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

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@276238 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/strings/basic.string/string.cons/string_view.fail.cpp

@@ -0,0 +1,23 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// explicit basic_string(basic_string_view<CharT, traits> sv, const Allocator& a = Allocator());
+
+#include <string>
+#include <string_view>
+
+void foo ( const string &s ) {}
+
+int main()
+{
+	std::string_view sv = "ABCDE";
+	foo(sv);	// requires implicit conversion from string_view to string
+}

test/std/strings/basic.string/string.cons/string_view.pass.cpp

@@ -0,0 +1,89 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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>
+
+// explicit basic_string(basic_string_view<CharT, traits> sv, const Allocator& a = Allocator());
+
+#include <string>
+#include <string_view>
+#include <stdexcept>
+#include <algorithm>
+#include <cassert>
+
+#include "test_macros.h"
+#include "test_allocator.h"
+#include "min_allocator.h"
+
+template <class charT>
+void
+test(std::basic_string_view<charT> sv)
+{
+    typedef std::basic_string<charT, std::char_traits<charT>, test_allocator<charT> > S;
+    typedef typename S::traits_type T;
+    typedef typename S::allocator_type A;
+    S s2(sv);
+    LIBCPP_ASSERT(s2.__invariants());
+    assert(s2.size() == sv.size());
+    assert(T::compare(s2.data(), sv.data(), sv.size()) == 0);
+    assert(s2.get_allocator() == A());
+    assert(s2.capacity() >= s2.size());
+}
+
+template <class charT, class A>
+void
+test(std::basic_string_view<charT> sv, const A& a)
+{
+    typedef std::basic_string<charT, std::char_traits<charT>, A> S;
+    typedef typename S::traits_type T;
+    S s2(sv, a);
+    LIBCPP_ASSERT(s2.__invariants());
+    assert(s2.size() == sv.size());
+    assert(T::compare(s2.data(), sv.data(), sv.size()) == 0);
+    assert(s2.get_allocator() == a);
+    assert(s2.capacity() >= s2.size());
+}
+
+int main()
+{
+    {
+    typedef test_allocator<char> A;
+    typedef std::basic_string_view<char, std::char_traits<char> > SV;
+
+    test(SV(""));
+    test(SV(""), A(2));
+
+    test(SV("1"));
+    test(SV("1") ,A(2));
+
+    test(SV("1234567980"));
+    test(SV("1234567980"), A(2));
+
+    test(SV("123456798012345679801234567980123456798012345679801234567980"));
+    test(SV("123456798012345679801234567980123456798012345679801234567980"), A(2));
+    }
+#if TEST_STD_VER >= 11
+    {
+    typedef min_allocator<char> A;
+    typedef std::basic_string_view<char, std::char_traits<char> > SV;
+
+    test(SV(""));
+    test(SV(""), A());
+
+    test(SV("1"));
+    test(SV("1") ,A());
+
+    test(SV("1234567980"));
+    test(SV("1234567980"), A());
+
+    test(SV("123456798012345679801234567980123456798012345679801234567980"));
+    test(SV("123456798012345679801234567980123456798012345679801234567980"), A());
+    }
+#endif
+}