// Protocol Buffers - Google's data interchange format

// Copyright 2014 Google Inc.  All rights reserved.

// https://developers.google.com/protocol-buffers/

//

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// met:

//

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#ifndef GOOGLE_PROTOBUF_CASTS_H__

#define GOOGLE_PROTOBUF_CASTS_H__

#include <google/protobuf/stubs/common.h>

#include <google/protobuf/port_def.inc>

#include <type_traits>

namespace google {

namespace protobuf {

namespace internal {

// Use implicit_cast as a safe version of static_cast or const_cast

// for upcasting in the type hierarchy (i.e. casting a pointer to Foo

// to a pointer to SuperclassOfFoo or casting a pointer to Foo to

// a const pointer to Foo).

// When you use implicit_cast, the compiler checks that the cast is safe.

// Such explicit implicit_casts are necessary in surprisingly many

// situations where C++ demands an exact type match instead of an

// argument type convertible to a target type.

//

// The From type can be inferred, so the preferred syntax for using

// implicit_cast is the same as for static_cast etc.:

//

//   implicit_cast<ToType>(expr)

//

// implicit_cast would have been part of the C++ standard library,

// but the proposal was submitted too late.  It will probably make

// its way into the language in the future.

template<typename To, typename From>

inline To implicit_cast(From const &f) {

  return f;

}

// When you upcast (that is, cast a pointer from type Foo to type

// SuperclassOfFoo), it's fine to use implicit_cast<>, since upcasts

// always succeed.  When you downcast (that is, cast a pointer from

// type Foo to type SubclassOfFoo), static_cast<> isn't safe, because

// how do you know the pointer is really of type SubclassOfFoo?  It

// could be a bare Foo, or of type DifferentSubclassOfFoo.  Thus,

// when you downcast, you should use this macro.  In debug mode, we

// use dynamic_cast<> to double-check the downcast is legal (we die

// if it's not).  In normal mode, we do the efficient static_cast<>

// instead.  Thus, it's important to test in debug mode to make sure

// the cast is legal!

//    This is the only place in the code we should use dynamic_cast<>.

// In particular, you SHOULDN'T be using dynamic_cast<> in order to

// do RTTI (eg code like this:

//    if (dynamic_cast<Subclass1>(foo)) HandleASubclass1Object(foo);

//    if (dynamic_cast<Subclass2>(foo)) HandleASubclass2Object(foo);

// You should design the code some other way not to need this.

template<typename To, typename From>     // use like this: down_cast<T*>(foo);

inline To down_cast(From* f) {                   // so we only accept pointers

  // Ensures that To is a sub-type of From *.  This test is here only

  // for compile-time type checking, and has no overhead in an

  // optimized build at run-time, as it will be optimized away

  // completely.

  if (false) {

    implicit_cast<From*, To>(0);

  }

#if !defined(NDEBUG) && PROTOBUF_RTTI

  assert(f == nullptr || dynamic_cast<To>(f) != nullptr);  // RTTI: debug mode only!

#endif

  return static_cast<To>(f);

}

template<typename To, typename From>    // use like this: down_cast<T&>(foo);

inline To down_cast(From& f) {

  typedef typename std::remove_reference<To>::type* ToAsPointer;

  // Ensures that To is a sub-type of From *.  This test is here only

  // for compile-time type checking, and has no overhead in an

  // optimized build at run-time, as it will be optimized away

  // completely.

  if (false) {

    implicit_cast<From*, ToAsPointer>(0);

  }

#if !defined(NDEBUG) && PROTOBUF_RTTI

  // RTTI: debug mode only!

  assert(dynamic_cast<ToAsPointer>(&f) != nullptr);

#endif

  return *static_cast<ToAsPointer>(&f);

}

template<typename To, typename From>

inline To bit_cast(const From& from) {

  static_assert(sizeof(From) == sizeof(To), "bit_cast_with_different_sizes");

  To dest;

  memcpy(&dest, &from, sizeof(dest));

  return dest;

}

Unexecuted instantiation: unsigned int google::protobuf::internal::bit_cast<unsigned int, float>(float const&)

Unexecuted instantiation: float google::protobuf::internal::bit_cast<float, unsigned int>(unsigned int const&)

Unexecuted instantiation: unsigned long google::protobuf::internal::bit_cast<unsigned long, double>(double const&)

Unexecuted instantiation: double google::protobuf::internal::bit_cast<double, unsigned long>(unsigned long const&)

}  // namespace internal

// We made these internal so that they would show up as such in the docs,

// but we don't want to stick "internal::" in front of them everywhere.

using internal::implicit_cast;

using internal::down_cast;

using internal::bit_cast;

}  // namespace protobuf

}  // namespace google

#include <google/protobuf/port_undef.inc>

#endif  // GOOGLE_PROTOBUF_CASTS_H__