111 lines
2.9 KiB
Python
111 lines
2.9 KiB
Python
#
|
|
# This file is part of pyasn1 software.
|
|
#
|
|
# Copyright (c) 2005-2018, Ilya Etingof <etingof@gmail.com>
|
|
# License: http://snmplabs.com/pyasn1/license.html
|
|
#
|
|
import sys
|
|
|
|
try:
|
|
import platform
|
|
|
|
implementation = platform.python_implementation()
|
|
|
|
except (ImportError, AttributeError):
|
|
implementation = 'CPython'
|
|
|
|
from pyasn1.compat.octets import oct2int, null, ensureString
|
|
|
|
if sys.version_info[0:2] < (3, 2) or implementation != 'CPython':
|
|
from binascii import a2b_hex, b2a_hex
|
|
|
|
if sys.version_info[0] > 2:
|
|
long = int
|
|
|
|
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()
|