FFI

A foreign function interface (FFI) is a mechanism for call external routines.

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FFI calls are the simplest way to implement external functions in the VM.

The function must be implemented according to the prototype:

vm_value_t (*vm_foreign_function_t)(vm_thread_t **thread, uint8_t fn, uint32_t arg)

Where thread is the current thread, and fn is a parameter for internal use of the function.

The pointer to this function must be added to the array of foreign functions (foreign_functions in the thread state).

To call it, use: CALL_FOREIGN u8 u32 @u32 where first u8 is the fn parameter, second u32 is an arbitrary argument and third @u32 is the index in foreign_functions array.

The function must return a value that will be assigned to ret_val