decoder.py 文件源码

def valueDecoder(self, substrate, asn1Spec,
                     tagSet=None, length=None, state=None,
                     decodeFun=None, substrateFun=None,
                     **options):
        head, tail = substrate[:length], substrate[length:]
        if not head or length != 1:
            raise error.PyAsn1Error('Not single-octet Boolean payload')
        byte = oct2int(head[0])
        # CER/DER specifies encoding of TRUE as 0xFF and FALSE as 0x0, while
        # BER allows any non-zero value as TRUE; cf. sections 8.2.2. and 11.1 
        # in http://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf
        if byte == 0xff:
            value = 1
        elif byte == 0x00:
            value = 0
        else:
            raise error.PyAsn1Error('Unexpected Boolean payload: %s' % byte)
        return self._createComponent(asn1Spec, tagSet, value), tail

# TODO: prohibit non-canonical encoding