dashdemux: add support for HTTP HEAD method of time sync

The urn:mpeg:dash:utc:http-head:2014 method of time synchronisation
uses an HTTP HEAD request to a specified URL and then parses the
Date: HTTP response header.

This commit adds support to dashdemux for this method of time
synchronisation by making a HEAD request and then parsing the Date:
response.

This commit adds support to gstfragment to return the HTTP headers
and to uridownloader to support HEAD requests. To avoid creating a
new API, the RANGE get function is re-used (abused?) with start=-1
and end=-1 to indicate a HEAD request.

https://bugzilla.gnome.org/show_bug.cgi?id=752413

3 files changed, 56 insertions, 6 deletions

diff --git a/gst-libs/gst/uridownloader/gstfragment.c b/gst-libs/gst/uridownloader/gstfragment.c
index 3f9552bd0..6d415930b 100644
--- a/gst-libs/gst/uridownloader/gstfragment.c
+++ b/gst-libs/gst/uridownloader/gstfragment.c
@@ -167,6 +167,7 @@ gst_fragment_init (GstFragment * fragment)
   fragment->name = g_strdup ("");
   fragment->completed = FALSE;
   fragment->discontinuous = FALSE;
+  fragment->headers = NULL;
 }
 
 GstFragment *
@@ -183,6 +184,8 @@ gst_fragment_finalize (GObject * gobject)
   g_free (fragment->uri);
   g_free (fragment->redirect_uri);
   g_free (fragment->name);
+  if (fragment->headers)
+    gst_structure_free (fragment->headers);
   g_mutex_clear (&fragment->priv->lock);
 
   G_OBJECT_CLASS (gst_fragment_parent_class)->finalize (gobject);
diff --git a/gst-libs/gst/uridownloader/gstfragment.h b/gst-libs/gst/uridownloader/gstfragment.h
index bdf04f3cd..a8e0a545c 100644
--- a/gst-libs/gst/uridownloader/gstfragment.h
+++ b/gst-libs/gst/uridownloader/gstfragment.h
@@ -44,6 +44,8 @@ struct _GstFragment
   gchar * uri;                  /* URI of the fragment */
   gchar * redirect_uri;         /* Redirect target if any */
   gboolean redirect_permanent;  /* If the redirect is permanent */
+  gint64 range_start;
+  gint64 range_end;
 
   gchar * name;                 /* Name of the fragment */
   gboolean completed;           /* Whether the fragment is complete or not */
@@ -53,6 +55,7 @@ struct _GstFragment
   guint64 stop_time;            /* Stop time of the fragment */
   gboolean index;               /* Index of the fragment */
   gboolean discontinuous;       /* Whether this fragment is discontinuous or not */
+  GstStructure *headers;        /* HTTP request/response headers */
 
   GstFragmentPrivate *priv;
 };
diff --git a/gst-libs/gst/uridownloader/gsturidownloader.c b/gst-libs/gst/uridownloader/gsturidownloader.c
index 3d5a215d2..72e5e79b2 100644
--- a/gst-libs/gst/uridownloader/gsturidownloader.c
+++ b/gst-libs/gst/uridownloader/gsturidownloader.c
@@ -178,6 +178,20 @@ gst_uri_downloader_sink_event (GstPad * pad, GstObject * parent,
       gst_event_unref (event);
       break;
     }
+    case GST_EVENT_CUSTOM_DOWNSTREAM_STICKY:{
+      const GstStructure *str;
+      str = gst_event_get_structure (event);
+      if (gst_structure_has_name (str, "http-headers")) {
+        GST_OBJECT_LOCK (downloader);
+        if (downloader->priv->download != NULL) {
+          if (downloader->priv->download->headers)
+            gst_structure_free (downloader->priv->download->headers);
+          downloader->priv->download->headers = gst_structure_copy (str);
+        }
+        GST_OBJECT_UNLOCK (downloader);
+      }
+    }
+      /* falls through */
     default:
       ret = gst_pad_event_default (pad, parent, event);
       break;
@@ -428,6 +442,23 @@ gst_uri_downloader_set_uri (GstUriDownloader * downloader, const gchar * uri,
   return TRUE;
 }
 
+static gboolean
+gst_uri_downloader_set_method (GstUriDownloader * downloader,
+    const gchar * method)
+{
+  GObjectClass *gobject_class;
+
+  if (!downloader->priv->urisrc)
+    return FALSE;
+
+  gobject_class = G_OBJECT_GET_CLASS (downloader->priv->urisrc);
+  if (g_object_class_find_property (gobject_class, "method")) {
+    g_object_set (downloader->priv->urisrc, "method", method, NULL);
+    return TRUE;
+  }
+  return FALSE;
+}
+
 GstFragment *
 gst_uri_downloader_fetch_uri (GstUriDownloader * downloader,
     const gchar * uri, const gchar * referer, gboolean compress,
@@ -477,6 +508,8 @@ gst_uri_downloader_fetch_uri_with_range (GstUriDownloader *
   if (downloader->priv->download)
     g_object_unref (downloader->priv->download);
   downloader->priv->download = gst_fragment_new ();
+  downloader->priv->download->range_start = range_start;
+  downloader->priv->download->range_end = range_end;
   GST_OBJECT_UNLOCK (downloader);
   ret = gst_element_set_state (downloader->priv->urisrc, GST_STATE_READY);
   GST_OBJECT_LOCK (downloader);
@@ -490,9 +523,16 @@ gst_uri_downloader_fetch_uri_with_range (GstUriDownloader *
     goto quit;
   }
 
-  if (!gst_uri_downloader_set_range (downloader, range_start, range_end)) {
-    GST_WARNING_OBJECT (downloader, "Failed to set range");
-    goto quit;
+  if (range_start < 0 && range_end < 0) {
+    if (!gst_uri_downloader_set_method (downloader, "HEAD")) {
+      GST_WARNING_OBJECT (downloader, "Failed to set HTTP method");
+      goto quit;
+    }
+  } else {
+    if (!gst_uri_downloader_set_range (downloader, range_start, range_end)) {
+      GST_WARNING_OBJECT (downloader, "Failed to set range");
+      goto quit;
+    }
   }
 
   GST_OBJECT_UNLOCK (downloader);
@@ -531,9 +571,13 @@ gst_uri_downloader_fetch_uri_with_range (GstUriDownloader *
   download = downloader->priv->download;
   downloader->priv->download = NULL;
   if (!downloader->priv->got_buffer) {
-    g_object_unref (download);
-    download = NULL;
-    GST_ERROR_OBJECT (downloader, "Didn't retrieve a buffer before EOS");
+    if (download->range_start < 0 && download->range_end < 0) {
+      /* HEAD request, so we don't expect a response */
+    } else {
+      g_object_unref (download);
+      download = NULL;
+      GST_ERROR_OBJECT (downloader, "Didn't retrieve a buffer before EOS");
+    }
   }
 
   if (download != NULL)