cos / mirrors / cros / chromiumos / chromite / refs/heads/stabilize-12428.B / . / lib / iter_utils.py

# -*- coding: utf-8 -*- | |

# Copyright 2016 The Chromium OS Authors. All rights reserved. | |

# Use of this source code is governed by a BSD-style license that can be | |

# found in the LICENSE file. | |

"""Utility functions for dealing with iterators.""" | |

from __future__ import print_function | |

import itertools | |

def IntersectIntervals(intervals): | |

"""Gets the intersection of a set of intervals. | |

Args: | |

intervals: A list of interval groups, where each interval group is itself | |

a list of (start, stop) tuples (ordered by start time and | |

non-overlapping). | |

Returns: | |

An interval group, as a list of (start, stop) tuples, corresponding to the | |

intersection (i.e. overlap) of the given |intervals|. | |

""" | |

if not intervals: | |

return [] | |

intersection = [] | |

indices = [0] * len(intervals) | |

lengths = [len(i) for i in intervals] | |

while all(i < l for i, l in zip(indices, lengths)): | |

current_intervals = [intervals[i][j] for (i, j) in | |

zip(itertools.count(), indices)] | |

start = max([s[0] for s in current_intervals]) | |

end, end_index = min([(e[1], i) for e, i in | |

zip(current_intervals, itertools.count())]) | |

if start < end: | |

intersection.append((start, end)) | |

indices[end_index] += 1 | |

return intersection | |

def SplitToChunks(input_iter, chunk_size): | |

"""Split an iterator into chunks. | |

This function walks 1 entire chunk of |input_iter| at a time, but does not | |

walk past that chunk until necessary. | |

Examples: | |

list(SplitToChunks([1, 2, 3, 4, 5], 3)) -> [[1, 2, 3], [4, 5] | |

Args: | |

input_iter: iterable or generator to be split into chunks | |

chunk_size: the maximum size of each chunk | |

Returns: | |

An iterable of chunks, where each chunk is of maximum size chunk_size. | |

""" | |

count = 0 | |

l = [] | |

for item in input_iter: | |

l.append(item) | |

count += 1 | |

if count == chunk_size: | |

yield l | |

l = [] | |

count = 0 | |

if l: | |

yield l |