Remove global static non const variables #767
Description
Currently there are sever global static variables that can make using libsrtp from multiple sub projects problematic. All non const variables should be removed.
Current known ones include crypto_kernel, srtp_event_handler, srtp_err_report_handler & debug modules.
There are two options for removing them:
- Add them all as members of srtp_t so they are created and managed per srtp_t.
- Add them to a new libsrtp_t that can be then shared between a select number of srtp_t.
The first option is nice in that it cleans up the API, there will no longer need to be srtp_int() / srtp_shutdown(). The downside is that there will be duplication and a crypto kernel will effectively be initialized for each srtp_t created. The initialization may not be too expensive but the self test are. To prevent some of the over head the self test can be initially disabled and a explicit srtp_self_test() can be used if validation is required.
The second option requires there to be a new layer to the API that must be call before each srtp_t is created and requires the application to manage the libsrtp_t. It has the benefit of only needing to initialize and self test the crypto kernel once.
There is maybe a third options that combines the two, where it is either possible to create a libsrtp_t that can be shared with by many srtp_t's or a srtp_t can create it's own libsrtp_t if one was not provided.
The initial proposal is to go with option 1, removing the need for srtp_init() / srtp_shutdown(). The self test will be disabled by default but a srtp_verify_self() will be added.
The event handler can easily be moved to srtp_t. The debugging is less critical but it should be possible to also move it to a srtp_t.