thrifty-runtime/src/main/java/com/microsoft/thrifty/protocol/JsonProtocol.java
private static byte hexVal(byte ch) throws IOException {
        if ((ch >= '0') && (ch <= '9')) {
            return (byte) ((char) ch - '0');
        } else if ((ch >= 'a') && (ch <= 'f')) {
            return (byte) ((char) ch - 'a' + 10);
        } else {
            throw new ProtocolException("Expected hex character");
        }
    }
private static byte hexVal(byte ch) throws IOException {
        if ((ch >= '0') && (ch <= '9')) {
            return (byte) ((char) ch - '0');
        } else if ((ch >= 'a') && (ch <= 'f')) {
            return (byte) ((char) ch - 'a' + 10);
        } else {
            throw new ProtocolException("Expected hex character");
        }
    }
corresponding hex value