libcxx/include/__algorithm/search.h

// -*- 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___ALGORITHM_SEARCH_H
#define _LIBCPP___ALGORITHM_SEARCH_H

#include <__algorithm/comp.h>
#include <__config>
#include <__iterator/iterator_traits.h>
#include <utility>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

_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 - _D1(__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 + _D1(__len2));
      ++__m1; // no need to check range on __m1 because __s guarantees we have enough source
      if (!__pred(*__m1, *__m2)) {
        ++__first1;
        break;
      }
    }
  }
}

template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
_LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator1
search(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2, _ForwardIterator2 __last2,
       _BinaryPredicate __pred) {
  return _VSTD::__search<_BinaryPredicate&>(
             __first1, __last1, __first2, __last2, __pred,
             typename iterator_traits<_ForwardIterator1>::iterator_category(),
             typename iterator_traits<_ForwardIterator2>::iterator_category()).first;
}

template <class _ForwardIterator1, class _ForwardIterator2>
_LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator1
search(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2, _ForwardIterator2 __last2) {
  typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
  typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
  return _VSTD::search(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>());
}

#if _LIBCPP_STD_VER > 14
template <class _ForwardIterator, class _Searcher>
_LIBCPP_NODISCARD_EXT _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
search(_ForwardIterator __f, _ForwardIterator __l, const _Searcher& __s) {
  return __s(__f, __l).first;
}

#endif

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___ALGORITHM_SEARCH_H