PRInt32 prefixLen = aAttributeKey.Length() - sizeof(kNameSpaceDef);
PRInt32 prefixLen = aAttributeKey.Length() - kNameSpaceDef_Length - 1;
RDFContentSinkImpl::IsXMLNSDirective(const nsAString& aAttributeKey, nsIAtom** aPrefix){    // Look for `xmlns' at the start of the attribute name    if (!Substring(aAttributeKey, 0, sizeof(kNameSpaceDef) - 1).Equals(NS_LITERAL_STRING(kNameSpaceDef)))        return PR_FALSE;    PRInt32 prefixLen = aAttributeKey.Length() - sizeof(kNameSpaceDef);    if (prefixLen <= 0) {        // they're setting the default namespace; leave `prefix'        // as nsnull.    }    else {        // make sure there's a `:' character        nsAString::const_iterator iter;        if (*aAttributeKey.BeginReading(iter).advance(sizeof(kNameSpaceDef) - 1)                != kNameSpaceSeparator)            return PR_FALSE;        // if the caller wants the prefix back, compute it for them.        if (aPrefix)            *aPrefix = NS_NewAtom(Substring(aAttributeKey,                                            sizeof(kNameSpaceDef), prefixLen));    }    return PR_TRUE;}