1 // Copyright 2011 Google Inc. 2 // All rights reserved. 3 // 4 // Redistribution and use in source and binary forms, with or without 5 // modification, are permitted provided that the following conditions are 6 // met: 7 // 8 // * Redistributions of source code must retain the above copyright 9 // notice, this list of conditions and the following disclaimer. 10 // * Redistributions in binary form must reproduce the above copyright 11 // notice, this list of conditions and the following disclaimer in the 12 // documentation and/or other materials provided with the distribution. 13 // * Neither the name of Google Inc. nor the names of its contributors 14 // may be used to endorse or promote products derived from this software 15 // without specific prior written permission. 16 // 17 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 18 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 19 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 20 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 21 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 22 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 23 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 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. 48 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. 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. 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 88 lutok::stack_cleaner::forget(void) 89 { 90 _pimpl->original_depth = _pimpl->state_ref.get_top(); 91 } 92