from types import IntType, TupleType, StringType, FloatType, LongType, ListType, DictType, NoneType
from struct import pack, unpack
from cStringIO import StringIO
class EncodeError(Exception):
pass
class DecodeError(Exception):
pass
#contains dictionary of coding functions, where the dictionary key is the type.
encoder = {}
def enc_dict_type(obj):
data = "".join([encoder[type(i)](i) for i in obj.items()])
return "%s%s%s" % ("D", pack("!L", len(data)), data)
encoder[DictType] = enc_dict_type
def enc_list_type(obj):
data = "".join([encoder[type(i)](i) for i in obj])
return "%s%s%s" % ("L", pack("!L", len(data)), data)
encoder[ListType] = enc_list_type
def enc_tuple_type(obj):
data = "".join([encoder[type(i)](i) for i in obj])
return "%s%s%s" % ("T", pack("!L", len(data)), data)
encoder[TupleType] = enc_tuple_type
def enc_int_type(obj):
return "%s%s" % ("I", pack("!i", obj))
encoder[IntType] = enc_int_type
def enc_float_type(obj):
return "%s%s" % ("F", pack("!f", obj))
encoder[FloatType] = enc_float_type
def enc_long_type(obj):
obj = hex(obj)[2:-1]
return "%s%s%s" % ("B", pack("!L", len(obj)), obj)
encoder[LongType] = enc_long_type
def enc_string_type(obj):
return "%s%s%s" % ("S", pack("!L", len(obj)), obj)
encoder[StringType] = enc_string_type
def enc_none_type(obj):
return "N"
encoder[NoneType] = enc_none_type
def encode(obj):
"""Encode simple Python types into a binary string."""
try:
return encoder[type(obj)](obj)
except KeyError, e:
raise EncodeError, "Type not supported. (%s)" % e
#contains dictionary of decoding functions, where the dictionary key is the type prefix used.
decoder = {}
def build_sequence(data, cast=list):
size = unpack('!L', data.read(4))[0]
items = []
data_tell = data.tell
data_read = data.read
items_append = items.append
start_position = data.tell()
while (data_tell() - start_position) < size:
T = data_read(1)
value = decoder[T](data)
items_append(value)
return cast(items)
def dec_tuple_type(data):
return build_sequence(data, cast=tuple)
decoder["T"] = dec_tuple_type
def dec_list_type(data):
return build_sequence(data, cast=list)
decoder["L"] = dec_list_type
def dec_dict_type(data):
return build_sequence(data, cast=dict)
decoder["D"] = dec_dict_type
def dec_long_type(data):
size = unpack('!L', data.read(4))[0]
value = long(data.read(size),16)
return value
decoder["B"] = dec_long_type
def dec_string_type(data):
size = unpack('!L', data.read(4))[0]
value = str(data.read(size))
return value
decoder["S"] = dec_string_type
def dec_float_type(data):
value = unpack('!f', data.read(4))[0]
return value
decoder["F"] = dec_float_type
def dec_int_type(data):
value = unpack('!i', data.read(4))[0]
return value
decoder['I'] = dec_int_type
def dec_none_type(data):
return None
decoder['N'] = dec_none_type
def decode(data):
"""
Decode a binary string into the original Python types.
"""
buffer = StringIO(data)
try:
value = decoder[buffer.read(1)](buffer)
except KeyError, e:
raise DecodeError, "Type prefix not supported. (%s)" % e
return value
if __name__ == "__main__":
value = [None,["simon","wittber"],(1,2),{1:2.1,3:4.3},999999999999999999999999999999999999999]
data = encode(value)
print data
x = decode(data)
for item in zip(value,x):
print item[0],"---",item[1]
print "-" * 10
print x
