Edit File: xdrlib.py
"""Implements (a subset of) Sun XDR -- eXternal Data Representation. See: RFC 1014 """ import struct from io import BytesIO from functools import wraps __all__ = ["Error", "Packer", "Unpacker", "ConversionError"] # exceptions class Error(Exception): """Exception class for this module. Use: except xdrlib.Error as var: # var has the Error instance for the exception Public ivars: msg -- contains the message """ def __init__(self, msg): self.msg = msg def __repr__(self): return repr(self.msg) def __str__(self): return str(self.msg) class ConversionError(Error): pass def raise_conversion_error(function): """ Wrap any raised struct.errors in a ConversionError. """ @wraps(function) def result(self, value): try: return function(self, value) except struct.error as e: raise ConversionError(e.args[0]) from None return result class Packer: """Pack various data representations into a buffer.""" def __init__(self): self.reset() def reset(self): self.__buf = BytesIO() def get_buffer(self): return self.__buf.getvalue() # backwards compatibility get_buf = get_buffer @raise_conversion_error def pack_uint(self, x): self.__buf.write(struct.pack('>L', x)) @raise_conversion_error def pack_int(self, x): self.__buf.write(struct.pack('>l', x)) pack_enum = pack_int def pack_bool(self, x): if x: self.__buf.write(b'\0\0\0\1') else: self.__buf.write(b'\0\0\0\0') def pack_uhyper(self, x): try: self.pack_uint(x>>32 & 0xffffffff) except (TypeError, struct.error) as e: raise ConversionError(e.args[0]) from None try: self.pack_uint(x & 0xffffffff) except (TypeError, struct.error) as e: raise ConversionError(e.args[0]) from None pack_hyper = pack_uhyper @raise_conversion_error def pack_float(self, x): self.__buf.write(struct.pack('>f', x)) @raise_conversion_error def pack_double(self, x): self.__buf.write(struct.pack('>d', x)) def pack_fstring(self, n, s): if n < 0: raise ValueError('fstring size must be nonnegative') data = s[:n] n = ((n+3)//4)*4 data = data + (n - len(data)) * b'\0' self.__buf.write(data) pack_fopaque = pack_fstring def pack_string(self, s): n = len(s) self.pack_uint(n) self.pack_fstring(n, s) pack_opaque = pack_string pack_bytes = pack_string def pack_list(self, list, pack_item): for item in list: self.pack_uint(1) pack_item(item) self.pack_uint(0) def pack_farray(self, n, list, pack_item): if len(list) != n: raise ValueError('wrong array size') for item in list: pack_item(item) def pack_array(self, list, pack_item): n = len(list) self.pack_uint(n) self.pack_farray(n, list, pack_item) class Unpacker: """Unpacks various data representations from the given buffer.""" def __init__(self, data): self.reset(data) def reset(self, data): self.__buf = data self.__pos = 0 def get_position(self): return self.__pos def set_position(self, position): self.__pos = position def get_buffer(self): return self.__buf def done(self): if self.__pos < len(self.__buf): raise Error('unextracted data remains') def unpack_uint(self): i = self.__pos self.__pos = j = i+4 data = self.__buf[i:j] if len(data) < 4: raise EOFError return struct.unpack('>L', data)[0] def unpack_int(self): i = self.__pos self.__pos = j = i+4 data = self.__buf[i:j] if len(data) < 4: raise EOFError return struct.unpack('>l', data)[0] unpack_enum = unpack_int def unpack_bool(self): return bool(self.unpack_int()) def unpack_uhyper(self): hi = self.unpack_uint() lo = self.unpack_uint() return int(hi)<<32 | lo def unpack_hyper(self): x = self.unpack_uhyper() if x >= 0x8000000000000000: x = x - 0x10000000000000000 return x def unpack_float(self): i = self.__pos self.__pos = j = i+4 data = self.__buf[i:j] if len(data) < 4: raise EOFError return struct.unpack('>f', data)[0] def unpack_double(self): i = self.__pos self.__pos = j = i+8 data = self.__buf[i:j] if len(data) < 8: raise EOFError return struct.unpack('>d', data)[0] def unpack_fstring(self, n): if n < 0: raise ValueError('fstring size must be nonnegative') i = self.__pos j = i + (n+3)//4*4 if j > len(self.__buf): raise EOFError self.__pos = j return self.__buf[i:i+n] unpack_fopaque = unpack_fstring def unpack_string(self): n = self.unpack_uint() return self.unpack_fstring(n) unpack_opaque = unpack_string unpack_bytes = unpack_string def unpack_list(self, unpack_item): list = [] while 1: x = self.unpack_uint() if x == 0: break if x != 1: raise ConversionError('0 or 1 expected, got %r' % (x,)) item = unpack_item() list.append(item) return list def unpack_farray(self, n, unpack_item): list = [] for i in range(n): list.append(unpack_item()) return list def unpack_array(self, unpack_item): n = self.unpack_uint() return self.unpack_farray(n, unpack_item)
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