Indicates that the parameter is an IN parameter.

When a java object is passed to a native function as a pointer (for example jnr.ffi.Pointer, jnr.ffi.Struct, java.nio.ByteBuffer), then a temporary native memory block is allocated, the java data is copied to the temporary memory and the address of the temporary memory is passed to the function. After the function returns, the java data is automatically updated from the contents of the native memory.

As this extra copying can be expensive, parameters can be annotated with @In so the data is only copied from java IN to native memory, but not copied back OUT from native memory to java memory.

Parameters with neither a @In nor a @Out annotation will copy both ways.