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 (at) 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 37 namespace ceres { 38 39 // Identity metafunction. 40 template <class T> 41 struct 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. 59 template<typename To> 60 inline 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. 66 template<typename To, typename From> 67 inline 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 89 template<typename To, typename From> // use like this: down_cast<T*>(foo); 90 inline 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
