Application: gvSIG desktop

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

See: RFC 1014

"""

import struct

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

# exceptions

class Error:

    """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 = ''

    def get_buffer(self):

        return self.__buf

    # backwards compatibility

    get_buf = get_buffer

    def pack_uint(self, x):

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

    pack_int = pack_uint

    pack_enum = pack_int

    def pack_bool(self, x):

        if x: self.__buf = self.__buf + '\0\0\0\1'

        else: self.__buf = self.__buf + '\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 = self.__buf + struct.pack('>f', x)

        except struct.error, msg:

            raise ConversionError, msg

    def pack_double(self, x):

        try: self.__buf = self.__buf + 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'

        n = ((n+3)/4)*4

        data = s[:n]

        data = data + (n - len(data)) * '\0'

        self.__buf = self.__buf + 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

    unpack_bool = 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 ' + `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)

# test suite

def _test():

    p = Packer()

    packtest = [

        (p.pack_uint,    (9,)),

        (p.pack_bool,    (None,)),

        (p.pack_bool,    ('hello',)),

        (p.pack_uhyper,  (45L,)),

        (p.pack_float,   (1.9,)),

        (p.pack_double,  (1.9,)),

        (p.pack_string,  ('hello world',)),

        (p.pack_list,    (range(5), p.pack_uint)),

        (p.pack_array,   (['what', 'is', 'hapnin', 'doctor'], p.pack_string)),

        ]

    succeedlist = [1] * len(packtest)

    count = 0

    for method, args in packtest:

        print 'pack test', count,

        try:

            apply(method, args)

            print 'succeeded'

        except ConversionError, var:

            print 'ConversionError:', var.msg

            succeedlist[count] = 0

        count = count + 1

    data = p.get_buffer()

    # now verify

    up = Unpacker(data)

    unpacktest = [

        (up.unpack_uint,   (), lambda x: x == 9),

        (up.unpack_bool,   (), lambda x: not x),

        (up.unpack_bool,   (), lambda x: x),

        (up.unpack_uhyper, (), lambda x: x == 45L),

        (up.unpack_float,  (), lambda x: 1.89 < x < 1.91),

        (up.unpack_double, (), lambda x: 1.89 < x < 1.91),

        (up.unpack_string, (), lambda x: x == 'hello world'),

        (up.unpack_list,   (up.unpack_uint,), lambda x: x == range(5)),

        (up.unpack_array,  (up.unpack_string,),

         lambda x: x == ['what', 'is', 'hapnin', 'doctor']),

        ]

    count = 0

    for method, args, pred in unpacktest:

        print 'unpack test', count,

        try:

            if succeedlist[count]:

                x = apply(method, args)

                print pred(x) and 'succeeded' or 'failed', ':', x

            else:

                print 'skipping'

        except ConversionError, var:

            print 'ConversionError:', var.msg

        count = count + 1

if __name__ == '__main__':

    _test()