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+// Copyright 2011 Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+//   notice, this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above copyright
+//   notice, this list of conditions and the following disclaimer in the
+//   documentation and/or other materials provided with the distribution.
+// * Neither the name of Google Inc. nor the names of its contributors
+//   may be used to endorse or promote products derived from this software
+//   without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+/// \file stack_cleaner.hpp
+/// Provides the stack_cleaner class.
+
+#if !defined(LUTOK_STACK_CLEANER_HPP)
+#define LUTOK_STACK_CLEANER_HPP
+
+#include <memory>
+
+#include <lutok/state.hpp>
+
+namespace lutok {
+
+
+/// A RAII model for values on the Lua stack.
+///
+/// At creation time, the object records the current depth of the Lua stack and,
+/// during destruction, restores the recorded depth by popping as many stack
+/// entries as required.  As a corollary, the stack can only grow during the
+/// lifetime of a stack_cleaner object (or shrink, but cannot become shorter
+/// than the depth recorded at creation time).
+///
+/// Use this class as follows:
+///
+/// state s;
+/// {
+///     stack_cleaner cleaner1(s);
+///     s.push_integer(3);
+///     s.push_integer(5);
+///     ... do stuff here ...
+///     for (...) {
+///         stack_cleaner cleaner2(s);
+///         s.load_string("...");
+///         s.pcall(0, 1, 0);
+///         ... do stuff here ...
+///     }
+///     // cleaner2 destroyed; the result of pcall is gone.
+/// }
+/// // cleaner1 destroyed; the integers 3 and 5 are gone.
+///
+/// You must give a name to the instantiated objects even if they cannot be
+/// accessed later.  Otherwise, the instance will be destroyed right away and
+/// will not have the desired effect.
+class stack_cleaner {
+    struct impl;
+
+    /// Pointer to the shared internal implementation.
+    std::auto_ptr< impl > _pimpl;
+
+    /// Disallow copies.
+    stack_cleaner(const stack_cleaner&);
+
+    /// Disallow assignment.
+    stack_cleaner& operator=(const stack_cleaner&);
+
+public:
+    stack_cleaner(state&);
+    ~stack_cleaner(void);
+
+    void forget(void);
+};
+
+
+}  // namespace lutok
+
+#endif  // !defined(LUTOK_STACK_CLEANER_HPP)