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'''Base58 encoding
Implementations of Base58 and Base58Check endcodings that are compatible
with the bitcoin network.
'''
# This module is based upon base58 snippets found scattered over many bitcoin
# tools written in python. From what I gather the original source is from a
# forum post by Gavin Andresen, so direct your praise to him.
# This module adds shiny packaging and support for python3.
from hashlib import sha256
__version__ = '1.0.3'
# 58 character alphabet used
alphabet = b'123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
if bytes == str: # python2
iseq, bseq, buffer = (
lambda s: map(ord, s),
lambda s: ''.join(map(chr, s)),
lambda s: s,
)
else: # python3
iseq, bseq, buffer = (
lambda s: s,
bytes,
lambda s: s.buffer,
)
def scrub_input(v):
if isinstance(v, str) and not isinstance(v, bytes):
v = v.encode('ascii')
if not isinstance(v, bytes):
raise TypeError(
"a bytes-like object is required (also str), not '%s'" %
type(v).__name__)
return v
def b58encode_int(i, default_one=True):
'''Encode an integer using Base58'''
if not i and default_one:
return alphabet[0:1]
string = b""
while i:
i, idx = divmod(i, 58)
string = alphabet[idx:idx+1] + string
return string
def b58encode(v):
'''Encode a string using Base58'''
v = scrub_input(v)
nPad = len(v)
v = v.lstrip(b'\0')
nPad -= len(v)
p, acc = 1, 0
for c in iseq(reversed(v)):
acc += p * c
p = p << 8
result = b58encode_int(acc, default_one=False)
return (alphabet[0:1] * nPad + result)
def b58decode_int(v):
'''Decode a Base58 encoded string as an integer'''
v = v.rstrip()
v = scrub_input(v)
decimal = 0
for char in v:
decimal = decimal * 58 + alphabet.index(char)
return decimal
def b58decode(v):
'''Decode a Base58 encoded string'''
v = v.rstrip()
v = scrub_input(v)
origlen = len(v)
v = v.lstrip(alphabet[0:1])
newlen = len(v)
acc = b58decode_int(v)
result = []
while acc > 0:
acc, mod = divmod(acc, 256)
result.append(mod)
return (b'\0' * (origlen - newlen) + bseq(reversed(result)))
def b58encode_check(v):
'''Encode a string using Base58 with a 4 character checksum'''
digest = sha256(sha256(v).digest()).digest()
return b58encode(v + digest[:4])
def b58decode_check(v):
'''Decode and verify the checksum of a Base58 encoded string'''
result = b58decode(v)
result, check = result[:-4], result[-4:]
digest = sha256(sha256(result).digest()).digest()
if check != digest[:4]:
raise ValueError("Invalid checksum")
return result
def main():
'''Base58 encode or decode FILE, or standard input, to standard output.'''
import sys
import argparse
stdout = buffer(sys.stdout)
parser = argparse.ArgumentParser(description=main.__doc__)
parser.add_argument(
'file',
metavar='FILE',
nargs='?',
type=argparse.FileType('r'),
default='-')
parser.add_argument(
'-d', '--decode',
action='store_true',
help='decode data')
parser.add_argument(
'-c', '--check',
action='store_true',
help='append a checksum before encoding')
args = parser.parse_args()
fun = {
(False, False): b58encode,
(False, True): b58encode_check,
(True, False): b58decode,
(True, True): b58decode_check
}[(args.decode, args.check)]
data = buffer(args.file).read()
try:
result = fun(data)
except Exception as e:
sys.exit(e)
if not isinstance(result, bytes):
result = result.encode('ascii')
stdout.write(result)
if __name__ == '__main__':
main()
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