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https://gitlab.freedesktop.org/gstreamer/gstreamer.git
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API: Add gst_util_array_binary_search() for binary searchs on a sorted array
This will be mostly useful in all elements that have some kind of internal seek/index table. Currently almost all of them (or even all of them) are using a linear search although the used array is already sorted, wasting some CPU time without good reason. Fixes bug #573623.
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6 changed files with 216 additions and 0 deletions
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@ -2363,10 +2363,14 @@ gst_util_seqnum_compare
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gst_util_set_object_arg
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gst_util_set_value_from_string
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gst_util_get_timestamp
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GstSearchMode
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gst_util_array_binary_search
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<SUBSECTION Private>
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GST_HAVE_UNALIGNED_ACCESS
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gst_util_guint64_to_gdouble
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gst_util_gdouble_to_guint64
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GST_TYPE_SEARCH_MODE
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gst_search_mode_get_type
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</SECTION>
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<SECTION>
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@ -1073,6 +1073,7 @@ init_post (GOptionContext * context, GOptionGroup * group, gpointer data,
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g_type_class_ref (gst_uri_type_get_type ());
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g_type_class_ref (gst_parse_error_get_type ());
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g_type_class_ref (gst_parse_flags_get_type ());
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g_type_class_ref (gst_search_mode_get_type ());
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gst_structure_get_type ();
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_gst_value_initialize ();
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@ -3624,3 +3624,91 @@ gst_util_get_timestamp (void)
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return GST_TIMEVAL_TO_TIME (now);
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#endif
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}
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/**
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* gst_util_array_binary_search:
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* @array: the sorted input array
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* @num_elements: number of elements in the array
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* @element_size: size of every element in bytes
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* @search_func: function to compare two elements, @search_data will always be passed as second argument
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* @mode: search mode that should be used
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* @search_data: element that should be found
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* @user_data: data to pass to @search_func
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*
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* Searches inside @array for @search_data by using the comparison function
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* @search_func. @array must be sorted ascending.
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*
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* As @search_data is always passed as second argument to @search_func it's
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* not required that @search_data has the same type as the array elements.
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*
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* The complexity of this search function is O(log (num_elements)).
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*
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* Returns: The address of the found element or %NULL if nothing was found
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*
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* Since: 0.10.23
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*/
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gpointer
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gst_util_array_binary_search (gpointer array, guint num_elements,
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gsize element_size, GCompareDataFunc search_func, GstSearchMode mode,
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gconstpointer search_data, gpointer user_data)
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{
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glong left = 0, right = num_elements - 1, m;
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gint ret;
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guint8 *data = (guint8 *) array;
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g_return_val_if_fail (array != NULL, NULL);
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g_return_val_if_fail (element_size > 0, NULL);
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g_return_val_if_fail (search_func != NULL, NULL);
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/* 0. No elements => return NULL */
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if (num_elements == 0)
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return NULL;
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/* 1. If search_data is before the 0th element return the 0th element */
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ret = search_func (data, search_data, user_data);
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if ((ret >= 0 && mode == GST_SEARCH_MODE_AFTER) || ret == 0)
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return data;
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else if (ret > 0)
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return NULL;
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/* 2. If search_data is after the last element return the last element */
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ret =
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search_func (data + (num_elements - 1) * element_size, search_data,
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user_data);
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if ((ret <= 0 && mode == GST_SEARCH_MODE_BEFORE) || ret == 0)
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return data + (num_elements - 1) * element_size;
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else if (ret < 0)
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return NULL;
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/* 3. else binary search */
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while (TRUE) {
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m = left + (right - left) / 2;
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ret = search_func (data + m * element_size, search_data, user_data);
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if (ret == 0) {
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return data + m * element_size;
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} else if (ret < 0) {
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left = m + 1;
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} else {
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right = m - 1;
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}
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/* No exact match found */
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if (right < left) {
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if (mode == GST_SEARCH_MODE_EXACT) {
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return NULL;
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} else if (mode == GST_SEARCH_MODE_AFTER) {
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if (ret < 0)
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return (m < num_elements) ? data + (m + 1) * element_size : NULL;
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else
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return data + m * element_size;
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} else {
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if (ret < 0)
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return data + m * element_size;
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else
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return (m > 0) ? data + (m - 1) * element_size : NULL;
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}
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}
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}
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}
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@ -1134,6 +1134,24 @@ GstElement * gst_parse_bin_from_description_full (const gchar * b
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GstClockTime gst_util_get_timestamp (void);
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/**
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* GstSearchMode:
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* @GST_SEARCH_MODE_EXACT : Only search for exact matches.
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* @GST_SEARCH_MODE_BEFORE: Search for an exact match or the element just before.
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* @GST_SEARCH_MODE_AFTER : Search for an exact match or the element just after.
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*
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* The different search modes.
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*
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* Since: 0.10.23
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*/
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typedef enum {
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GST_SEARCH_MODE_EXACT = 0,
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GST_SEARCH_MODE_BEFORE,
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GST_SEARCH_MODE_AFTER
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} GstSearchMode;
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gpointer gst_util_array_binary_search (gpointer array, guint num_elements, gsize element_size, GCompareDataFunc search_func, GstSearchMode mode, gconstpointer search_data, gpointer user_data);
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G_END_DECLS
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#endif /* __GST_UTILS_H__ */
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@ -610,6 +610,108 @@ GST_START_TEST (test_set_value_from_string)
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GST_END_TEST;
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static gint
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_binary_search_compare (guint32 * a, guint32 * b)
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{
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return *a - *b;
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}
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GST_START_TEST (test_binary_search)
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{
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guint32 data[257];
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guint32 *match;
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guint32 search_element = 121 * 2;
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guint i;
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for (i = 0; i < 257; i++)
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data[i] = (i + 1) * 2;
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match =
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(guint32 *) gst_util_array_binary_search (data, 257, sizeof (guint32),
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(GCompareDataFunc) _binary_search_compare, GST_SEARCH_MODE_EXACT,
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&search_element, NULL);
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fail_unless (match != NULL);
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fail_unless_equals_int (match - data, 120);
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match =
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(guint32 *) gst_util_array_binary_search (data, 257, sizeof (guint32),
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(GCompareDataFunc) _binary_search_compare, GST_SEARCH_MODE_BEFORE,
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&search_element, NULL);
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fail_unless (match != NULL);
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fail_unless_equals_int (match - data, 120);
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match =
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(guint32 *) gst_util_array_binary_search (data, 257, sizeof (guint32),
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(GCompareDataFunc) _binary_search_compare, GST_SEARCH_MODE_AFTER,
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&search_element, NULL);
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fail_unless (match != NULL);
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fail_unless_equals_int (match - data, 120);
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search_element = 0;
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match =
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(guint32 *) gst_util_array_binary_search (data, 257, sizeof (guint32),
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(GCompareDataFunc) _binary_search_compare, GST_SEARCH_MODE_EXACT,
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&search_element, NULL);
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fail_unless (match == NULL);
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match =
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(guint32 *) gst_util_array_binary_search (data, 257, sizeof (guint32),
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(GCompareDataFunc) _binary_search_compare, GST_SEARCH_MODE_AFTER,
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&search_element, NULL);
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fail_unless (match != NULL);
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fail_unless_equals_int (match - data, 0);
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match =
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(guint32 *) gst_util_array_binary_search (data, 257, sizeof (guint32),
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(GCompareDataFunc) _binary_search_compare, GST_SEARCH_MODE_BEFORE,
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&search_element, NULL);
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fail_unless (match == NULL);
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search_element = 1000;
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match =
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(guint32 *) gst_util_array_binary_search (data, 257, sizeof (guint32),
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(GCompareDataFunc) _binary_search_compare, GST_SEARCH_MODE_EXACT,
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&search_element, NULL);
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fail_unless (match == NULL);
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match =
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(guint32 *) gst_util_array_binary_search (data, 257, sizeof (guint32),
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(GCompareDataFunc) _binary_search_compare, GST_SEARCH_MODE_AFTER,
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&search_element, NULL);
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fail_unless (match == NULL);
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match =
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(guint32 *) gst_util_array_binary_search (data, 257, sizeof (guint32),
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(GCompareDataFunc) _binary_search_compare, GST_SEARCH_MODE_BEFORE,
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&search_element, NULL);
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fail_unless (match != NULL);
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fail_unless_equals_int (match - data, 256);
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search_element = 121 * 2 - 1;
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match =
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(guint32 *) gst_util_array_binary_search (data, 257, sizeof (guint32),
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(GCompareDataFunc) _binary_search_compare, GST_SEARCH_MODE_EXACT,
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&search_element, NULL);
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fail_unless (match == NULL);
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match =
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(guint32 *) gst_util_array_binary_search (data, 257, sizeof (guint32),
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(GCompareDataFunc) _binary_search_compare, GST_SEARCH_MODE_AFTER,
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&search_element, NULL);
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fail_unless (match != NULL);
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fail_unless_equals_int (match - data, 120);
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match =
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(guint32 *) gst_util_array_binary_search (data, 257, sizeof (guint32),
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(GCompareDataFunc) _binary_search_compare, GST_SEARCH_MODE_BEFORE,
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&search_element, NULL);
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fail_unless (match != NULL);
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fail_unless_equals_int (match - data, 119);
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}
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GST_END_TEST;
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static Suite *
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gst_utils_suite (void)
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{
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@ -630,6 +732,7 @@ gst_utils_suite (void)
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tcase_add_test (tc_chain, test_element_found_tags);
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tcase_add_test (tc_chain, test_element_unlink);
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tcase_add_test (tc_chain, test_set_value_from_string);
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tcase_add_test (tc_chain, test_binary_search);
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return s;
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}
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@ -784,6 +784,7 @@ EXPORTS
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gst_registry_xml_write_cache
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gst_resource_error_get_type
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gst_resource_error_quark
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gst_search_mode_get_type
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gst_seek_flags_get_type
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gst_seek_type_get_type
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gst_segment_clip
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@ -970,6 +971,7 @@ EXPORTS
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gst_uri_protocol_is_supported
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gst_uri_protocol_is_valid
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gst_uri_type_get_type
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gst_util_array_binary_search
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gst_util_dump_mem
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gst_util_gdouble_to_guint64
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gst_util_get_timestamp
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