"""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円0円0円1円')
 else: self.__buf.write(b'0円0円0円0円')

 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円'
 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)