def verify(self, zipfile=None):
        """Configure the VerifyingZipFile `zipfile` by verifying its signature 
        and setting expected hashes for every hash in RECORD.
        Caller must complete the verification process by completely reading 
        every file in the archive (e.g. with extractall)."""
        sig = None
        if zipfile is None:
            zipfile = self.zipfile
        zipfile.strict = True

        record_name = '/'.join((self.distinfo_name, 'RECORD'))
        sig_name = '/'.join((self.distinfo_name, 'RECORD.jws'))
        # tolerate s/mime signatures:
        smime_sig_name = '/'.join((self.distinfo_name, 'RECORD.p7s'))
        zipfile.set_expected_hash(record_name, None)
        zipfile.set_expected_hash(sig_name, None)
        zipfile.set_expected_hash(smime_sig_name, None)
        record = zipfile.read(record_name)

        record_digest = urlsafe_b64encode(hashlib.sha256(record).digest())
        try:
            sig = from_json(native(zipfile.read(sig_name)))
        except KeyError:  # no signature
            pass
        if sig:
            headers, payload = signatures.verify(sig)
            if payload['hash'] != "sha256=" + native(record_digest):
                msg = "RECORD.sig claimed RECORD hash {0} != computed hash {1}."
                raise BadWheelFile(msg.format(payload['hash'],
                                              native(record_digest)))

        reader = csv.reader((native(r) for r in record.splitlines()))

        for row in reader:
            filename = row[0]
            hash = row[1]
            if not hash:
                if filename not in (record_name, sig_name):
                    sys.stderr.write("%s has no hash!\n" % filename)
                continue
            algo, data = row[1].split('=', 1)
            assert algo == "sha256", "Unsupported hash algorithm"
            zipfile.set_expected_hash(filename, urlsafe_b64decode(binary(data)))
Configure the VerifyingZipFile `zipfile` by verifying its signature 
        and setting expected hashes for every hash in RECORD.
        Caller must complete the verification process by completely reading 
        every file in the archive (e.g. with extractall).