[GitHub] [beam] tvalentyn commented on a change in pull request #15901: BEAM-13189 Python TextIO: add escapechar feature.

[GitBox <gi...@apache.org>]

tvalentyn commented on a change in pull request #15901:
URL: https://github.com/apache/beam/pull/15901#discussion_r745961276



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File path: sdks/python/apache_beam/io/textio.py
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@@ -362,6 +391,15 @@ def _is_self_overlapping(delimiter):
         return True
     return False
 
+  def _is_escaped(self, read_buffer, position):
+    # Returns True if byte at position is preceded with an odd number
+    # of escapechar bytes or False if preceded by 0 or even escapes
+    # (the even number means that all the escapes are escaped themselves).
+    for current_pos in reversed(range(-1, position)):
+      if read_buffer.data[current_pos:current_pos + 1] != self._escapechar:

Review comment:
       This logic is a little tricky to follow:
   1. why do we go to -1 ?
   2. can we compare a single byte at a position instead of a 1-character range?
   
   why not to count `preceding_escape_chars` in a loop and then  `return preceding_escape_chars % 2 == 1` ?




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