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| # Copyright 2016 Grist Labs, Inc. | |
| # | |
| # Licensed under the Apache License, Version 2.0 (the "License"); | |
| # you may not use this file except in compliance with the License. | |
| # You may obtain a copy of the License at | |
| # | |
| # http://www.apache.org/licenses/LICENSE-2.0 | |
| # | |
| # Unless required by applicable law or agreed to in writing, software | |
| # distributed under the License is distributed on an "AS IS" BASIS, | |
| # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
| # See the License for the specific language governing permissions and | |
| # limitations under the License. | |
| import bisect | |
| import re | |
| from typing import Dict, List, Tuple | |
| _line_start_re = re.compile(r'^', re.M) | |
| class LineNumbers(object): | |
| """ | |
| Class to convert between character offsets in a text string, and pairs (line, column) of 1-based | |
| line and 0-based column numbers, as used by tokens and AST nodes. | |
| This class expects unicode for input and stores positions in unicode. But it supports | |
| translating to and from utf8 offsets, which are used by ast parsing. | |
| """ | |
| def __init__(self, text): | |
| # type: (str) -> None | |
| # A list of character offsets of each line's first character. | |
| self._line_offsets = [m.start(0) for m in _line_start_re.finditer(text)] | |
| self._text = text | |
| self._text_len = len(text) | |
| self._utf8_offset_cache = {} # type: Dict[int, List[int]] # maps line num to list of char offset for each byte in line | |
| def from_utf8_col(self, line, utf8_column): | |
| # type: (int, int) -> int | |
| """ | |
| Given a 1-based line number and 0-based utf8 column, returns a 0-based unicode column. | |
| """ | |
| offsets = self._utf8_offset_cache.get(line) | |
| if offsets is None: | |
| end_offset = self._line_offsets[line] if line < len(self._line_offsets) else self._text_len | |
| line_text = self._text[self._line_offsets[line - 1] : end_offset] | |
| offsets = [i for i,c in enumerate(line_text) for byte in c.encode('utf8')] | |
| offsets.append(len(line_text)) | |
| self._utf8_offset_cache[line] = offsets | |
| return offsets[max(0, min(len(offsets)-1, utf8_column))] | |
| def line_to_offset(self, line, column): | |
| # type: (int, int) -> int | |
| """ | |
| Converts 1-based line number and 0-based column to 0-based character offset into text. | |
| """ | |
| line -= 1 | |
| if line >= len(self._line_offsets): | |
| return self._text_len | |
| elif line < 0: | |
| return 0 | |
| else: | |
| return min(self._line_offsets[line] + max(0, column), self._text_len) | |
| def offset_to_line(self, offset): | |
| # type: (int) -> Tuple[int, int] | |
| """ | |
| Converts 0-based character offset to pair (line, col) of 1-based line and 0-based column | |
| numbers. | |
| """ | |
| offset = max(0, min(self._text_len, offset)) | |
| line_index = bisect.bisect_right(self._line_offsets, offset) - 1 | |
| return (line_index + 1, offset - self._line_offsets[line_index]) | |