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- #
- # This file is part of pyasn1 software.
- #
- # Copyright (c) 2005-2020, Ilya Etingof <etingof@gmail.com>
- # License: https://pyasn1.readthedocs.io/en/latest/license.html
- #
- import sys
- import platform
-
- from pyasn1.compat.octets import oct2int, null, ensureString
-
-
- implementation = platform.python_implementation()
-
- if sys.version_info[0] < 3:
- from binascii import a2b_hex, b2a_hex
-
- def from_bytes(octets, signed=False):
- if not octets:
- return 0
-
- value = long(b2a_hex(ensureString(octets)), 16)
-
- if signed and oct2int(octets[0]) & 0x80:
- return value - (1 << len(octets) * 8)
-
- return value
-
- def to_bytes(value, signed=False, length=0):
- if value < 0:
- if signed:
- bits = bitLength(value)
-
- # two's complement form
- maxValue = 1 << bits
- valueToEncode = (value + maxValue) % maxValue
-
- else:
- raise OverflowError('can\'t convert negative int to unsigned')
- elif value == 0 and length == 0:
- return null
- else:
- bits = 0
- valueToEncode = value
-
- hexValue = hex(valueToEncode)[2:]
- if hexValue.endswith('L'):
- hexValue = hexValue[:-1]
-
- if len(hexValue) & 1:
- hexValue = '0' + hexValue
-
- # padding may be needed for two's complement encoding
- if value != valueToEncode or length:
- hexLength = len(hexValue) * 4
-
- padLength = max(length, bits)
-
- if padLength > hexLength:
- hexValue = '00' * ((padLength - hexLength - 1) // 8 + 1) + hexValue
- elif length and hexLength - length > 7:
- raise OverflowError('int too big to convert')
-
- firstOctet = int(hexValue[:2], 16)
-
- if signed:
- if firstOctet & 0x80:
- if value >= 0:
- hexValue = '00' + hexValue
- elif value < 0:
- hexValue = 'ff' + hexValue
-
- octets_value = a2b_hex(hexValue)
-
- return octets_value
-
- def bitLength(number):
- # bits in unsigned number
- hexValue = hex(abs(number))
- bits = len(hexValue) - 2
- if hexValue.endswith('L'):
- bits -= 1
- if bits & 1:
- bits += 1
- bits *= 4
- # TODO: strip lhs zeros
- return bits
-
- else:
-
- def from_bytes(octets, signed=False):
- return int.from_bytes(bytes(octets), 'big', signed=signed)
-
- def to_bytes(value, signed=False, length=0):
- length = max(value.bit_length(), length)
-
- if signed and length % 8 == 0:
- length += 1
-
- return value.to_bytes(length // 8 + (length % 8 and 1 or 0), 'big', signed=signed)
-
- def bitLength(number):
- return int(number).bit_length()
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