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Added py_ssz

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vbuterin committed Aug 4, 2017
1 parent b6ab900 commit 53e70d9bdf3b635dcd5ac450834cf558c101ab43
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The MIT License (MIT)
Copyright (c) 2015 Vitalik Buterin
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
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## Simple serialization - an alternative to RLP that's much simpler.
### The spec:
encode(string) = enc3b(len(string)) + string
Where `enc3b(x)` encodes `x` as three bytes, in big-endian format
encode(list) = enc3b(8388608 + sum(len([encode(x) for x in list]))) + \
b''.join([encode(x) for x in list])
And that's it!
Examples:
cow -> \x00\x00\x03cow
[dog, horse] -> \x80\x00\x0e\x00\x00\x03dog\x00\x00\x05horse
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from .py_ssz import encode, decode
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from .utils import int_to_big_endian
from .serializers import Serializable, CountableList
def add_length_prefix(obj, is_list=False):
assert len(obj) <= 8388607
return bytes([(len(obj) >> 16) + 128 * is_list,
(len(obj) >> 8) % 256,
len(obj) % 256]) + obj
def encode(obj):
if isinstance(obj, bytes):
return add_length_prefix(obj)
elif isinstance(obj, str):
return add_length_prefix(obj.encode('utf-8'))
elif isinstance(obj, int):
assert obj >= 0
return add_length_prefix(int_to_big_endian(obj))
elif isinstance(obj, list):
res = b''
for o in obj:
res += encode(o)
return add_length_prefix(res, True)
elif isinstance(obj, Serializable):
return encode(obj._s(obj))
def decode_raw(obj, pos=0):
startpos = pos
L = ((obj[pos] % 128) << 16) + (obj[pos+1] << 8) + obj[pos+2]
if obj[pos] < 128:
assert len(obj) >= pos+3+L
return obj[pos+3: pos+3+L], pos+3+L
else:
pos += 3
o = []
while pos < startpos+3+L:
sub, pos = decode_raw(obj, pos)
o.append(sub)
assert pos == startpos+3+L
return o, pos
def decode(obj, cls=None, *args, **kwargs):
decoded, endpos = decode_raw(obj)
assert endpos == len(obj)
if cls is None:
return decoded
return cls._d(decoded, *args, **kwargs)
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from .utils import int_to_big_endian, big_endian_to_int
class Serializable():
@classmethod
def _s(cls, obj):
o = []
for field, serializer in obj.__class__.fields:
member = getattr(obj, field)
if isinstance(serializer, Serializable):
assert isinstance(member, serializer)
o.append(serializer._s(member))
return o
@classmethod
def _d(cls, data, *args, **kwargs):
obj = cls(*args, **kwargs)
assert len(data) == len(cls.fields)
for datum, (field, serializer) in zip(data, cls.fields):
setattr(obj, field, serializer._d(datum))
return obj
def int_in_range(_min, _max):
class c():
@classmethod
def _s(cls, x):
assert isinstance(x, int) and x >= _min and x <= _max
return int_to_big_endian(x)
@classmethod
def _d(cls, x):
assert len(x) == 0 or x[0] != 0
return big_endian_to_int(x)
return c
big_endian_int = int_in_range(0, 2**256-1)
int256 = int_in_range(0, 2**2048-1)
def bytesn(n):
class c():
@classmethod
def _s(cls, x):
assert isinstance(x, bytes) and len(x) == n
return x
@classmethod
def _d(cls, x):
return x
return c
hash32 = bytesn(32)
class binary():
@classmethod
def _s(cls, x):
assert isinstance(x, bytes)
return x
@classmethod
def _d(cls, x):
return x
def CountableList(ser):
class c():
@classmethod
def _s(cls, vals):
assert isinstance(vals, list)
return [ser._s(v) for v in vals]
@classmethod
def _d(cls, vals):
return [ser._d(v) for v in vals]
return c
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from math import ceil
def int_to_big_endian(value):
byte_length = max(ceil(value.bit_length() / 8), 1)
return (value).to_bytes(byte_length, byteorder='big')
def big_endian_to_int(value):
return int.from_bytes(value, byteorder='big')
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# -*- coding: utf-8 -*-
from setuptools import setup, find_packages
with open('README.md') as f:
readme = f.read()
with open('LICENSE') as f:
license = f.read()
setup(
name='py_ssz',
version='1.0.0',
description='Python implementation of SimpleSerialize',
long_description=readme,
author='Vitalik Buterin',
author_email='',
url='https://github.com/ethereum/research',
license=license,
packages=find_packages(exclude=('tests', 'docs')),
install_requires=[
],
)
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from py_ssz import encode, decode
from py_ssz.serializers import big_endian_int, binary, hash32, CountableList, Serializable
from py_ssz.utils import int_to_big_endian
assert decode(encode(b'cow')) == b'cow'
assert decode(encode(123)) == int_to_big_endian(123)
assert decode(encode([b'cow', b'horse', b'pig'])) == [b'cow', b'horse', b'pig']
assert decode(encode([b'cow', b'horse', [b'o', b'q']])) == [b'cow', b'horse', [b'o', b'q']]
assert decode(encode([[], [[]], [[], [[]]]])) == [[], [[]], [[], [[]]]]
class Foo(Serializable):
fields = [
('bar', big_endian_int),
('baz', binary)
]
def __init__(self, bar=0, baz=b''):
self.bar = bar
self.baz = baz
assert encode(Foo(3, b'cow')) == encode([3, b'cow'])
foo2 = decode(encode(Foo(3, b'cow')), Foo)
assert foo2.bar == 3 and foo2.baz == b'cow'
class Foo2(Serializable):
fields = [
('bat', Foo),
('bau', CountableList(big_endian_int)),
('bav', CountableList(Foo))
]
x = Foo2()
x.bat = Foo(3, b'cow')
x.bau = [4,5,6,7,8]
x.bav = [Foo(5, b'horse'), Foo(7, b'mongoose')]
assert encode(x) == encode([[3, b'cow'], [4,5,6,7,8], [[5, b'horse'], [7, b'mongoose']]])

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