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Diffstat (limited to 'src/google/protobuf/stubs/template_util.h')
| -rw-r--r-- | src/google/protobuf/stubs/template_util.h | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/src/google/protobuf/stubs/template_util.h b/src/google/protobuf/stubs/template_util.h new file mode 100644 index 0000000..4f30ffa --- /dev/null +++ b/src/google/protobuf/stubs/template_util.h @@ -0,0 +1,138 @@ +// Copyright 2005 Google Inc. +// All rights reserved. +// +// 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: lar@google.com (Laramie Leavitt) +// +// Template metaprogramming utility functions. +// +// This code is compiled directly on many platforms, including client +// platforms like Windows, Mac, and embedded systems. Before making +// any changes here, make sure that you're not breaking any platforms. +// +// +// The names choosen here reflect those used in tr1 and the boost::mpl +// library, there are similar operations used in the Loki library as +// well. I prefer the boost names for 2 reasons: +// 1. I think that portions of the Boost libraries are more likely to +// be included in the c++ standard. +// 2. It is not impossible that some of the boost libraries will be +// included in our own build in the future. +// Both of these outcomes means that we may be able to directly replace +// some of these with boost equivalents. +// +#ifndef GOOGLE_PROTOBUF_TEMPLATE_UTIL_H_ +#define GOOGLE_PROTOBUF_TEMPLATE_UTIL_H_ + +namespace google { +namespace protobuf { +namespace internal { + +// Types small_ and big_ are guaranteed such that sizeof(small_) < +// sizeof(big_) +typedef char small_; + +struct big_ { + char dummy[2]; +}; + +// Identity metafunction. +template <class T> +struct identity_ { + typedef T type; +}; + +// integral_constant, defined in tr1, is a wrapper for an integer +// value. We don't really need this generality; we could get away +// with hardcoding the integer type to bool. We use the fully +// general integer_constant for compatibility with tr1. + +template<class T, T v> +struct integral_constant { + static const T value = v; + typedef T value_type; + typedef integral_constant<T, v> type; +}; + +template <class T, T v> const T integral_constant<T, v>::value; + + +// Abbreviations: true_type and false_type are structs that represent boolean +// true and false values. Also define the boost::mpl versions of those names, +// true_ and false_. +typedef integral_constant<bool, true> true_type; +typedef integral_constant<bool, false> false_type; +typedef true_type true_; +typedef false_type false_; + +// if_ is a templatized conditional statement. +// if_<cond, A, B> is a compile time evaluation of cond. +// if_<>::type contains A if cond is true, B otherwise. +template<bool cond, typename A, typename B> +struct if_{ + typedef A type; +}; + +template<typename A, typename B> +struct if_<false, A, B> { + typedef B type; +}; + + +// type_equals_ is a template type comparator, similar to Loki IsSameType. +// type_equals_<A, B>::value is true iff "A" is the same type as "B". +// +// New code should prefer base::is_same, defined in base/type_traits.h. +// It is functionally identical, but is_same is the standard spelling. +template<typename A, typename B> +struct type_equals_ : public false_ { +}; + +template<typename A> +struct type_equals_<A, A> : public true_ { +}; + +// and_ is a template && operator. +// and_<A, B>::value evaluates "A::value && B::value". +template<typename A, typename B> +struct and_ : public integral_constant<bool, (A::value && B::value)> { +}; + +// or_ is a template || operator. +// or_<A, B>::value evaluates "A::value || B::value". +template<typename A, typename B> +struct or_ : public integral_constant<bool, (A::value || B::value)> { +}; + + +} // namespace internal +} // namespace protobuf +} // namespace google + +#endif // GOOGLE_PROTOBUF_TEMPLATE_UTIL_H_ |