1 | /* |
---|
2 | * ORXONOX - the hottest 3D action shooter ever to exist |
---|
3 | * > www.orxonox.net < |
---|
4 | * |
---|
5 | * |
---|
6 | * License notice: |
---|
7 | * |
---|
8 | * This program is free software; you can redistribute it and/or |
---|
9 | * modify it under the terms of the GNU General Public License |
---|
10 | * as published by the Free Software Foundation; either version 2 |
---|
11 | * of the License, or (at your option) any later version. |
---|
12 | * |
---|
13 | * This program is distributed in the hope that it will be useful, |
---|
14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
---|
15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
---|
16 | * GNU General Public License for more details. |
---|
17 | * |
---|
18 | * You should have received a copy of the GNU General Public License |
---|
19 | * along with this program; if not, write to the Free Software |
---|
20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
---|
21 | * |
---|
22 | * Author: |
---|
23 | * Benjamin Grauer |
---|
24 | * Fabian 'x3n' Landau |
---|
25 | * Reto Grieder (direct conversion tests) |
---|
26 | * Co-authors: |
---|
27 | * ... |
---|
28 | */ |
---|
29 | |
---|
30 | /*! |
---|
31 | @file |
---|
32 | @brief Definition and Implementation of the Convert class. |
---|
33 | */ |
---|
34 | |
---|
35 | #ifndef _Converter_H__ |
---|
36 | #define _Converter_H__ |
---|
37 | |
---|
38 | #include "UtilPrereqs.h" |
---|
39 | |
---|
40 | #include <string> |
---|
41 | #include <sstream> |
---|
42 | #include <istream> |
---|
43 | #include <ostream> |
---|
44 | |
---|
45 | #include "Debug.h" |
---|
46 | |
---|
47 | // Gcc generates warnings when implicitely casting from float to int for instance. |
---|
48 | // This is however exactly what convertValue does, so we need to suppress the warnings. |
---|
49 | // They only occur in when using the ImplicitConversion template. |
---|
50 | #if ORXONOX_COMPILER == ORXONOX_COMPILER_GNUC |
---|
51 | # pragma GCC system_header |
---|
52 | #endif |
---|
53 | |
---|
54 | /////////////////////////////////////////////// |
---|
55 | // Static detection for conversion functions // |
---|
56 | /////////////////////////////////////////////// |
---|
57 | /* The idea to use the sizeof() operator on return functions to determine function existance |
---|
58 | is described in 'Moder C++ design' by Alexandrescu (2001). */ |
---|
59 | |
---|
60 | namespace conversionTests |
---|
61 | { |
---|
62 | // A struct that is guaranteed to be larger than any return type of our conversion functions. |
---|
63 | // So we simply add all the sizes of the return types plus a little bit more. |
---|
64 | struct VeryBigStruct |
---|
65 | { |
---|
66 | char intSize[sizeof(int)]; |
---|
67 | char issSize[sizeof(std::istringstream)]; |
---|
68 | char ossSize[sizeof(std::ostringstream)]; |
---|
69 | char boolSize[sizeof(bool)]; |
---|
70 | char addingMore[4096]; // just to be sure ;) |
---|
71 | }; |
---|
72 | } |
---|
73 | |
---|
74 | namespace conversion_another_namespace |
---|
75 | { |
---|
76 | // We want to keep the templates for the convert functions out of global namespace so that there |
---|
77 | // are no ambiguities. These templates are never used anyway, they only serve to detect whether |
---|
78 | // there is a global funciton for a specific conversion or not. |
---|
79 | // Why the seperate namespace? --> see 'using' statement at the end of conversionTests:: |
---|
80 | //template <class AnyToType, class AnyFromType> |
---|
81 | //conversionTests::VeryBigStruct explicitConversion(AnyToType* output, const AnyFromType input); |
---|
82 | //template <class Any, int Dummy> |
---|
83 | //conversionTests::VeryBigStruct operator<<(std::ostream& outstream, const Any& anything); |
---|
84 | //template <class Any, int Dummy> |
---|
85 | //conversionTests::VeryBigStruct operator>>(std::istream& instream, const Any& anything); |
---|
86 | } |
---|
87 | |
---|
88 | namespace conversionTests |
---|
89 | { |
---|
90 | // disable warnings about possible loss of data |
---|
91 | #if ORXONOX_COMPILER == ORXONOX_COMPILER_MSVC |
---|
92 | # pragma warning(push) |
---|
93 | # pragma warning(disable:4244) |
---|
94 | #endif |
---|
95 | |
---|
96 | template <class FromType, class ToType> |
---|
97 | class ImplicitConversion |
---|
98 | { |
---|
99 | private: |
---|
100 | ImplicitConversion(); ImplicitConversion(const ImplicitConversion&); ~ImplicitConversion(); |
---|
101 | // Gets chosen only if there is an implicit conversion from FromType to ToType. |
---|
102 | static int test(ToType); |
---|
103 | // Accepts any argument. Why do we not use a template? The reason is that with templates, |
---|
104 | // the function above is only taken iff it is an exact type match. But since we want to |
---|
105 | // check for implicit conversion, we have to use the ellipsis. |
---|
106 | static VeryBigStruct test(...); |
---|
107 | static FromType object; // helper object to handle private c'tor and d'tor |
---|
108 | public: |
---|
109 | // test(object) only has 'VerySmallStruct' return type iff the compiler doesn't choose test(...) |
---|
110 | enum { exists = !(sizeof(test(object)) == sizeof(VeryBigStruct)) }; |
---|
111 | }; |
---|
112 | |
---|
113 | #if ORXONOX_COMPILER == ORXONOX_COMPILER_MSVC |
---|
114 | # pragma warning(pop) |
---|
115 | #endif |
---|
116 | |
---|
117 | //template <class FromType, class ToType> |
---|
118 | //class ExplicitConversion |
---|
119 | //{ |
---|
120 | //private: |
---|
121 | // ExplicitConversion(); ExplicitConversion(const ExplicitConversion&); ~ExplicitConversion(); |
---|
122 | // static FromType objectFromType; // helper object to handle private c'tor and d'tor |
---|
123 | // static ToType objectToType; // helper object to handle private c'tor and d'tor |
---|
124 | //public: |
---|
125 | // enum { exists = !(sizeof(explicitConversion(&objectToType, objectFromType)) == sizeof(VeryBigStruct)) }; |
---|
126 | //}; |
---|
127 | |
---|
128 | //template <class Type> |
---|
129 | //class IStreamOperator |
---|
130 | //{ |
---|
131 | // IStreamOperator(); IStreamOperator(const IStreamOperator&); ~IStreamOperator(); |
---|
132 | // static std::istream istream_; // helper object to perform the '>>' operation |
---|
133 | // static Type object; // helper object to handle private c'tor and d'tor |
---|
134 | //public: |
---|
135 | // enum { exists = !(sizeof(istream_ >> object) == sizeof(VeryBigStruct)) }; |
---|
136 | //}; |
---|
137 | |
---|
138 | //template <class Type> |
---|
139 | //class OStreamOperator |
---|
140 | //{ |
---|
141 | // OStreamOperator(); OStreamOperator(const OStreamOperator&); ~OStreamOperator(); |
---|
142 | // static std::ostream ostream_; // helper object to perform the '<<' operation |
---|
143 | // static Type object; // helper object to handle private c'tor and d'tor |
---|
144 | //public: |
---|
145 | // enum { exists = !(sizeof(ostream_ << object) == sizeof(VeryBigStruct)) }; |
---|
146 | //}; |
---|
147 | |
---|
148 | // Somehow msvc and gcc don't like it when using function arguments that have a type |
---|
149 | // in a third namespace. The global namespace functions then get overridden by the |
---|
150 | // templates above. So we simply put the generic ones in a another namespace. |
---|
151 | // Note: DON'T place this statement before a class template. That would trigger |
---|
152 | // a heavy bug (namespace leakage) in msvc 2005. |
---|
153 | //using namespace conversion_another_namespace; |
---|
154 | } |
---|
155 | |
---|
156 | |
---|
157 | //////////////////////////////////// |
---|
158 | //// ACTUAL CONVERSION SEQUENCE //// |
---|
159 | //////////////////////////////////// |
---|
160 | /* |
---|
161 | There is a distinct priority when choosing the right conversion function: |
---|
162 | Overwrites: |
---|
163 | 1. (Partial) template specialisation of ConverterExplicit::convert |
---|
164 | 2. Global functions explicitConversion(ToType* output, const FromType input) |
---|
165 | Fallbacks: |
---|
166 | 3. Any possible implicit conversion. This includes FooBar --> int if FooBar defines operator float(). |
---|
167 | 4. Global or member operators for stringstream when converting from or to std::string (or FROM const char*) |
---|
168 | 5. Function that simply displays "Could not convert value" with information obtained from typeid(). |
---|
169 | |
---|
170 | A note: There has to be an exact type match (or according to the rules of template spec.) except for 3. |
---|
171 | |
---|
172 | There are obviously a lot of ways to specifiy a user defined conversion. What should I use? |
---|
173 | When using any non-template function based conversion (implicit conversion, explicitConversion, << or >>) |
---|
174 | then you should consider that this function has to be defined prior to including this file. |
---|
175 | If you do not whish do do that, you will have to spcecialsize the ConverterExplicit template. |
---|
176 | There is a not so obvious advantage of the other way (non-template): You could declare each conversion function |
---|
177 | in the Prereqs file of the corresponding library. Then you can use the conversion everywhere. |
---|
178 | This is not possible with template specialisations even when defining them in this file (You would create |
---|
179 | a circular dependency when using a class from Core for instance, because complete template specialisations |
---|
180 | get compiled anyway (there is no template parameter)). |
---|
181 | */ |
---|
182 | |
---|
183 | namespace |
---|
184 | { |
---|
185 | // little template that maps to ints to entire types (Alexandrescu 2001) |
---|
186 | template <int I> |
---|
187 | struct Int2Type { }; |
---|
188 | } |
---|
189 | |
---|
190 | |
---|
191 | /////////////////// |
---|
192 | // No Conversion // |
---|
193 | /////////////////// |
---|
194 | |
---|
195 | namespace conversion |
---|
196 | { |
---|
197 | // Default template for stringtream, no Conversion possible |
---|
198 | template <class ToType, class FromType> |
---|
199 | struct ConverterSS |
---|
200 | { |
---|
201 | static bool convert(ToType* output, FromType input) |
---|
202 | { |
---|
203 | COUT(2) << "Could not convert value of type " << typeid(FromType).name() |
---|
204 | << " to type " << typeid(ToType).name() << std::endl; |
---|
205 | return false; |
---|
206 | } |
---|
207 | }; |
---|
208 | } |
---|
209 | |
---|
210 | |
---|
211 | ///////////// |
---|
212 | // OStream // |
---|
213 | ///////////// |
---|
214 | |
---|
215 | namespace fallbackTemplates |
---|
216 | { |
---|
217 | template <class Any> |
---|
218 | bool operator <<(std::ostream& outstream, const Any& anything) |
---|
219 | { |
---|
220 | COUT(2) << "Could not convert value of type " << typeid(Any).name() |
---|
221 | << " to std::string" << std::endl; |
---|
222 | return false; |
---|
223 | } |
---|
224 | } |
---|
225 | |
---|
226 | namespace conversion |
---|
227 | { |
---|
228 | //using namespace fallbackTemplates; |
---|
229 | // template that evaluates whether OStringStream is possible for conversions to std::string |
---|
230 | template <class FromType> |
---|
231 | struct ConverterSS<std::string, FromType> |
---|
232 | { |
---|
233 | // probe for '<<' ostream operator |
---|
234 | static bool convert(std::string* output, const FromType& input) |
---|
235 | { |
---|
236 | std::ostringstream oss; |
---|
237 | if (oss << input) |
---|
238 | { |
---|
239 | (*output) = oss.str(); |
---|
240 | return true; |
---|
241 | } |
---|
242 | else |
---|
243 | return false; |
---|
244 | } |
---|
245 | }; |
---|
246 | |
---|
247 | } |
---|
248 | |
---|
249 | |
---|
250 | ///////////// |
---|
251 | // IStream // |
---|
252 | ///////////// |
---|
253 | |
---|
254 | namespace fallbackTemplates |
---|
255 | { |
---|
256 | template <class Any> |
---|
257 | bool operator >>(std::istream& instream, const Any& anything) |
---|
258 | { |
---|
259 | COUT(2) << "Could not convert std::string value to type " << typeid(ToType).name() << std::endl; |
---|
260 | return false; |
---|
261 | } |
---|
262 | } |
---|
263 | |
---|
264 | namespace conversion |
---|
265 | { |
---|
266 | // template that evaluates whether IStringStream is possible for conversions from std::string |
---|
267 | template <class ToType> |
---|
268 | struct ConverterSS<ToType, std::string> |
---|
269 | { |
---|
270 | static bool convert(ToType* output, const std::string& input) |
---|
271 | { |
---|
272 | std::istringstream iss(input); |
---|
273 | if (iss >> (*output)) |
---|
274 | { |
---|
275 | return true; |
---|
276 | } |
---|
277 | else |
---|
278 | return false; |
---|
279 | } |
---|
280 | }; |
---|
281 | |
---|
282 | using namespace fallbackTemplates; |
---|
283 | } |
---|
284 | |
---|
285 | |
---|
286 | /////////////////// |
---|
287 | // Implicit Cast // |
---|
288 | /////////////////// |
---|
289 | |
---|
290 | // We can cast implicitely |
---|
291 | template <class ToType, class FromType> |
---|
292 | inline bool convertImplicitely(ToType* output, const FromType& input, ::Int2Type<true>) |
---|
293 | { |
---|
294 | (*output) = static_cast<ToType>(input); |
---|
295 | return true; |
---|
296 | } |
---|
297 | // static cast no possible, try stringstream conversion next |
---|
298 | template <class ToType, class FromType> |
---|
299 | inline bool convertImplicitely(ToType* output, const FromType& input, ::Int2Type<false>) |
---|
300 | { |
---|
301 | return conversion::ConverterSS<ToType, FromType>::convert(output, input); |
---|
302 | } |
---|
303 | |
---|
304 | |
---|
305 | ///////////////////////// |
---|
306 | // Explicit conversion // |
---|
307 | ///////////////////////// |
---|
308 | |
---|
309 | namespace fallbackTemplates |
---|
310 | { |
---|
311 | // We want to keep the templates for the convert functions out of global namespace so that there |
---|
312 | // are no ambiguities. These templates are never used anyway, they only serve to detect whether |
---|
313 | // there is a global funciton for a specific conversion or not. |
---|
314 | // Note: Don't put these functions in a separate namespace and add a 'using' directive here. |
---|
315 | // For MS sake, just don't! |
---|
316 | template <class ToType, class FromType> |
---|
317 | bool explicitConversion(ToType* output, const FromType input) |
---|
318 | { |
---|
319 | // try implict conversion by probing first because we use '...' instead of a template |
---|
320 | const bool probe = conversionTests::ImplicitConversion<FromType, ToType>::exists; |
---|
321 | //using namespace conversion; |
---|
322 | return convertImplicitely(output, input, ::Int2Type<probe>()); |
---|
323 | } |
---|
324 | } |
---|
325 | |
---|
326 | |
---|
327 | ///////////////////// |
---|
328 | // Local Overwrite // |
---|
329 | ///////////////////// |
---|
330 | |
---|
331 | // Template that is used when no explicit template specialisation is available. |
---|
332 | // Try explicitConversion() function next. |
---|
333 | template <class ToType, class FromType> |
---|
334 | struct ConverterExplicit |
---|
335 | { |
---|
336 | static bool convert(ToType* output, const FromType& input) |
---|
337 | { |
---|
338 | using namespace fallbackTemplates; |
---|
339 | return explicitConversion(output, input); |
---|
340 | } |
---|
341 | }; |
---|
342 | |
---|
343 | |
---|
344 | ////////////////////// |
---|
345 | // Public Functions // |
---|
346 | ////////////////////// |
---|
347 | |
---|
348 | /** |
---|
349 | @brief |
---|
350 | Converts any value to any other as long as there exits a conversion. |
---|
351 | Otherwise, the conversion will generate a runtime warning. |
---|
352 | For information about the different conversion methods (user defined too), see the section |
---|
353 | 'Actual conversion sequence' in this file above. |
---|
354 | */ |
---|
355 | template <class ToType, class FromType> |
---|
356 | inline bool convertValue(ToType* output, const FromType& input) |
---|
357 | { |
---|
358 | // check whether we can convert one type to the other explicitely via explicit template specialisations |
---|
359 | return ConverterExplicit<ToType, FromType>::convert(output, input); |
---|
360 | } |
---|
361 | |
---|
362 | // For compatibility reasons. The same, but with capital ConvertValue |
---|
363 | template<class FromType, class ToType> |
---|
364 | inline bool ConvertValue(ToType* output, const FromType& input) |
---|
365 | { |
---|
366 | return convertValue(output, input); |
---|
367 | } |
---|
368 | |
---|
369 | // Calls convertValue and returns true if the conversion was successful. |
---|
370 | // Otherwise the fallback is used. |
---|
371 | template<class FromType, class ToType> |
---|
372 | inline bool ConvertValue(ToType* output, const FromType& input, const ToType& fallback) |
---|
373 | { |
---|
374 | if (convertValue(output, input)) |
---|
375 | return true; |
---|
376 | |
---|
377 | (*output) = fallback; |
---|
378 | return false; |
---|
379 | } |
---|
380 | |
---|
381 | // Directly returns the converted value, even if the conversion was not successful. |
---|
382 | template<class FromType, class ToType> |
---|
383 | inline ToType getConvertedValue(const FromType& input) |
---|
384 | { |
---|
385 | ToType output; |
---|
386 | ConvertValue(&output, input); |
---|
387 | return output; |
---|
388 | } |
---|
389 | |
---|
390 | // Directly returns the converted value, but uses the fallback on failure. |
---|
391 | template<class FromType, class ToType> |
---|
392 | inline ToType getConvertedValue(const FromType& input, const ToType& fallback) |
---|
393 | { |
---|
394 | ToType output; |
---|
395 | ConvertValue(&output, input, fallback); |
---|
396 | return output; |
---|
397 | } |
---|
398 | |
---|
399 | // Like getConvertedValue, but the template argument order is in reverse. |
---|
400 | // That means you can call it exactly like static_cast<ToType>(fromTypeValue). |
---|
401 | template<class ToType, class FromType> |
---|
402 | inline ToType conversion_cast(const FromType& input) |
---|
403 | { |
---|
404 | ToType output; |
---|
405 | ConvertValue(&output, input); |
---|
406 | return output; |
---|
407 | } |
---|
408 | |
---|
409 | // Like conversion_cast above, but uses a fallback on failure. |
---|
410 | template<class ToType, class FromType> |
---|
411 | inline ToType conversion_cast(const FromType& input, const ToType& fallback) |
---|
412 | { |
---|
413 | ToType output; |
---|
414 | ConvertValue(&output, input, fallback); |
---|
415 | return output; |
---|
416 | } |
---|
417 | |
---|
418 | |
---|
419 | //////////////////////////////// |
---|
420 | // Special string conversions // |
---|
421 | //////////////////////////////// |
---|
422 | |
---|
423 | // delegate conversion from const char* to std::string |
---|
424 | template <class ToType> |
---|
425 | inline bool explicitConversion(ToType* output, const char* input) |
---|
426 | { |
---|
427 | return ConverterExplicit<ToType, std::string>::convert(output, input); |
---|
428 | } |
---|
429 | |
---|
430 | // These conversions would exhibit ambiguous << or >> operators when using stringstream |
---|
431 | inline bool explicitConversion(std::string* output, const char input) |
---|
432 | { |
---|
433 | *output = std::string(1, input); |
---|
434 | return true; |
---|
435 | } |
---|
436 | inline bool explicitConversion(std::string* output, const unsigned char input) |
---|
437 | { |
---|
438 | *output = std::string(1, input); |
---|
439 | return true; |
---|
440 | } |
---|
441 | inline bool explicitConversion(char* output, const std::string input) |
---|
442 | { |
---|
443 | if (input != "") |
---|
444 | *output = input[0]; |
---|
445 | else |
---|
446 | *output = '\0'; |
---|
447 | return true; |
---|
448 | } |
---|
449 | inline bool explicitConversion(unsigned char* output, const std::string input) |
---|
450 | { |
---|
451 | if (input != "") |
---|
452 | *output = input[0]; |
---|
453 | else |
---|
454 | *output = '\0'; |
---|
455 | return true; |
---|
456 | } |
---|
457 | |
---|
458 | #endif /* _Convert_H__ */ |
---|