WutThreadDriver.cpp

/****************************************************************************
 * Platform Abstraction Layer (WUT driver)
 * Daryl Borth 2026
 * WutThreadDriver.cpp
 *
 * Wraps wut/coreinit OSThread and OSMutex
 ***************************************************************************/
#include <coreinit/thread.h>
#include <coreinit/mutex.h>
#include <coreinit/time.h>
#include <coreinit/condition.h>
#include <malloc.h>
 
#include "WutThreadDriver.h"
 
namespace
{
    struct WutThreadHandle
    {
        OSThread * thread = nullptr;
        void * stack = nullptr;
        ThreadEntry entry = nullptr;
        void * arg = nullptr;
    };
 
    // OSThreadEntryPointFn is int(*)(int argc, const char ** argv). There is
    // no generic void* userdata slot in OSCreateThread - by convention (as
    // used throughout wut homebrew) the raw argv pointer itself, not *argv,
    // is repurposed to carry a single opaque payload pointer.
    int WutThreadTrampoline(int argc, const char ** argv)
    {
        (void)argc;
        WutThreadHandle * handle = reinterpret_cast<WutThreadHandle *>(argv);
        handle->entry(handle->arg);
        return 0;
    }
 
    int MapWutPriority(ThreadPriority priority)
    {
        switch (priority)
        {
            case ThreadPriority::Idle:         return 31;
            case ThreadPriority::Low:          return 24;
            case ThreadPriority::Normal:       return 16;
            case ThreadPriority::High:         return 10;
            case ThreadPriority::TimeCritical: return 3;
            default:                           return 16;
        }
    }
}
 
void WutThreadDriver::init()
{
}
 
void WutThreadDriver::shutdown()
{
}
 
bool WutThreadDriver::createThread(ThreadEntry entry, void * arg, uint32_t stackSize, ThreadPriority priority, void ** outHandle)
{
    WutThreadHandle * handle = new WutThreadHandle();
    handle->entry = entry;
    handle->arg = arg;
 
    // OSThread control blocks must be allocated by the caller (8-byte
    // aligned per wut's WUT_CHECK_SIZE/OSThread layout); the stack likewise
    // needs a real aligned allocation since OSCreateThread takes the raw
    // top-of-stack address, not a size hint.
    handle->thread = static_cast<OSThread *>(memalign(8, sizeof(OSThread)));
    if(!handle->thread)
    {
        delete handle;
        return false;
    }
 
    uint32_t alignedStackSize = (stackSize + 31) & ~31u;
    handle->stack = memalign(32, alignedStackSize);
    if(!handle->stack)
    {
        free(handle->thread);
        delete handle;
        return false;
    }
 
    // Publish the handle to the caller's storage BEFORE resuming the new
    // thread, same rationale as OgcThreadDriver::createThread - entry() may
    // reference *outHandle itself as its first action.
    *outHandle = handle;
    uint8_t * stackTop = static_cast<uint8_t *>(handle->stack) + alignedStackSize;
    int nativePriority = MapWutPriority(priority);
 
    BOOL ok = OSCreateThread(handle->thread, WutThreadTrampoline, 0, reinterpret_cast<char *>(handle),
        stackTop, alignedStackSize, nativePriority, OS_THREAD_ATTRIB_AFFINITY_ANY);
 
    if(!ok)
    {
        *outHandle = nullptr;
        free(handle->stack);
        free(handle->thread);
        delete handle;
        return false;
    }
 
    // OSCreateThread starts threads with a suspend count of 1 - they don't
    // run until explicitly resumed.
    OSResumeThread(handle->thread);
 
    return true;
}
 
void WutThreadDriver::joinThread(void * thread)
{
    if(!thread)
        return;
 
    WutThreadHandle * handle = static_cast<WutThreadHandle *>(thread);
    OSJoinThread(handle->thread, nullptr);
    free(handle->stack);
    free(handle->thread);
    delete handle;
}
 
void WutThreadDriver::cancelThread(void * thread)
{
    if(!thread)
        return;
 
    // OSCancelThread only requests cancellation - it takes effect the next
    // time the target thread hits a cancellation point (implicitly tested
    // in mutex/spinlock operations), so there's no way to know from here
    // when the thread is actually done touching its stack/control block.
    // Best effort, request the cancellation and intentionally leak the
    // thread/stack allocation rather than risk freeing memory the thread
    // may still be running on. Prefer signalling the thread to exit
    // cooperatively and calling joinThread() instead, which does clean up
    // properly.
    WutThreadHandle * handle = static_cast<WutThreadHandle *>(thread);
    OSCancelThread(handle->thread);
    delete handle;
}
 
void WutThreadDriver::suspendThread(void * thread)
{
    if(!thread)
        return;
 
    OSSuspendThread(static_cast<WutThreadHandle *>(thread)->thread);
}
 
void WutThreadDriver::resumeThread(void * thread)
{
    if(!thread)
        return;
 
    OSResumeThread(static_cast<WutThreadHandle *>(thread)->thread);
}
 
bool WutThreadDriver::isThreadSuspended(void * thread)
{
    if(!thread)
        return false;
 
    return OSIsThreadSuspended(static_cast<WutThreadHandle *>(thread)->thread) != FALSE;
}
 
void * WutThreadDriver::createMutex()
{
    OSMutex * mutex = new OSMutex();
    OSInitMutex(mutex);
    return mutex;
}
 
void WutThreadDriver::destroyMutex(void * mutex)
{
    if(!mutex)
        return;
 
    delete static_cast<OSMutex *>(mutex);
}
 
void WutThreadDriver::lockMutex(void * mutex)
{
    if(!mutex)
        return;
 
    OSLockMutex(static_cast<OSMutex *>(mutex));
}
 
void WutThreadDriver::unlockMutex(void * mutex)
{
    if(!mutex)
        return;
 
    OSUnlockMutex(static_cast<OSMutex *>(mutex));
}
 
void * WutThreadDriver::createCond()
{
    OSCondition * cond = new OSCondition();
    OSInitCond(cond);
    return cond;
}
 
void WutThreadDriver::destroyCond(void * cond)
{
    if(!cond)
        return;
 
    delete static_cast<OSCondition *>(cond);
}
 
void WutThreadDriver::waitCond(void * cond, void * mutex)
{
    if(!cond || !mutex)
        return;
 
    // OSWaitCond unlocks mutex, sleeps, and reacquires it before
    // returning - same contract as ThreadDriver::waitCond.
    OSWaitCond(static_cast<OSCondition *>(cond), static_cast<OSMutex *>(mutex));
}
 
void WutThreadDriver::signalCond(void * cond)
{
    if(!cond)
        return;
 
    // OSSignalCond already wakes every waiter (it's notify_all, not
    // notify_one) - matches ThreadDriver::signalCond's contract exactly.
    OSSignalCond(static_cast<OSCondition *>(cond));
}
 
 
void WutThreadDriver::sleepMilliseconds(uint32_t ms)
{
    OSSleepTicks(OSMillisecondsToTicks(ms));
}
 
uintptr_t WutThreadDriver::getCurrentThreadId()
{
    // OSGetCurrentThread() returns the OSThread* of the calling thread -
    // including the app's original/main thread, which (unlike threads
    // created via createThread() above) was never itself heap-allocated
    // by this driver. The pointer alone is a stable, comparable identity
    // for as long as that thread exists, which is all ThreadId needs.
    return reinterpret_cast<uintptr_t>(OSGetCurrentThread());
}