Implement std::string_view as described in http://wg21.link/P0254R1. Reviewed as https://reviews.llvm.org/D21459

llvm-svn: 276238
diff --git a/libcxx/test/std/strings/string.view/string.view.access/data.pass.cpp b/libcxx/test/std/strings/string.view/string.view.access/data.pass.cpp
new file mode 100644
index 0000000..2f5301f
--- /dev/null
+++ b/libcxx/test/std/strings/string.view/string.view.access/data.pass.cpp
@@ -0,0 +1,50 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+
+// <string_view>
+
+// constexpr const _CharT* data() const noexcept;
+
+#include <string_view>
+#include <cassert>
+
+#include "test_macros.h"
+
+template <typename CharT>
+void test ( const CharT *s, size_t len ) {
+    std::basic_string_view<CharT> sv ( s, len );
+    assert ( sv.length() == len );
+    assert ( sv.data() == s );
+    }
+
+int main () {
+    test ( "ABCDE", 5 );
+    test ( "a", 1 );
+
+    test ( L"ABCDE", 5 );
+    test ( L"a", 1 );
+
+#if TEST_STD_VER >= 11
+    test ( u"ABCDE", 5 );
+    test ( u"a", 1 );
+
+    test ( U"ABCDE", 5 );
+    test ( U"a", 1 );
+#endif
+
+#if _LIBCPP_STD_VER > 11
+    {
+    constexpr const char *s = "ABC";
+    constexpr std::basic_string_view<char> sv( s, 2 );
+    static_assert( sv.length() ==  2,  "" );
+    static_assert( sv.data() == s, "" );
+    }
+#endif
+}