presto-rcfile/src/main/java/io/prestosql/rcfile/text/BinaryEncoding.java/BinaryEncoding/decodeValueInto
class BinaryEncoding:    @Override
    public void decodeValueInto(int depth, BlockBuilder builder, Slice slice, int offset, int length)
    {
        byte[] data = slice.getBytes(offset, length);
        type.writeSlice(builder, Slices.wrappedBuffer(base64Decoder.decode(data)));
    }