early-access version 1611

externals/SDL/src/thread/generic/SDL_syssem.c

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+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2020 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"
+
+/* An implementation of semaphores using mutexes and condition variables */
+
+#include "SDL_timer.h"
+#include "SDL_thread.h"
+#include "SDL_systhread_c.h"
+
+
+#if SDL_THREADS_DISABLED
+
+SDL_sem *
+SDL_CreateSemaphore(Uint32 initial_value)
+{
+    SDL_SetError("SDL not built with thread support");
+    return (SDL_sem *) 0;
+}
+
+void
+SDL_DestroySemaphore(SDL_sem * sem)
+{
+}
+
+int
+SDL_SemTryWait(SDL_sem * sem)
+{
+    return SDL_SetError("SDL not built with thread support");
+}
+
+int
+SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
+{
+    return SDL_SetError("SDL not built with thread support");
+}
+
+int
+SDL_SemWait(SDL_sem * sem)
+{
+    return SDL_SetError("SDL not built with thread support");
+}
+
+Uint32
+SDL_SemValue(SDL_sem * sem)
+{
+    return 0;
+}
+
+int
+SDL_SemPost(SDL_sem * sem)
+{
+    return SDL_SetError("SDL not built with thread support");
+}
+
+#else
+
+struct SDL_semaphore
+{
+    Uint32 count;
+    Uint32 waiters_count;
+    SDL_mutex *count_lock;
+    SDL_cond *count_nonzero;
+};
+
+SDL_sem *
+SDL_CreateSemaphore(Uint32 initial_value)
+{
+    SDL_sem *sem;
+
+    sem = (SDL_sem *) SDL_malloc(sizeof(*sem));
+    if (!sem) {
+        SDL_OutOfMemory();
+        return NULL;
+    }
+    sem->count = initial_value;
+    sem->waiters_count = 0;
+
+    sem->count_lock = SDL_CreateMutex();
+    sem->count_nonzero = SDL_CreateCond();
+    if (!sem->count_lock || !sem->count_nonzero) {
+        SDL_DestroySemaphore(sem);
+        return NULL;
+    }
+
+    return sem;
+}
+
+/* WARNING:
+   You cannot call this function when another thread is using the semaphore.
+*/
+void
+SDL_DestroySemaphore(SDL_sem * sem)
+{
+    if (sem) {
+        sem->count = 0xFFFFFFFF;
+        while (sem->waiters_count > 0) {
+            SDL_CondSignal(sem->count_nonzero);
+            SDL_Delay(10);
+        }
+        SDL_DestroyCond(sem->count_nonzero);
+        if (sem->count_lock) {
+            SDL_LockMutex(sem->count_lock);
+            SDL_UnlockMutex(sem->count_lock);
+            SDL_DestroyMutex(sem->count_lock);
+        }
+        SDL_free(sem);
+    }
+}
+
+int
+SDL_SemTryWait(SDL_sem * sem)
+{
+    int retval;
+
+    if (!sem) {
+        return SDL_SetError("Passed a NULL semaphore");
+    }
+
+    retval = SDL_MUTEX_TIMEDOUT;
+    SDL_LockMutex(sem->count_lock);
+    if (sem->count > 0) {
+        --sem->count;
+        retval = 0;
+    }
+    SDL_UnlockMutex(sem->count_lock);
+
+    return retval;
+}
+
+int
+SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
+{
+    int retval;
+
+    if (!sem) {
+        return SDL_SetError("Passed a NULL semaphore");
+    }
+
+    /* A timeout of 0 is an easy case */
+    if (timeout == 0) {
+        return SDL_SemTryWait(sem);
+    }
+
+    SDL_LockMutex(sem->count_lock);
+    ++sem->waiters_count;
+    retval = 0;
+    while ((sem->count == 0) && (retval != SDL_MUTEX_TIMEDOUT)) {
+        retval = SDL_CondWaitTimeout(sem->count_nonzero,
+                                     sem->count_lock, timeout);
+    }
+    --sem->waiters_count;
+    if (retval == 0) {
+        --sem->count;
+    }
+    SDL_UnlockMutex(sem->count_lock);
+
+    return retval;
+}
+
+int
+SDL_SemWait(SDL_sem * sem)
+{
+    return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
+}
+
+Uint32
+SDL_SemValue(SDL_sem * sem)
+{
+    Uint32 value;
+
+    value = 0;
+    if (sem) {
+        SDL_LockMutex(sem->count_lock);
+        value = sem->count;
+        SDL_UnlockMutex(sem->count_lock);
+    }
+    return value;
+}
+
+int
+SDL_SemPost(SDL_sem * sem)
+{
+    if (!sem) {
+        return SDL_SetError("Passed a NULL semaphore");
+    }
+
+    SDL_LockMutex(sem->count_lock);
+    if (sem->waiters_count > 0) {
+        SDL_CondSignal(sem->count_nonzero);
+    }
+    ++sem->count;
+    SDL_UnlockMutex(sem->count_lock);
+
+    return 0;
+}
+
+#endif /* SDL_THREADS_DISABLED */
+/* vi: set ts=4 sw=4 expandtab: */