SDL

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/*
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  Simple DirectMedia Layer
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  Copyright (C) 1997-2024 Sam Lantinga <slouken@libsdl.org>
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  This software is provided 'as-is', without any express or implied
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  warranty.  In no event will the authors be held liable for any damages
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  arising from the use of this software.
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  Permission is granted to anyone to use this software for any purpose,
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  including commercial applications, and to alter it and redistribute it
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  freely, subject to the following restrictions:
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  1. The origin of this software must not be misrepresented; you must not
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     claim that you wrote the original software. If you use this software
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     in a product, an acknowledgment in the product documentation would be
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     appreciated but is not required.
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  2. Altered source versions must be plainly marked as such, and must not be
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     misrepresented as being the original software.
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  3. This notice may not be removed or altered from any source distribution.
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*/
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#include "SDL_internal.h"
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#include <shared_mutex>
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#include <system_error>
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#include <Windows.h>
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struct SDL_RWLock
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{
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    std::shared_mutex cpp_mutex;
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    SDL_ThreadID write_owner;
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};
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extern "C"
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SDL_RWLock *SDL_CreateRWLock(void)
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{
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    try {
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        SDL_RWLock *rwlock = new SDL_RWLock;
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        return rwlock;
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    } catch (std::system_error &ex) {
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        SDL_SetError("unable to create a C++ rwlock: code=%d; %s", ex.code(), ex.what());
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        return NULL;
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    } catch (std::bad_alloc &) {
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        SDL_OutOfMemory();
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        return NULL;
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    }
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}
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extern "C"
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void SDL_DestroyRWLock(SDL_RWLock *rwlock)
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{
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    if (rwlock) {
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        delete rwlock;
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    }
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}
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extern "C"
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void SDL_LockRWLockForReading(SDL_RWLock *rwlock) SDL_NO_THREAD_SAFETY_ANALYSIS  // clang doesn't know about NULL mutexes
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{
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    if (rwlock) {
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        try {
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            rwlock->cpp_mutex.lock_shared();
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        } catch (std::system_error &/*ex*/) {
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            SDL_assert(!"Error trying to lock rwlock for reading");  // assume we're in a lot of trouble if this assert fails.
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            //return SDL_SetError("unable to lock a C++ rwlock: code=%d; %s", ex.code(), ex.what());
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        }
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    }
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}
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extern "C"
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void SDL_LockRWLockForWriting(SDL_RWLock *rwlock) SDL_NO_THREAD_SAFETY_ANALYSIS // clang doesn't know about NULL mutexes
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{
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    if (rwlock) {
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        try {
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            rwlock->cpp_mutex.lock();
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            rwlock->write_owner = SDL_GetCurrentThreadID();
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        } catch (std::system_error &/*ex*/) {
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            SDL_assert(!"Error trying to lock rwlock for writing");  // assume we're in a lot of trouble if this assert fails.
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            //return SDL_SetError("unable to lock a C++ rwlock: code=%d; %s", ex.code(), ex.what());
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        }
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    }
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}
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extern "C"
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SDL_bool SDL_TryLockRWLockForReading(SDL_RWLock *rwlock)
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{
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    bool result = true;
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    if (rwlock) {
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        result = rwlock->cpp_mutex.try_lock_shared();
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    }
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    return result;
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}
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extern "C"
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SDL_bool SDL_TryLockRWLockForWriting(SDL_RWLock *rwlock)
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{
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    bool result = true;
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    if (rwlock) {
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        result = rwlock->cpp_mutex.try_lock();
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        if (result) {
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            rwlock->write_owner = SDL_GetCurrentThreadID();
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        }
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    }
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    return result;
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}
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extern "C"
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void SDL_UnlockRWLock(SDL_RWLock *rwlock) SDL_NO_THREAD_SAFETY_ANALYSIS  // clang doesn't know about NULL mutexes
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{
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    if (rwlock) {
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        if (rwlock->write_owner == SDL_GetCurrentThreadID()) {
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            rwlock->write_owner = 0;
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            rwlock->cpp_mutex.unlock();
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        } else {
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            rwlock->cpp_mutex.unlock_shared();
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        }
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    }
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}
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