blob: 2f1340635f0bc0a6e3d24b2198df8ebee268d0f5 [file] [log] [blame]
# -*- coding: utf-8 -*-
# Copyright 2018 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.
"""A collection of classes/functions to manipulate strings."""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import bisect
class StringTooLongError(Exception):
"""Raised when string is too long to manipulate."""
def join_longest_with_length_limit(string_list, length_limit, separator='',
"""Join strings to meet length limit and yield results.
Join strings from |string_list| using |separator| and yield the results.
Each result string should be as long as possible while still shorter than
|length_limit|. In other words, this function yields minimum number of
result strings.
An error will be raised when any string in |string_list| is longer than
|length_limit| because the result string joined must be longer than
|length_limit| in any case.
@param string_list: A list of strings to be joined.
@param length_limit: The maximum length of the result string.
@param separator: The separator to join strings.
@param do_join: join the result list to string if True, else just return the
result list.
@yield The result string.
@throws StringTooLongError when any string in |string_list| is longer than
# The basic idea is, always select longest string which shorter than length
# limit, then update the limit with subtracting the length of selected
# string plus separator. Repeat the process until no more strings shorter
# than the updated limit. Then yield the result and start next loop.
string_list = sorted(string_list, key=len)
# The length of longest string should shorter than the limit.
if len(string_list[-1]) > length_limit:
raise StringTooLongError('At least one string is longer than length '
'limit: %s' % length_limit)
length_list = [len(s) for s in string_list]
len_sep = len(separator)
length_limit += len_sep
# Call str.join directly when possible.
if sum(length_list) + len_sep * len(string_list) <= length_limit:
yield separator.join(string_list) if do_join else string_list
result = []
new_length_limit = length_limit
while string_list:
index = bisect.bisect_right(length_list,
new_length_limit - len_sep) - 1
if index < 0: # All available strings are longer than the limit.
yield separator.join(result) if do_join else result
result = []
new_length_limit = length_limit
new_length_limit -= length_list.pop(index) + len_sep
if result:
yield separator.join(result) if do_join else result