2 # Workalike python implementation of Bitcoin's CDataStream class.
8 class SerializationError(Exception):
9 """ Thrown when there's a problem deserializing or serializing """
11 class BCDataStream(object):
20 def write(self, bytes): # Initialize with string of bytes
21 if self.input is None:
26 def map_file(self, file, start): # Initialize with bytes from file
27 self.input = mmap.mmap(file.fileno(), 0, access=mmap.ACCESS_READ)
28 self.read_cursor = start
29 def seek_file(self, position):
30 self.read_cursor = position
34 def read_string(self):
35 # Strings are encoded depending on length:
36 # 0 to 252 : 1-byte-length followed by bytes (if any)
37 # 253 to 65,535 : byte'253' 2-byte-length followed by bytes
38 # 65,536 to 4,294,967,295 : byte '254' 4-byte-length followed by bytes
39 # ... and the Bitcoin client is coded to understand:
40 # greater than 4,294,967,295 : byte '255' 8-byte-length followed by bytes of string
41 # ... but I don't think it actually handles any strings that big.
42 if self.input is None:
43 raise SerializationError("call write(bytes) before trying to deserialize")
46 length = self.read_compact_size()
48 raise SerializationError("attempt to read past end of buffer")
50 return self.read_bytes(length)
52 def write_string(self, string):
53 # Length-encoded as with read-string
54 self.write_compact_size(len(string))
57 def read_bytes(self, length):
59 result = self.input[self.read_cursor:self.read_cursor+length]
60 self.read_cursor += length
63 raise SerializationError("attempt to read past end of buffer")
67 def read_boolean(self): return self.read_bytes(1)[0] != chr(0)
68 def read_int16(self): return self._read_num('<h')
69 def read_uint16(self): return self._read_num('<H')
70 def read_int32(self): return self._read_num('<i')
71 def read_uint32(self): return self._read_num('<I')
72 def read_int64(self): return self._read_num('<q')
73 def read_uint64(self): return self._read_num('<Q')
75 def write_boolean(self, val): return self.write(chr(1) if val else chr(0))
76 def write_int16(self, val): return self._write_num('<h', val)
77 def write_uint16(self, val): return self._write_num('<H', val)
78 def write_int32(self, val): return self._write_num('<i', val)
79 def write_uint32(self, val): return self._write_num('<I', val)
80 def write_int64(self, val): return self._write_num('<q', val)
81 def write_uint64(self, val): return self._write_num('<Q', val)
83 def read_compact_size(self):
84 size = ord(self.input[self.read_cursor])
87 size = self._read_num('<H')
89 size = self._read_num('<I')
91 size = self._read_num('<Q')
94 def write_compact_size(self, size):
96 raise SerializationError("attempt to write size < 0")
101 self._write_num('<H', size)
104 self._write_num('<I', size)
107 self._write_num('<Q', size)
109 def _read_num(self, format):
110 (i,) = struct.unpack_from(format, self.input, self.read_cursor)
111 self.read_cursor += struct.calcsize(format)
114 def _write_num(self, format, num):
115 s = struct.pack(format, num)