| # Copyright (C) 2018 and later: Unicode, Inc. and others. |
| # License & terms of use: http://www.unicode.org/copyright.html |
| |
| import io |
| |
| class CommentStripper(object): |
| """Removes lines starting with "//" from a file stream.""" |
| |
| def __init__(self, f): |
| self.f = f |
| self.state = 0 |
| |
| def read(self, size=-1): |
| bytes = self.f.read(size) |
| # TODO: Do we need to read more bytes if comments were stripped |
| # in order to obey the size request? |
| return "".join(self._strip_comments(bytes)) |
| |
| def _strip_comments(self, bytes): |
| for byte in bytes: |
| if self.state == 0: |
| # state 0: start of a line |
| if byte == "/": |
| self.state = 1 |
| elif byte == "\n": |
| self.state = 0 |
| yield byte |
| else: |
| self.state = 2 |
| yield byte |
| elif self.state == 1: |
| # state 1: read a single '/' |
| if byte == "/": |
| self.state = 3 |
| elif byte == "\n": |
| self.state = 0 |
| yield "/" # the one that was skipped |
| yield "\n" |
| else: |
| self.state = 2 |
| yield "/" # the one that was skipped |
| yield byte |
| elif self.state == 2: |
| # state 2: middle of a line, no comment |
| if byte == "\n": |
| self.state = 0 |
| yield byte |
| elif self.state == 3: |
| # state 3: inside a comment |
| if byte == "\n": |
| self.state = 0 |
