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 | /** Functions that convert values between different types. |
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31 | @file |
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32 | @par Usage |
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33 | There are three ways to use the conversions depending on what you need. <br> |
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34 | - For simply converting values without having to know whether the conversion |
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35 | was successful (for instance float --> string), use orxonox::multi_cast |
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36 | which effectively works exactly like static_cast, etc. |
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37 | @code |
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38 | float input = 42.0; |
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39 | std::string output = multi_cast<std::string>(input); |
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40 | @endcode |
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41 | - If you care about whether the conversion was successful, |
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42 | use orxonox::convertValue. |
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43 | @code |
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44 | std::string input("3.4"); |
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45 | float output; |
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46 | bool success = convertValue(&output, input); |
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47 | @endcode |
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48 | - If you care about success and if you can also feed a fallback value, |
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49 | use orxonox::convertValue. |
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50 | @code |
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51 | std::string input("3.4"); |
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52 | float output; |
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53 | bool success = convertValue(&output, input, 0.0); |
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54 | @endcode |
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55 | - If success doesn't matter but you can feed a fallback value, |
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56 | use orxonox::getConvertedValue. |
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57 | @code |
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58 | std::string input("3.4"); |
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59 | float output = getConvertedValue(input, 0.0); |
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60 | @endcode |
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61 | @details |
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62 | The back end of these functions are the actual implementations for the |
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63 | specific conversions, for instance from Ogre::Vector3 to std::string and |
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64 | vice versa. Some of them also use the iostream operators. <br> |
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65 | The real deal is evaluating which function is needed for a conversion based |
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66 | on the input and output type. But there are lots of catches in conjunction |
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67 | with templates which explains why there are so many functions in this file. |
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68 | <br> <br> |
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69 | @par Search Order |
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70 | Finding the right function is governed by priority rules: <br> |
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71 | -# (Partial) template specialisation of orxonox::ConverterExplicit::convert() |
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72 | -# An implicit conversion. This includes 'FooBar' to 'int' if FooBar |
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73 | defines operator int() or float(). |
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74 | -# Global or member operators for iostream when converting from or |
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75 | to std::string (and FROM const char*) |
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76 | -# (Partial) template specialisation of orxonox::ConverterFallback::convert() |
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77 | -# Fallback function that displays "Could not convert value" with type |
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78 | information obtained from typeid(). |
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79 | @par Implementing conversion functions |
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80 | To do that you probably need to know a thing or two about the types |
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81 | involved. So, get ready with that. <br> |
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82 | Usually the best way to do it is specialising of the orxonox::ConverterFallback |
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83 | template, like this: |
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84 | @code |
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85 | template <> |
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86 | struct _UtilExport ConverterFallback<std::string, MyType> |
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87 | { |
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88 | static bool convert(MyType* output, const std::string& input) |
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89 | { |
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90 | ... |
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91 | return success; |
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92 | } |
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93 | }; |
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94 | @endcode |
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95 | This piece of code converts an std::string to MyType and returns whether the |
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96 | conversion was successful. You can also use partial specialisation.<br> |
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97 | The advantage with orxonox::ConverterFallback is that it has a low priority |
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98 | meaning that when there is an implicit conversion or an iostream method, that |
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99 | comes first and you don't have to deal with it (and the accompanying |
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100 | function call ambiguity). <br> |
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101 | However sometimes you would like to explicitely replace such a conversion. |
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102 | That's where orxonox::ConverterExplicit comes in handy (for instance we |
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103 | replaced the operator << conversions for Ogre::VectorX with our own functions). |
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104 | @note |
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105 | There has to be an exact type match when using template specialisations. <br> |
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106 | Template specialisations can be defined after including this file. |
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107 | But any implicit cast function or iostream operator has to be included |
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108 | in this file! |
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109 | @par Understanding the Code |
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110 | In order to understand how the templates work, it is probably best to study |
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111 | the functions in order of calling. There are lots of comments explaining |
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112 | what happens, but you'll need to understand a deal about partial template |
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113 | specialisation and function headers are matched in C++. |
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114 | */ |
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115 | |
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116 | #ifndef _Converter_H__ |
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117 | #define _Converter_H__ |
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118 | |
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119 | #include "UtilPrereqs.h" |
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120 | |
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121 | #include <string> |
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122 | #include <sstream> |
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123 | #include <typeinfo> |
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124 | #include <loki/TypeManip.h> |
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125 | |
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126 | #include "Debug.h" |
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127 | #include "TemplateUtils.h" |
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128 | |
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129 | namespace orxonox |
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130 | { |
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131 | /////////////////// |
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132 | // No Conversion // |
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133 | /////////////////// |
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134 | |
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135 | /// Default template. No conversion available at all. |
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136 | template <class FromType, class ToType> |
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137 | struct ConverterFallback |
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138 | { |
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139 | FORCEINLINE static bool convert(ToType* output, const FromType& input) |
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140 | { |
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141 | COUT(2) << "Could not convert value of type " << typeid(FromType).name() |
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142 | << " to type " << typeid(ToType).name() << std::endl; |
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143 | return false; |
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144 | } |
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145 | }; |
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146 | |
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147 | /// If all else fails, try a dynamic_cast for pointer types. |
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148 | template <class FromType, class ToType> |
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149 | struct ConverterFallback<FromType*, ToType*> |
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150 | { |
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151 | FORCEINLINE static bool convert(ToType** output, FromType* const input) |
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152 | { |
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153 | ToType* temp = dynamic_cast<ToType*>(input); |
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154 | if (temp) |
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155 | { |
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156 | *output = temp; |
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157 | return true; |
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158 | } |
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159 | else |
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160 | return false; |
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161 | } |
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162 | }; |
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163 | } |
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164 | |
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165 | |
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166 | /////////////////////// |
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167 | // ConverterFallback // |
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168 | /////////////////////// |
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169 | |
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170 | /** Fallback template for stringstream |
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171 | @details |
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172 | Neither FromType nor ToType was std::string, therefore |
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173 | delegate to orxonox::ConverterFallback |
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174 | */ |
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175 | template <class FromType, class ToType> |
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176 | struct ConverterStringStream |
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177 | { |
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178 | FORCEINLINE static bool convert(ToType* output, const FromType& input) |
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179 | { |
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180 | return orxonox::ConverterFallback<FromType, ToType>::convert(output, input); |
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181 | } |
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182 | }; |
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183 | |
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184 | |
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185 | ///////////// |
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186 | // OStream // |
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187 | ///////////// |
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188 | |
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189 | /// Extra namespace to avoid exposing the iostream operators in it |
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190 | namespace fallbackTemplates |
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191 | { |
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192 | /// Fallback operator <<() (delegates to orxonox::ConverterFallback) |
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193 | template <class FromType> |
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194 | FORCEINLINE bool operator <<(std::ostream& outstream, const FromType& input) |
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195 | { |
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196 | std::string temp; |
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197 | if (orxonox::ConverterFallback<FromType, std::string>::convert(&temp, input)) |
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198 | { |
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199 | std::operator <<(outstream, temp); |
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200 | return true; |
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201 | } |
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202 | else |
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203 | return false; |
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204 | } |
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205 | } |
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206 | |
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207 | /// Template that evaluates whether we can convert to std::string via ostringstream |
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208 | template <class FromType> |
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209 | struct ConverterStringStream<FromType, std::string> |
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210 | { |
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211 | FORCEINLINE static bool convert(std::string* output, const FromType& input) |
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212 | { |
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213 | using namespace fallbackTemplates; |
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214 | // this operator call only chooses fallbackTemplates::operator<<() |
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215 | // if there's no other fitting function |
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216 | std::ostringstream oss; |
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217 | // Note: std::ostream has operator!() to tell whether any error flag was set |
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218 | if (oss << input) |
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219 | { |
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220 | (*output) = oss.str(); |
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221 | return true; |
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222 | } |
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223 | else |
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224 | return false; |
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225 | } |
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226 | }; |
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227 | |
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228 | |
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229 | ///////////// |
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230 | // IStream // |
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231 | ///////////// |
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232 | |
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233 | namespace fallbackTemplates |
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234 | { |
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235 | /// Fallback operator >>() (delegates to orxonox::ConverterFallback) |
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236 | template <class ToType> |
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237 | FORCEINLINE bool operator >>(std::istream& instream, ToType& output) |
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238 | { |
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239 | std::string input(static_cast<std::istringstream&>(instream).str()); |
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240 | return orxonox::ConverterFallback<std::string, ToType>::convert(&output, input); |
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241 | } |
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242 | } |
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243 | |
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244 | /// Template that evaluates whether we can convert from std::string via istringstream |
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245 | template <class ToType> |
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246 | struct ConverterStringStream<std::string, ToType> |
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247 | { |
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248 | FORCEINLINE static bool convert(ToType* output, const std::string& input) |
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249 | { |
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250 | using namespace fallbackTemplates; |
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251 | // this operator call chooses fallbackTemplates::operator>>() |
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252 | // only if there's no other fitting function |
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253 | std::istringstream iss(input); |
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254 | // Note: std::istream has operator!() to tell whether any error flag was set |
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255 | if (iss >> (*output)) |
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256 | { |
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257 | return true; |
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258 | } |
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259 | else |
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260 | return false; |
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261 | } |
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262 | }; |
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263 | |
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264 | namespace orxonox |
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265 | { |
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266 | /////////////////// |
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267 | // Implicit Cast // |
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268 | /////////////////// |
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269 | |
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270 | /// %Template delegates to ::ConverterStringStream |
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271 | template <class FromType, class ToType> |
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272 | FORCEINLINE bool convertImplicitely(ToType* output, const FromType& input, Loki::Int2Type<false>) |
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273 | { |
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274 | return ConverterStringStream<FromType, ToType>::convert(output, input); |
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275 | } |
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276 | |
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277 | /// Makes an implicit cast from \a FromType to \a ToType |
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278 | template <class FromType, class ToType> |
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279 | FORCEINLINE bool convertImplicitely(ToType* output, const FromType& input, Loki::Int2Type<true>) |
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280 | { |
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281 | (*output) = static_cast<ToType>(input); |
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282 | return true; |
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283 | } |
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284 | |
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285 | |
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286 | //////////////////////////////// |
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287 | // ConverterExplicit Fallback // |
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288 | //////////////////////////////// |
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289 | |
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290 | /** Default template if no orxonox::ConverterExplicit is available |
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291 | @details |
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292 | Evaluates whether \a FromType can be implicitly converted to \a ToType |
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293 | by the use the ImplicitConversion magic. |
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294 | */ |
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295 | template <class FromType, class ToType> |
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296 | struct ConverterExplicit |
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297 | { |
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298 | enum { probe = ImplicitConversion<FromType, ToType>::exists }; |
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299 | FORCEINLINE static bool convert(ToType* output, const FromType& input) |
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300 | { |
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301 | // Use the probe's value to delegate to the right function |
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302 | return convertImplicitely(output, input, Loki::Int2Type<probe>()); |
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303 | } |
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304 | }; |
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305 | |
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306 | |
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307 | ////////////////////// |
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308 | // Public Functions // |
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309 | ////////////////////// |
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310 | |
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311 | /** |
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312 | @brief |
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313 | Converts any value to any other as long as there exists a conversion. |
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314 | @details |
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315 | Otherwise, the conversion will generate a runtime warning and return false. |
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316 | @see Convert.h |
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317 | @param output |
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318 | A pointer to the variable where the converted value will be stored |
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319 | @param input |
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320 | The original value |
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321 | */ |
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322 | template <class FromType, class ToType> |
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323 | FORCEINLINE bool convertValue(ToType* output, const FromType& input) |
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324 | { |
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325 | return ConverterExplicit<FromType, ToType>::convert(output, input); |
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326 | } |
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327 | |
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328 | // Calls convertValue and returns true if the conversion was successful. |
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329 | // Otherwise the fallback is used. |
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330 | /** |
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331 | @brief |
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332 | Converts any value to any other as long as there exists a conversion. |
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333 | Otherwise, the conversion will generate a runtime warning and return false. |
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334 | If the conversion doesn't succeed, \a fallback is written to \a output. |
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335 | @see Convert.h |
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336 | @param output |
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337 | A pointer to the variable where the converted value will be stored |
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338 | @param input |
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339 | The original value |
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340 | @param fallback |
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341 | A default value that gets written to '*output' if there is no conversion. |
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342 | */ |
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343 | template<class FromType, class ToType> |
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344 | FORCEINLINE bool convertValue(ToType* output, const FromType& input, const ToType& fallback) |
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345 | { |
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346 | if (convertValue(output, input)) |
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347 | return true; |
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348 | else |
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349 | { |
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350 | (*output) = fallback; |
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351 | return false; |
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352 | } |
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353 | } |
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354 | |
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355 | /// Directly returns the converted value, but uses the fallback on failure. @see convertValue |
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356 | template<class FromType, class ToType> |
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357 | FORCEINLINE ToType getConvertedValue(const FromType& input, const ToType& fallback) |
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358 | { |
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359 | ToType output; |
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360 | convertValue(&output, input, fallback); |
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361 | return output; |
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362 | } |
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363 | |
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364 | /** |
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365 | @brief |
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366 | Converts any value to any other as long as there exists a conversion. |
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367 | @details |
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368 | Use exactly the way you use static_cast, etc. <br> |
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369 | A failed conversion will return a default instance of \a ToType |
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370 | (possibly uninitialised) |
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371 | @see Convert.h |
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372 | @param input |
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373 | The original value |
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374 | */ |
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375 | template<class ToType, class FromType> |
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376 | FORCEINLINE ToType multi_cast(const FromType& input) |
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377 | { |
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378 | ToType output; |
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379 | convertValue(&output, input); |
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380 | return output; |
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381 | } |
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382 | |
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383 | //////////////////////////////// |
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384 | // Special string conversions // |
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385 | //////////////////////////////// |
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386 | |
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387 | /// Delegates conversion from const char* to std::string |
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388 | template <class ToType> |
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389 | struct ConverterExplicit<const char*, ToType> |
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390 | { |
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391 | FORCEINLINE static bool convert(ToType* output, const char* input) |
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392 | { |
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393 | return convertValue<std::string, ToType>(output, input); |
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394 | } |
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395 | }; |
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396 | |
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397 | /// Conversion would exhibit ambiguous << or >> operators when using iostream |
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398 | template <> |
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399 | struct ConverterExplicit<char, std::string> |
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400 | { |
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401 | FORCEINLINE static bool convert(std::string* output, const char input) |
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402 | { |
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403 | *output = input; |
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404 | return true; |
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405 | } |
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406 | }; |
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407 | /// Conversion would exhibit ambiguous << or >> operators when using iostream |
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408 | template <> |
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409 | struct ConverterExplicit<unsigned char, std::string> |
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410 | { |
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411 | FORCEINLINE static bool convert(std::string* output, const unsigned char input) |
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412 | { |
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413 | *output = input; |
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414 | return true; |
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415 | } |
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416 | }; |
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417 | /// Conversion would exhibit ambiguous << or >> operators when using iostream |
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418 | template <> |
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419 | struct ConverterExplicit<std::string, char> |
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420 | { |
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421 | FORCEINLINE static bool convert(char* output, const std::string& input) |
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422 | { |
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423 | if (!input.empty()) |
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424 | *output = input[0]; |
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425 | else |
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426 | *output = '\0'; |
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427 | return true; |
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428 | } |
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429 | }; |
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430 | /// Conversion would exhibit ambiguous << or >> operators when using iostream |
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431 | template <> |
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432 | struct ConverterExplicit<std::string, unsigned char> |
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433 | { |
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434 | FORCEINLINE static bool convert(unsigned char* output, const std::string& input) |
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435 | { |
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436 | if (!input.empty()) |
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437 | *output = input[0]; |
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438 | else |
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439 | *output = '\0'; |
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440 | return true; |
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441 | } |
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442 | }; |
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443 | |
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444 | |
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445 | /// Conversion from bool to std::string |
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446 | template <> |
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447 | struct ConverterExplicit<bool, std::string> |
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448 | { |
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449 | FORCEINLINE static bool convert(std::string* output, const bool& input) |
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450 | { |
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451 | if (input) |
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452 | *output = "true"; |
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453 | else |
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454 | *output = "false"; |
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455 | return true; |
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456 | } |
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457 | }; |
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458 | |
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459 | /// Conversion from std::string to bool |
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460 | template <> |
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461 | struct _UtilExport ConverterExplicit<std::string, bool> |
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462 | { |
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463 | static bool convert(bool* output, const std::string& input); |
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464 | }; |
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465 | } |
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466 | |
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467 | #endif /* _Convert_H__ */ |
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