Extensions

The major data structures and functions defined in the CSA specification can be extended methodically through extensions. Extensions are used to add additional fields to data structures and additional parameters to a function call. A standard generic data structure has been defined for these extensions. It consists of an item code, identifying the extension; an item data, holding the length of extension data or the data itself; an item reference, pointing to where the extension value is stored or NULL if there is no related item storage; and flags for the extension.

Extensions that are additional parameters to a function call may be input or output. That is, the extension may be passed as input parameters from the application to the CSA service or passed as output parameters from CSA service to the application. If an extension is an input parameter, the application allocates memory for the extension structure and any other structures associated with the extension. If an extension is an output parameter, the CSA service allocates the storage for the extension result, if necessary. In this case, the application must free the allocated storage with a csa_free() call.

If an extension that is not supported is requested, CSA_E_UNSUPPORTED_FUNCTION_EXT is returned.