1 files changed, 194 insertions, 0 deletions

diff --git a/contrib/SDL-3.2.8/src/thread/generic/SDL_sysrwlock.c b/contrib/SDL-3.2.8/src/thread/generic/SDL_sysrwlock.c
new file mode 100644
index 0000000..24caf51
--- /dev/null
+++ b/contrib/SDL-3.2.8/src/thread/generic/SDL_sysrwlock.c
@@ -0,0 +1,194 @@
+/*
+  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 rwlocks using mutexes, condition variables, and atomics.
+
+#include "SDL_systhread_c.h"
+
+#include "../generic/SDL_sysrwlock_c.h"
+
+/* If two implementations are to be compiled into SDL (the active one
+ * will be chosen at runtime), the function names need to be
+ * suffixed
+ */
+// !!! FIXME: this is quite a tapdance with macros and the build system, maybe we can simplify how we do this. --ryan.
+#ifndef SDL_THREAD_GENERIC_RWLOCK_SUFFIX
+#define SDL_CreateRWLock_generic SDL_CreateRWLock
+#define SDL_DestroyRWLock_generic SDL_DestroyRWLock
+#define SDL_LockRWLockForReading_generic SDL_LockRWLockForReading
+#define SDL_LockRWLockForWriting_generic SDL_LockRWLockForWriting
+#define SDL_UnlockRWLock_generic SDL_UnlockRWLock
+#endif
+
+struct SDL_RWLock
+{
+#ifdef SDL_THREADS_DISABLED
+    int unused;
+#else
+    SDL_Mutex *lock;
+    SDL_Condition *condition;
+    SDL_ThreadID writer_thread;
+    SDL_AtomicInt reader_count;
+    SDL_AtomicInt writer_count;
+#endif
+};
+
+SDL_RWLock *SDL_CreateRWLock_generic(void)
+{
+    SDL_RWLock *rwlock = (SDL_RWLock *) SDL_calloc(1, sizeof (*rwlock));
+
+    if (!rwlock) {
+        return NULL;
+    }
+
+#ifndef SDL_THREADS_DISABLED
+    rwlock->lock = SDL_CreateMutex();
+    if (!rwlock->lock) {
+        SDL_free(rwlock);
+        return NULL;
+    }
+
+    rwlock->condition = SDL_CreateCondition();
+    if (!rwlock->condition) {
+        SDL_DestroyMutex(rwlock->lock);
+        SDL_free(rwlock);
+        return NULL;
+    }
+
+    SDL_SetAtomicInt(&rwlock->reader_count, 0);
+    SDL_SetAtomicInt(&rwlock->writer_count, 0);
+#endif
+
+    return rwlock;
+}
+
+void SDL_DestroyRWLock_generic(SDL_RWLock *rwlock)
+{
+    if (rwlock) {
+#ifndef SDL_THREADS_DISABLED
+        SDL_DestroyMutex(rwlock->lock);
+        SDL_DestroyCondition(rwlock->condition);
+#endif
+        SDL_free(rwlock);
+    }
+}
+
+void SDL_LockRWLockForReading_generic(SDL_RWLock *rwlock) SDL_NO_THREAD_SAFETY_ANALYSIS  // clang doesn't know about NULL mutexes
+{
+#ifndef SDL_THREADS_DISABLED
+    if (rwlock) {
+        // !!! FIXME: these don't have to be atomic, we always gate them behind a mutex.
+        SDL_LockMutex(rwlock->lock);
+        SDL_assert(SDL_GetAtomicInt(&rwlock->writer_count) == 0);  // shouldn't be able to grab lock if there's a writer!
+        SDL_AddAtomicInt(&rwlock->reader_count, 1);
+        SDL_UnlockMutex(rwlock->lock);   // other readers can attempt to share the lock.
+    }
+#endif
+}
+
+void SDL_LockRWLockForWriting_generic(SDL_RWLock *rwlock) SDL_NO_THREAD_SAFETY_ANALYSIS  // clang doesn't know about NULL mutexes
+{
+#ifndef SDL_THREADS_DISABLED
+    if (rwlock) {
+        SDL_LockMutex(rwlock->lock);
+        while (SDL_GetAtomicInt(&rwlock->reader_count) > 0) {  // while something is holding the shared lock, keep waiting.
+            SDL_WaitCondition(rwlock->condition, rwlock->lock);  // release the lock and wait for readers holding the shared lock to release it, regrab the lock.
+        }
+
+        // we hold the lock!
+        SDL_AddAtomicInt(&rwlock->writer_count, 1);  // we let these be recursive, but the API doesn't require this. It _does_ trust you unlock correctly!
+    }
+#endif
+}
+
+bool SDL_TryLockRWLockForReading_generic(SDL_RWLock *rwlock)
+{
+#ifndef SDL_THREADS_DISABLED
+    if (rwlock) {
+        if (!SDL_TryLockMutex(rwlock->lock)) {
+            // !!! FIXME: there is a small window where a reader has to lock the mutex, and if we hit that, we will return SDL_RWLOCK_TIMEDOUT even though we could have shared the lock.
+            return false;
+        }
+
+        SDL_assert(SDL_GetAtomicInt(&rwlock->writer_count) == 0);  // shouldn't be able to grab lock if there's a writer!
+        SDL_AddAtomicInt(&rwlock->reader_count, 1);
+        SDL_UnlockMutex(rwlock->lock);   // other readers can attempt to share the lock.
+    }
+#endif
+
+    return true;
+}
+
+#ifndef SDL_THREAD_GENERIC_RWLOCK_SUFFIX
+bool SDL_TryLockRWLockForReading(SDL_RWLock *rwlock)
+{
+    return SDL_TryLockRWLockForReading_generic(rwlock);
+}
+#endif
+
+bool SDL_TryLockRWLockForWriting_generic(SDL_RWLock *rwlock)
+{
+#ifndef SDL_THREADS_DISABLED
+    if (rwlock) {
+        if (!SDL_TryLockMutex(rwlock->lock)) {
+            return false;
+        }
+
+        if (SDL_GetAtomicInt(&rwlock->reader_count) > 0) {  // a reader is using the shared lock, treat it as unavailable.
+            SDL_UnlockMutex(rwlock->lock);
+            return false;
+        }
+
+        // we hold the lock!
+        SDL_AddAtomicInt(&rwlock->writer_count, 1);  // we let these be recursive, but the API doesn't require this. It _does_ trust you unlock correctly!
+    }
+#endif
+
+    return true;
+}
+
+#ifndef SDL_THREAD_GENERIC_RWLOCK_SUFFIX
+bool SDL_TryLockRWLockForWriting(SDL_RWLock *rwlock)
+{
+    return SDL_TryLockRWLockForWriting_generic(rwlock);
+}
+#endif
+
+void SDL_UnlockRWLock_generic(SDL_RWLock *rwlock) SDL_NO_THREAD_SAFETY_ANALYSIS  // clang doesn't know about NULL mutexes
+{
+#ifndef SDL_THREADS_DISABLED
+    if (rwlock) {
+        SDL_LockMutex(rwlock->lock);  // recursive lock for writers, readers grab lock to make sure things are sane.
+
+        if (SDL_GetAtomicInt(&rwlock->reader_count) > 0) {  // we're a reader
+            SDL_AddAtomicInt(&rwlock->reader_count, -1);
+            SDL_BroadcastCondition(rwlock->condition);  // alert any pending writers to attempt to try to grab the lock again.
+        } else if (SDL_GetAtomicInt(&rwlock->writer_count) > 0) {  // we're a writer
+            SDL_AddAtomicInt(&rwlock->writer_count, -1);
+            SDL_UnlockMutex(rwlock->lock);  // recursive unlock.
+        }
+
+        SDL_UnlockMutex(rwlock->lock);
+    }
+#endif
+}
+