root / lib / utils / algo.py @ 5d94c034
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# Copyright (C) 2006, 2007, 2010, 2011 Google Inc.
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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 as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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"""Utility functions with algorithms.
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"""
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import re |
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import time |
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import itertools |
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from ganeti import compat |
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from ganeti.utils import text |
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_SORTER_GROUPS = 8
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_SORTER_RE = re.compile("^%s(.*)$" % (_SORTER_GROUPS * "(\D+|\d+)?")) |
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def UniqueSequence(seq): |
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"""Returns a list with unique elements.
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Element order is preserved.
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@type seq: sequence
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@param seq: the sequence with the source elements
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@rtype: list
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@return: list of unique elements from seq
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"""
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seen = set()
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return [i for i in seq if i not in seen and not seen.add(i)] |
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def JoinDisjointDicts(dict_a, dict_b): |
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"""Joins dictionaries with no conflicting keys.
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Enforces the constraint that the two key sets must be disjoint, and then
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merges the two dictionaries in a new dictionary that is returned to the
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caller.
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@type dict_a: dict
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@param dict_a: the first dictionary
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@type dict_b: dict
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@param dict_b: the second dictionary
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@rtype: dict
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@return: a new dictionary containing all the key/value pairs contained in the
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two dictionaries.
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"""
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assert not (set(dict_a) & set(dict_b)), ("Duplicate keys found while joining" |
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" %s and %s" % (dict_a, dict_b))
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result = dict_a.copy() |
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result.update(dict_b) |
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return result
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def FindDuplicates(seq): |
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"""Identifies duplicates in a list.
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Does not preserve element order.
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@type seq: sequence
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@param seq: Sequence with source elements
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@rtype: list
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@return: List of duplicate elements from seq
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"""
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dup = set()
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seen = set()
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for item in seq: |
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if item in seen: |
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dup.add(item) |
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else:
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seen.add(item) |
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return list(dup) |
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def _NiceSortTryInt(val): |
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"""Attempts to convert a string to an integer.
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"""
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if val and val.isdigit(): |
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return int(val) |
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else:
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return val
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def NiceSortKey(value): |
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"""Extract key for sorting.
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"""
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return [_NiceSortTryInt(grp)
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for grp in _SORTER_RE.match(value).groups()] |
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def NiceSort(values, key=None): |
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"""Sort a list of strings based on digit and non-digit groupings.
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Given a list of names C{['a1', 'a10', 'a11', 'a2']} this function
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will sort the list in the logical order C{['a1', 'a2', 'a10',
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'a11']}.
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The sort algorithm breaks each name in groups of either only-digits
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or no-digits. Only the first eight such groups are considered, and
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after that we just use what's left of the string.
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@type values: list
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@param values: the names to be sorted
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@type key: callable or None
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@param key: function of one argument to extract a comparison key from each
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list element, must return string
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@rtype: list
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@return: a copy of the name list sorted with our algorithm
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"""
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if key is None: |
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keyfunc = NiceSortKey |
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else:
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keyfunc = lambda value: NiceSortKey(key(value))
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return sorted(values, key=keyfunc) |
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def InvertDict(dict_in): |
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"""Inverts the key/value mapping of a dict.
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@param dict_in: The dict to invert
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@return: the inverted dict
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"""
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return dict(zip(dict_in.values(), dict_in.keys())) |
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def InsertAtPos(src, pos, other): |
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"""Inserts C{other} at given C{pos} into C{src}.
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@note: This function does not modify C{src} in place but returns a new copy
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@type src: list
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@param src: The source list in which we want insert elements
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@type pos: int
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@param pos: The position where we want to start insert C{other}
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@type other: list
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@param other: The other list to insert into C{src}
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@return: A copy of C{src} with C{other} inserted at C{pos}
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"""
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new = src[:pos] |
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new.extend(other) |
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new.extend(src[pos:]) |
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return new
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def SequenceToDict(seq, key=compat.fst): |
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"""Converts a sequence to a dictionary with duplicate detection.
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@type seq: sequen
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@param seq: Input sequence
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@type key: callable
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@param key: Function for retrieving dictionary key from sequence element
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@rtype: dict
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"""
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keys = map(key, seq)
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duplicates = FindDuplicates(keys) |
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if duplicates:
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raise ValueError("Duplicate keys found: %s" % text.CommaJoin(duplicates)) |
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assert len(keys) == len(seq) |
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return dict(zip(keys, seq)) |
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def _MakeFlatToDict(data): |
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"""Helper function for C{FlatToDict}.
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This function is recursively called
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@param data: The input data as described in C{FlatToDict}, already splitted
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@returns: The so far converted dict
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"""
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if not compat.fst(compat.fst(data)): |
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assert len(data) == 1, \ |
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"not bottom most element, found %d elements, expected 1" % len(data) |
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return compat.snd(compat.fst(data))
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keyfn = lambda e: compat.fst(e).pop(0) |
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return dict([(k, _MakeFlatToDict(list(g))) |
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for (k, g) in itertools.groupby(sorted(data), keyfn)]) |
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def FlatToDict(data, field_sep="/"): |
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"""Converts a flat structure to a fully fledged dict.
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It accept a list of tuples in the form::
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[
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("foo/bar", {"key1": "data1", "key2": "data2"}),
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("foo/baz", {"key3" :"data3" }),
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]
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where the first element is the key separated by C{field_sep}.
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This would then return::
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{
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"foo": {
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"bar": {"key1": "data1", "key2": "data2"},
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"baz": {"key3" :"data3" },
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},
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}
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@type data: list of tuple
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@param data: Input list to convert
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@type field_sep: str
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@param field_sep: The separator for the first field of the tuple
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@returns: A dict based on the input list
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"""
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return _MakeFlatToDict([(keys.split(field_sep), value)
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for (keys, value) in data]) |
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class RunningTimeout(object): |
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"""Class to calculate remaining timeout when doing several operations.
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"""
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__slots__ = [ |
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"_allow_negative",
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"_start_time",
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"_time_fn",
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"_timeout",
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] |
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def __init__(self, timeout, allow_negative, _time_fn=time.time): |
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"""Initializes this class.
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@type timeout: float
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@param timeout: Timeout duration
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@type allow_negative: bool
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@param allow_negative: Whether to return values below zero
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@param _time_fn: Time function for unittests
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"""
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object.__init__(self) |
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if timeout is not None and timeout < 0.0: |
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raise ValueError("Timeout must not be negative") |
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self._timeout = timeout
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self._allow_negative = allow_negative
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self._time_fn = _time_fn
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self._start_time = None |
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def Remaining(self): |
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"""Returns the remaining timeout.
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"""
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if self._timeout is None: |
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return None |
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# Get start time on first calculation
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if self._start_time is None: |
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self._start_time = self._time_fn() |
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# Calculate remaining time
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remaining_timeout = self._start_time + self._timeout - self._time_fn() |
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if not self._allow_negative: |
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# Ensure timeout is always >= 0
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return max(0.0, remaining_timeout) |
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return remaining_timeout
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