1There are two libraries defined in this directory: 2First, com.android.mediadrm.signer.jar is a shared java library 3containing classes required by unbundled apps running on devices that use 4the certficate provisioning and private key signing capabilities provided 5by the MediaDrm API. 6Second, com.android.mediadrm.signer.stubs.jar is a stub for the shared library 7which provides build-time APIs to the unbundled clients. 8 9At runtime, the shared library is added to the classloader of the app via the 10<uses-library> tag. And since Java always tries to load a class from the 11parent classloader, regardless of whether the stub library is linked to the 12app statically or dynamically, the real classes are loaded from the shared 13library. 14 15--- Rules of this library --- 16o The stub library is effectively a PUBLIC API for unbundled CAST receivers 17 that may be distributed outside the system image. So it MUST BE API STABLE. 18 You can add but not remove. The rules are the same as for the 19 public platform SDK API. 20o This library can see and instantiate internal platform classes, but it must not 21 expose them in any public method (or by extending them via inheritance). This would 22 break clients of the library because they cannot see the internal platform classes. 23 24This library is distributed in the system image, and loaded as 25a shared library. So you can change the implementation, but not 26the interface. In this way it is like framework.jar. 27 28--- Why does this library exist? --- 29 30Unbundled apps cannot use internal platform classes. 31 32This library will eventually be replaced when the provisioned certificate- 33based signing infrastructure that is currently defined in the support library 34is reintegrated with the framework in a new API. That API isn't ready yet so 35this library is a compromise to make new capabilities available to the system 36without exposing the full surface area of the support library. 37 38