--- Libc/Libc-1725.40.4/sys/OSMemoryNotification.c
+++ Libc/Libc-825.25/sys/OSMemoryNotification.c
@@ -21,11 +21,115 @@
  * @APPLE_LICENSE_HEADER_END@
  */
 
-// Legacy symbols preserved for binary compatibility.
+#include <errno.h>
+#include <libkern/OSMemoryNotification.h>
+#include <mach/mach.h>
+#include <notify.h>
+#include <stdlib.h>
+#include <sys/time.h>
+#include <dispatch/dispatch.h>
+#include <dispatch/private.h>
 
 const char *kOSMemoryNotificationName = "com.apple.system.memorystatus";
 
-int OSMemoryNotificationCurrentLevel(void)
+struct _OSMemoryNotification {
+	int token;
+	mach_port_t port;
+};
+
+int
+OSMemoryNotificationCreate(OSMemoryNotificationRef *note)
 {
-	return 0; // OSMemoryNotificationLevelNormal
+	OSMemoryNotificationRef ref = malloc(sizeof(struct _OSMemoryNotification));
+
+	if (NULL == ref) {
+		return ENOMEM;
+	}
+	
+	if (NOTIFY_STATUS_OK != notify_register_mach_port(kOSMemoryNotificationName, &ref->port, 0, &ref->token))
+		return ENOMEM;
+
+	*note = ref;
+
+	return 0;
 }
+
+int
+OSMemoryNotificationDestroy(OSMemoryNotificationRef note)
+{
+	if (NOTIFY_STATUS_OK != notify_cancel(note->token))
+		return EINVAL;
+
+	if (KERN_SUCCESS != mach_port_deallocate(mach_task_self(), note->port))
+		return EINVAL;
+
+	free(note);
+
+	return 0;
+}
+		
+int
+OSMemoryNotificationWait(OSMemoryNotificationRef note, OSMemoryNotificationLevel *level)
+{
+	return OSMemoryNotificationTimedWait(note, level, NULL);
+}
+
+static mach_msg_timeout_t
+abs_to_timeout(const struct timeval *abstime)
+{
+	struct timeval rel, now;
+
+	gettimeofday(&now, NULL);
+
+	rel.tv_usec = abstime->tv_usec - now.tv_usec;
+	rel.tv_sec = abstime->tv_sec - now.tv_sec;
+	if (rel.tv_usec < 0) {
+		rel.tv_usec += 1000000;
+		rel.tv_sec--;
+	}
+	if (((int)rel.tv_sec < 0) || ((rel.tv_sec == 0) && (rel.tv_usec == 0))) {
+		return 0;
+	}
+	return rel.tv_sec * 1000 + rel.tv_usec / 1000;
+}
+
+int
+OSMemoryNotificationTimedWait(OSMemoryNotificationRef note, OSMemoryNotificationLevel *level, const struct timeval *abstime)
+{
+    dispatch_semaphore_t sema = dispatch_semaphore_create(0);
+    dispatch_retain(sema);
+    
+    dispatch_source_t memoryNotificationSource = dispatch_source_create(DISPATCH_SOURCE_TYPE_VM, 0, DISPATCH_VM_PRESSURE, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0));
+    dispatch_source_set_event_handler(memoryNotificationSource, ^{
+        dispatch_semaphore_signal(sema);
+        dispatch_release(sema);
+    });
+
+    dispatch_resume(memoryNotificationSource);
+    
+    dispatch_time_t waitTime = DISPATCH_TIME_FOREVER;
+    if (abstime) {
+        mach_msg_timeout_t timeout = abs_to_timeout(abstime);
+        waitTime = dispatch_time(DISPATCH_TIME_NOW, timeout * 1e6);
+    }
+    
+    long ret = dispatch_semaphore_wait(sema, waitTime);
+
+    dispatch_release(sema);
+    dispatch_release(memoryNotificationSource);
+
+    if (ret != 0) {
+        return ETIMEDOUT;
+    }
+    
+    if (level) {
+        *level = OSMemoryNotificationLevelUrgent;
+    }
+    
+    return 0;
+}
+
+OSMemoryNotificationLevel OSMemoryNotificationCurrentLevel(void)
+{
+	return OSMemoryNotificationLevelNormal;
+}