private void assertNotFreed() {
        if (buf == null) {
            throw new IllegalStateException("Cannot call a method after free() has been called.");
        }
    }
A standard implementation of the Blob interface.
<p>
By having an implementation, we do not have to
require usage of the java.sql.rowset module.

@author Per Minborg
@since 3.2.0
runtime-parent/runtime-typemapper/src/main/java/com/speedment/runtime/typemapper/largeobject/StandardBlob.java