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85 lines
2.2 KiB
85 lines
2.2 KiB
# -*- coding: utf-8 -*-
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# Copyright 2017 Mike Fährmann
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License version 2 as
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# published by the Free Software Foundation.
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"""Utility functions"""
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import sys
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from . import exception
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def parse_range(rangespec):
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"""Parse an integer range string and return the resulting ranges
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Examples
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parse_range("-2,4,6-8,10-") -> [(1,2), (4,4), (6,8), (10,INTMAX)]
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parse_range(" - 3 , 4- 4, 2-6") -> [(1,3), (4,4), (2,6)]
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"""
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ranges = []
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for group in rangespec.split(","):
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parts = group.split("-", maxsplit=1)
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try:
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if len(parts) == 1:
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beg = int(parts[0])
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end = beg
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else:
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beg = int(parts[0]) if parts[0].strip() else 1
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end = int(parts[1]) if parts[1].strip() else sys.maxsize
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ranges.append((beg, end) if beg <= end else (end, beg))
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except ValueError:
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pass
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return ranges
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def optimize_range(ranges):
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"""Simplify/Combine a parsed list of ranges
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Examples
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optimize_range([(2,4), (4,6), (5,8)]) -> [(2,8)]
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optimize_range([(1,1), (2,2), (3,6), (8,9))]) -> [(1,6), (8-9)]
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"""
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if len(ranges) <= 1:
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return ranges
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ranges.sort()
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riter = iter(ranges)
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result = []
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beg, end = next(riter)
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for lower, upper in riter:
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if lower > end+1:
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result.append((beg, end))
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beg, end = lower, upper
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elif upper > end:
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end = upper
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result.append((beg, end))
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return result
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class RangePredicate():
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"""Predicate; is True if the current index is in the given range"""
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def __init__(self, rangespec):
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self.ranges = optimize_range(parse_range(rangespec))
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self.index = 0
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if self.ranges:
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self.lower, self.upper = self.ranges[0][0], self.ranges[-1][1]
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else:
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self.lower, self.upper = 0, 0
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def __bool__(self):
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self.index += 1
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if self.index > self.upper:
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raise exception.StopExtraction()
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for lower, upper in self.ranges:
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if lower <= self.index <= upper:
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return True
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return False
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