1 //===- iterator_range.h - A range adaptor for iterators ---------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 /// \file 9 /// This provides a very simple, boring adaptor for a begin and end iterator 10 /// into a range type. This should be used to build range views that work well 11 /// with range based for loops and range based constructors. 12 /// 13 /// Note that code here follows more standards-based coding conventions as it 14 /// is mirroring proposed interfaces for standardization. 15 /// 16 //===----------------------------------------------------------------------===// 17 18 #ifndef LLVM_ADT_ITERATOR_RANGE_H 19 #define LLVM_ADT_ITERATOR_RANGE_H 20 21 #include "llvm/ADT/ADL.h" 22 #include <type_traits> 23 #include <utility> 24 25 namespace llvm { 26 27 template <typename From, typename To, typename = void> 28 struct explicitly_convertible : std::false_type {}; 29 30 template <typename From, typename To> 31 struct explicitly_convertible< 32 From, To, 33 std::void_t<decltype(static_cast<To>( 34 std::declval<std::add_rvalue_reference_t<From>>()))>> : std::true_type { 35 }; 36 37 /// A range adaptor for a pair of iterators. 38 /// 39 /// This just wraps two iterators into a range-compatible interface. Nothing 40 /// fancy at all. 41 template <typename IteratorT> 42 class iterator_range { 43 IteratorT begin_iterator, end_iterator; 44 45 public: 46 #if __GNUC__ == 7 || (__GNUC__ == 8 && __GNUC_MINOR__ < 4) 47 // Be careful no to break gcc-7 and gcc-8 < 8.4 on the mlir target. 48 // See https://github.com/llvm/llvm-project/issues/63843 49 template <typename Container> 50 #else 51 template <typename Container, 52 std::enable_if_t<explicitly_convertible< 53 detail::IterOfRange<Container>, IteratorT>::value> * = nullptr> 54 #endif 55 iterator_range(Container &&c) 56 : begin_iterator(adl_begin(c)), end_iterator(adl_end(c)) { 57 } 58 iterator_range(IteratorT begin_iterator, IteratorT end_iterator) 59 : begin_iterator(std::move(begin_iterator)), 60 end_iterator(std::move(end_iterator)) {} 61 62 IteratorT begin() const { return begin_iterator; } 63 IteratorT end() const { return end_iterator; } 64 bool empty() const { return begin_iterator == end_iterator; } 65 }; 66 67 template <typename Container> 68 iterator_range(Container &&) -> iterator_range<detail::IterOfRange<Container>>; 69 70 /// Convenience function for iterating over sub-ranges. 71 /// 72 /// This provides a bit of syntactic sugar to make using sub-ranges 73 /// in for loops a bit easier. Analogous to std::make_pair(). 74 template <class T> iterator_range<T> make_range(T x, T y) { 75 return iterator_range<T>(std::move(x), std::move(y)); 76 } 77 78 template <typename T> iterator_range<T> make_range(std::pair<T, T> p) { 79 return iterator_range<T>(std::move(p.first), std::move(p.second)); 80 } 81 82 } 83 84 #endif 85