// Ceres Solver - A fast non-linear least squares minimizer

// Copyright 2015 Google Inc. All rights reserved.

// http://ceres-solver.org/

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are met:

//

// * Redistributions of source code must retain the above copyright notice,

//   this list of conditions and the following disclaimer.

// * Redistributions in binary form must reproduce the above copyright notice,

//   this list of conditions and the following disclaimer in the documentation

//   and/or other materials provided with the distribution.

// * Neither the name of Google Inc. nor the names of its contributors may be

//   used to endorse or promote products derived from this software without

//   specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE

// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

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// POSSIBILITY OF SUCH DAMAGE.

//

// Author: keir@google.com (Keir Mierle)

#ifndef CERES_INTERNAL_CASTS_H_

#define CERES_INTERNAL_CASTS_H_

#include <cassert>

#include <cstddef>  // For NULL.

namespace ceres {

// Identity metafunction.

template <class T>

struct identity_ {

  typedef T type;

};

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

// for implicit conversions. For example:

// - Upcasting in a type hierarchy.

// - Performing arithmetic conversions (int32 to int64, int to double, etc.).

// - Adding const or volatile qualifiers.

//

// In general, implicit_cast can be used to convert this code

//   To to = from;

//   DoSomething(to);

// to this

//   DoSomething(implicit_cast<To>(from));

//

// base::identity_ is used to make a non-deduced context, which

// forces all callers to explicitly specify the template argument.

template<typename To>

inline To implicit_cast(typename identity_<To>::type to) {

  return to;

}

// This version of implicit_cast is used when two template arguments

// are specified. It's obsolete and should not be used.

template<typename To, typename From>

inline To implicit_cast(typename identity_<From>::type 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.

  // TODO(csilvers): This should use COMPILE_ASSERT.

  if (false) {

    implicit_cast<From*, To>(NULL);

  }

  // uses RTTI in dbg and fastbuild. asserts are disabled in opt builds.

  assert(f == NULL || dynamic_cast<To>(f) != NULL);  // NOLINT

  return static_cast<To>(f);

}

}  // namespace ceres

#endif  // CERES_INTERNAL_CASTS_H_