[clang] [lld] [compiler-rt] [clang-tools-extra] [llvm] [lldb] [mlir] [libcxx] [libc++][ranges] Implement ranges::contains_subrange (PR #66963)

[Mark de Wever via cfe-commits]

================
@@ -0,0 +1,145 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_RANGES_CONTAINS_SUBRANGE_H
+#define _LIBCPP___ALGORITHM_RANGES_CONTAINS_SUBRANGE_H
+
+#include <__algorithm/ranges_search.h>
+#include <__config>
+#include <__functional/identity.h>
+#include <__functional/ranges_operations.h>
+#include <__functional/reference_wrapper.h>
+#include <__iterator/concepts.h>
+#include <__iterator/distance.h>
+#include <__iterator/indirectly_comparable.h>
+#include <__iterator/projected.h>
+#include <__ranges/access.h>
+#include <__ranges/concepts.h>
+#include <__utility/move.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER >= 23
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace ranges {
+namespace __contains_subrange {
+struct __fn {
+  template <forward_iterator _Iter1,
+            sentinel_for<_Iter1> _Sent1,
+            forward_iterator _Iter2,
+            sentinel_for<_Iter2> _Sent2,
+            class _Pred,
+            class _Proj1,
+            class _Proj2,
+            class _Offset = int>
+  static _LIBCPP_HIDE_FROM_ABI constexpr bool __contains_subrange_fn_impl(
+      _Iter1 __first1,
+      _Sent1 __last1,
+      _Iter2 __first2,
+      _Sent2 __last2,
+      _Pred& __pred,
+      _Proj1& __proj1,
+      _Proj2& __proj2,
+      _Offset __offset) {
+    if (__offset < 0)
+      return false;
+    else {
+      auto result = ranges::search(
+          std::move(__first1),
+          std::move(__last1),
+          std::move(__first2),
+          std::move(__last2),
+          std::ref(__pred),
+          std::ref(__proj1),
+          std::ref(__proj2));
+      return result.empty() == false;
+    }
+  }
+
+  template <forward_iterator _Iter1,
+            sentinel_for<_Iter1> _Sent1,
+            forward_iterator _Iter2,
+            sentinel_for<_Iter2> _Sent2,
+            class _Pred  = ranges::equal_to,
+            class _Proj1 = identity,
+            class _Proj2 = identity>
+    requires indirectly_comparable<_Iter1, _Iter2, _Pred, _Proj1, _Proj2>
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr bool operator()(
+      _Iter1 __first1,
+      _Sent1 __last1,
+      _Iter2 __first2,
+      _Sent2 __last2,
+      _Pred __pred   = {},
+      _Proj1 __proj1 = {},
+      _Proj2 __proj2 = {}) const {
+    int __n1     = ranges::distance(__first1, __last1);
+    int __n2     = ranges::distance(__first2, __last2);
+    if (__n2 == 0)
+      return true;
+    int __offset = __n1 - __n2;
+
+    return __contains_subrange_fn_impl(
+        std::move(__first1),
+        std::move(__last1),
+        std::move(__first2),
+        std::move(__last2),
+        __pred,
+        __proj1,
+        __proj2,
+        std::move(__offset));
+  }
+
+  template <forward_range _Range1,
+            forward_range _Range2,
+            class _Pred  = ranges::equal_to,
+            class _Proj1 = identity,
+            class _Proj2 = identity>
+    requires indirectly_comparable<iterator_t<_Range1>, iterator_t<_Range2>, _Pred, _Proj1, _Proj2>
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr bool operator()(
+      _Range1&& __range1, _Range2&& __range2, _Pred __pred = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const {
+    int __n1 = 0;
+    int __n2 = 0;
+
+    if constexpr (sized_range<_Range1> && sized_range<_Range2>) {
+      __n1 = ranges::size(__range1);
+      __n2 = ranges::size(__range2);
+    } else {
+      __n1 = ranges::distance(__range1);
+      __n2 = ranges::distance(__range2);
+    }
+
+    if (__n2 == 0)
+      return true;
+    int __offset = __n1 - __n2;
+    return __contains_subrange_fn_impl(
+        ranges::begin(__range1),
+        ranges::end(__range1),
+        ranges::begin(__range2),
+        ranges::end(__range2),
+        __pred,
+        __proj1,
+        __proj2,
+        __offset);
+  }
+};
+} // namespace __contains_subrange
+
+inline namespace __cpo {
+inline constexpr auto contains_subrange = __contains_subrange::__fn{};
----------------
mordante wrote:

This function needs to be exported from modules. See https://github.com/llvm/llvm-project/blob/main/libcxx/modules/std/algorithm.inc#L44

https://github.com/llvm/llvm-project/pull/66963