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Bug 347293 - GstValueList comparison is flawed
GstValueList comparison is flawed
Product: GStreamer
Classification: Platform
Component: gstreamer (core)
git master
Other Linux
: Normal normal
: 0.10.10
Assigned To: GStreamer Maintainers
GStreamer Maintainers
Depends on:
Reported: 2006-07-12 09:08 UTC by Jan Schmidt
Modified: 2006-07-31 16:34 UTC
See Also:
GNOME target: ---
GNOME version: ---

Description Jan Schmidt 2006-07-12 09:08:51 UTC
Looking at the code in gstvalue.c, it seems that GstValueLists are considered equal if
a) they are the same length
b) All items in list A exist in list B.

This is faulty if list A contains duplicates.

A better algorithm might be:

1. If lists are not the same length, return UNORDERED
2. Copy list B -> B'
3. For each item I in list A:
   3a. If I does not exist in B', return UNORDERED
   3b. Remove I from B'
4. If B' is not empty, return UNORDERED
5. Return EQUAL
Comment 1 Wim Taymans 2006-07-14 09:45:25 UTC
Something like this?

/* Do an unordered compare of the contents of a list */
static int
gst_value_compare_list (const GValue * value1, const GValue * value2)
  guint i, j;
  GArray *array1 = value1->data[0].v_pointer;
  GArray *array2 = value2->data[0].v_pointer;
  GValue *v1;
  GValue *v2;
  gint len, to_remove;
  guint8 *removed;

  /* get length and do initial length check. */
  len = array1->len;
  if (len != array2->len)

  /* place to mark removed value indices of array2 */
  removed = g_newa (guint8, len);
  memset (removed, 0, len);
  to_remove = len;

  /* loop over array1, all items should be in array2. When we find an
   * item in array2, remove it from array2 by marking it as removed */
  for (i = 0; i < len; i++) {
    v1 = &g_array_index (array1, GValue, i);
    for (j = 0; j < len; j++) {
      /* item is removed, we can skip it */
      if (removed[j])
      v2 = &g_array_index (array2, GValue, j);
      if (gst_value_compare (v1, v2) == GST_VALUE_EQUAL) {
        /* mark item as removed now that we found it in array2 and
         * decrement the number of remaining items in array2. */
        removed[j] = 1;
    /* item in array1 and not in array2, UNORDERED */
    if (j == len)
  /* if not all items were removed, array2 contained something not in array1 */
  if (to_remove != 0)

  /* arrays are equal */
Comment 2 Wim Taymans 2006-07-31 16:34:50 UTC
        * gst/gstvalue.c: (gst_value_compare_list):
        Fix GstValueList comparison code. Fixes #347293.

        * tests/check/gst/gstvalue.c: (GST_START_TEST):
        Check to test GstValueList comparison.