Data: fix up out-of-order log lines

This is important because we rely on monotonically increasing timestamps for
binary searches in various places.

Overhead for an already sorted file with 1 million lines is less than 5%.

debug-viewer/GstDebugViewer/Data.py

@@ -183,6 +183,75 @@ class Producer (object):
         for consumer in self.consumers:
             consumer.handle_load_finished ()
 
+class SortHelper (object):
+
+    def __init__ (self, fileobj, offsets):
+
+        self._gen = self.__gen (fileobj, offsets)
+        self._gen.next ()
+
+        # Override in the instance, for performance (this gets called in an
+        # inner loop):
+        self.find_insert_position = self._gen.send
+
+    @staticmethod
+    def find_insert_position (insert_time_string):
+
+        # Stub for documentary purposes.
+
+        pass
+
+    @staticmethod
+    def __gen (fileobj, offsets):
+
+        from math import floor
+        tell = fileobj.tell
+        seek = fileobj.seek
+        read = fileobj.read
+        time_len = len (time_args (0))
+
+        # We remember the previous insertion point. This gives a nice speed up
+        # for larger bubbles which are already sorted. TODO: In practice, log
+        # lines only get out of order across threads. Need to check if it pays
+        # to parse the thread here and maintain multiple insertion points for
+        # heavily interleaved parts of the log.
+        pos = 0
+        pos_time_string = ""
+
+        insert_pos = None
+        while True:
+            insert_time_string = (yield insert_pos)
+
+            save_offset = tell ()
+
+            if pos_time_string <= insert_time_string:
+                lo = pos
+                hi = len (offsets)
+            else:
+                lo = 0
+                hi = pos
+
+            # This is a bisection search, except we don't cut the range in the
+            # middle each time, but at the 90th percentile. This is because
+            # logs are "mostly sorted", so the insertion point is much more
+            # likely to be at the end anyways:
+            while lo < hi:
+                mid = int (floor (lo * 0.1 + hi * 0.9))
+                seek (offsets[mid])
+                mid_time_string = read (time_len)
+                if insert_time_string < mid_time_string:
+                    hi = mid
+                else:
+                    lo = mid + 1
+            pos = lo
+            # Caller will replace row at pos with the new one, so this is
+            # correct:
+            pos_time_string = insert_time_string
+
+            insert_pos = pos
+
+            seek (save_offset)
+
 class LineCache (Producer):
 
     _lines_per_iteration = 50000
@@ -233,17 +302,33 @@ class LineCache (Producer):
 
         self.__fileobj.seek (0)
         limit = self._lines_per_iteration
+        last_line = ""
         i = 0
+        sort_helper = SortHelper (self.__fileobj, offsets)
+        find_insert_position = sort_helper.find_insert_position
         while True:
             offset = tell ()
             line = readline ()
             if not line:
                 break
+            # if line[18] == "\x1b":
+            #     line = strip_escape (line)
             match = rexp_match (line)
             if match is None:
                 continue
-            levels_append (dict_levels_get (match.group (1), debug_level_none))
-            offsets_append (offset)
+
+            # Timestamp is in the very beginning of the row, and can be sorted
+            # by lexical comparison. That's why we don't bother parsing the
+            # time to integer. We also don't have to take a substring here,
+            # which would be a useless memcpy.
+            if line >= last_line:
+                levels_append (dict_levels_get (match.group (1), debug_level_none))
+                offsets_append (offset)
+                last_line = line
+            else:
+                pos = find_insert_position (line)
+                levels.insert (pos, dict_levels_get (match.group (1), debug_level_none))
+                offsets.insert (pos, offset)
             i += 1
             if i >= limit:
                 i = 0