1 | /* |
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2 | * ORXONOX - the hottest 3D action shooter ever to exist |
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3 | * > www.orxonox.net < |
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4 | * |
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5 | * |
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6 | * License notice: |
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7 | * |
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8 | * This program is free software; you can redistribute it and/or |
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9 | * modify it under the terms of the GNU General Public License |
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10 | * as published by the Free Software Foundation; either version 2 |
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11 | * of the License, or (at your option) any later version. |
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12 | * |
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13 | * This program is distributed in the hope that it will be useful, |
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14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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16 | * GNU General Public License for more details. |
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17 | * |
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18 | * You should have received a copy of the GNU General Public License |
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19 | * along with this program; if not, write to the Free Software |
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20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
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21 | * |
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22 | * Author: |
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23 | * Reto Grieder |
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24 | * Fabian 'x3n' Landau |
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25 | * Benjamin Grauer |
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26 | * Co-authors: |
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27 | * ... |
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28 | */ |
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29 | |
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30 | /*! |
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31 | @file |
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32 | @brief Definition and Implementation of the Convert class. |
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33 | */ |
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34 | |
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35 | #ifndef _Converter_H__ |
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36 | #define _Converter_H__ |
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37 | |
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38 | #include "UtilPrereqs.h" |
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39 | |
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40 | #include <string> |
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41 | #include <sstream> |
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42 | #include <typeinfo> |
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43 | #include <loki/TypeManip.h> |
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44 | |
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45 | #include "Debug.h" |
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46 | #include "TemplateUtils.h" |
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47 | |
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48 | //////////////////////////////////// |
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49 | //// ACTUAL CONVERSION SEQUENCE //// |
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50 | //////////////////////////////////// |
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51 | /* |
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52 | There is a distinct priority when choosing the right conversion function: |
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53 | Overwrite: |
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54 | 1. (Partial) template specialisation of ConverterExplicit::convert() |
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55 | Fallbacks: |
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56 | 2. Any possible implicit conversion. This includes 'FooBar' --> 'int' if FooBar defines operator float(). |
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57 | 3. Global or member operators for stringstream when converting from or to std::string (or FROM const char*) |
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58 | 4. (Partial) template specialisation of ConverterFallback::convert() |
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59 | 5. Function that simply displays "Could not convert value" with type information obtained from typeid(). |
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60 | |
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61 | Notes: |
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62 | There has to be an exact type match when using template specialisations. |
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63 | Template specialisations can be defined after including this file. Any implicit cast function or iostream |
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64 | operator has to be declared BEFORE this file gets parsed. |
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65 | |
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66 | Defining your own functions: |
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67 | There are obviously 4 ways to specify a user defined conversion. What should you use? |
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68 | |
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69 | Usually, ConverterFallback fits quite well. You won't have to deal with the conversion from |
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70 | 'MyClass' to 'MyClass' by using another explicit template specialisation to avoid ambiguities. |
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71 | |
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72 | However if you want to overwrite an implicit conversion or an iostream operator, you really need to |
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73 | make use of ConverterExplicit. We have to do this for the Ogre classes for instance because they |
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74 | define stream operators we don't particulary like. |
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75 | */ |
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76 | |
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77 | namespace orxonox |
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78 | { |
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79 | /////////////////// |
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80 | // No Conversion // |
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81 | /////////////////// |
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82 | |
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83 | // Default template. No conversion available at all. |
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84 | template <class FromType, class ToType> |
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85 | struct ConverterFallback |
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86 | { |
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87 | FORCEINLINE static bool convert(ToType* output, const FromType& input) |
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88 | { |
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89 | COUT(2) << "Could not convert value of type " << typeid(FromType).name() |
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90 | << " to type " << typeid(ToType).name() << std::endl; |
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91 | return false; |
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92 | } |
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93 | }; |
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94 | |
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95 | // If all else fails, try a dynamic_cast for pointer types. |
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96 | template <class FromType, class ToType> |
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97 | struct ConverterFallback<FromType*, ToType*> |
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98 | { |
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99 | FORCEINLINE static bool convert(ToType** output, FromType* const input) |
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100 | { |
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101 | ToType* temp = dynamic_cast<ToType*>(input); |
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102 | if (temp) |
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103 | { |
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104 | *output = temp; |
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105 | return true; |
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106 | } |
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107 | else |
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108 | return false; |
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109 | } |
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110 | }; |
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111 | |
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112 | //////////// |
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113 | // upcast // |
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114 | //////////// |
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115 | namespace detail |
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116 | { |
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117 | // perform a static cast if ToType is a base of FromType |
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118 | template<class ToType, class FromType> |
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119 | FORCEINLINE ToType upcast(FromType input, Loki::Int2Type<true>) |
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120 | { |
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121 | return static_cast<ToType>(input); |
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122 | } |
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123 | |
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124 | // return zero if ToType is not a base of FromType |
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125 | template<class ToType, class FromType> |
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126 | FORCEINLINE ToType upcast(FromType input, Loki::Int2Type<false>) |
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127 | { |
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128 | return 0; |
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129 | } |
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130 | } |
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131 | |
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132 | // performs an upcast if ToType is a base of FromType, returns zero otherwise |
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133 | template <class ToType, class FromType> |
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134 | FORCEINLINE ToType upcast(FromType input) |
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135 | { |
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136 | enum { probe = ImplicitConversion<FromType, ToType>::exists }; |
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137 | return detail::upcast<ToType, FromType>(input, Loki::Int2Type<probe>()); |
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138 | } |
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139 | } |
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140 | |
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141 | |
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142 | /////////////////////// |
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143 | // ConverterFallback // |
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144 | /////////////////////// |
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145 | |
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146 | // Default template for stringstream |
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147 | template <class FromType, class ToType> |
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148 | struct ConverterStringStream |
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149 | { |
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150 | FORCEINLINE static bool convert(ToType* output, const FromType& input) |
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151 | { |
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152 | return orxonox::ConverterFallback<FromType, ToType>::convert(output, input); |
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153 | } |
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154 | }; |
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155 | |
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156 | |
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157 | ///////////// |
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158 | // OStream // |
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159 | ///////////// |
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160 | |
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161 | namespace fallbackTemplates |
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162 | { |
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163 | template <class FromType> |
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164 | FORCEINLINE bool operator <<(std::ostream& outstream, const FromType& input) |
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165 | { |
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166 | std::string temp; |
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167 | if (orxonox::ConverterFallback<FromType, std::string>::convert(&temp, input)) |
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168 | { |
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169 | std::operator <<(outstream, temp); |
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170 | return true; |
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171 | } |
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172 | else |
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173 | return false; |
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174 | } |
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175 | } |
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176 | |
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177 | // template that evaluates whether we can convert to std::string via ostringstream |
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178 | template <class FromType> |
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179 | struct ConverterStringStream<FromType, std::string> |
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180 | { |
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181 | FORCEINLINE static bool convert(std::string* output, const FromType& input) |
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182 | { |
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183 | using namespace fallbackTemplates; |
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184 | // this operator call only chooses fallbackTemplates::operator<< if there's no other fitting function |
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185 | std::ostringstream oss; |
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186 | if (oss << input) |
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187 | { |
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188 | (*output) = oss.str(); |
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189 | return true; |
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190 | } |
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191 | else |
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192 | return false; |
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193 | } |
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194 | }; |
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195 | |
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196 | |
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197 | ///////////// |
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198 | // IStream // |
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199 | ///////////// |
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200 | |
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201 | namespace fallbackTemplates |
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202 | { |
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203 | template <class ToType> |
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204 | FORCEINLINE bool operator >>(std::istream& instream, ToType& output) |
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205 | { |
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206 | return orxonox::ConverterFallback<std::string, ToType> |
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207 | ::convert(&output, static_cast<std::istringstream&>(instream).str()); |
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208 | } |
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209 | } |
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210 | |
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211 | // template that evaluates whether we can convert from std::string via ostringstream |
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212 | template <class ToType> |
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213 | struct ConverterStringStream<std::string, ToType> |
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214 | { |
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215 | FORCEINLINE static bool convert(ToType* output, const std::string& input) |
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216 | { |
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217 | using namespace fallbackTemplates; |
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218 | std::istringstream iss(input); |
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219 | // this operator call only chooses fallbackTemplates::operator>> if there's no other fitting function |
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220 | if (iss >> (*output)) |
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221 | { |
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222 | return true; |
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223 | } |
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224 | else |
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225 | return false; |
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226 | } |
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227 | }; |
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228 | |
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229 | namespace orxonox |
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230 | { |
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231 | |
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232 | /////////////////// |
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233 | // Implicit Cast // |
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234 | /////////////////// |
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235 | |
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236 | // implicit cast not possible, try stringstream conversion next |
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237 | template <class FromType, class ToType> |
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238 | FORCEINLINE bool convertImplicitely(ToType* output, const FromType& input, Loki::Int2Type<false>) |
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239 | { |
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240 | return ConverterStringStream<FromType, ToType>::convert(output, input); |
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241 | } |
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242 | |
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243 | // We can cast implicitely |
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244 | template <class FromType, class ToType> |
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245 | FORCEINLINE bool convertImplicitely(ToType* output, const FromType& input, Loki::Int2Type<true>) |
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246 | { |
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247 | (*output) = static_cast<ToType>(input); |
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248 | return true; |
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249 | } |
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250 | |
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251 | |
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252 | //////////////////////////////// |
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253 | // ConverterExplicit Fallback // |
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254 | //////////////////////////////// |
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255 | |
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256 | // Default template if no specialisation is available |
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257 | template <class FromType, class ToType> |
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258 | struct ConverterExplicit |
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259 | { |
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260 | enum { probe = ImplicitConversion<FromType, ToType>::exists }; |
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261 | FORCEINLINE static bool convert(ToType* output, const FromType& input) |
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262 | { |
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263 | // Try implict cast and probe first. If a simple cast is not possible, it will not compile |
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264 | // We therefore have to out source it into another template function |
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265 | return convertImplicitely(output, input, Loki::Int2Type<probe>()); |
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266 | } |
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267 | }; |
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268 | |
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269 | |
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270 | ////////////////////// |
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271 | // Public Functions // |
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272 | ////////////////////// |
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273 | |
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274 | /** |
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275 | @brief |
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276 | Converts any value to any other as long as there exists a conversion. |
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277 | Otherwise, the conversion will generate a runtime warning and return false. |
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278 | For information about the different conversion methods (user defined too), see the section |
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279 | 'Actual conversion sequence' in this file above. |
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280 | @param output |
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281 | A pointer to the variable where the converted value will be stored |
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282 | @param input |
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283 | The original value |
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284 | */ |
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285 | template <class FromType, class ToType> |
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286 | FORCEINLINE bool convertValue(ToType* output, const FromType& input) |
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287 | { |
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288 | return ConverterExplicit<FromType, ToType>::convert(output, input); |
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289 | } |
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290 | |
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291 | // Calls convertValue and returns true if the conversion was successful. |
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292 | // Otherwise the fallback is used. |
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293 | /** |
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294 | @brief |
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295 | Converts any value to any other as long as there exists a conversion. |
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296 | Otherwise, the conversion will generate a runtime warning and return false. |
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297 | For information about the different conversion methods (user defined too), see the section |
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298 | 'Actual conversion sequence' in this file above. |
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299 | If the conversion doesn't succeed, 'fallback' is written to '*output'. |
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300 | @param output |
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301 | A pointer to the variable where the converted value will be stored |
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302 | @param input |
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303 | The original value |
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304 | @param fallback |
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305 | A default value that gets written to '*output' if there is no conversion. |
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306 | */ |
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307 | template<class FromType, class ToType> |
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308 | FORCEINLINE bool convertValue(ToType* output, const FromType& input, const ToType& fallback) |
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309 | { |
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310 | if (convertValue(output, input)) |
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311 | return true; |
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312 | else |
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313 | { |
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314 | (*output) = fallback; |
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315 | return false; |
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316 | } |
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317 | } |
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318 | |
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319 | // Directly returns the converted value, even if the conversion was not successful. |
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320 | template<class FromType, class ToType> |
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321 | FORCEINLINE ToType getConvertedValue(const FromType& input) |
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322 | { |
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323 | ToType output; |
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324 | convertValue(&output, input); |
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325 | return output; |
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326 | } |
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327 | |
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328 | // Directly returns the converted value, but uses the fallback on failure. |
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329 | template<class FromType, class ToType> |
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330 | FORCEINLINE ToType getConvertedValue(const FromType& input, const ToType& fallback) |
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331 | { |
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332 | ToType output; |
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333 | convertValue(&output, input, fallback); |
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334 | return output; |
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335 | } |
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336 | |
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337 | // Like getConvertedValue, but the template argument order is in reverse. |
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338 | // That means you can call it exactly like static_cast<ToType>(fromTypeValue). |
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339 | template<class ToType, class FromType> |
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340 | FORCEINLINE ToType multi_cast(const FromType& input) |
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341 | { |
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342 | ToType output; |
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343 | convertValue(&output, input); |
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344 | return output; |
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345 | } |
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346 | |
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347 | //////////////////////////////// |
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348 | // Special string conversions // |
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349 | //////////////////////////////// |
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350 | |
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351 | // Delegate conversion from const char* to std::string |
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352 | template <class ToType> |
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353 | struct ConverterExplicit<const char*, ToType> |
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354 | { |
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355 | FORCEINLINE static bool convert(ToType* output, const char* input) |
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356 | { |
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357 | return convertValue<std::string, ToType>(output, input); |
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358 | } |
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359 | }; |
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360 | |
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361 | // These conversions would exhibit ambiguous << or >> operators when using stringstream |
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362 | template <> |
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363 | struct ConverterExplicit<char, std::string> |
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364 | { |
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365 | FORCEINLINE static bool convert(std::string* output, const char input) |
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366 | { |
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367 | *output = input; |
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368 | return true; |
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369 | } |
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370 | }; |
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371 | template <> |
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372 | struct ConverterExplicit<unsigned char, std::string> |
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373 | { |
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374 | FORCEINLINE static bool convert(std::string* output, const unsigned char input) |
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375 | { |
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376 | *output = input; |
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377 | return true; |
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378 | } |
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379 | }; |
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380 | template <> |
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381 | struct ConverterExplicit<std::string, char> |
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382 | { |
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383 | FORCEINLINE static bool convert(char* output, const std::string& input) |
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384 | { |
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385 | if (!input.empty()) |
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386 | *output = input[0]; |
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387 | else |
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388 | *output = '\0'; |
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389 | return true; |
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390 | } |
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391 | }; |
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392 | template <> |
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393 | struct ConverterExplicit<std::string, unsigned char> |
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394 | { |
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395 | FORCEINLINE static bool convert(unsigned char* output, const std::string& input) |
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396 | { |
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397 | if (!input.empty()) |
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398 | *output = input[0]; |
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399 | else |
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400 | *output = '\0'; |
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401 | return true; |
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402 | } |
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403 | }; |
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404 | |
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405 | |
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406 | // bool to std::string |
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407 | template <> |
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408 | struct ConverterExplicit<bool, std::string> |
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409 | { |
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410 | FORCEINLINE static bool convert(std::string* output, const bool& input) |
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411 | { |
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412 | if (input) |
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413 | *output = "true"; |
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414 | else |
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415 | *output = "false"; |
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416 | return true; |
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417 | } |
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418 | }; |
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419 | |
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420 | // std::string to bool |
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421 | template <> |
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422 | struct _UtilExport ConverterExplicit<std::string, bool> |
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423 | { |
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424 | static bool convert(bool* output, const std::string& input); |
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425 | }; |
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426 | } |
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427 | |
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428 | #endif /* _Convert_H__ */ |
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