[libc++][P1679] add string contains

C++23 string contains implementation and tests

Paper: https://wg21.link/P1679R3
Standard (string): https://eel.is/c++draft/string.contains
Standard (string_view): https://eel.is/c++draft/string.view.ops#lib:contains,basic_string_view

Differential Revision: https://reviews.llvm.org/D93912

3 files changed, 206 insertions, 0 deletions

diff --git a/libcxx/test/std/strings/string.view/string.view.template/contains.char.pass.cpp b/libcxx/test/std/strings/string.view/string.view.template/contains.char.pass.cpp
new file mode 100644
index 000000000000..658e10d21182
--- /dev/null
+++ b/libcxx/test/std/strings/string.view/string.view.template/contains.char.pass.cpp
@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++2a
+
+// <string_view>
+
+//   constexpr bool contains(charT x) const noexcept;
+
+#include <string_view>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr bool test()
+{
+    using SV = std::string_view;
+
+    SV sv1 {};
+    SV sv2 {"abcde", 5};
+
+    ASSERT_NOEXCEPT(sv1.contains('e'));
+
+    assert(!sv1.contains('c'));
+    assert(!sv1.contains('e'));
+    assert(!sv1.contains('x'));
+    assert( sv2.contains('c'));
+    assert( sv2.contains('e'));
+    assert(!sv2.contains('x'));
+
+    return true;
+}
+
+int main(int, char**)
+{
+    test();
+    static_assert(test());
+
+    return 0;
+}
diff --git a/libcxx/test/std/strings/string.view/string.view.template/contains.ptr.pass.cpp b/libcxx/test/std/strings/string.view/string.view.template/contains.ptr.pass.cpp
new file mode 100644
index 000000000000..f22e77d38d06
--- /dev/null
+++ b/libcxx/test/std/strings/string.view/string.view.template/contains.ptr.pass.cpp
@@ -0,0 +1,74 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++2a
+
+// <string_view>
+
+//   constexpr bool contains(const CharT *x) const;
+
+#include <string_view>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr bool test()
+{
+    using SV = std::string_view;
+
+    const char* s = "abcde";
+    SV sv0;
+    SV sv1 {s + 4, 1};
+    SV sv3 {s + 2, 3};
+    SV svNot {"xyz", 3};
+
+    assert( sv0.contains(""));
+    assert(!sv0.contains("e"));
+
+    assert( sv1.contains(""));
+    assert(!sv1.contains("d"));
+    assert( sv1.contains("e"));
+    assert(!sv1.contains("de"));
+    assert(!sv1.contains("cd"));
+    assert(!sv1.contains("cde"));
+    assert(!sv1.contains("bcde"));
+    assert(!sv1.contains("abcde"));
+    assert(!sv1.contains("xyz"));
+
+    assert( sv3.contains(""));
+    assert( sv3.contains("d"));
+    assert( sv3.contains("e"));
+    assert( sv3.contains("de"));
+    assert( sv3.contains("cd"));
+    assert(!sv3.contains("ce"));
+    assert( sv3.contains("cde"));
+    assert(!sv3.contains("edc"));
+    assert(!sv3.contains("bcde"));
+    assert(!sv3.contains("abcde"));
+    assert(!sv3.contains("xyz"));
+
+    assert( svNot.contains(""));
+    assert(!svNot.contains("d"));
+    assert(!svNot.contains("e"));
+    assert(!svNot.contains("de"));
+    assert(!svNot.contains("cd"));
+    assert(!svNot.contains("cde"));
+    assert(!svNot.contains("bcde"));
+    assert(!svNot.contains("abcde"));
+    assert( svNot.contains("xyz"));
+    assert(!svNot.contains("zyx"));
+
+    return true;
+}
+
+int main(int, char**)
+{
+    test();
+    static_assert(test());
+
+    return 0;
+}
diff --git a/libcxx/test/std/strings/string.view/string.view.template/contains.string_view.pass.cpp b/libcxx/test/std/strings/string.view/string.view.template/contains.string_view.pass.cpp
new file mode 100644
index 000000000000..0b7976846173
--- /dev/null
+++ b/libcxx/test/std/strings/string.view/string.view.template/contains.string_view.pass.cpp
@@ -0,0 +1,88 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++2a
+
+// <string_view>
+
+//   constexpr bool contains(string_view x) const noexcept;
+
+#include <string_view>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr bool test()
+{
+    using SV = std::string_view;
+
+    const char* s = "abcde";
+    SV sv0;
+    SV sv1 {s + 1, 1};
+    SV sv2 {s + 1, 2};
+    SV sv3 {s + 1, 3};
+    SV sv4 {s + 1, 4};
+    SV sv5 {s    , 5};
+    SV svNot  {"xyz", 3};
+    SV svNot2 {"bd" , 2};
+    SV svNot3 {"dcb", 3};
+
+    ASSERT_NOEXCEPT(sv0.contains(sv0));
+
+    assert( sv0.contains(sv0));
+    assert(!sv0.contains(sv1));
+
+    assert( sv1.contains(sv0));
+    assert( sv1.contains(sv1));
+    assert(!sv1.contains(sv2));
+    assert(!sv1.contains(sv3));
+    assert(!sv1.contains(sv4));
+    assert(!sv1.contains(sv5));
+    assert(!sv1.contains(svNot));
+    assert(!sv1.contains(svNot2));
+    assert(!sv1.contains(svNot3));
+
+    assert( sv3.contains(sv0));
+    assert( sv3.contains(sv1));
+    assert( sv3.contains(sv2));
+    assert( sv3.contains(sv3));
+    assert(!sv3.contains(sv4));
+    assert(!sv3.contains(sv5));
+    assert(!sv3.contains(svNot));
+    assert(!sv3.contains(svNot2));
+    assert(!sv3.contains(svNot3));
+
+    assert( sv5.contains(sv0));
+    assert( sv5.contains(sv1));
+    assert( sv5.contains(sv2));
+    assert( sv5.contains(sv3));
+    assert( sv5.contains(sv4));
+    assert( sv5.contains(sv5));
+    assert(!sv5.contains(svNot));
+    assert(!sv5.contains(svNot2));
+    assert(!sv5.contains(svNot3));
+
+    assert( svNot.contains(sv0));
+    assert(!svNot.contains(sv1));
+    assert(!svNot.contains(sv2));
+    assert(!svNot.contains(sv3));
+    assert(!svNot.contains(sv4));
+    assert(!svNot.contains(sv5));
+    assert( svNot.contains(svNot));
+    assert(!svNot.contains(svNot2));
+    assert(!svNot.contains(svNot3));
+
+    return true;
+}
+
+int main(int, char**)
+{
+    test();
+    static_assert(test());
+
+    return 0;
+}