IOP OS

IOP OS is a set of functions in IOS's networking code that convert Revolution OS calls to IOS syscalls; for example, OSAlloc is implemented as a call to IOS_Alloc.

Toggling interrupts

Disabling interrupts is simulated by locking a mutex (but not an OSMutex) implemented as a message queue and changing the current thread priority to 0x38. While this does not completely prevent concurrent execution within the module,^[check] it is enough for most uses of OSDisableInterrupts.

Threads

Threads are implemented as a proxy to IOS threads. Because of this, OSThreadQueue is only used for suspended queues.

struct OSThread {
	int threadId;
	int priority;
	void *threadSpecific;
	struct OSThread *next;
}

struct OSThreadQueue {
	struct OSThread *head;
	struct OSThread *tail;
}

Mutexes

Mutexes are implemented as message queues that are read from to lock the mutex and sent to to unlock the mutex.

struct OSMutex {
	int mqid;
	int mq;
	int count;
	int owner; // thread id
}