Adding upstream version 1:7.0.4.upstream/1%7.0.4upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 89 insertions, 0 deletions

diff --git a/include/o3tl/lazy_update.hxx b/include/o3tl/lazy_update.hxx
new file mode 100644
index 000000000..951a9bb7b
--- /dev/null
+++ b/include/o3tl/lazy_update.hxx
@@ -0,0 +1,89 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * 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/.
+ *
+ * This file incorporates work covered by the following license notice:
+ *
+ *   Licensed to the Apache Software Foundation (ASF) under one or more
+ *   contributor license agreements. See the NOTICE file distributed
+ *   with this work for additional information regarding copyright
+ *   ownership. The ASF licenses this file to you under the Apache
+ *   License, Version 2.0 (the "License"); you may not use this file
+ *   except in compliance with the License. You may obtain a copy of
+ *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
+ */
+
+#ifndef INCLUDED_O3TL_LAZY_UPDATE_HXX
+#define INCLUDED_O3TL_LAZY_UPDATE_HXX
+
+#include <utility>
+
+namespace o3tl
+{
+    /** Update output object lazily
+
+        This template collects data in input type, and updates the
+        output type with the given update functor, but only if the
+        output is requested. Useful if updating is expensive, or input
+        changes frequently, but output is only comparatively seldom
+        used.
+
+        @example
+        <pre>
+LazyUpdate<InType,OutType,decltype(F)> myValue(F);
+*myValue = newInput;
+myValue->updateInput( this, that, those );
+
+output( *myValue );
+        </pre>
+        or
+        <pre>
+output( myValue.getOutValue() );
+        </pre>
+        if the compiler does not recognize the const context.
+     */
+    template<typename In, typename Out, typename Func> class LazyUpdate {
+    public:
+        LazyUpdate(Func const & func): func_(func), input_(), dirty_(true) {}
+
+        In const & getInValue() const { return input_; }
+
+        Out const & getOutValue() const { return update(); }
+
+        In & operator *() {
+            dirty_ = true;
+            return input_;
+        }
+
+        In * operator ->() {
+            dirty_ = true;
+            return &input_;
+        }
+
+        Out const & operator *() const { return update();  }
+
+        Out const * operator ->() const { return &update(); }
+
+    private:
+        Out const & update() const {
+            if (dirty_) {
+                output_ = func_(input_);
+                dirty_ = false;
+            }
+            return output_;
+        }
+
+        Func const func_;
+        In input_;
+        mutable Out output_;
+        mutable bool dirty_;
+    };
+}
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */