109 lines
4.5 KiB
C
109 lines
4.5 KiB
C
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// Ceres Solver - A fast non-linear least squares minimizer
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// Copyright 2015 Google Inc. All rights reserved.
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// http://ceres-solver.org/
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are met:
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//
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// * Redistributions of source code must retain the above copyright notice,
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// this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above copyright notice,
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// this list of conditions and the following disclaimer in the documentation
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// and/or other materials provided with the distribution.
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// * Neither the name of Google Inc. nor the names of its contributors may be
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// used to endorse or promote products derived from this software without
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// specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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// POSSIBILITY OF SUCH DAMAGE.
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//
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// Author: keir@google.com (Keir Mierle)
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#ifndef CERES_INTERNAL_CASTS_H_
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#define CERES_INTERNAL_CASTS_H_
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#include <cassert>
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#include <cstddef> // For NULL.
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namespace ceres {
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// Identity metafunction.
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template <class T>
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struct identity_ {
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typedef T type;
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};
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// Use implicit_cast as a safe version of static_cast or const_cast
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// for implicit conversions. For example:
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// - Upcasting in a type hierarchy.
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// - Performing arithmetic conversions (int32 to int64, int to double, etc.).
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// - Adding const or volatile qualifiers.
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//
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// In general, implicit_cast can be used to convert this code
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// To to = from;
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// DoSomething(to);
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// to this
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// DoSomething(implicit_cast<To>(from));
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//
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// base::identity_ is used to make a non-deduced context, which
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// forces all callers to explicitly specify the template argument.
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template<typename To>
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inline To implicit_cast(typename identity_<To>::type to) {
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return to;
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}
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// This version of implicit_cast is used when two template arguments
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// are specified. It's obsolete and should not be used.
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template<typename To, typename From>
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inline To implicit_cast(typename identity_<From>::type const &f) {
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return f;
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}
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// When you upcast (that is, cast a pointer from type Foo to type
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// SuperclassOfFoo), it's fine to use implicit_cast<>, since upcasts
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// always succeed. When you downcast (that is, cast a pointer from
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// type Foo to type SubclassOfFoo), static_cast<> isn't safe, because
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// how do you know the pointer is really of type SubclassOfFoo? It
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// could be a bare Foo, or of type DifferentSubclassOfFoo. Thus,
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// when you downcast, you should use this macro. In debug mode, we
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// use dynamic_cast<> to double-check the downcast is legal (we die
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// if it's not). In normal mode, we do the efficient static_cast<>
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// instead. Thus, it's important to test in debug mode to make sure
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// the cast is legal!
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// This is the only place in the code we should use dynamic_cast<>.
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// In particular, you SHOULDN'T be using dynamic_cast<> in order to
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// do RTTI (eg code like this:
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// if (dynamic_cast<Subclass1>(foo)) HandleASubclass1Object(foo);
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// if (dynamic_cast<Subclass2>(foo)) HandleASubclass2Object(foo);
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// You should design the code some other way not to need this.
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template<typename To, typename From> // use like this: down_cast<T*>(foo);
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inline To down_cast(From* f) { // so we only accept pointers
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// Ensures that To is a sub-type of From *. This test is here only
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// for compile-time type checking, and has no overhead in an
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// optimized build at run-time, as it will be optimized away
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// completely.
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// TODO(csilvers): This should use COMPILE_ASSERT.
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if (false) {
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implicit_cast<From*, To>(NULL);
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}
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// uses RTTI in dbg and fastbuild. asserts are disabled in opt builds.
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assert(f == NULL || dynamic_cast<To>(f) != NULL); // NOLINT
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return static_cast<To>(f);
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}
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} // namespace ceres
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#endif // CERES_INTERNAL_CASTS_H_
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