"""Implements (a subset of) Sun XDR -- eXternal Data Representation.

See: RFC 1014

"""

import struct

try:

    from cStringIO import StringIO as _StringIO

except ImportError:

    from StringIO import StringIO as _StringIO

__all__ = ["Error", "Packer", "Unpacker", "ConversionError"]

# exceptions

class Error(Exception):

    """Exception class for this module. Use:

    except xdrlib.Error, 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

class Packer:

    """Pack various data representations into a buffer."""

    def __init__(self):

        self.reset()

    def reset(self):

        self.__buf = _StringIO()

    def get_buffer(self):

        return self.__buf.getvalue()

    # backwards compatibility

    get_buf = get_buffer

    def pack_uint(self, x):

        self.__buf.write(struct.pack('>L', x))

    pack_int = pack_uint

    pack_enum = pack_int

    def pack_bool(self, x):

        if x: self.__buf.write('\0\0\0\1')

        else: self.__buf.write('\0\0\0\0')

    def pack_uhyper(self, x):

        self.pack_uint(x>>32 & 0xffffffffL)

        self.pack_uint(x & 0xffffffffL)

    pack_hyper = pack_uhyper

    def pack_float(self, x):

        try: self.__buf.write(struct.pack('>f', x))

        except struct.error, msg:

            raise ConversionError, msg

    def pack_double(self, x):

        try: self.__buf.write(struct.pack('>d', x))

        except struct.error, msg:

            raise ConversionError, msg

    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)) * '\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

        x = struct.unpack('>L', data)[0]

        try:

            return int(x)

        except OverflowError:

            return x

    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 long(hi)<<32 | lo

    def unpack_hyper(self):

        x = self.unpack_uhyper()

        if x >= 0x8000000000000000L:

            x = x - 0x10000000000000000L

        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)