llvm/ADT/iterator_range.h

0001 //===- iterator_range.h - A range adaptor for iterators ---------*- C++ -*-===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008 /// \file
0009 /// This provides a very simple, boring adaptor for a begin and end iterator
0010 /// into a range type. This should be used to build range views that work well
0011 /// with range based for loops and range based constructors.
0012 ///
0013 /// Note that code here follows more standards-based coding conventions as it
0014 /// is mirroring proposed interfaces for standardization.
0015 ///
0016 //===----------------------------------------------------------------------===//
0017
0018 #ifndef LLVM_ADT_ITERATOR_RANGE_H
0019 #define LLVM_ADT_ITERATOR_RANGE_H
0020
0021 #include "llvm/ADT/ADL.h"
0022 #include <type_traits>
0023 #include <utility>
0024
0025 namespace llvm {
0026
0027 template <typename From, typename To, typename = void>
0028 struct explicitly_convertible : std::false_type {};
0029
0030 template <typename From, typename To>
0031 struct explicitly_convertible<
0032     From, To,
0033     std::void_t<decltype(static_cast<To>(
0034         std::declval<std::add_rvalue_reference_t<From>>()))>> : std::true_type {
0035 };
0036
0037 /// A range adaptor for a pair of iterators.
0038 ///
0039 /// This just wraps two iterators into a range-compatible interface. Nothing
0040 /// fancy at all.
0041 template <typename IteratorT>
0042 class iterator_range {
0043   IteratorT begin_iterator, end_iterator;
0044
0045 public:
0046 #if defined(__GNUC__) &&                                                       \
0047     (__GNUC__ == 7 || (__GNUC__ == 8 && __GNUC_MINOR__ < 4))
0048   // Be careful no to break gcc-7 and gcc-8 < 8.4 on the mlir target.
0049   // See https://github.com/llvm/llvm-project/issues/63843
0050   template <typename Container>
0051 #else
0052   template <
0053       typename Container,
0054       std::enable_if_t<explicitly_convertible<
0055           llvm::detail::IterOfRange<Container>, IteratorT>::value> * = nullptr>
0056 #endif
0057   iterator_range(Container &&c)
0058       : begin_iterator(adl_begin(c)), end_iterator(adl_end(c)) {
0059   }
0060   iterator_range(IteratorT begin_iterator, IteratorT end_iterator)
0061       : begin_iterator(std::move(begin_iterator)),
0062         end_iterator(std::move(end_iterator)) {}
0063
0064   IteratorT begin() const { return begin_iterator; }
0065   IteratorT end() const { return end_iterator; }
0066   bool empty() const { return begin_iterator == end_iterator; }
0067 };
0068
0069 template <typename Container>
0070 iterator_range(Container &&)
0071     -> iterator_range<llvm::detail::IterOfRange<Container>>;
0072
0073 /// Convenience function for iterating over sub-ranges.
0074 ///
0075 /// This provides a bit of syntactic sugar to make using sub-ranges
0076 /// in for loops a bit easier. Analogous to std::make_pair().
0077 template <class T> iterator_range<T> make_range(T x, T y) {
0078   return iterator_range<T>(std::move(x), std::move(y));
0079 }
0080
0081 template <typename T> iterator_range<T> make_range(std::pair<T, T> p) {
0082   return iterator_range<T>(std::move(p.first), std::move(p.second));
0083 }
0084
0085 }
0086
0087 #endif