161 lines
4.0 KiB
Python
161 lines
4.0 KiB
Python
# -*- coding: utf-8 -*-
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#
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# Copyright 2011 Sybren A. Stüvel <sybren@stuvel.eu>
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Python compatibility wrappers."""
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from __future__ import absolute_import
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import sys
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from struct import pack
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try:
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MAX_INT = sys.maxsize
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except AttributeError:
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MAX_INT = sys.maxint
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MAX_INT64 = (1 << 63) - 1
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MAX_INT32 = (1 << 31) - 1
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MAX_INT16 = (1 << 15) - 1
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# Determine the word size of the processor.
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if MAX_INT == MAX_INT64:
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# 64-bit processor.
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MACHINE_WORD_SIZE = 64
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elif MAX_INT == MAX_INT32:
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# 32-bit processor.
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MACHINE_WORD_SIZE = 32
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else:
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# Else we just assume 64-bit processor keeping up with modern times.
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MACHINE_WORD_SIZE = 64
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try:
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# < Python3
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unicode_type = unicode
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have_python3 = False
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except NameError:
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# Python3.
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unicode_type = str
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have_python3 = True
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# Fake byte literals.
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if str is unicode_type:
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def byte_literal(s):
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return s.encode('latin1')
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else:
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def byte_literal(s):
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return s
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# ``long`` is no more. Do type detection using this instead.
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try:
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integer_types = (int, long)
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except NameError:
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integer_types = (int,)
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b = byte_literal
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try:
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# Python 2.6 or higher.
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bytes_type = bytes
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except NameError:
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# Python 2.5
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bytes_type = str
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# To avoid calling b() multiple times in tight loops.
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ZERO_BYTE = b('\x00')
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EMPTY_BYTE = b('')
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def is_bytes(obj):
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"""
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Determines whether the given value is a byte string.
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:param obj:
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The value to test.
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:returns:
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``True`` if ``value`` is a byte string; ``False`` otherwise.
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"""
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return isinstance(obj, bytes_type)
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def is_integer(obj):
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"""
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Determines whether the given value is an integer.
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:param obj:
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The value to test.
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:returns:
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``True`` if ``value`` is an integer; ``False`` otherwise.
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"""
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return isinstance(obj, integer_types)
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def byte(num):
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"""
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Converts a number between 0 and 255 (both inclusive) to a base-256 (byte)
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representation.
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Use it as a replacement for ``chr`` where you are expecting a byte
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because this will work on all current versions of Python::
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:param num:
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An unsigned integer between 0 and 255 (both inclusive).
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:returns:
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A single byte.
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"""
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return pack("B", num)
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def get_word_alignment(num, force_arch=64,
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_machine_word_size=MACHINE_WORD_SIZE):
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"""
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Returns alignment details for the given number based on the platform
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Python is running on.
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:param num:
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Unsigned integral number.
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:param force_arch:
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If you don't want to use 64-bit unsigned chunks, set this to
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anything other than 64. 32-bit chunks will be preferred then.
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Default 64 will be used when on a 64-bit machine.
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:param _machine_word_size:
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(Internal) The machine word size used for alignment.
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:returns:
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4-tuple::
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(word_bits, word_bytes,
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max_uint, packing_format_type)
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"""
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max_uint64 = 0xffffffffffffffff
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max_uint32 = 0xffffffff
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max_uint16 = 0xffff
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max_uint8 = 0xff
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if force_arch == 64 and _machine_word_size >= 64 and num > max_uint32:
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# 64-bit unsigned integer.
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return 64, 8, max_uint64, "Q"
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elif num > max_uint16:
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# 32-bit unsigned integer
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return 32, 4, max_uint32, "L"
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elif num > max_uint8:
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# 16-bit unsigned integer.
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return 16, 2, max_uint16, "H"
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else:
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# 8-bit unsigned integer.
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return 8, 1, max_uint8, "B"
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