libcxx/include/__algorithm/pop_heap.h

   1 //===----------------------------------------------------------------------===//
   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
   9 #ifndef _LIBCPP___ALGORITHM_POP_HEAP_H
  10 #define _LIBCPP___ALGORITHM_POP_HEAP_H
  11
  12 #include <__algorithm/comp.h>
  13 #include <__algorithm/comp_ref_type.h>
  14 #include <__algorithm/iterator_operations.h>
  15 #include <__algorithm/push_heap.h>
  16 #include <__algorithm/sift_down.h>
  17 #include <__assert>
  18 #include <__config>
  19 #include <__iterator/iterator_traits.h>
  20 #include <__type_traits/is_assignable.h>
  21 #include <__type_traits/is_constructible.h>
  22 #include <__utility/move.h>
  23
  24 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  25 #  pragma GCC system_header
  26 #endif
  27
  28 _LIBCPP_PUSH_MACROS
  29 #include <__undef_macros>
  30
  31 _LIBCPP_BEGIN_NAMESPACE_STD
  32
  33 template <class _AlgPolicy, class _Compare, class _RandomAccessIterator>
  34 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void
  35 __pop_heap(_RandomAccessIterator __first,
  36            _RandomAccessIterator __last,
  37            _Compare& __comp,
  38            typename iterator_traits<_RandomAccessIterator>::difference_type __len) {
  39   // Calling `pop_heap` on an empty range is undefined behavior, but in practice it will be a no-op.
  40   _LIBCPP_ASSERT_PEDANTIC(__len > 0, "The heap given to pop_heap must be non-empty");
  41
  42   __comp_ref_type<_Compare> __comp_ref = __comp;
  43
  44   using value_type = typename iterator_traits<_RandomAccessIterator>::value_type;
  45   if (__len > 1) {
  46     value_type __top             = _IterOps<_AlgPolicy>::__iter_move(__first); // create a hole at __first
  47     _RandomAccessIterator __hole = std::__floyd_sift_down<_AlgPolicy>(__first, __comp_ref, __len);
  48     --__last;
  49
  50     if (__hole == __last) {
  51       *__hole = std::move(__top);
  52     } else {
  53       *__hole = _IterOps<_AlgPolicy>::__iter_move(__last);
  54       ++__hole;
  55       *__last = std::move(__top);
  56       std::__sift_up<_AlgPolicy>(__first, __hole, __comp_ref, __hole - __first);
  57     }
  58   }
  59 }
  60
  61 template <class _RandomAccessIterator, class _Compare>
  62 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void
  63 pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp) {
  64   static_assert(std::is_copy_constructible<_RandomAccessIterator>::value, "Iterators must be copy constructible.");
  65   static_assert(std::is_copy_assignable<_RandomAccessIterator>::value, "Iterators must be copy assignable.");
  66
  67   typename iterator_traits<_RandomAccessIterator>::difference_type __len = __last - __first;
  68   std::__pop_heap<_ClassicAlgPolicy>(std::move(__first), std::move(__last), __comp, __len);
  69 }
  70
  71 template <class _RandomAccessIterator>
  72 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void
  73 pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last) {
  74   std::pop_heap(std::move(__first), std::move(__last), __less<>());
  75 }
  76
  77 _LIBCPP_END_NAMESPACE_STD
  78
  79 _LIBCPP_POP_MACROS
  80
  81 #endif // _LIBCPP___ALGORITHM_POP_HEAP_H