from datetime import datetime
import operator
class Field(object):
idx = 0
def __init__(self):
Field.idx += 1
self.id = Field.idx
def repr(self):
return self.__class__.__name__
def __repr__(self):
if hasattr(self, 'name'):
return '<Field %s "%s">' % (self.repr(), self.name)
return super(Field, self).__repr__()
class Int(Field):
encoders = {}
decoders = {}
@classmethod
def encoder(cls, n):
if n not in cls.encoders:
exec ('def enc(n):\n' +
' assert n == n & 0x%s, "Arithmetic overflow"\n' +
' return "".join((%s,))'
) % ('ff' * n,
','.join('chr((n >> %d) & 0xff)' % (i * 8)
for i in range(0, n)))
cls.encoders[n] = enc
return cls.encoders[n]
@classmethod
def decoder(cls, n):
if n not in cls.decoders:
cls.decoders[n] = eval('lambda data, offset: ' +
'|'.join('ord(data[offset + %d]) << %d' % (i, i * 8)
for i in range(0, n)))
return cls.decoders[n]
def __init__(self, size):
super(Int, self).__init__()
self.size = size
self.encode = self.encoder(size)
self.decode = self.decoder(size)
if self.__class__ == Int:
self.marshall = self.encode
def unmarshall(self, data, offset):
return self.size, self.decode(data, offset)
def marshall(self, val):
return self.encode(val)
def repr(self):
return '%s(%d)' % (self.__class__.__name__, self.size)
class Size(Int):
def __init__(self, size, extra=0):
super(Size, self).__init__(size)
self.extra = extra
def marshall(self, val):
return lambda vals, i: self.encode(
reduce(lambda n, i: n + len(vals[i]),
range(i + 1, len(vals)),
self.extra))
class Date(Int):
def __init__(self):
super(Date, self).__init__(4)
def unmarshall(self, data, offset):
val = self.decode(data, offset)
return 4, datetime.fromtimestamp(val)
def marshall(self, val):
return self.encode(int(val.strftime('%s')))
class Data(Int):
def __init__(self, size=2):
super(Data, self).__init__(size)
def unmarshall(self, data, offset):
n = self.decode(data, offset)
offset += self.size
assert offset + n <= len(data), "String too long to unpack"
return self.size + n, data[offset:offset + n]
def marshall(self, val):
if isinstance(val, unicode):
val = val.encode('UTF-8')
return [self.encode(len(val)), val]
# Note: Py3K strings are Unicode by default. They can't store binary
# data.
class String(Data):
def unmarshall(self, data, offset):
off, val = super(String, self).unmarshall(data, offset)
return off, val.decode('UTF-8')
def marshall(self, val):
if isinstance(val, str):
# Check for valid UTF-8
str.decode('UTF-8')
else:
val = val.encode('UTF-8')
return super(String, self).marshall(val)
class Array(Int):
def __init__(self, size, spec):
super(Array, self).__init__(size)
self.spec = spec
def unmarshall(self, data, offset):
start = offset
n = self.decode(data, offset)
offset += self.size
res = []
for i in range(0, n):
size, val = self.spec.unmarshall(data, offset)
if isinstance(val, list):
res += val
else:
res.append(val)
offset += size
return offset - start, res
def marshall(self, vals):
res = [self.encode(len(vals))]
for val in vals:
val = self.spec.marshall(val)
if isinstance(val, list):
res += val
else:
res.append(val)
return res
# vim:se sts=4 sw=4 et: