SDL/src/thread/stdcpp/SDL_systhread.cpp

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2024 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"

/* Thread management routines for SDL */

extern "C" {
#include "../SDL_thread_c.h"
#include "../SDL_systhread.h"
}

#include <mutex>
#include <thread>
#include <system_error>

#ifdef SDL_PLATFORM_WINRT
#include <Windows.h>
#endif

static void RunThread(void *args)
{
    SDL_RunThread((SDL_Thread *)args);
}

extern "C" int
SDL_SYS_CreateThread(SDL_Thread *thread)
{
    try {
        // !!! FIXME: no way to set a thread stack size here.
        std::thread cpp_thread(RunThread, thread);
        thread->handle = (void *)new std::thread(std::move(cpp_thread));
        return 0;
    } catch (std::system_error &ex) {
        return SDL_SetError("unable to start a C++ thread: code=%d; %s", ex.code(), ex.what());
    } catch (std::bad_alloc &) {
        return SDL_OutOfMemory();
    }
}

extern "C" void
SDL_SYS_SetupThread(const char *name)
{
    // Make sure a thread ID gets assigned ASAP, for debugging purposes:
    SDL_GetCurrentThreadID();
    return;
}

extern "C" SDL_ThreadID
SDL_GetCurrentThreadID(void)
{
#ifdef SDL_PLATFORM_WINRT
    return GetCurrentThreadId();
#else
    // HACK: Mimic a thread ID, if one isn't otherwise available.
    static thread_local SDL_ThreadID current_thread_id = 0;
    static SDL_ThreadID next_thread_id = 1;
    static std::mutex next_thread_id_mutex;

    if (current_thread_id == 0) {
        std::lock_guard<std::mutex> lock(next_thread_id_mutex);
        current_thread_id = next_thread_id;
        ++next_thread_id;
    }

    return current_thread_id;
#endif
}

extern "C" int
SDL_SYS_SetThreadPriority(SDL_ThreadPriority priority)
{
#ifdef SDL_PLATFORM_WINRT
    int value;

    if (priority == SDL_THREAD_PRIORITY_LOW) {
        value = THREAD_PRIORITY_LOWEST;
    } else if (priority == SDL_THREAD_PRIORITY_HIGH) {
        value = THREAD_PRIORITY_HIGHEST;
    } else if (priority == SDL_THREAD_PRIORITY_TIME_CRITICAL) {
        // FIXME: WinRT does not support TIME_CRITICAL! -flibit
        SDL_LogWarn(SDL_LOG_CATEGORY_SYSTEM, "TIME_CRITICAL unsupported, falling back to HIGHEST");
        value = THREAD_PRIORITY_HIGHEST;
    } else {
        value = THREAD_PRIORITY_NORMAL;
    }
    if (!SetThreadPriority(GetCurrentThread(), value)) {
        return WIN_SetError("SetThreadPriority()");
    }
    return 0;
#else
    return SDL_Unsupported();
#endif
}

extern "C" void
SDL_SYS_WaitThread(SDL_Thread *thread)
{
    if (!thread) {
        return;
    }

    try {
        std::thread *cpp_thread = (std::thread *)thread->handle;
        if (cpp_thread->joinable()) {
            cpp_thread->join();
        }
    } catch (std::system_error &) {
        // An error occurred when joining the thread.  SDL_WaitThread does not,
        // however, seem to provide a means to report errors to its callers
        // though!
    }
}

extern "C" void
SDL_SYS_DetachThread(SDL_Thread *thread)
{
    if (!thread) {
        return;
    }

    try {
        std::thread *cpp_thread = (std::thread *)thread->handle;
        if (cpp_thread->joinable()) {
            cpp_thread->detach();
        }
    } catch (std::system_error &) {
        // An error occurred when detaching the thread.  SDL_DetachThread does not,
        // however, seem to provide a means to report errors to its callers
        // though!
    }
}

extern "C" SDL_TLSData *
SDL_SYS_GetTLSData(void)
{
    return SDL_Generic_GetTLSData();
}

extern "C" int
SDL_SYS_SetTLSData(SDL_TLSData *data)
{
    return SDL_Generic_SetTLSData(data);
}