144 lines
3.5 KiB
C
144 lines
3.5 KiB
C
/*
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Simple DirectMedia Layer
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Copyright (C) 1997-2022 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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#ifdef SDL_THREAD_N3DS
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/* An implementation of semaphores using libctru's LightSemaphore */
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#include <3ds.h>
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#include "SDL_thread.h"
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#include "SDL_timer.h"
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int WaitOnSemaphoreFor(SDL_sem *sem, Uint32 timeout);
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struct SDL_semaphore
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{
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LightSemaphore semaphore;
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};
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SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)
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{
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SDL_sem *sem;
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if (initial_value > SDL_MAX_SINT16) {
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SDL_SetError("Initial semaphore value too high for this platform");
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return NULL;
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}
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sem = (SDL_sem *)SDL_malloc(sizeof(*sem));
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if (sem == NULL) {
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SDL_OutOfMemory();
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return NULL;
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}
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LightSemaphore_Init(&sem->semaphore, initial_value, SDL_MAX_SINT16);
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return sem;
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}
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/* WARNING:
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You cannot call this function when another thread is using the semaphore.
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*/
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void SDL_DestroySemaphore(SDL_sem *sem)
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{
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SDL_free(sem);
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}
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int SDL_SemTryWait(SDL_sem *sem)
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{
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if (sem == NULL) {
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return SDL_InvalidParamError("sem");
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}
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if (LightSemaphore_TryAcquire(&sem->semaphore, 1) != 0) {
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/* If we failed, yield to avoid starvation on busy waits */
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svcSleepThread(1);
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return SDL_MUTEX_TIMEDOUT;
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}
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return 0;
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}
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int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
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{
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if (sem == NULL) {
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return SDL_InvalidParamError("sem");
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}
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if (timeout == SDL_MUTEX_MAXWAIT) {
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LightSemaphore_Acquire(&sem->semaphore, 1);
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return 0;
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}
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if (LightSemaphore_TryAcquire(&sem->semaphore, 1) != 0) {
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return WaitOnSemaphoreFor(sem, timeout);
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}
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return 0;
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}
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int WaitOnSemaphoreFor(SDL_sem *sem, Uint32 timeout)
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{
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Uint64 stop_time = SDL_GetTicks64() + timeout;
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Uint64 current_time = SDL_GetTicks64();
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while (current_time < stop_time) {
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if (LightSemaphore_TryAcquire(&sem->semaphore, 1) == 0) {
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return 0;
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}
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/* 100 microseconds seems to be the sweet spot */
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svcSleepThread(100000LL);
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current_time = SDL_GetTicks64();
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}
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/* If we failed, yield to avoid starvation on busy waits */
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svcSleepThread(1);
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return SDL_MUTEX_TIMEDOUT;
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}
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int SDL_SemWait(SDL_sem *sem)
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{
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return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
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}
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Uint32 SDL_SemValue(SDL_sem *sem)
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{
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if (sem == NULL) {
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SDL_InvalidParamError("sem");
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return 0;
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}
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return sem->semaphore.current_count;
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}
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int SDL_SemPost(SDL_sem *sem)
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{
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if (sem == NULL) {
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return SDL_InvalidParamError("sem");
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}
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LightSemaphore_Release(&sem->semaphore, 1);
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return 0;
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}
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#endif /* SDL_THREAD_N3DS */
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/* vi: set sts=4 ts=4 sw=4 expandtab: */
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