1 // Copyright 2024 The PDFium Authors 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef CORE_FXCRT_TEMPLATE_UTIL_H_ 6 #define CORE_FXCRT_TEMPLATE_UTIL_H_ 7 8 #include <stddef.h> 9 #include <iosfwd> 10 #include <iterator> 11 #include <type_traits> 12 #include <utility> 13 14 #include "build/build_config.h" 15 16 namespace pdfium { 17 18 template <class T> struct is_non_const_reference : std::false_type {}; 19 template <class T> struct is_non_const_reference<T&> : std::true_type {}; 20 template <class T> struct is_non_const_reference<const T&> : std::false_type {}; 21 22 namespace internal { 23 24 // Uses expression SFINAE to detect whether using operator<< would work. 25 template <typename T, typename = void> 26 struct SupportsOstreamOperator : std::false_type {}; 27 template <typename T> 28 struct SupportsOstreamOperator<T, 29 decltype(void(std::declval<std::ostream&>() 30 << std::declval<T>()))> 31 : std::true_type {}; 32 33 // Used to detech whether the given type is an iterator. This is normally used 34 // with std::enable_if to provide disambiguation for functions that take 35 // templatzed iterators as input. 36 template <typename T, typename = void> 37 struct is_iterator : std::false_type {}; 38 39 template <typename T> 40 struct is_iterator< 41 T, 42 std::void_t<typename std::iterator_traits<T>::iterator_category>> 43 : std::true_type {}; 44 45 } // namespace internal 46 47 } // namespace pdfium 48 49 #endif // CORE_FXCRT_TEMPLATE_UTIL_H_ 50