINK_FILE_MODE_APPEND    = 2,
+  GST_FILE_SINK_FILE_MODE_OVERWRITE = 3,
+} GstFileSinkFileMode;
+
 /**
  * GstFileSink:
  *
@@ -84,6 +99,8 @@ struct _GstFileSink {
   /* For default buffer mode */
   GstBufferList *buffer_list;
 
+  gint  file_mode;
+
   /* For full buffer mode */
   guint8 *buffer;
   gsize   allocated_buffer_size;