1// Ceres Solver - A fast non-linear least squares minimizer 2// Copyright 2010, 2011, 2012 Google Inc. All rights reserved. 3// http://code.google.com/p/ceres-solver/ 4// 5// Redistribution and use in source and binary forms, with or without 6// modification, are permitted provided that the following conditions are met: 7// 8// * Redistributions of source code must retain the above copyright notice, 9// this list of conditions and the following disclaimer. 10// * Redistributions in binary form must reproduce the above copyright notice, 11// this list of conditions and the following disclaimer in the documentation 12// and/or other materials provided with the distribution. 13// * Neither the name of Google Inc. nor the names of its contributors may be 14// used to endorse or promote products derived from this software without 15// specific prior written permission. 16// 17// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 18// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 21// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 22// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 23// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 24// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 25// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 26// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 27// POSSIBILITY OF SUCH DAMAGE. 28// 29// Author: keir@google.com (Keir Mierle) 30 31#ifndef CERES_INTERNAL_CASTS_H_ 32#define CERES_INTERNAL_CASTS_H_ 33 34#include <cassert> 35#include <cstddef> // For NULL. 36 37namespace ceres { 38 39// Identity metafunction. 40template <class T> 41struct identity_ { 42 typedef T type; 43}; 44 45// Use implicit_cast as a safe version of static_cast or const_cast 46// for implicit conversions. For example: 47// - Upcasting in a type hierarchy. 48// - Performing arithmetic conversions (int32 to int64, int to double, etc.). 49// - Adding const or volatile qualifiers. 50// 51// In general, implicit_cast can be used to convert this code 52// To to = from; 53// DoSomething(to); 54// to this 55// DoSomething(implicit_cast<To>(from)); 56// 57// base::identity_ is used to make a non-deduced context, which 58// forces all callers to explicitly specify the template argument. 59template<typename To> 60inline To implicit_cast(typename identity_<To>::type to) { 61 return to; 62} 63 64// This version of implicit_cast is used when two template arguments 65// are specified. It's obsolete and should not be used. 66template<typename To, typename From> 67inline To implicit_cast(typename identity_<From>::type const &f) { 68 return f; 69} 70 71// When you upcast (that is, cast a pointer from type Foo to type 72// SuperclassOfFoo), it's fine to use implicit_cast<>, since upcasts 73// always succeed. When you downcast (that is, cast a pointer from 74// type Foo to type SubclassOfFoo), static_cast<> isn't safe, because 75// how do you know the pointer is really of type SubclassOfFoo? It 76// could be a bare Foo, or of type DifferentSubclassOfFoo. Thus, 77// when you downcast, you should use this macro. In debug mode, we 78// use dynamic_cast<> to double-check the downcast is legal (we die 79// if it's not). In normal mode, we do the efficient static_cast<> 80// instead. Thus, it's important to test in debug mode to make sure 81// the cast is legal! 82// This is the only place in the code we should use dynamic_cast<>. 83// In particular, you SHOULDN'T be using dynamic_cast<> in order to 84// do RTTI (eg code like this: 85// if (dynamic_cast<Subclass1>(foo)) HandleASubclass1Object(foo); 86// if (dynamic_cast<Subclass2>(foo)) HandleASubclass2Object(foo); 87// You should design the code some other way not to need this. 88 89template<typename To, typename From> // use like this: down_cast<T*>(foo); 90inline To down_cast(From* f) { // so we only accept pointers 91 // Ensures that To is a sub-type of From *. This test is here only 92 // for compile-time type checking, and has no overhead in an 93 // optimized build at run-time, as it will be optimized away 94 // completely. 95 96 // TODO(csilvers): This should use COMPILE_ASSERT. 97 if (false) { 98 implicit_cast<From*, To>(NULL); 99 } 100 101 // uses RTTI in dbg and fastbuild. asserts are disabled in opt builds. 102 assert(f == NULL || dynamic_cast<To>(f) != NULL); // NOLINT 103 return static_cast<To>(f); 104} 105 106} // namespace ceres 107 108#endif // CERES_INTERNAL_CASTS_H_ 109