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