once.c

#include "clod_thread_config.h"
#include "debug.h"
#include <clod/thread.h>
#include "yield.h"
 
#define ZERO 0
#define BUSY 1
#define DONE 2
 
bool clod_once_do(clod_once *once) {
    while (1) {
        clod_once state = clod_atomic_load(once);
 
        #if CLOD_DEBUG_THREAD
        if (state != ZERO && state != BUSY && state != DONE) {
            debug(CLOD_DEBUG_THREAD, "called clod_once_do with an invalid value.");
        }
        #endif
 
        if (state == ZERO && clod_atomic_cas(once, &state, BUSY))
            return true;
 
        while (state == BUSY) {
            for (int i = 0; i < 500 && state == BUSY; i++) {
                clod_pause();
                state = clod_atomic_load(once);
            }
 
            clod_yield();
            state = clod_atomic_load(once);
        }
 
        if (state == DONE)
            return false;
    }
}
 
void clod_once_done(clod_once *once) {
    #if CLOD_DEBUG_THREAD
    clod_once expected = BUSY;
    if (!clod_atomic_cas(once, &expected, DONE)) {
        debug(CLOD_DEBUG_THREAD, "called clod_once_done with an invalid value.");
    }
    #else
    clod_atomic_store(once, DONE);
    #endif
}