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1 | /*============================================================================= |
2 | Copyright (c) 2007-2011 Hartmut Kaiser | |
3 | Copyright (c) Christopher Diggins 2005 | |
4 | Copyright (c) Pablo Aguilar 2005 | |
5 | Copyright (c) Kevlin Henney 2001 | |
6 | ||
7 | Distributed under the Boost Software License, Version 1.0. (See accompanying | |
8 | file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
9 | ||
10 | The class boost::spirit::hold_any is built based on the any class | |
11 | published here: http://www.codeproject.com/cpp/dynamic_typing.asp. It adds | |
12 | support for std streaming operator<<() and operator>>(). | |
13 | ==============================================================================*/ | |
14 | #if !defined(BOOST_SPIRIT_HOLD_ANY_MAY_02_2007_0857AM) | |
15 | #define BOOST_SPIRIT_HOLD_ANY_MAY_02_2007_0857AM | |
16 | ||
17 | #if defined(_MSC_VER) | |
18 | #pragma once | |
19 | #endif | |
20 | ||
21 | #include <boost/config.hpp> | |
22 | #include <boost/type_traits/remove_reference.hpp> | |
23 | #include <boost/type_traits/is_reference.hpp> | |
24 | #include <boost/throw_exception.hpp> | |
25 | #include <boost/static_assert.hpp> | |
26 | #include <boost/mpl/bool.hpp> | |
27 | #include <boost/assert.hpp> | |
28 | #include <boost/detail/sp_typeinfo.hpp> | |
29 | ||
30 | #include <stdexcept> | |
31 | #include <typeinfo> | |
32 | #include <algorithm> | |
33 | #include <iosfwd> | |
34 | ||
35 | /////////////////////////////////////////////////////////////////////////////// | |
36 | #if BOOST_WORKAROUND(BOOST_MSVC, >= 1400) | |
37 | # pragma warning(push) | |
38 | # pragma warning(disable: 4100) // 'x': unreferenced formal parameter | |
39 | # pragma warning(disable: 4127) // conditional expression is constant | |
40 | #endif | |
41 | ||
42 | /////////////////////////////////////////////////////////////////////////////// | |
43 | namespace boost { namespace spirit | |
44 | { | |
45 | struct bad_any_cast | |
46 | : std::bad_cast | |
47 | { | |
48 | bad_any_cast(boost::detail::sp_typeinfo const& src, boost::detail::sp_typeinfo const& dest) | |
49 | : from(src.name()), to(dest.name()) | |
50 | {} | |
51 | ||
52 | virtual const char* what() const throw() { return "bad any cast"; } | |
53 | ||
54 | const char* from; | |
55 | const char* to; | |
56 | }; | |
57 | ||
58 | namespace detail | |
59 | { | |
60 | // function pointer table | |
61 | template <typename Char> | |
62 | struct fxn_ptr_table | |
63 | { | |
64 | boost::detail::sp_typeinfo const& (*get_type)(); | |
65 | void (*static_delete)(void**); | |
66 | void (*destruct)(void**); | |
67 | void (*clone)(void* const*, void**); | |
68 | void (*move)(void* const*, void**); | |
69 | std::basic_istream<Char>& (*stream_in)(std::basic_istream<Char>&, void**); | |
70 | std::basic_ostream<Char>& (*stream_out)(std::basic_ostream<Char>&, void* const*); | |
71 | }; | |
72 | ||
73 | // static functions for small value-types | |
74 | template <typename Small> | |
75 | struct fxns; | |
76 | ||
77 | template <> | |
78 | struct fxns<mpl::true_> | |
79 | { | |
80 | template<typename T, typename Char> | |
81 | struct type | |
82 | { | |
83 | static boost::detail::sp_typeinfo const& get_type() | |
84 | { | |
85 | return BOOST_SP_TYPEID(T); | |
86 | } | |
87 | static void static_delete(void** x) | |
88 | { | |
89 | reinterpret_cast<T*>(x)->~T(); | |
90 | } | |
91 | static void destruct(void** x) | |
92 | { | |
93 | reinterpret_cast<T*>(x)->~T(); | |
94 | } | |
95 | static void clone(void* const* src, void** dest) | |
96 | { | |
97 | new (dest) T(*reinterpret_cast<T const*>(src)); | |
98 | } | |
99 | static void move(void* const* src, void** dest) | |
100 | { | |
101 | *reinterpret_cast<T*>(dest) = | |
102 | *reinterpret_cast<T const*>(src); | |
103 | } | |
104 | static std::basic_istream<Char>& | |
105 | stream_in (std::basic_istream<Char>& i, void** obj) | |
106 | { | |
107 | i >> *reinterpret_cast<T*>(obj); | |
108 | return i; | |
109 | } | |
110 | static std::basic_ostream<Char>& | |
111 | stream_out(std::basic_ostream<Char>& o, void* const* obj) | |
112 | { | |
113 | o << *reinterpret_cast<T const*>(obj); | |
114 | return o; | |
115 | } | |
116 | }; | |
117 | }; | |
118 | ||
119 | // static functions for big value-types (bigger than a void*) | |
120 | template <> | |
121 | struct fxns<mpl::false_> | |
122 | { | |
123 | template<typename T, typename Char> | |
124 | struct type | |
125 | { | |
126 | static boost::detail::sp_typeinfo const& get_type() | |
127 | { | |
128 | return BOOST_SP_TYPEID(T); | |
129 | } | |
130 | static void static_delete(void** x) | |
131 | { | |
132 | // destruct and free memory | |
133 | delete (*reinterpret_cast<T**>(x)); | |
134 | } | |
135 | static void destruct(void** x) | |
136 | { | |
137 | // destruct only, we'll reuse memory | |
138 | (*reinterpret_cast<T**>(x))->~T(); | |
139 | } | |
140 | static void clone(void* const* src, void** dest) | |
141 | { | |
142 | *dest = new T(**reinterpret_cast<T* const*>(src)); | |
143 | } | |
144 | static void move(void* const* src, void** dest) | |
145 | { | |
146 | **reinterpret_cast<T**>(dest) = | |
147 | **reinterpret_cast<T* const*>(src); | |
148 | } | |
149 | static std::basic_istream<Char>& | |
150 | stream_in(std::basic_istream<Char>& i, void** obj) | |
151 | { | |
152 | i >> **reinterpret_cast<T**>(obj); | |
153 | return i; | |
154 | } | |
155 | static std::basic_ostream<Char>& | |
156 | stream_out(std::basic_ostream<Char>& o, void* const* obj) | |
157 | { | |
158 | o << **reinterpret_cast<T* const*>(obj); | |
159 | return o; | |
160 | } | |
161 | }; | |
162 | }; | |
163 | ||
164 | template <typename T> | |
165 | struct get_table | |
166 | { | |
167 | typedef mpl::bool_<(sizeof(T) <= sizeof(void*))> is_small; | |
168 | ||
169 | template <typename Char> | |
170 | static fxn_ptr_table<Char>* get() | |
171 | { | |
172 | static fxn_ptr_table<Char> static_table = | |
173 | { | |
174 | fxns<is_small>::template type<T, Char>::get_type, | |
175 | fxns<is_small>::template type<T, Char>::static_delete, | |
176 | fxns<is_small>::template type<T, Char>::destruct, | |
177 | fxns<is_small>::template type<T, Char>::clone, | |
178 | fxns<is_small>::template type<T, Char>::move, | |
179 | fxns<is_small>::template type<T, Char>::stream_in, | |
180 | fxns<is_small>::template type<T, Char>::stream_out | |
181 | }; | |
182 | return &static_table; | |
183 | } | |
184 | }; | |
185 | ||
186 | /////////////////////////////////////////////////////////////////////// | |
187 | struct empty {}; | |
188 | ||
189 | template <typename Char> | |
190 | inline std::basic_istream<Char>& | |
191 | operator>> (std::basic_istream<Char>& i, empty&) | |
192 | { | |
193 | // If this assertion fires you tried to insert from a std istream | |
194 | // into an empty hold_any instance. This simply can't work, because | |
195 | // there is no way to figure out what type to extract from the | |
196 | // stream. | |
197 | // The only way to make this work is to assign an arbitrary | |
198 | // value of the required type to the hold_any instance you want to | |
199 | // stream to. This assignment has to be executed before the actual | |
200 | // call to the operator>>(). | |
201 | BOOST_ASSERT(false && | |
202 | "Tried to insert from a std istream into an empty " | |
203 | "hold_any instance"); | |
204 | return i; | |
205 | } | |
206 | ||
207 | template <typename Char> | |
208 | inline std::basic_ostream<Char>& | |
209 | operator<< (std::basic_ostream<Char>& o, empty const&) | |
210 | { | |
211 | return o; | |
212 | } | |
213 | } | |
214 | ||
215 | /////////////////////////////////////////////////////////////////////////// | |
216 | template <typename Char> | |
217 | class basic_hold_any | |
218 | { | |
219 | public: | |
220 | // constructors | |
221 | template <typename T> | |
222 | explicit basic_hold_any(T const& x) | |
223 | : table(spirit::detail::get_table<T>::template get<Char>()), object(0) | |
224 | { | |
225 | if (spirit::detail::get_table<T>::is_small::value) | |
226 | new (&object) T(x); | |
227 | else | |
228 | object = new T(x); | |
229 | } | |
230 | ||
231 | basic_hold_any() | |
232 | : table(spirit::detail::get_table<spirit::detail::empty>::template get<Char>()), | |
233 | object(0) | |
234 | { | |
235 | } | |
236 | ||
237 | basic_hold_any(basic_hold_any const& x) | |
238 | : table(spirit::detail::get_table<spirit::detail::empty>::template get<Char>()), | |
239 | object(0) | |
240 | { | |
241 | assign(x); | |
242 | } | |
243 | ||
244 | ~basic_hold_any() | |
245 | { | |
246 | table->static_delete(&object); | |
247 | } | |
248 | ||
249 | // assignment | |
250 | basic_hold_any& assign(basic_hold_any const& x) | |
251 | { | |
252 | if (&x != this) { | |
253 | // are we copying between the same type? | |
254 | if (table == x.table) { | |
255 | // if so, we can avoid reallocation | |
256 | table->move(&x.object, &object); | |
257 | } | |
258 | else { | |
259 | reset(); | |
260 | x.table->clone(&x.object, &object); | |
261 | table = x.table; | |
262 | } | |
263 | } | |
264 | return *this; | |
265 | } | |
266 | ||
267 | template <typename T> | |
268 | basic_hold_any& assign(T const& x) | |
269 | { | |
270 | // are we copying between the same type? | |
271 | spirit::detail::fxn_ptr_table<Char>* x_table = | |
272 | spirit::detail::get_table<T>::template get<Char>(); | |
273 | if (table == x_table) { | |
274 | // if so, we can avoid deallocating and re-use memory | |
275 | table->destruct(&object); // first destruct the old content | |
276 | if (spirit::detail::get_table<T>::is_small::value) { | |
277 | // create copy on-top of object pointer itself | |
278 | new (&object) T(x); | |
279 | } | |
280 | else { | |
281 | // create copy on-top of old version | |
282 | new (object) T(x); | |
283 | } | |
284 | } | |
285 | else { | |
286 | if (spirit::detail::get_table<T>::is_small::value) { | |
287 | // create copy on-top of object pointer itself | |
288 | table->destruct(&object); // first destruct the old content | |
289 | new (&object) T(x); | |
290 | } | |
291 | else { | |
292 | reset(); // first delete the old content | |
293 | object = new T(x); | |
294 | } | |
295 | table = x_table; // update table pointer | |
296 | } | |
297 | return *this; | |
298 | } | |
299 | ||
300 | // assignment operator | |
301 | #ifdef BOOST_HAS_RVALUE_REFS | |
302 | template <typename T> | |
303 | basic_hold_any& operator=(T&& x) | |
304 | { | |
305 | return assign(std::forward<T>(x)); | |
306 | } | |
307 | #else | |
308 | template <typename T> | |
309 | basic_hold_any& operator=(T& x) | |
310 | { | |
311 | return assign(x); | |
312 | } | |
313 | ||
314 | template <typename T> | |
315 | basic_hold_any& operator=(T const& x) | |
316 | { | |
317 | return assign(x); | |
318 | } | |
319 | #endif | |
320 | ||
321 | // utility functions | |
322 | basic_hold_any& swap(basic_hold_any& x) | |
323 | { | |
324 | std::swap(table, x.table); | |
325 | std::swap(object, x.object); | |
326 | return *this; | |
327 | } | |
328 | ||
329 | boost::detail::sp_typeinfo const& type() const | |
330 | { | |
331 | return table->get_type(); | |
332 | } | |
333 | ||
334 | template <typename T> | |
335 | T const& cast() const | |
336 | { | |
337 | if (type() != BOOST_SP_TYPEID(T)) | |
338 | throw bad_any_cast(type(), BOOST_SP_TYPEID(T)); | |
339 | ||
340 | return spirit::detail::get_table<T>::is_small::value ? | |
341 | *reinterpret_cast<T const*>(&object) : | |
342 | *reinterpret_cast<T const*>(object); | |
343 | } | |
344 | ||
345 | // implicit casting is disabled by default for compatibility with boost::any | |
346 | #ifdef BOOST_SPIRIT_ANY_IMPLICIT_CASTING | |
347 | // automatic casting operator | |
348 | template <typename T> | |
349 | operator T const& () const { return cast<T>(); } | |
350 | #endif // implicit casting | |
351 | ||
352 | bool empty() const | |
353 | { | |
354 | return table == spirit::detail::get_table<spirit::detail::empty>::template get<Char>(); | |
355 | } | |
356 | ||
357 | void reset() | |
358 | { | |
359 | if (!empty()) | |
360 | { | |
361 | table->static_delete(&object); | |
362 | table = spirit::detail::get_table<spirit::detail::empty>::template get<Char>(); | |
363 | object = 0; | |
364 | } | |
365 | } | |
366 | ||
367 | // these functions have been added in the assumption that the embedded | |
368 | // type has a corresponding operator defined, which is completely safe | |
369 | // because spirit::hold_any is used only in contexts where these operators | |
370 | // do exist | |
371 | template <typename Char_> | |
372 | friend inline std::basic_istream<Char_>& | |
373 | operator>> (std::basic_istream<Char_>& i, basic_hold_any<Char_>& obj) | |
374 | { | |
375 | return obj.table->stream_in(i, &obj.object); | |
376 | } | |
377 | ||
378 | template <typename Char_> | |
379 | friend inline std::basic_ostream<Char_>& | |
380 | operator<< (std::basic_ostream<Char_>& o, basic_hold_any<Char_> const& obj) | |
381 | { | |
382 | return obj.table->stream_out(o, &obj.object); | |
383 | } | |
384 | ||
385 | #ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS | |
386 | private: // types | |
387 | template <typename T, typename Char_> | |
388 | friend T* any_cast(basic_hold_any<Char_> *); | |
389 | #else | |
390 | public: // types (public so any_cast can be non-friend) | |
391 | #endif | |
392 | // fields | |
393 | spirit::detail::fxn_ptr_table<Char>* table; | |
394 | void* object; | |
395 | }; | |
396 | ||
397 | // boost::any-like casting | |
398 | template <typename T, typename Char> | |
399 | inline T* any_cast (basic_hold_any<Char>* operand) | |
400 | { | |
401 | if (operand && operand->type() == BOOST_SP_TYPEID(T)) { | |
402 | return spirit::detail::get_table<T>::is_small::value ? | |
403 | reinterpret_cast<T*>(&operand->object) : | |
404 | reinterpret_cast<T*>(operand->object); | |
405 | } | |
406 | return 0; | |
407 | } | |
408 | ||
409 | template <typename T, typename Char> | |
410 | inline T const* any_cast(basic_hold_any<Char> const* operand) | |
411 | { | |
412 | return any_cast<T>(const_cast<basic_hold_any<Char>*>(operand)); | |
413 | } | |
414 | ||
415 | template <typename T, typename Char> | |
416 | T any_cast(basic_hold_any<Char>& operand) | |
417 | { | |
418 | typedef BOOST_DEDUCED_TYPENAME remove_reference<T>::type nonref; | |
419 | ||
420 | ||
421 | nonref* result = any_cast<nonref>(&operand); | |
422 | if(!result) | |
423 | boost::throw_exception(bad_any_cast(operand.type(), BOOST_SP_TYPEID(T))); | |
424 | return *result; | |
425 | } | |
426 | ||
427 | template <typename T, typename Char> | |
428 | T const& any_cast(basic_hold_any<Char> const& operand) | |
429 | { | |
430 | typedef BOOST_DEDUCED_TYPENAME remove_reference<T>::type nonref; | |
431 | ||
432 | ||
433 | return any_cast<nonref const&>(const_cast<basic_hold_any<Char> &>(operand)); | |
434 | } | |
435 | ||
436 | /////////////////////////////////////////////////////////////////////////////// | |
437 | // backwards compatibility | |
438 | typedef basic_hold_any<char> hold_any; | |
439 | typedef basic_hold_any<wchar_t> whold_any; | |
440 | ||
441 | namespace traits | |
442 | { | |
443 | template <typename T> | |
444 | struct is_hold_any : mpl::false_ {}; | |
445 | ||
446 | template <typename Char> | |
447 | struct is_hold_any<basic_hold_any<Char> > : mpl::true_ {}; | |
448 | } | |
449 | ||
450 | }} // namespace boost::spirit | |
451 | ||
452 | /////////////////////////////////////////////////////////////////////////////// | |
453 | #if BOOST_WORKAROUND(BOOST_MSVC, >= 1400) | |
454 | # pragma warning(pop) | |
455 | #endif | |
456 | ||
457 | #endif |