Security-59306.11.20.tar.gz

[apple/security.git] / OSX / utilities / sec_action.h

diff --git a/OSX/utilities/sec_action.h b/OSX/utilities/sec_action.h
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+/*
+ * Copyright (c) 2017 Apple Inc. All Rights Reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+#ifndef _SEC_ACTION_H_
+#define _SEC_ACTION_H_
+
+#include <dispatch/dispatch.h>
+
+/*
+ * Simple dispatch-based mechanism to coalesce high-frequency actions like
+ * notifications. Sample usage:
+ *
+ *  static void
+ *  notify_frequent_event(void)
+ *  {
+ *      static dispatch_once_t once;
+ *      static sec_action_t action;
+ *
+ *      dispatch_once(&once, ^{
+ *          action = sec_action_create("frequent_event", 2);
+ *          sec_action_set_handler(action, ^{
+ *              (void)notify_post("com.apple.frequent_event");
+ *          });
+ *      });
+ *
+ *      sec_action_perform(action);
+ *  }
+ *
+ * The above will prevent com.apple.frequent_event from being posted more than
+ * once every 2 seconds. For example, if notify_frequent_event is called 1000 times
+ * over the span of 1.9s, the handler will be called twice, at 0s and 2s (approx).
+ *
+ * Default behavior is to perform actions on a queue with the same QOS as the caller.
+ * If the action should be performed on a specific serial queue, the function
+ * sec_action_create_with_queue can alternatively be used.
+ */
+
+typedef dispatch_source_t sec_action_t;
+
+__BEGIN_DECLS
+
+DISPATCH_MALLOC DISPATCH_RETURNS_RETAINED DISPATCH_WARN_RESULT DISPATCH_NONNULL_ALL DISPATCH_NOTHROW
+sec_action_t
+sec_action_create(const char *label, uint64_t interval);
+
+DISPATCH_MALLOC DISPATCH_RETURNS_RETAINED DISPATCH_WARN_RESULT DISPATCH_NOTHROW
+sec_action_t
+sec_action_create_with_queue(dispatch_queue_t queue, const char *label, uint64_t interval);
+
+DISPATCH_NONNULL_ALL DISPATCH_NOTHROW
+void
+sec_action_set_handler(sec_action_t action, dispatch_block_t handler);
+
+DISPATCH_NONNULL_ALL
+void
+sec_action_perform(sec_action_t action);
+
+__END_DECLS
+
+#endif /* _SEC_ACTION_H_ */