presto-spi/src/main/java/io/prestosql/spi/block/ByteArrayBlockEncoding.java/ByteArrayBlockEncoding/readBlock
class ByteArrayBlockEncoding:    @Override
    public Block readBlock(BlockEncodingSerde blockEncodingSerde, SliceInput sliceInput)
    {
        int positionCount = sliceInput.readInt();

        boolean[] valueIsNull = decodeNullBits(sliceInput, positionCount).orElse(null);

        byte[] values = new byte[positionCount];
        for (int position = 0; position < positionCount; position++) {
            if (valueIsNull == null || !valueIsNull[position]) {
                values[position] = sliceInput.readByte();
            }
        }

        return new ByteArrayBlock(0, positionCount, valueIsNull, values);
    }