ttmlparse: Collect buffers until detecting complete xml document

Given buffer could be fragmented and we might need to
collect buffers until end tag is detected. And/or, a buffer
can consist of multiple ttml documents.

Fixes: https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/issues/494

ext/ttml/gstttmlparse.c

@@ -427,11 +427,11 @@ feed_textbuf (GstTtmlParse * self, GstBuffer * buf)
   input = convert_encoding (self, (const gchar *) data, avail, &consumed);
 
   if (input && consumed > 0) {
-    if (self->textbuf) {
-      g_string_free (self->textbuf, TRUE);
-      self->textbuf = NULL;
-    }
+    if (!self->textbuf)
       self->textbuf = g_string_new (input);
+    else
+      self->textbuf = g_string_append (self->textbuf, input);
+
     gst_adapter_unmap (self->adapter);
     gst_adapter_flush (self->adapter, consumed);
   } else {
@@ -446,9 +446,11 @@ handle_buffer (GstTtmlParse * self, GstBuffer * buf)
 {
   GstFlowReturn ret = GST_FLOW_OK;
   GstCaps *caps = NULL;
-  GList *subtitle_list, *subtitle;
+  GList *subtitle_list = NULL;
+  GList *iter;
   GstClockTime begin = GST_BUFFER_PTS (buf);
   GstClockTime duration = GST_BUFFER_DURATION (buf);
+  guint consumed;
 
   if (self->first_buffer) {
     GstMapInfo map;
@@ -474,19 +476,31 @@ handle_buffer (GstTtmlParse * self, GstBuffer * buf)
     self->need_segment = FALSE;
   }
 
-  subtitle_list = ttml_parse (self->textbuf->str, begin, duration);
+  do {
+    consumed = ttml_parse (self->textbuf->str, begin, duration, &subtitle_list);
 
-  for (subtitle = subtitle_list; subtitle; subtitle = subtitle->next) {
-    GstBuffer *op_buffer = subtitle->data;
+    if (!consumed) {
+      GST_DEBUG_OBJECT (self, "need more data");
+      return ret;
+    }
+
+    self->textbuf = g_string_erase (self->textbuf, 0, consumed);
+
+    for (iter = subtitle_list; iter; iter = g_list_next (iter)) {
+      GstBuffer *op_buffer = GST_BUFFER (iter->data);
       self->segment.position = GST_BUFFER_PTS (op_buffer);
 
       ret = gst_pad_push (self->srcpad, op_buffer);
 
-    if (ret != GST_FLOW_OK)
+      if (ret != GST_FLOW_OK) {
         GST_DEBUG_OBJECT (self, "flow: %s", gst_flow_get_name (ret));
+        break;
+      }
     }
 
     g_list_free (subtitle_list);
+  } while (TRUE);
+
   return ret;
 }
 

ext/ttml/ttmlparse.c

@@ -1926,9 +1926,11 @@ ttml_find_child (xmlNodePtr parent, const gchar * name)
   return child;
 }
 
+#define TTML_END_TAG "</tt>"
 
-GList *
-ttml_parse (const gchar * input, GstClockTime begin, GstClockTime duration)
+guint
+ttml_parse (const gchar * input, GstClockTime begin, GstClockTime duration,
+    GList ** parsed)
 {
   xmlDocPtr doc;
   xmlNodePtr root_node, head_node, body_node;
@@ -1938,30 +1940,45 @@ ttml_parse (const gchar * input, GstClockTime begin, GstClockTime duration)
   gchar *value;
   guint cellres_x, cellres_y;
   TtmlWhitespaceMode doc_whitespace_mode = TTML_WHITESPACE_MODE_DEFAULT;
+  guint consumed = 0;
+  gchar *end_tt;
 
+  g_return_val_if_fail (parsed != NULL, 0);
+
+  *parsed = NULL;
   if (!g_utf8_validate (input, -1, NULL)) {
     GST_CAT_ERROR (ttmlparse_debug, "Input isn't valid UTF-8.");
-    return NULL;
+    return 0;
   }
   GST_CAT_LOG (ttmlparse_debug, "Input:\n%s", input);
 
+  end_tt = g_strrstr (input, TTML_END_TAG);
+
+  if (!end_tt) {
+    GST_CAT_DEBUG (ttmlparse_debug, "Need more data");
+    return 0;
+  }
+
+  consumed = end_tt - input + strlen (TTML_END_TAG);
+
   styles_table = g_hash_table_new_full (g_str_hash, g_str_equal, g_free,
       (GDestroyNotify) ttml_delete_element);
   regions_table = g_hash_table_new_full (g_str_hash, g_str_equal, g_free,
       (GDestroyNotify) ttml_delete_element);
 
   /* Parse input. */
-  doc = xmlReadMemory (input, strlen (input), "any_doc_name", NULL, 0);
+  doc = xmlReadMemory (input, consumed, "any_doc_name", NULL, 0);
   if (!doc) {
     GST_CAT_ERROR (ttmlparse_debug, "Failed to parse document.");
-    return NULL;
+    return 0;
   }
+
   root_node = xmlDocGetRootElement (doc);
 
   if (xmlStrcmp (root_node->name, (const xmlChar *) "tt") != 0) {
     GST_CAT_ERROR (ttmlparse_debug, "Root element of document is not tt:tt.");
     xmlFreeDoc (doc);
-    return NULL;
+    return 0;
   }
 
   if ((value = ttml_get_xml_property (root_node, "cellResolution"))) {
@@ -1988,8 +2005,9 @@ ttml_parse (const gchar * input, GstClockTime begin, GstClockTime duration)
   if (!(head_node = ttml_find_child (root_node, "head"))) {
     GST_CAT_ERROR (ttmlparse_debug, "No <head> element found.");
     xmlFreeDoc (doc);
-    return NULL;
+    return 0;
   }
+
   ttml_parse_head (head_node, styles_table, regions_table);
 
   if ((body_node = ttml_find_child (root_node, "body"))) {
@@ -2030,5 +2048,7 @@ ttml_parse (const gchar * input, GstClockTime begin, GstClockTime duration)
   g_hash_table_destroy (styles_table);
   g_hash_table_destroy (regions_table);
 
-  return output_buffers;
+  *parsed = output_buffers;
+
+  return consumed;
 }

ext/ttml/ttmlparse.h

@@ -27,8 +27,8 @@
 
 G_BEGIN_DECLS
 
-GList *ttml_parse (const gchar * file, GstClockTime begin,
-    GstClockTime duration);
+guint ttml_parse (const gchar * file, GstClockTime begin,
+    GstClockTime duration, GList **parsed);
 
 G_END_DECLS
 #endif /* _TTML_PARSE_H_ */