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111 lines
2.9 KiB
111 lines
2.9 KiB
#
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# This file is part of pyasn1 software.
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#
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# Copyright (c) 2005-2019, Ilya Etingof <etingof@gmail.com>
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# License: http://snmplabs.com/pyasn1/license.html
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#
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import sys
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try:
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import platform
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implementation = platform.python_implementation()
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except (ImportError, AttributeError):
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implementation = 'CPython'
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from pyasn1.compat.octets import oct2int, null, ensureString
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if sys.version_info[0:2] < (3, 2) or implementation != 'CPython':
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from binascii import a2b_hex, b2a_hex
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if sys.version_info[0] > 2:
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long = int
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def from_bytes(octets, signed=False):
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if not octets:
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return 0
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value = long(b2a_hex(ensureString(octets)), 16)
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if signed and oct2int(octets[0]) & 0x80:
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return value - (1 << len(octets) * 8)
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return value
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def to_bytes(value, signed=False, length=0):
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if value < 0:
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if signed:
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bits = bitLength(value)
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# two's complement form
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maxValue = 1 << bits
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valueToEncode = (value + maxValue) % maxValue
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else:
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raise OverflowError('can\'t convert negative int to unsigned')
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elif value == 0 and length == 0:
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return null
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else:
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bits = 0
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valueToEncode = value
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hexValue = hex(valueToEncode)[2:]
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if hexValue.endswith('L'):
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hexValue = hexValue[:-1]
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if len(hexValue) & 1:
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hexValue = '0' + hexValue
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# padding may be needed for two's complement encoding
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if value != valueToEncode or length:
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hexLength = len(hexValue) * 4
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padLength = max(length, bits)
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if padLength > hexLength:
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hexValue = '00' * ((padLength - hexLength - 1) // 8 + 1) + hexValue
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elif length and hexLength - length > 7:
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raise OverflowError('int too big to convert')
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firstOctet = int(hexValue[:2], 16)
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if signed:
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if firstOctet & 0x80:
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if value >= 0:
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hexValue = '00' + hexValue
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elif value < 0:
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hexValue = 'ff' + hexValue
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octets_value = a2b_hex(hexValue)
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return octets_value
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def bitLength(number):
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# bits in unsigned number
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hexValue = hex(abs(number))
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bits = len(hexValue) - 2
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if hexValue.endswith('L'):
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bits -= 1
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if bits & 1:
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bits += 1
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bits *= 4
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# TODO: strip lhs zeros
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return bits
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else:
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def from_bytes(octets, signed=False):
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return int.from_bytes(bytes(octets), 'big', signed=signed)
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def to_bytes(value, signed=False, length=0):
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length = max(value.bit_length(), length)
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if signed and length % 8 == 0:
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length += 1
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return value.to_bytes(length // 8 + (length % 8 and 1 or 0), 'big', signed=signed)
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def bitLength(number):
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return int(number).bit_length()
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