diskimage-builder/diskimage_builder/block_device/utils.py

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# Copyright 2016 Andreas Florath (andreas@florath.net)
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import re
SIZE_UNIT_SPECS = [
["TiB", 1024**4],
["GiB", 1024**3],
["MiB", 1024**2],
["KiB", 1024**1],
["TB", 1000**4],
["GB", 1000**3],
["MB", 1000**2],
["KB", 1000**1],
["T", 1000**4],
["G", 1000**3],
["M", 1000**2],
["K", 1000**1],
["B", 1],
["", 1], # No unit -> size is given in bytes
]
# Basic RE to check and split floats (without exponent)
# and a given unit specification (which must be non-numerical).
size_unit_spec_re = re.compile("^([\d\.]*) ?([a-zA-Z0-9_]*)$")
def _split_size_unit_spec(size_unit_spec):
"""Helper function to split unit specification into parts.
The first part is the numeric part - the second one is the unit.
"""
match = size_unit_spec_re.match(size_unit_spec)
if match is None:
raise RuntimeError("Invalid size unit spec [%s]" % size_unit_spec)
return match.group(1), match.group(2)
def _get_unit_factor(unit_str):
"""Helper function to get the unit factor.
The given unit_str needs to be a string of the
SIZE_UNIT_SPECS table.
If the unit is not found, a runtime error is raised.
"""
for spec_key, spec_value in SIZE_UNIT_SPECS:
if unit_str == spec_key:
return spec_value
raise RuntimeError("unit_str [%s] not known" % unit_str)
def parse_abs_size_spec(size_spec):
size_cnt_str, size_unit_str = _split_size_unit_spec(size_spec)
unit_factor = _get_unit_factor(size_unit_str)
return int(unit_factor * (
float(size_cnt_str) if len(size_cnt_str) > 0 else 1))
def parse_rel_size_spec(size_spec, abs_size):
"""Parses size specifications - can be relative like 50%
In addition to the absolute parsing also a relative
parsing is done. If the size specification ends in '%',
then the relative size of the given 'abs_size' is returned.
"""
if size_spec[-1] == '%':
percent = float(size_spec[:-1])
return True, int(abs_size * percent / 100.0)
return False, parse_abs_size_spec(size_spec)