“In/out/inout” in a AIDL interface parameter value?

In AIDL, the "out" tag specifies an output-only parameter. In other words, it's a parameter that contains no interesting data on input, but will be filled with data during the method.

For example, a method that copies an array of bytes might be specified like this:

void copyArray(in byte[] source, out byte[] dest); 

The "inout" tag indicates that the parameter has meaning on both input and output. For example:

void charsToUpper(inout char[] chars); 

This is important because the contents of every parameter must be marshalled (serialized, transmitted, received, and deserialized). The in/out tags allow the Binder to skip the marshalling step for better performance.

转载：http://stackoverflow.com/questions/4700225/in-out-inout-in-a-aidl-interface-parameter-value