text: // -*- C++ -*-
  //===----------------------------------------------------------------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef _LIBCPP___FUNCTIONAL___SEARCH_H
  #define _LIBCPP___FUNCTIONAL___SEARCH_H
  
  #include <__config>
  #include <__iterator/iterator_traits.h>
  #include <utility>
  
  #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  #pragma GCC system_header
  #endif
  
  _LIBCPP_PUSH_MACROS
  #include <__undef_macros>
  
  _LIBCPP_BEGIN_NAMESPACE_STD
  
  template <class _BinaryPredicate, class _ForwardIterator1, class _ForwardIterator2>
  pair<_ForwardIterator1, _ForwardIterator1>
      _LIBCPP_CONSTEXPR_AFTER_CXX11 __search(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
                                             _ForwardIterator2 __first2, _ForwardIterator2 __last2,
                                             _BinaryPredicate __pred, forward_iterator_tag, forward_iterator_tag) {
    if (__first2 == __last2)
      return _VSTD::make_pair(__first1, __first1); // Everything matches an empty sequence
    while (true) {
      // Find first element in sequence 1 that matchs *__first2, with a mininum of loop checks
      while (true) {
        if (__first1 == __last1) // return __last1 if no element matches *__first2
          return _VSTD::make_pair(__last1, __last1);
        if (__pred(*__first1, *__first2))
          break;
        ++__first1;
      }
      // *__first1 matches *__first2, now match elements after here
      _ForwardIterator1 __m1 = __first1;
      _ForwardIterator2 __m2 = __first2;
      while (true) {
        if (++__m2 == __last2) // If pattern exhausted, __first1 is the answer (works for 1 element pattern)
          return _VSTD::make_pair(__first1, __m1);
        if (++__m1 == __last1) // Otherwise if source exhaused, pattern not found
          return _VSTD::make_pair(__last1, __last1);
        if (!__pred(*__m1, *__m2)) // if there is a mismatch, restart with a new __first1
        {
          ++__first1;
          break;
        } // else there is a match, check next elements
      }
    }
  }
  
  template <class _BinaryPredicate, class _RandomAccessIterator1, class _RandomAccessIterator2>
  _LIBCPP_CONSTEXPR_AFTER_CXX11 pair<_RandomAccessIterator1, _RandomAccessIterator1>
  __search(_RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1, _RandomAccessIterator2 __first2,
           _RandomAccessIterator2 __last2, _BinaryPredicate __pred, random_access_iterator_tag,
           random_access_iterator_tag) {
    typedef typename iterator_traits<_RandomAccessIterator1>::difference_type _D1;
    typedef typename iterator_traits<_RandomAccessIterator2>::difference_type _D2;
    // Take advantage of knowing source and pattern lengths.  Stop short when source is smaller than pattern
    const _D2 __len2 = __last2 - __first2;
    if (__len2 == 0)
      return _VSTD::make_pair(__first1, __first1);
    const _D1 __len1 = __last1 - __first1;
    if (__len1 < __len2)
      return _VSTD::make_pair(__last1, __last1);
    const _RandomAccessIterator1 __s = __last1 - (__len2 - 1); // Start of pattern match can't go beyond here
  
    while (true) {
      while (true) {
        if (__first1 == __s)
          return _VSTD::make_pair(__last1, __last1);
        if (__pred(*__first1, *__first2))
          break;
        ++__first1;
      }
  
      _RandomAccessIterator1 __m1 = __first1;
      _RandomAccessIterator2 __m2 = __first2;
      while (true) {
        if (++__m2 == __last2)
          return _VSTD::make_pair(__first1, __first1 + __len2);
        ++__m1; // no need to check range on __m1 because __s guarantees we have enough source
        if (!__pred(*__m1, *__m2)) {
          ++__first1;
          break;
        }
      }
    }
  }
  
  _LIBCPP_END_NAMESPACE_STD
  
  _LIBCPP_POP_MACROS
  
  #endif // _LIBCPP___FUNCTIONAL___SEARCH_H
  