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
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>
implicit_cast(typename identity_<To>::type 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>
implicit_cast(typename identity_<From>::type const & f)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);
down_cast(From * f)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