external/bsd/lutok/dist/stack_cleaner.hpp

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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
  39 namespace 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.
  71 class 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
  83 public:
  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)