public static byte toBinaryFromHex(byte ch) {
        if (ch >= 'A' && ch <= 'F') {
            return (byte) ((byte) 10 + (byte) (ch - 'A'));
        }
        // else
        return (byte) (ch - '0');
    }
Takes a ASCII digit in the range A-F0-9 and returns the corresponding integer/ordinal value.

@param ch The hex digit.
@return The converted hex value as a byte.
stroom-bytebuffer/src/main/java/stroom/bytebuffer/hbase/Bytes.java