src/gromacs/utility/any.h

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  35 /*! \libinternal \file
  36  * \brief
  37  * Declares gmx::Any.
  38  *
  39  * \author Teemu Murtola <teemu.murtola@gmail.com>
  40  * \inlibraryapi
  41  * \ingroup module_utility
  42  */
  43 #ifndef GMX_UTILITY_ANY_H
  44 #define GMX_UTILITY_ANY_H
  45
  46 #include <memory>
  47 #include <string>
  48 #include <type_traits>
  49 #include <typeindex>
  50 #include <typeinfo>
  51 #include <utility>
  52
  53 #include "gromacs/utility/gmxassert.h"
  54
  55 namespace gmx
  56 {
  57
  58 /*! \libinternal \brief
  59  * Represents a dynamically typed value of an arbitrary type.
  60  *
  61  * To create a any, either initialize it as empty, or with the create()
  62  * method (or the equivalent constructor, if the type parameter can be deduced
  63  * and is clear to the reader from the context).
  64  *
  65  * To query the type of the contents in the any, use isEmpty(), type(), and
  66  * isType().
  67  *
  68  * To access the value, you need to know the type as a compile-time constant
  69  * (e.g., through branching based on isType()), and then use cast() or
  70  * tryCast().
  71  *
  72  * Methods in this class do not throw unless otherwise indicated.
  73  *
  74  * This provides essentially the same functionality as boost::any.
  75  *
  76  * \ingroup module_utility
  77  */
  78 class Any
  79 {
  80     public:
  81         /*! \brief
  82          * Creates a any that holds the given value.
  83          *
  84          * \throws std::bad_alloc if out of memory.
  85          *
  86          * This method allows explicitly specifying the template argument,
  87          * contrary to the templated constructor.
  88          */
  89         template <typename T>
  90         static Any create(const T &value) { return Any(value); }
  91         /*! \brief
  92          * Creates a any that holds the given value.
  93          *
  94          * \throws std::bad_alloc if out of memory.
  95          *
  96          * In addition to allowing specifying the template argument, this
  97          * method avoids copying when move-construction is possible.
  98          */
  99         template <typename T>
 100         static Any create(T &&value) { return Any(std::forward<T>(value)); }
 101
 102         //! Creates an empty any value.
 103         Any() {}
 104         /*! \brief
 105          * Creates a any that holds the given value.
 106          *
 107          * \throws std::bad_alloc if out of memory.
 108          */
 109         template <typename T, typename = std::enable_if_t<!std::is_same<T, Any>::value> >
 110         explicit Any(T &&value)
 111             : content_(new Content < std::decay_t < T>>(std::forward<T>(value)))
 112         {
 113         }
 114         /*! \brief
 115          * Creates a deep copy of a any.
 116          *
 117          * \throws std::bad_alloc if out of memory.
 118          */
 119         Any(const Any &other) : content_(other.cloneContent()) {}
 120         //! Move-constructs a any.
 121         Any(Any &&other) noexcept : content_(std::move(other.content_)) {}
 122         /*! \brief
 123          * Assigns the any.
 124          *
 125          * \throws std::bad_alloc if out of memory.
 126          */
 127         Any &operator=(const Any &other)
 128         {
 129             content_ = other.cloneContent();
 130             return *this;
 131         }
 132         //! Move-assigns the any.
 133         Any &operator=(Any &&other) noexcept
 134         {
 135             content_ = std::move(other.content_);
 136             return *this;
 137         }
 138
 139         //! Whether any value is stored.
 140         bool isEmpty() const { return content_ == nullptr; }
 141         //! Returns the dynamic type of the value that is currently stored.
 142         std::type_index type() const
 143         {
 144             const std::type_info &info
 145                 = !isEmpty() ? content_->typeInfo() : typeid(void);
 146             return std::type_index(info);
 147         }
 148         //! Returns whether the type stored matches the template parameter.
 149         template <typename T>
 150         bool isType() const
 151         {
 152             return !isEmpty() && content_->typeInfo() == typeid(T);
 153         }
 154
 155         /*! \brief
 156          * Tries to get the value as the given type.
 157          *
 158          * \tparam T  Type to get.
 159          * \returns Pointer to the value, or nullptr if the type does not match
 160          *     the stored value.
 161          */
 162         template <typename T>
 163         const T *tryCast() const
 164         {
 165             return isType<T>() ? &static_cast<Content<T> *>(content_.get())->value_ : nullptr;
 166         }
 167         /*! \brief
 168          * Gets the value when the type is known.
 169          *
 170          * \tparam T  Type to get (which must match what the any stores).
 171          *
 172          * Asserts if the any is empty or does not contain the requested type.
 173          */
 174         template <typename T>
 175         const T &cast() const
 176         {
 177             const T *value = tryCast<T>();
 178             GMX_RELEASE_ASSERT(value != nullptr, "Cast to incorrect type");
 179             return *value;
 180         }
 181         /*! \brief
 182          * Tries to get the value as the given type as a non-const pointer.
 183          *
 184          * \tparam T  Type to get.
 185          * \returns Pointer to the value, or nullptr if the type does not match
 186          *     the stored value.
 187          *
 188          * This method allows modifying the value in-place, which is useful
 189          * with more complicated data structures.
 190          */
 191         template <typename T>
 192         T *tryCastRef()
 193         {
 194             return isType<T>() ? &static_cast<Content<T> *>(content_.get())->value_ : nullptr;
 195         }
 196         /*! \brief
 197          * Gets the value when the type is known as a modifiable reference.
 198          *
 199          * \tparam T  Type to get (which must match what the any stores).
 200          *
 201          * Asserts if the any is empty or does not contain the requested type.
 202          */
 203         template <typename T>
 204         T &castRef()
 205         {
 206             T *value = tryCastRef<T>();
 207             GMX_RELEASE_ASSERT(value != nullptr, "Cast to incorrect type");
 208             return *value;
 209         }
 210
 211     private:
 212         class IContent
 213         {
 214             public:
 215                 virtual ~IContent() {}
 216                 virtual const std::type_info &typeInfo() const = 0;
 217                 virtual std::unique_ptr<IContent> clone() const = 0;
 218         };
 219
 220         template <typename T>
 221         class Content : public IContent
 222         {
 223             public:
 224                 explicit Content(const T &value) : value_(value) {}
 225                 explicit Content(T &&value) : value_(std::move(value)) {}
 226
 227                 const std::type_info &typeInfo() const override { return typeid(T); }
 228                 std::unique_ptr<IContent> clone() const override { return std::make_unique<Content>(value_); }
 229
 230                 T value_;
 231         };
 232
 233         //! Creates a deep copy of the content.
 234         std::unique_ptr<IContent> cloneContent() const
 235         {
 236             return content_ != nullptr ? content_->clone() : nullptr;
 237         }
 238
 239         std::unique_ptr<IContent> content_;
 240 };
 241
 242 //! \cond libapi
 243 /*! \brief
 244  * Converts a Any value to a string.
 245  *
 246  * As the name suggests, only some types of "simple" values (such as int) are
 247  * supported.  Asserts for unsupported types.
 248  *
 249  * \ingroup module_utility
 250  */
 251 std::string simpleValueToString(const Any &value);
 252 //! \endcond
 253
 254 } // namespace gmx
 255
 256 #endif