Macro ffi_helpers::export_task

macro_rules! export_task {
    ($(#[$attr : meta]) * Task : $Task : ty ; spawn : $spawn : ident ;
 $($tokens : tt) *) => { ... };
    ($(#[$attr : meta]) * Task : $Task : ty ; poll : $poll : ident ;
 $($tokens : tt) *) => { ... };
    ($(#[$attr : meta]) * Task : $Task : ty ; handle_destroy : $handle_destructor
 : ident ; $($tokens : tt) *) => { ... };
    ($(#[$attr : meta]) * Task : $Task : ty ; result_destroy : $result_destroy :
 ident ; $($tokens : tt) *) => { ... };
    ($(#[$attr : meta]) * Task : $Task : ty ; wait : $wait : ident ;
 $($tokens : tt) *) => { ... };
    ($(#[$attr : meta]) * Task : $Task : ty ; cancel : $cancel : ident ;
 $($tokens : tt) *) => { ... };
    ($(#[$attr : meta]) * Task : $Task : ty ; cancelled : $cancelled : ident ;
 $($tokens : tt) *) => { ... };
    ($(#[$attr : meta]) * Task : $Task : ty ;) => { ... };
}

Convenience macro to define the FFI bindings for working with a Task.

This is implemented as an incremental TT muncher which lets you define the functions you’ll need. These are:

• spawn: The function for spawning a task on a background thread, returning a TaskHandle
• poll: A function for receiving the result if it’s available
• wait: Block the current thread until we get either a result or an error
• cancel: Cancel the background task
• cancelled: Has the task already been cancelled?
• result_destroy: A destructor for the task’s result
• handle_destroy: A destructor for the TaskHandle, for cleaning up the task once you’re done with it

You’ll always need to provide the concrete Task type in the macro’s first “argument”.