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// 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
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// 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_