COIN-OR::LEMON - Graph Library

source: lemon/lemon/bits/variant.h @ 461:1229dc2f1d36

Last change on this file since 461:1229dc2f1d36 was 452:9dfaf6efc36f, checked in by Peter Kovacs <kpeter@…>, 11 years ago

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1/* -*- mode: C++; indent-tabs-mode: nil; -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library.
4 *
5 * Copyright (C) 2003-2008
6 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
7 * (Egervary Research Group on Combinatorial Optimization, EGRES).
8 *
9 * Permission to use, modify and distribute this software is granted
10 * provided that this copyright notice appears in all copies. For
11 * precise terms see the accompanying LICENSE file.
12 *
13 * This software is provided "AS IS" with no warranty of any kind,
14 * express or implied, and with no claim as to its suitability for any
15 * purpose.
16 *
17 */
18
19#ifndef LEMON_BITS_VARIANT_H
20#define LEMON_BITS_VARIANT_H
21
22#include <lemon/assert.h>
23
24// \file
25// \brief Variant types
26
27namespace lemon {
28
29  namespace _variant_bits {
30
31    template <int left, int right>
32    struct CTMax {
33      static const int value = left < right ? right : left;
34    };
35
36  }
37
38
39  // \brief Simple Variant type for two types
40  //
41  // Simple Variant type for two types. The Variant type is a type-safe
42  // union. C++ has strong limitations for using unions, for
43  // example you cannot store a type with non-default constructor or
44  // destructor in a union. This class always knowns the current
45  // state of the variant and it cares for the proper construction
46  // and destruction.
47  template <typename _First, typename _Second>
48  class BiVariant {
49  public:
50
51    // \brief The \c First type.
52    typedef _First First;
53    // \brief The \c Second type.
54    typedef _Second Second;
55
56    // \brief Constructor
57    //
58    // This constructor initalizes to the default value of the \c First
59    // type.
60    BiVariant() {
61      flag = true;
62      new(reinterpret_cast<First*>(data)) First();
63    }
64
65    // \brief Constructor
66    //
67    // This constructor initalizes to the given value of the \c First
68    // type.
69    BiVariant(const First& f) {
70      flag = true;
71      new(reinterpret_cast<First*>(data)) First(f);
72    }
73
74    // \brief Constructor
75    //
76    // This constructor initalizes to the given value of the \c
77    // Second type.
78    BiVariant(const Second& s) {
79      flag = false;
80      new(reinterpret_cast<Second*>(data)) Second(s);
81    }
82
83    // \brief Copy constructor
84    //
85    // Copy constructor
86    BiVariant(const BiVariant& bivariant) {
87      flag = bivariant.flag;
88      if (flag) {
89        new(reinterpret_cast<First*>(data)) First(bivariant.first());
90      } else {
91        new(reinterpret_cast<Second*>(data)) Second(bivariant.second());
92      }
93    }
94
95    // \brief Destrcutor
96    //
97    // Destructor
98    ~BiVariant() {
99      destroy();
100    }
101
102    // \brief Set to the default value of the \c First type.
103    //
104    // This function sets the variant to the default value of the \c
105    // First type.
106    BiVariant& setFirst() {
107      destroy();
108      flag = true;
109      new(reinterpret_cast<First*>(data)) First();
110      return *this;
111    }
112
113    // \brief Set to the given value of the \c First type.
114    //
115    // This function sets the variant to the given value of the \c
116    // First type.
117    BiVariant& setFirst(const First& f) {
118      destroy();
119      flag = true;
120      new(reinterpret_cast<First*>(data)) First(f);
121      return *this;
122    }
123
124    // \brief Set to the default value of the \c Second type.
125    //
126    // This function sets the variant to the default value of the \c
127    // Second type.
128    BiVariant& setSecond() {
129      destroy();
130      flag = false;
131      new(reinterpret_cast<Second*>(data)) Second();
132      return *this;
133    }
134
135    // \brief Set to the given value of the \c Second type.
136    //
137    // This function sets the variant to the given value of the \c
138    // Second type.
139    BiVariant& setSecond(const Second& s) {
140      destroy();
141      flag = false;
142      new(reinterpret_cast<Second*>(data)) Second(s);
143      return *this;
144    }
145
146    // \brief Operator form of the \c setFirst()
147    BiVariant& operator=(const First& f) {
148      return setFirst(f);
149    }
150
151    // \brief Operator form of the \c setSecond()
152    BiVariant& operator=(const Second& s) {
153      return setSecond(s);
154    }
155
156    // \brief Assign operator
157    BiVariant& operator=(const BiVariant& bivariant) {
158      if (this == &bivariant) return *this;
159      destroy();
160      flag = bivariant.flag;
161      if (flag) {
162        new(reinterpret_cast<First*>(data)) First(bivariant.first());
163      } else {
164        new(reinterpret_cast<Second*>(data)) Second(bivariant.second());
165      }
166      return *this;
167    }
168
169    // \brief Reference to the value
170    //
171    // Reference to the value of the \c First type.
172    // \pre The BiVariant should store value of \c First type.
173    First& first() {
174      LEMON_DEBUG(flag, "Variant wrong state");
175      return *reinterpret_cast<First*>(data);
176    }
177
178    // \brief Const reference to the value
179    //
180    // Const reference to the value of the \c First type.
181    // \pre The BiVariant should store value of \c First type.
182    const First& first() const {
183      LEMON_DEBUG(flag, "Variant wrong state");
184      return *reinterpret_cast<const First*>(data);
185    }
186
187    // \brief Operator form of the \c first()
188    operator First&() { return first(); }
189    // \brief Operator form of the const \c first()
190    operator const First&() const { return first(); }
191
192    // \brief Reference to the value
193    //
194    // Reference to the value of the \c Second type.
195    // \pre The BiVariant should store value of \c Second type.
196    Second& second() {
197      LEMON_DEBUG(!flag, "Variant wrong state");
198      return *reinterpret_cast<Second*>(data);
199    }
200
201    // \brief Const reference to the value
202    //
203    // Const reference to the value of the \c Second type.
204    // \pre The BiVariant should store value of \c Second type.
205    const Second& second() const {
206      LEMON_DEBUG(!flag, "Variant wrong state");
207      return *reinterpret_cast<const Second*>(data);
208    }
209
210    // \brief Operator form of the \c second()
211    operator Second&() { return second(); }
212    // \brief Operator form of the const \c second()
213    operator const Second&() const { return second(); }
214
215    // \brief %True when the variant is in the first state
216    //
217    // %True when the variant stores value of the \c First type.
218    bool firstState() const { return flag; }
219
220    // \brief %True when the variant is in the second state
221    //
222    // %True when the variant stores value of the \c Second type.
223    bool secondState() const { return !flag; }
224
225  private:
226
227    void destroy() {
228      if (flag) {
229        reinterpret_cast<First*>(data)->~First();
230      } else {
231        reinterpret_cast<Second*>(data)->~Second();
232      }
233    }
234
235    char data[_variant_bits::CTMax<sizeof(First), sizeof(Second)>::value];
236    bool flag;
237  };
238
239  namespace _variant_bits {
240
241    template <int _idx, typename _TypeMap>
242    struct Memory {
243
244      typedef typename _TypeMap::template Map<_idx>::Type Current;
245
246      static void destroy(int index, char* place) {
247        if (index == _idx) {
248          reinterpret_cast<Current*>(place)->~Current();
249        } else {
250          Memory<_idx - 1, _TypeMap>::destroy(index, place);
251        }
252      }
253
254      static void copy(int index, char* to, const char* from) {
255        if (index == _idx) {
256          new (reinterpret_cast<Current*>(to))
257            Current(reinterpret_cast<const Current*>(from));
258        } else {
259          Memory<_idx - 1, _TypeMap>::copy(index, to, from);
260        }
261      }
262
263    };
264
265    template <typename _TypeMap>
266    struct Memory<-1, _TypeMap> {
267
268      static void destroy(int, char*) {
269        LEMON_DEBUG(false, "Variant wrong index.");
270      }
271
272      static void copy(int, char*, const char*) {
273        LEMON_DEBUG(false, "Variant wrong index.");
274      }
275    };
276
277    template <int _idx, typename _TypeMap>
278    struct Size {
279      static const int value =
280      CTMax<sizeof(typename _TypeMap::template Map<_idx>::Type),
281            Size<_idx - 1, _TypeMap>::value>::value;
282    };
283
284    template <typename _TypeMap>
285    struct Size<0, _TypeMap> {
286      static const int value =
287      sizeof(typename _TypeMap::template Map<0>::Type);
288    };
289
290  }
291
292  // \brief Variant type
293  //
294  // Simple Variant type. The Variant type is a type-safe union.
295  // C++ has strong limitations for using unions, for example you
296  // cannot store type with non-default constructor or destructor in
297  // a union. This class always knowns the current state of the
298  // variant and it cares for the proper construction and
299  // destruction.
300  //
301  // \param _num The number of the types which can be stored in the
302  // variant type.
303  // \param _TypeMap This class describes the types of the Variant. The
304  // _TypeMap::Map<index>::Type should be a valid type for each index
305  // in the range {0, 1, ..., _num - 1}. The \c VariantTypeMap is helper
306  // class to define such type mappings up to 10 types.
307  //
308  // And the usage of the class:
309  //\code
310  // typedef Variant<3, VariantTypeMap<int, std::string, double> > MyVariant;
311  // MyVariant var;
312  // var.set<0>(12);
313  // std::cout << var.get<0>() << std::endl;
314  // var.set<1>("alpha");
315  // std::cout << var.get<1>() << std::endl;
316  // var.set<2>(0.75);
317  // std::cout << var.get<2>() << std::endl;
318  //\endcode
319  //
320  // The result of course:
321  //\code
322  // 12
323  // alpha
324  // 0.75
325  //\endcode
326  template <int _num, typename _TypeMap>
327  class Variant {
328  public:
329
330    static const int num = _num;
331
332    typedef _TypeMap TypeMap;
333
334    // \brief Constructor
335    //
336    // This constructor initalizes to the default value of the \c type
337    // with 0 index.
338    Variant() {
339      flag = 0;
340      new(reinterpret_cast<typename TypeMap::template Map<0>::Type*>(data))
341        typename TypeMap::template Map<0>::Type();
342    }
343
344
345    // \brief Copy constructor
346    //
347    // Copy constructor
348    Variant(const Variant& variant) {
349      flag = variant.flag;
350      _variant_bits::Memory<num - 1, TypeMap>::copy(flag, data, variant.data);
351    }
352
353    // \brief Assign operator
354    //
355    // Assign operator
356    Variant& operator=(const Variant& variant) {
357      if (this == &variant) return *this;
358      _variant_bits::Memory<num - 1, TypeMap>::
359        destroy(flag, data);
360      flag = variant.flag;
361      _variant_bits::Memory<num - 1, TypeMap>::
362        copy(flag, data, variant.data);
363      return *this;
364    }
365
366    // \brief Destrcutor
367    //
368    // Destructor
369    ~Variant() {
370      _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);
371    }
372
373    // \brief Set to the default value of the type with \c _idx index.
374    //
375    // This function sets the variant to the default value of the
376    // type with \c _idx index.
377    template <int _idx>
378    Variant& set() {
379      _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);
380      flag = _idx;
381      new(reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>(data))
382        typename TypeMap::template Map<_idx>::Type();
383      return *this;
384    }
385
386    // \brief Set to the given value of the type with \c _idx index.
387    //
388    // This function sets the variant to the given value of the type
389    // with \c _idx index.
390    template <int _idx>
391    Variant& set(const typename _TypeMap::template Map<_idx>::Type& init) {
392      _variant_bits::Memory<num - 1, TypeMap>::destroy(flag, data);
393      flag = _idx;
394      new(reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>(data))
395        typename TypeMap::template Map<_idx>::Type(init);
396      return *this;
397    }
398
399    // \brief Gets the current value of the type with \c _idx index.
400    //
401    // Gets the current value of the type with \c _idx index.
402    template <int _idx>
403    const typename TypeMap::template Map<_idx>::Type& get() const {
404      LEMON_DEBUG(_idx == flag, "Variant wrong index");
405      return *reinterpret_cast<const typename TypeMap::
406        template Map<_idx>::Type*>(data);
407    }
408
409    // \brief Gets the current value of the type with \c _idx index.
410    //
411    // Gets the current value of the type with \c _idx index.
412    template <int _idx>
413    typename _TypeMap::template Map<_idx>::Type& get() {
414      LEMON_DEBUG(_idx == flag, "Variant wrong index");
415      return *reinterpret_cast<typename TypeMap::template Map<_idx>::Type*>
416        (data);
417    }
418
419    // \brief Returns the current state of the variant.
420    //
421    // Returns the current state of the variant.
422    int state() const {
423      return flag;
424    }
425
426  private:
427
428    char data[_variant_bits::Size<num - 1, TypeMap>::value];
429    int flag;
430  };
431
432  namespace _variant_bits {
433
434    template <int _index, typename _List>
435    struct Get {
436      typedef typename Get<_index - 1, typename _List::Next>::Type Type;
437    };
438
439    template <typename _List>
440    struct Get<0, _List> {
441      typedef typename _List::Type Type;
442    };
443
444    struct List {};
445
446    template <typename _Type, typename _List>
447    struct Insert {
448      typedef _List Next;
449      typedef _Type Type;
450    };
451
452    template <int _idx, typename _T0, typename _T1, typename _T2,
453              typename _T3, typename _T4, typename _T5, typename _T6,
454              typename _T7, typename _T8, typename _T9>
455    struct Mapper {
456      typedef List L10;
457      typedef Insert<_T9, L10> L9;
458      typedef Insert<_T8, L9> L8;
459      typedef Insert<_T7, L8> L7;
460      typedef Insert<_T6, L7> L6;
461      typedef Insert<_T5, L6> L5;
462      typedef Insert<_T4, L5> L4;
463      typedef Insert<_T3, L4> L3;
464      typedef Insert<_T2, L3> L2;
465      typedef Insert<_T1, L2> L1;
466      typedef Insert<_T0, L1> L0;
467      typedef typename Get<_idx, L0>::Type Type;
468    };
469
470  }
471
472  // \brief Helper class for Variant
473  //
474  // Helper class to define type mappings for Variant. This class
475  // converts the template parameters to be mappable by integer.
476  // \see Variant
477  template <
478    typename _T0,
479    typename _T1 = void, typename _T2 = void, typename _T3 = void,
480    typename _T4 = void, typename _T5 = void, typename _T6 = void,
481    typename _T7 = void, typename _T8 = void, typename _T9 = void>
482  struct VariantTypeMap {
483    template <int _idx>
484    struct Map {
485      typedef typename _variant_bits::
486      Mapper<_idx, _T0, _T1, _T2, _T3, _T4, _T5, _T6, _T7, _T8, _T9>::Type
487      Type;
488    };
489  };
490
491}
492
493
494#endif
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