Index: third_party/cld/base/template_util.h |
=================================================================== |
--- third_party/cld/base/template_util.h (revision 0) |
+++ third_party/cld/base/template_util.h (revision 0) |
@@ -0,0 +1,96 @@ |
+// Copyright (c) 2006-2009 The Chromium Authors. All rights reserved. |
+// Use of this source code is governed by a BSD-style license that can be |
+// found in the LICENSE file. |
+ |
+// 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 BASE_TEMPLATE_UTIL_H_ |
+#define BASE_TEMPLATE_UTIL_H_ |
+ |
+namespace base { |
+ |
+// Types small_ and big_ are guaranteed such that sizeof(small_) < |
+// sizeof(big_) |
+typedef char small_; |
+ |
+struct big_ { |
+ char dummy[2]; |
+}; |
+ |
+// 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". |
+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)> { |
+}; |
+ |
+ |
+} // Close namespace base |
+ |
+#endif // BASE_TEMPLATE_UTIL_H_ |
Property changes on: third_party\cld\base\template_util.h |
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Added: svn:eol-style |
+ LF |