Implement a generic polled Alarm function. This merely removes the system

dependent portion of the lib/Support/SlowOperationTimer code into the
lib/System implementation where it can be ported to different platforms.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24937 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/System/Alarm.h

@@ -0,0 +1,42 @@
+//===- llvm/System/Alarm.h - Alarm Generation support  ----------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Reid Spencer and is distributed under the
+// University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides an operating system independent interface to alarm(2) 
+// type functionality. The Alarm class allows a one-shot alarm to be set up 
+// at some number of seconds in the future. When the alarm triggers, a method
+// is called to process the event
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SYSTEM_ALARM_H
+#define LLVM_SYSTEM_ALARM_H
+
+namespace llvm {
+namespace sys {
+
+  /// This function registers an alarm to trigger some number of \p seconds in 
+  /// the future. When that time arrives, the \p callback is called. You can
+  /// only call this once. Each time 
+  /// @returns nothing
+  void SetupAlarm(
+    unsigned seconds ///< Number of seconds in future when alarm arrives
+  );
+
+  /// This function terminates the alarm previously set up 
+  /// @returns nothing
+  void TerminateAlarm();
+
+  /// This function acquires the status of the alarm. 
+  /// @returns -1=cancelled, 0=untriggered, 1=triggered
+  int AlarmStatus();
+
+} // End sys namespace
+} // End llvm namespace
+
+#endif