def match_link_dest(cls, string, offset):
offset = shift_whitespace(string, offset + 1)
if offset == len(string):
return None
if string[offset] == '<':
escaped = False
for i, c in enumerate(string[offset + 1:], start=offset + 1):
if c == '\\' and not escaped:
escaped = True
elif c == ' ' or c == '\n' or (c == '<' and not escaped):
return None
elif c == '>' and not escaped:
return offset, i + 1, string[offset + 1:i]
elif escaped:
escaped = False
return None
else:
escaped = False
count = 0
for i, c in enumerate(string[offset:], start=offset):
if c == '\\' and not escaped:
escaped = True
elif c in whitespace:
break
elif not escaped:
if c == '(':
count += 1
elif c == ')':
count -= 1
elif is_control_char(c):
return None
elif escaped:
escaped = False
if count != 0:
return None
return offset, i, string[offset:i]
def test_is_control_char(self):
char = chr(0)
self.assertTrue(is_control_char(char))
self.assertFalse(is_control_char('a'))