ber.py 文件源码

def decode_next(self):
        if self.idx >= len(self.content):
            return None
        ident = byte_ord(self.content[self.idx])
        self.idx += 1
        if (ident & 31) == 31:
            # identifier > 30
            ident = 0
            while self.idx < len(self.content):
                t = byte_ord(self.content[self.idx])
                self.idx += 1
                ident = (ident << 7) | (t & 0x7f)
                if not (t & 0x80):
                    break
        if self.idx >= len(self.content):
            return None
        # now fetch length
        size = byte_ord(self.content[self.idx])
        self.idx += 1
        if size & 0x80:
            # more complimicated...
            # FIXME: theoretically should handle indefinite-length (0x80)
            t = size & 0x7f
            if self.idx + t > len(self.content):
                return None
            size = paramiko.util.inflate_long(
                self.content[self.idx: self.idx + t], True)
            self.idx += t
        if self.idx + size > len(self.content):
            # can't fit
            return None
        data = self.content[self.idx: self.idx + size]
        self.idx += size
        # now switch on id
        if ident == 0x30:
            # sequence
            return self.decode_sequence(data)
        elif ident == 2:
            # int
            return paramiko.util.inflate_long(data)
        else:
            # 1: boolean (00 false, otherwise true)
            raise BERException(
                'Unknown ber encoding type %d (robey is lazy)' % ident)