Improved string_view support

include/ghc/filesystem.hpp

@@ -218,6 +218,31 @@
 #endif
 #endif  // GHC_EXPAND_IMPL
 
+// After standard library includes.
+// Standard library support for std::string_view.
+#if defined(__cpp_lib_string_view)
+#define GHC_HAS_STD_STRING_VIEW
+#elif defined(_LIBCPP_VERSION) && (_LIBCPP_VERSION >= 4000) && (__cplusplus >= 201402)
+#define GHC_HAS_STD_STRING_VIEW
+#elif defined(_GLIBCXX_RELEASE) && (_GLIBCXX_RELEASE >= 7) && (__cplusplus >= 201703)
+#define GHC_HAS_STD_STRING_VIEW
+#elif defined(_MSC_VER) && (_MSC_VER >= 1910 && _MSVC_LANG >= 201703)
+#define GHC_HAS_STD_STRING_VIEW
+#endif
+
+// Standard library support for std::experimental::string_view.
+#if defined(_LIBCPP_VERSION) && (_LIBCPP_VERSION >= 3700 && _LIBCPP_VERSION < 7000) && (__cplusplus >= 201402)
+#define GHC_HAS_STD_EXPERIMENTAL_STRING_VIEW
+#elif defined(__GNUC__) && (((__GNUC__ == 4) && (__GNUC_MINOR__ >= 9)) || (__GNUC__ > 4)) && (__cplusplus >= 201402)
+#define GHC_HAS_STD_EXPERIMENTAL_STRING_VIEW
+#endif
+
+#if defined(GHC_HAS_STD_STRING_VIEW)
+#include <string_view>
+#elif defined(GHC_HAS_STD_EXPERIMENTAL_STRING_VIEW)
+#include <experimental/string_view>
+#endif
+
 //- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 // Behaviour Switches (see README.md, should match the config in test/filesystem_test.cpp):
 //- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -277,6 +302,16 @@
 namespace ghc {
 namespace filesystem {
 
+#if defined(GHC_HAS_CUSTOM_STRING_VIEW)
+#define GHC_WITH_STRING_VIEW
+#elif defined(GHC_HAS_STD_STRING_VIEW)
+#define GHC_WITH_STRING_VIEW
+using std::basic_string_view;
+#elif defined(GHC_HAS_STD_EXPERIMENTAL_STRING_VIEW)
+#define GHC_WITH_STRING_VIEW
+using std::experimental::basic_string_view;
+#endif
+
 // temporary existing exception type for yet unimplemented parts
 class GHC_FS_API_CLASS not_implemented_exception : public std::logic_error
 {
@@ -354,9 +389,13 @@ public:
     struct _is_basic_string<std::basic_string<CharT, std::char_traits<CharT>, std::allocator<CharT>>> : std::true_type
     {
     };
-#ifdef __cpp_lib_string_view
+#ifdef GHC_WITH_STRING_VIEW
+    template <class CharT, class Traits>
+    struct _is_basic_string<basic_string_view<CharT, Traits>> : std::true_type
+    {
+    };
     template <class CharT>
-    struct _is_basic_string<std::basic_string_view<CharT>> : std::true_type
+    struct _is_basic_string<basic_string_view<CharT, std::char_traits<CharT>>> : std::true_type
     {
     };
 #endif
@@ -417,8 +456,8 @@ public:
     // 30.10.8.4.4 concatenation
     path& operator+=(const path& x);
     path& operator+=(const string_type& x);
-#ifdef __cpp_lib_string_view
+#ifdef GHC_WITH_STRING_VIEW
-    path& operator+=(std::basic_string_view<value_type> x);
+    path& operator+=(basic_string_view<value_type> x);
 #endif
     path& operator+=(const value_type* x);
     path& operator+=(value_type x);
@@ -471,8 +510,8 @@ public:
     // 30.10.8.4.8 compare
     int compare(const path& p) const noexcept;
     int compare(const string_type& s) const;
-#ifdef __cpp_lib_string_view
+#ifdef GHC_WITH_STRING_VIEW
-    int compare(std::basic_string_view<value_type> s) const;
+    int compare(basic_string_view<value_type> s) const;
 #endif
     int compare(const value_type* s) const;
 
@@ -1521,8 +1560,8 @@ inline StringType fromUtf8(const Utf8String& utf8String, const typename StringTy
 template <class StringType, typename charT, std::size_t N>
 inline StringType fromUtf8(const charT (&utf8String)[N])
 {
-#ifdef __cpp_lib_string_view
+#ifdef GHC_WITH_STRING_VIEW
-    return fromUtf8<StringType>(std::basic_string_view<charT>(utf8String, N - 1));
+    return fromUtf8<StringType>(basic_string_view<charT>(utf8String, N - 1));
 #else
     return fromUtf8<StringType>(std::basic_string<charT>(utf8String, N - 1));
 #endif
@@ -1576,7 +1615,11 @@ inline std::string toUtf8(const strT& unicodeString)
 template <typename charT>
 inline std::string toUtf8(const charT* unicodeString)
 {
+#ifdef GHC_WITH_STRING_VIEW
+    return toUtf8(basic_string_view<charT, std::char_traits<charT>>(unicodeString));
+#else
     return toUtf8(std::basic_string<charT, std::char_traits<charT>>(unicodeString));
+#endif
 }
 
 #ifdef GHC_USE_WCHAR_T
@@ -1622,7 +1665,11 @@ inline std::wstring toWChar(const strT& unicodeString)
 template <typename charT>
 inline std::wstring toWChar(const charT* unicodeString)
 {
+#ifdef GHC_WITH_STRING_VIEW
+    return toWChar(basic_string_view<charT, std::char_traits<charT>>(unicodeString));
+#else
     return toWChar(std::basic_string<charT, std::char_traits<charT>>(unicodeString));
+#endif
 }
 #endif // GHC_USE_WCHAR_T
 
@@ -2464,8 +2511,8 @@ GHC_INLINE path& path::operator+=(const string_type& x)
     return concat(x);
 }
 
-#ifdef __cpp_lib_string_view
+#ifdef GHC_WITH_STRING_VIEW
-GHC_INLINE path& path::operator+=(std::basic_string_view<value_type> x)
+GHC_INLINE path& path::operator+=(basic_string_view<value_type> x)
 {
     return concat(x);
 }
@@ -2473,7 +2520,12 @@ GHC_INLINE path& path::operator+=(std::basic_string_view<value_type> x)
 
 GHC_INLINE path& path::operator+=(const value_type* x)
 {
-    return concat(string_type(x));
+#ifdef GHC_WITH_STRING_VIEW
+    basic_string_view<value_type> part(x);
+#else
+    string_type part(x);
+#endif
+    return concat(part);
 }
 
 GHC_INLINE path& path::operator+=(value_type x)
@@ -2501,7 +2553,11 @@ inline path::path_from_string<Source>& path::operator+=(const Source& x)
 template <class EcharT>
 inline path::path_type_EcharT<EcharT>& path::operator+=(EcharT x)
 {
+#ifdef GHC_WITH_STRING_VIEW
+    basic_string_view<EcharT> part(&x, 1);
+#else
     std::basic_string<EcharT> part(1, x);
+#endif
     concat(part);
     return *this;
 }
@@ -2799,8 +2855,8 @@ GHC_INLINE int path::compare(const string_type& s) const
     return compare(path(s));
 }
 
-#ifdef __cpp_lib_string_view
+#ifdef GHC_WITH_STRING_VIEW
-GHC_INLINE int path::compare(std::basic_string_view<value_type> s) const
+GHC_INLINE int path::compare(basic_string_view<value_type> s) const
 {
     return compare(path(s));
 }

test/filesystem_test.cpp

@@ -2740,31 +2740,44 @@ TEST_CASE("30.10.15.39 weakly_canonical", "[filesystem][operations][fs.op.weakly
 
 TEST_CASE("std::string_view support", "[filesystem][fs.string_view]")
 {
-#if __cpp_lib_string_view
+#if defined(GHC_HAS_STD_STRING_VIEW) || defined(GHC_HAS_STD_EXPERIMENTAL_STRING_VIEW)
+
+#if defined(GHC_HAS_STD_STRING_VIEW)
     using namespace std::literals;
+    using string_view = std::string_view;
+#if defined(IS_WCHAR_PATH) || defined(GHC_USE_WCHAR_T)
+    using wstring_view = std::wstring_view;
+#endif
+#elif defined(GHC_HAS_STD_EXPERIMENTAL_STRING_VIEW)
+    using string_view = std::experimental::string_view;
+#if defined(IS_WCHAR_PATH) || defined(GHC_USE_WCHAR_T)
+    using wstring_view = std::experimental::wstring_view;
+#endif
+#endif
+
     {
         std::string p("foo/bar");
-        std::string_view sv(p);
+        string_view sv(p);
         CHECK(fs::path(sv, fs::path::format::generic_format).generic_string() == "foo/bar");
         fs::path p2("fo");
-        p2 += std::string_view("o");
+        p2 += string_view("o");
         CHECK(p2 == "foo");
-        CHECK(p2.compare(std::string_view("foo")) == 0);
+        CHECK(p2.compare(string_view("foo")) == 0);
     }
     {
         auto p = fs::path{"XYZ"};
-        p /= std::string_view("Appendix");
+        p /= string_view("Appendix");
         CHECK(p == "XYZ/Appendix");
     }
 #if defined(IS_WCHAR_PATH) || defined(GHC_USE_WCHAR_T)
     {
         std::wstring p(L"foo/bar");
-        std::wstring_view sv(p);
+        wstring_view sv(p);
         CHECK(fs::path(sv, fs::path::format::generic_format).generic_string() == "foo/bar");
         fs::path p2(L"fo");
-        p2 += std::wstring_view(L"o");
+        p2 += wstring_view(L"o");
         CHECK(p2 == "foo");
-        CHECK(p2.compare(std::wstring_view(L"foo")) == 0);
+        CHECK(p2.compare(wstring_view(L"foo")) == 0);
     }
 #endif