thrifty-runtime/src/main/java/com/microsoft/thrifty/protocol/JsonProtocol.java
private ByteString readJsonBase64() throws IOException {
        ByteString str = readJsonString(false);
        return ByteString.decodeBase64(str.utf8());
    }
private ByteString readJsonBase64() throws IOException {
        ByteString str = readJsonString(false);
        return ByteString.decodeBase64(str.utf8());
    }
Read in a Json string containing base-64 encoded data and decode it.