src/thread/n3ds/SDL_systhread.c

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2025 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/
#include "SDL_internal.h"

#ifdef SDL_THREAD_N3DS

// Thread management routines for SDL

#include "../SDL_systhread.h"

// N3DS has very limited RAM (128MB), so we set a low default thread stack size.
#define N3DS_THREAD_STACK_SIZE_DEFAULT (80 * 1024)

#define N3DS_THREAD_PRIORITY_LOW           0x3F /**< Minimum priority */
#define N3DS_THREAD_PRIORITY_MEDIUM        0x2F /**< Slightly higher than main thread (0x30) */
#define N3DS_THREAD_PRIORITY_HIGH          0x19 /**< High priority for non-video work */
#define N3DS_THREAD_PRIORITY_TIME_CRITICAL 0x18 /**< Highest priority */

static size_t GetStackSize(size_t requested_size);

static void ThreadEntry(void *arg)
{
    SDL_RunThread((SDL_Thread *)arg);
    threadExit(0);
}


bool SDL_SYS_CreateThread(SDL_Thread *thread,
                          SDL_FunctionPointer pfnBeginThread,
                          SDL_FunctionPointer pfnEndThread)
{
    s32 priority = 0x30;
    int cpu = -1;
    size_t stack_size = GetStackSize(thread->stacksize);

    svcGetThreadPriority(&priority, CUR_THREAD_HANDLE);

    // prefer putting audio thread on system core
    if (thread->name && (SDL_strncmp(thread->name, "SDLAudioP", 9) == 0) && R_SUCCEEDED(APT_SetAppCpuTimeLimit(30))) {
        cpu = 1;
    }

    thread->handle = threadCreate(ThreadEntry,
                                  thread,
                                  stack_size,
                                  priority,
                                  cpu,
                                  false);

    if (!thread->handle) {
        return SDL_SetError("Couldn't create thread");
    }

    return true;
}

static size_t GetStackSize(size_t requested_size)
{
    if (requested_size == 0) {
        return N3DS_THREAD_STACK_SIZE_DEFAULT;
    }

    return requested_size;
}

void SDL_SYS_SetupThread(const char *name)
{
    return;
}

SDL_ThreadID SDL_GetCurrentThreadID(void)
{
    u32 thread_ID = 0;
    svcGetThreadId(&thread_ID, CUR_THREAD_HANDLE);
    return (SDL_ThreadID)thread_ID;
}

bool SDL_SYS_SetThreadPriority(SDL_ThreadPriority sdl_priority)
{
    s32 svc_priority;
    switch (sdl_priority) {
    case SDL_THREAD_PRIORITY_LOW:
        svc_priority = N3DS_THREAD_PRIORITY_LOW;
        break;
    case SDL_THREAD_PRIORITY_NORMAL:
        svc_priority = N3DS_THREAD_PRIORITY_MEDIUM;
        break;
    case SDL_THREAD_PRIORITY_HIGH:
        svc_priority = N3DS_THREAD_PRIORITY_HIGH;
        break;
    case SDL_THREAD_PRIORITY_TIME_CRITICAL:
        svc_priority = N3DS_THREAD_PRIORITY_TIME_CRITICAL;
        break;
    default:
        svc_priority = N3DS_THREAD_PRIORITY_MEDIUM;
    }
    if (svcSetThreadPriority(CUR_THREAD_HANDLE, svc_priority) < 0) {
        return SDL_SetError("svcSetThreadPriority failed");
    }
    return true;
}

void SDL_SYS_WaitThread(SDL_Thread *thread)
{
    Result res = threadJoin(thread->handle, U64_MAX);

    /*
      Detached threads can be waited on, but should NOT be cleaned manually
      as it would result in a fatal error.
    */
    if (R_SUCCEEDED(res) && SDL_GetThreadState(thread) != SDL_THREAD_DETACHED) {
        threadFree(thread->handle);
    }
}

void SDL_SYS_DetachThread(SDL_Thread *thread)
{
    threadDetach(thread->handle);
}

#endif // SDL_THREAD_N3DS