uridownloader: add support for range based downloads

Adds a new API gst_uri_downloader_fetch_uri_with_range that allows
downloading only a byte range from an URI. It uses a seek event
sent to the source to signal the range to be downloaded.

https://bugzilla.gnome.org/show_bug.cgi?id=702206

gst-libs/gst/uridownloader/gsturidownloader.c

@@ -320,6 +320,24 @@ gst_uri_downloader_cancel (GstUriDownloader * downloader)
   }
 }
 
+static gboolean
+gst_uri_downloader_set_range (GstUriDownloader * downloader,
+    gint64 range_start, gint64 range_end)
+{
+  g_return_val_if_fail (range_start >= 0, FALSE);
+  g_return_val_if_fail (range_end >= -1, FALSE);
+
+  if (range_start || (range_end >= 0)) {
+    GstEvent *seek;
+
+    seek = gst_event_new_seek (1.0, GST_FORMAT_BYTES, GST_SEEK_FLAG_FLUSH,
+        GST_SEEK_TYPE_SET, range_start, GST_SEEK_TYPE_SET, range_end);
+
+    return gst_element_send_event (downloader->priv->urisrc, seek);
+  }
+  return TRUE;
+}
+
 static gboolean
 gst_uri_downloader_set_uri (GstUriDownloader * downloader, const gchar * uri)
 {
@@ -352,6 +370,22 @@ gst_uri_downloader_set_uri (GstUriDownloader * downloader, const gchar * uri)
 
 GstFragment *
 gst_uri_downloader_fetch_uri (GstUriDownloader * downloader, const gchar * uri)
+{
+  return gst_uri_downloader_fetch_uri_with_range (downloader, uri, 0, -1);
+}
+
+/**
+ * gst_uri_downloader_fetch_uri_with_range:
+ * @downloader: the #GstUriDownloader
+ * @uri: the uri
+ * @range_start: the starting byte index
+ * @range_end: the final byte index, use -1 for unspecified
+ *
+ * Returns the downloaded #GstFragment
+ */
+GstFragment *
+gst_uri_downloader_fetch_uri_with_range (GstUriDownloader * downloader,
+    const gchar * uri, gint64 range_start, gint64 range_end)
 {
   GstStateChangeReturn ret;
   GstFragment *download = NULL;
@@ -363,12 +397,22 @@ gst_uri_downloader_fetch_uri (GstUriDownloader * downloader, const gchar * uri)
   }
 
   if (!gst_uri_downloader_set_uri (downloader, uri)) {
+    GST_WARNING_OBJECT (downloader, "Failed to set URI");
+    goto quit;
+  }
+
+  gst_bus_set_flushing (downloader->priv->bus, FALSE);
+  ret = gst_element_set_state (downloader->priv->urisrc, GST_STATE_READY);
+  if (ret == GST_STATE_CHANGE_FAILURE) {
+    goto quit;
+  }
+
+  if (!gst_uri_downloader_set_range (downloader, range_start, range_end)) {
+    GST_WARNING_OBJECT (downloader, "Failed to set range");
     goto quit;
   }
 
   downloader->priv->download = gst_fragment_new ();
-
-  gst_bus_set_flushing (downloader->priv->bus, FALSE);
   ret = gst_element_set_state (downloader->priv->urisrc, GST_STATE_PLAYING);
   if (ret == GST_STATE_CHANGE_FAILURE) {
     g_object_unref (downloader->priv->download);

gst-libs/gst/uridownloader/gsturidownloader.h

@@ -57,6 +57,7 @@ GType gst_uri_downloader_get_type (void);
 
 GstUriDownloader * gst_uri_downloader_new (void);
 GstFragment * gst_uri_downloader_fetch_uri (GstUriDownloader * downloader, const gchar * uri);
+GstFragment * gst_uri_downloader_fetch_uri_with_range (GstUriDownloader * downloader, const gchar * uri, gint64 range_start, gint64 range_end);
 void gst_uri_downloader_reset (GstUriDownloader *downloader);
 void gst_uri_downloader_cancel (GstUriDownloader *downloader);
 void gst_uri_downloader_free (GstUriDownloader *downloader);