string_view: add string_view capacity API libcxx tests

- taken from: llvm-mirror/libcxx@78d6a77

Author: KFilipek

tests/external/libcxx/string.view/string.view.capacity/capacity.pass.cpp

@@ -0,0 +1,104 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+
+// <string_view>
+
+// [string.view.capacity], capacity
+// constexpr size_type size()     const noexcept;
+// constexpr size_type length()   const noexcept;
+// constexpr size_type max_size() const noexcept;
+// constexpr bool empty()         const noexcept;
+
+#include <string_view>
+#include <cassert>
+
+#include "test_macros.h"
+
+template<typename SV>
+void test1 () {
+#if TEST_STD_VER > 11
+    {
+    constexpr SV sv1;
+    static_assert ( sv1.size() == 0, "" );
+    static_assert ( sv1.empty(), "");
+    static_assert ( sv1.size() == sv1.length(), "" );
+    static_assert ( sv1.max_size() > sv1.size(), "");
+    }
+#endif
+
+    {
+    SV sv1;
+    ASSERT_NOEXCEPT(sv1.size());
+    ASSERT_NOEXCEPT(sv1.empty());
+    ASSERT_NOEXCEPT(sv1.max_size());
+    ASSERT_NOEXCEPT(sv1.length());
+    assert ( sv1.size() == 0 );
+    assert ( sv1.empty());
+    assert ( sv1.size() == sv1.length());
+    assert ( sv1.max_size() > sv1.size());
+    }
+}
+
+template<typename CharT>
+void test2 ( const CharT *s, size_t len ) {
+    {
+    std::basic_string_view<CharT> sv1 ( s );
+    assert ( sv1.size() == len );
+    assert ( sv1.data() == s );
+    assert ( sv1.empty() == (len == 0));
+    assert ( sv1.size() == sv1.length());
+    assert ( sv1.max_size() > sv1.size());
+#if TEST_STD_VER > 14
+//  make sure we pick up std::size, too!
+    assert ( sv1.size() == std::size(sv1));
+    assert ( sv1.empty() == std::empty(sv1));
+#endif
+    }
+}
+
+int main(int, char**) {
+    test1<std::string_view> ();
+#if defined(__cpp_lib_char8_t) && __cpp_lib_char8_t >= 201811L
+    test1<std::u8string_view> ();
+#endif
+    test1<std::u16string_view> ();
+    test1<std::u32string_view> ();
+    test1<std::wstring_view> ();
+
+    test2 ( "ABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDE", 105 );
+    test2 ( "ABCDE", 5 );
+    test2 ( "a", 1 );
+    test2 ( "", 0 );
+
+    test2 ( L"ABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDE", 105 );
+    test2 ( L"ABCDE", 5 );
+    test2 ( L"a", 1 );
+    test2 ( L"", 0 );
+
+#if defined(__cpp_lib_char8_t) && __cpp_lib_char8_t >= 201811L
+    test2 ( u8"ABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDE", 105 );
+    test2 ( u8"ABCDE", 5 );
+    test2 ( u8"a", 1 );
+    test2 ( u8"", 0 );
+#endif
+
+#if TEST_STD_VER >= 11
+    test2 ( u"ABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDE", 105 );
+    test2 ( u"ABCDE", 5 );
+    test2 ( u"a", 1 );
+    test2 ( u"", 0 );
+
+    test2 ( U"ABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDE", 105 );
+    test2 ( U"ABCDE", 5 );
+    test2 ( U"a", 1 );
+    test2 ( U"", 0 );
+#endif
+
+  return 0;
+}