Mini Shell

# Implement (a subset of) Sun XDR -- RFC1014.


try:
    import struct
except ImportError:
    struct = None


Long = type(0L)


class Packer:

    def __init__(self):
        self.reset()

    def reset(self):
        self.buf = ''

    def get_buf(self):
        return self.buf

    def pack_uint(self, x):
        self.buf = self.buf + \
                (chr(int(x>>24 & 0xff)) + chr(int(x>>16 & 0xff)) + \
                 chr(int(x>>8 & 0xff)) + chr(int(x & 0xff)))
    if struct and struct.pack('l', 1) == '\0\0\0\1':
        def pack_uint(self, x):
            if type(x) == Long:
                x = int((x + 0x80000000L) % 0x100000000L \
                           - 0x80000000L)
            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(int(x>>32 & 0xffffffff))
        self.pack_uint(int(x & 0xffffffff))

    pack_hyper = pack_uhyper

    def pack_float(self, x):
        # XXX
        self.buf = self.buf + struct.pack('f', x)

    def pack_double(self, x):
        # XXX
        self.buf = self.buf + struct.pack('d', x)

    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

    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:

    def __init__(self, data):
        self.reset(data)

    def reset(self, data):
        self.buf = data
        self.pos = 0

    def done(self):
        if self.pos < len(self.buf):
            raise RuntimeError, '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 = long(ord(data[0]))<<24 | ord(data[1])<<16 | \
                ord(data[2])<<8 | ord(data[3])
        # Return a Python long only if the value is not representable
        # as a nonnegative Python int
        if x < 0x80000000L: x = int(x)
        return x
    if struct and struct.unpack('l', '\0\0\0\1') == 1:
        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)

    def unpack_int(self):
        x = self.unpack_uint()
        if x >= 0x80000000L: x = x - 0x100000000L
        return int(x)

    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):
        # XXX
        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):
        # XXX
        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

    def unpack_list(self, unpack_item):
        list = []
        while 1:
            x = self.unpack_uint()
            if x == 0: break
            if x <> 1:
                raise RuntimeError, '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)