101 lines
1.9 KiB
Python
101 lines
1.9 KiB
Python
#!/usr/bin/env python3
|
|
#
|
|
# bignum.py
|
|
#
|
|
# This file is copied from python-bitcoinlib.
|
|
#
|
|
# Distributed under the MIT software license, see the accompanying
|
|
# file COPYING or http://www.opensource.org/licenses/mit-license.php.
|
|
#
|
|
|
|
"""Bignum routines"""
|
|
|
|
|
|
import struct
|
|
|
|
|
|
# generic big endian MPI format
|
|
|
|
def bn_bytes(v, have_ext=False):
|
|
ext = 0
|
|
if have_ext:
|
|
ext = 1
|
|
return ((v.bit_length()+7)//8) + ext
|
|
|
|
def bn2bin(v):
|
|
s = bytearray()
|
|
i = bn_bytes(v)
|
|
while i > 0:
|
|
s.append((v >> ((i-1) * 8)) & 0xff)
|
|
i -= 1
|
|
return s
|
|
|
|
def bin2bn(s):
|
|
l = 0
|
|
for ch in s:
|
|
l = (l << 8) | ch
|
|
return l
|
|
|
|
def bn2mpi(v):
|
|
have_ext = False
|
|
if v.bit_length() > 0:
|
|
have_ext = (v.bit_length() & 0x07) == 0
|
|
|
|
neg = False
|
|
if v < 0:
|
|
neg = True
|
|
v = -v
|
|
|
|
s = struct.pack(b">I", bn_bytes(v, have_ext))
|
|
ext = bytearray()
|
|
if have_ext:
|
|
ext.append(0)
|
|
v_bin = bn2bin(v)
|
|
if neg:
|
|
if have_ext:
|
|
ext[0] |= 0x80
|
|
else:
|
|
v_bin[0] |= 0x80
|
|
return s + ext + v_bin
|
|
|
|
def mpi2bn(s):
|
|
if len(s) < 4:
|
|
return None
|
|
s_size = bytes(s[:4])
|
|
v_len = struct.unpack(b">I", s_size)[0]
|
|
if len(s) != (v_len + 4):
|
|
return None
|
|
if v_len == 0:
|
|
return 0
|
|
|
|
v_str = bytearray(s[4:])
|
|
neg = False
|
|
i = v_str[0]
|
|
if i & 0x80:
|
|
neg = True
|
|
i &= ~0x80
|
|
v_str[0] = i
|
|
|
|
v = bin2bn(v_str)
|
|
|
|
if neg:
|
|
return -v
|
|
return v
|
|
|
|
# bitcoin-specific little endian format, with implicit size
|
|
def mpi2vch(s):
|
|
r = s[4:] # strip size
|
|
r = r[::-1] # reverse string, converting BE->LE
|
|
return r
|
|
|
|
def bn2vch(v):
|
|
return bytes(mpi2vch(bn2mpi(v)))
|
|
|
|
def vch2mpi(s):
|
|
r = struct.pack(b">I", len(s)) # size
|
|
r += s[::-1] # reverse string, converting LE->BE
|
|
return r
|
|
|
|
def vch2bn(s):
|
|
return mpi2bn(vch2mpi(s))
|
|
|