initial commit, 4.5 stable

thirdparty/sdl/thread/generic/SDL_syssem.c

@@ -0,0 +1,183 @@
+/*
+  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"
+
+// An implementation of semaphores using mutexes and condition variables
+
+#include "SDL_systhread_c.h"
+
+#ifdef SDL_THREADS_DISABLED
+
+SDL_Semaphore *SDL_CreateSemaphore(Uint32 initial_value)
+{
+    SDL_SetError("SDL not built with thread support");
+    return NULL;
+}
+
+void SDL_DestroySemaphore(SDL_Semaphore *sem)
+{
+}
+
+bool SDL_WaitSemaphoreTimeoutNS(SDL_Semaphore *sem, Sint64 timeoutNS)
+{
+    return true;
+}
+
+Uint32 SDL_GetSemaphoreValue(SDL_Semaphore *sem)
+{
+    return 0;
+}
+
+void SDL_SignalSemaphore(SDL_Semaphore *sem)
+{
+    return;
+}
+
+#else
+
+struct SDL_Semaphore
+{
+    Uint32 count;
+    Uint32 waiters_count;
+    SDL_Mutex *count_lock;
+    SDL_Condition *count_nonzero;
+};
+
+SDL_Semaphore *SDL_CreateSemaphore(Uint32 initial_value)
+{
+    SDL_Semaphore *sem;
+
+    sem = (SDL_Semaphore *)SDL_malloc(sizeof(*sem));
+    if (!sem) {
+        return NULL;
+    }
+    sem->count = initial_value;
+    sem->waiters_count = 0;
+
+    sem->count_lock = SDL_CreateMutex();
+    sem->count_nonzero = SDL_CreateCondition();
+    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_Semaphore *sem)
+{
+    if (sem) {
+        sem->count = 0xFFFFFFFF;
+        while (sem->waiters_count > 0) {
+            SDL_SignalCondition(sem->count_nonzero);
+            SDL_Delay(10);
+        }
+        SDL_DestroyCondition(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);
+    }
+}
+
+bool SDL_WaitSemaphoreTimeoutNS(SDL_Semaphore *sem, Sint64 timeoutNS)
+{
+    bool result = false;
+
+    if (!sem) {
+        return true;
+    }
+
+    if (timeoutNS == 0) {
+        SDL_LockMutex(sem->count_lock);
+        if (sem->count > 0) {
+            --sem->count;
+            result = true;
+        }
+        SDL_UnlockMutex(sem->count_lock);
+    } else if (timeoutNS < 0) {
+        SDL_LockMutex(sem->count_lock);
+        ++sem->waiters_count;
+        while (sem->count == 0) {
+            SDL_WaitConditionTimeoutNS(sem->count_nonzero, sem->count_lock, -1);
+        }
+        --sem->waiters_count;
+        --sem->count;
+        result = true;
+        SDL_UnlockMutex(sem->count_lock);
+    } else {
+        Uint64 stop_time = SDL_GetTicksNS() + timeoutNS;
+
+        SDL_LockMutex(sem->count_lock);
+        ++sem->waiters_count;
+        while (sem->count == 0) {
+            Sint64 waitNS = (Sint64)(stop_time - SDL_GetTicksNS());
+            if (waitNS > 0) {
+                SDL_WaitConditionTimeoutNS(sem->count_nonzero, sem->count_lock, waitNS);
+            } else {
+                break;
+            }
+        }
+        --sem->waiters_count;
+
+        if (sem->count > 0) {
+            --sem->count;
+            result = true;
+        }
+        SDL_UnlockMutex(sem->count_lock);
+    }
+
+    return result;
+}
+
+Uint32 SDL_GetSemaphoreValue(SDL_Semaphore *sem)
+{
+    Uint32 value;
+
+    value = 0;
+    if (sem) {
+        SDL_LockMutex(sem->count_lock);
+        value = sem->count;
+        SDL_UnlockMutex(sem->count_lock);
+    }
+    return value;
+}
+
+void SDL_SignalSemaphore(SDL_Semaphore *sem)
+{
+    if (!sem) {
+        return;
+    }
+
+    SDL_LockMutex(sem->count_lock);
+    if (sem->waiters_count > 0) {
+        SDL_SignalCondition(sem->count_nonzero);
+    }
+    ++sem->count;
+    SDL_UnlockMutex(sem->count_lock);
+}
+
+#endif // SDL_THREADS_DISABLED