presto-rcfile/src/main/java/io/prestosql/rcfile/text/DoubleEncoding.java/DoubleEncoding/encodeValue
class DoubleEncoding:    private void encodeValue(Block block, int position, SliceOutput output)
    {
        double value = type.getDouble(block, position);
        buffer.setLength(0);
        buffer.append(value);
        for (int index = 0; index < buffer.length(); index++) {
            output.writeByte(buffer.charAt(index));
        }
    }