presto-spi/src/main/java/io/prestosql/spi/block/VariableWidthBlockBuilder.java/VariableWidthBlockBuilder/writeBytes
class VariableWidthBlockBuilder:    @Override
    public BlockBuilder writeBytes(Slice source, int sourceIndex, int length)
    {
        if (!initialized) {
            initializeCapacity();
        }
        sliceOutput.writeBytes(source, sourceIndex, length);
        currentEntrySize += length;
        return this;
    }