1 // Copyright 2011 Google Inc.
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3 //
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16 //
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27 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28
29 #include <cassert>
30 #include <cstring>
31
32 #include "stack_cleaner.hpp"
33 #include "state.ipp"
34
35
36 /// Internal implementation for lutok::stack_cleaner.
37 struct lutok::stack_cleaner::impl {
38 /// Reference to the Lua state this stack_cleaner refers to.
39 state& state_ref;
40
41 /// The depth of the Lua stack to be restored.
42 unsigned int original_depth;
43
44 /// Constructor.
45 ///
46 /// \param state_ref_ Reference to the Lua state.
47 /// \param original_depth_ The depth of the Lua stack.
impllutok::stack_cleaner::impl48 impl(state& state_ref_, const unsigned int original_depth_) :
49 state_ref(state_ref_),
50 original_depth(original_depth_)
51 {
52 }
53 };
54
55
56 /// Creates a new stack cleaner.
57 ///
58 /// This gathers the current height of the stack so that extra elements can be
59 /// popped during destruction.
60 ///
61 /// \param state_ The Lua state.
stack_cleaner(state & state_)62 lutok::stack_cleaner::stack_cleaner(state& state_) :
63 _pimpl(new impl(state_, state_.get_top()))
64 {
65 }
66
67
68 /// Pops any values from the stack not known at construction time.
69 ///
70 /// \pre The current height of the stack must be equal or greater to the height
71 /// of the stack when this object was instantiated.
~stack_cleaner(void)72 lutok::stack_cleaner::~stack_cleaner(void)
73 {
74 const unsigned int current_depth = _pimpl->state_ref.get_top();
75 assert(current_depth >= _pimpl->original_depth);
76 const unsigned int diff = current_depth - _pimpl->original_depth;
77 if (diff > 0)
78 _pimpl->state_ref.pop(diff);
79 }
80
81
82 /// Forgets about any elements currently in the stack.
83 ///
84 /// This allows a function to return values on the stack because all the
85 /// elements that are currently in the stack will not be touched during
86 /// destruction when the function is called.
87 void
forget(void)88 lutok::stack_cleaner::forget(void)
89 {
90 _pimpl->original_depth = _pimpl->state_ref.get_top();
91 }
92