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dirty_value.hpp
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00001 /* 00002 Copyright 2005-2007 Adobe Systems Incorporated 00003 Distributed under the MIT License (see accompanying file LICENSE_1_0_0.txt 00004 or a copy at http://stlab.adobe.com/licenses.html) 00005 */ 00006 00007 /*************************************************************************************************/ 00008 00009 #ifndef ADOBE_DIRTY_VALUE_HPP 00010 #define ADOBE_DIRTY_VALUE_HPP 00011 00012 /*************************************************************************************************/ 00013 00014 #include <adobe/config.hpp> 00015 00016 /*************************************************************************************************/ 00017 00018 namespace adobe { 00019 00020 /*************************************************************************************************/ 00021 00022 template <typename T> 00023 struct dirty_value 00024 { 00025 typedef T value_type; 00026 00027 dirty_value(const value_type& x = value_type()) : 00028 value_m(x), dirty_m(false) 00029 { } 00030 00031 dirty_value(const dirty_value& rhs) : 00032 value_m(rhs.value_m), dirty_m(false) 00033 { } 00034 00035 dirty_value& operator = (const value_type& rhs) 00036 { 00037 if (value_m == rhs) 00038 return *this; 00039 00040 value_m = rhs; 00041 dirty_m = true; 00042 return *this; 00043 } 00044 00045 dirty_value& operator = (const dirty_value& rhs) 00046 { return *this = rhs.value_m; } 00047 00048 const value_type& operator*() const 00049 { return value_m; } 00050 const value_type* operator->() const 00051 { return &value_m; } 00052 operator const value_type& () const 00053 { return value_m; } 00054 00055 void clean() 00056 { dirty_m = false; } 00057 00058 bool is_dirty() const 00059 { return dirty_m; } 00060 00061 struct cleaner 00062 { 00063 typedef dirty_value first_argument_type; 00064 typedef void result_type; 00065 00066 inline result_type operator()(first_argument_type& x) const 00067 { x.clean(); } 00068 }; 00069 00070 value_type value_m; 00071 bool dirty_m; 00072 }; 00073 00074 /*************************************************************************************************/ 00075 00076 /* 00077 NOTE (fbrereto) : We cannot use boost::totaly_ordered to implement 00078 these operations portably. The problem is that we do not know if T 00079 satifies the requirments for totally ordered or not - dirty_value is 00080 only totally ordered if T is. By splitting the operations out to 00081 seperate template functions they are only instantiated if and where 00082 they are used. 00083 */ 00084 00085 template <typename T> 00086 inline bool operator<(const dirty_value<T>& x, const dirty_value<T>& y) 00087 { return *x < *y; } 00088 00089 template <typename T> 00090 inline bool operator>(const dirty_value<T>& x, const dirty_value<T>& y) 00091 { return y < x; } 00092 00093 template <typename T> 00094 inline bool operator<=(const dirty_value<T>& x, const dirty_value<T>& y) 00095 { return !(y < x); } 00096 00097 template <typename T> 00098 inline bool operator>=(const dirty_value<T>& x, const dirty_value<T>& y) 00099 { return !(x < y); } 00100 00101 template <typename T> 00102 inline bool operator==(const dirty_value<T>& x, const dirty_value<T>& y) 00103 { return *x == *y; } 00104 00105 template <typename T> 00106 inline bool operator!=(const dirty_value<T>& x, const dirty_value<T>& y) 00107 { return !(x == y); } 00108 00109 /*************************************************************************************************/ 00110 00111 } // namespace adobe 00112 00113 /*************************************************************************************************/ 00114 00115 // ADOBE_DIRTY_VALUE_HPP 00116 #endif 00117 00118 /*************************************************************************************************/ | ||||||
