Where Online Learning is simpler!

The C and C++ Include Header Files

cat -n /usr/include/wabt/cast.h

     1	/*
     2	 * Copyright 2017 WebAssembly Community Group participants
     3	 *
     4	 * Licensed under the Apache License, Version 2.0 (the "License");
     5	 * you may not use this file except in compliance with the License.
     6	 * You may obtain a copy of the License at
     7	 *
     8	 *     http://www.apache.org/licenses/LICENSE-2.0
     9	 *
    10	 * Unless required by applicable law or agreed to in writing, software
    11	 * distributed under the License is distributed on an "AS IS" BASIS,
    12	 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13	 * See the License for the specific language governing permissions and
    14	 * limitations under the License.
    15	 */
    16	
    17	#ifndef WABT_CAST_H_
    18	#define WABT_CAST_H_
    19	
    20	#include <memory>
    21	#include <type_traits>
    22	
    23	#include "wabt/common.h"
    24	
    25	// Modeled after LLVM's dynamic casts:
    26	// http://llvm.org/docs/ProgrammersManual.html#the-isa-cast-and-dyn-cast-templates
    27	//
    28	// Use isa<T>(foo) to check whether foo is a T*:
    29	//
    30	//     if (isa<Minivan>(car)) {
    31	//        ...
    32	//     }
    33	//
    34	// Use cast<T>(foo) when you know that foo is a T* -- it will assert that the
    35	// type matches:
    36	//
    37	//     switch (car.type) {
    38	//       case CarType::Minivan: {
    39	//         auto minivan = cast<Minivan>(car);
    40	//         ...
    41	//       }
    42	//     }
    43	//
    44	// Use dyn_cast<T>(foo) as a combination if isa and cast, it will return
    45	// nullptr if the type doesn't match:
    46	//
    47	//     if (auto minivan = dyn_cast<Minivan>(car)) {
    48	//       ...
    49	//     }
    50	//
    51	//
    52	// To use these classes in a type hierarchy, you must implement classof:
    53	//
    54	//     enum CarType { Minivan, ... };
    55	//     struct Car { CarType type; ... };
    56	//     struct Minivan : Car {
    57	//       static bool classof(const Car* car) { return car->type == Minivan; }
    58	//       ...
    59	//     };
    60	//
    61	
    62	namespace wabt {
    63	
    64	template <typename Derived, typename Base>
    65	bool isa(const Base* base) {
    66	  WABT_STATIC_ASSERT((std::is_base_of<Base, Derived>::value));
    67	  return Derived::classof(base);
    68	}
    69	
    70	template <typename Derived, typename Base>
    71	const Derived* cast(const Base* base) {
    72	  assert(isa<Derived>(base));
    73	  return static_cast<const Derived*>(base);
    74	};
    75	
    76	template <typename Derived, typename Base>
    77	Derived* cast(Base* base) {
    78	  assert(isa<Derived>(base));
    79	  return static_cast<Derived*>(base);
    80	};
    81	
    82	template <typename Derived, typename Base>
    83	const Derived* dyn_cast(const Base* base) {
    84	  return isa<Derived>(base) ? static_cast<const Derived*>(base) : nullptr;
    85	};
    86	
    87	template <typename Derived, typename Base>
    88	Derived* dyn_cast(Base* base) {
    89	  return isa<Derived>(base) ? static_cast<Derived*>(base) : nullptr;
    90	};
    91	
    92	// Cast functionality for unique_ptr. isa and dyn_cast are not included because
    93	// they won't always pass ownership back to the caller.
    94	
    95	template <typename Derived, typename Base>
    96	std::unique_ptr<const Derived> cast(std::unique_ptr<const Base>&& base) {
    97	  assert(isa<Derived>(base.get()));
    98	  return std::unique_ptr<Derived>(static_cast<const Derived*>(base.release()));
    99	};
   100	
   101	template <typename Derived, typename Base>
   102	std::unique_ptr<Derived> cast(std::unique_ptr<Base>&& base) {
   103	  assert(isa<Derived>(base.get()));
   104	  return std::unique_ptr<Derived>(static_cast<Derived*>(base.release()));
   105	};
   106	
   107	}  // namespace wabt
   108	
   109	#endif  // WABT_CAST_H_