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28
29/// \file stack_cleaner.hpp
30/// Provides the stack_cleaner class.
31
32#if !defined(LUTOK_STACK_CLEANER_HPP)
33#define LUTOK_STACK_CLEANER_HPP
34
35#include <memory>
36
37#include <lutok/state.hpp>
38
39namespace lutok {
40
41
42/// A RAII model for values on the Lua stack.
43///
44/// At creation time, the object records the current depth of the Lua stack and,
45/// during destruction, restores the recorded depth by popping as many stack
46/// entries as required.  As a corollary, the stack can only grow during the
47/// lifetime of a stack_cleaner object (or shrink, but cannot become shorter
48/// than the depth recorded at creation time).
49///
50/// Use this class as follows:
51///
52/// state s;
53/// {
54///     stack_cleaner cleaner1(s);
55///     s.push_integer(3);
56///     s.push_integer(5);
57///     ... do stuff here ...
58///     for (...) {
59///         stack_cleaner cleaner2(s);
60///         s.load_string("...");
61///         s.pcall(0, 1, 0);
62///         ... do stuff here ...
63///     }
64///     // cleaner2 destroyed; the result of pcall is gone.
65/// }
66/// // cleaner1 destroyed; the integers 3 and 5 are gone.
67///
68/// You must give a name to the instantiated objects even if they cannot be
69/// accessed later.  Otherwise, the instance will be destroyed right away and
70/// will not have the desired effect.
71class stack_cleaner {
72    struct impl;
73
74    /// Pointer to the shared internal implementation.
75    std::auto_ptr< impl > _pimpl;
76
77    /// Disallow copies.
78    stack_cleaner(const stack_cleaner&);
79
80    /// Disallow assignment.
81    stack_cleaner& operator=(const stack_cleaner&);
82
83public:
84    stack_cleaner(state&);
85    ~stack_cleaner(void);
86
87    void forget(void);
88};
89
90
91}  // namespace lutok
92
93#endif  // !defined(LUTOK_STACK_CLEANER_HPP)
94