1 files changed, 55 insertions, 0 deletions
diff --git a/xpcom/glue/AutoRestore.h b/xpcom/glue/AutoRestore.h
new file mode 100644
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+++ b/xpcom/glue/AutoRestore.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* functions for restoring saved values at the end of a C++ scope */
+
+#ifndef mozilla_AutoRestore_h_
+#define mozilla_AutoRestore_h_
+
+#include "mozilla/Attributes.h" // MOZ_STACK_CLASS
+#include "mozilla/GuardObjects.h"
+
+namespace mozilla {
+
+/**
+ * Save the current value of a variable and restore it when the object
+ * goes out of scope.  For example:
+ *   {
+ *     AutoRestore<bool> savePainting(mIsPainting);
+ *     mIsPainting = true;
+ *
+ *     // ... your code here ...
+ *
+ *     // mIsPainting is reset to its old value at the end of this block
+ *   }
+ */
+template<class T>
+class MOZ_RAII AutoRestore
+{
+private:
+  T& mLocation;
+  T mValue;
+  MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
+public:
+  explicit AutoRestore(T& aValue MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
+    : mLocation(aValue)
+    , mValue(aValue)
+  {
+    MOZ_GUARD_OBJECT_NOTIFIER_INIT;
+  }
+  ~AutoRestore()
+  {
+    mLocation = mValue;
+  }
+  T SavedValue() const
+  {
+    return mValue;
+  }
+};
+
+} // namespace mozilla
+
+#endif /* !defined(mozilla_AutoRestore_h_) */