Added support for pre-c++17 experimental string_view (#607)

Added support for pre-c++17 experimental string_view

fmt/format.h

@@ -55,8 +55,15 @@
     (defined(_MSVC_LANG) && _MSVC_LANG > 201402L && _MSC_VER >= 1910)
 # include <string_view>
 # define FMT_HAS_STRING_VIEW 1
+# define FMT_HAS_EXPERIMENTAL_STRING_VIEW 0
 #else
 # define FMT_HAS_STRING_VIEW 0
+# if (FMT_HAS_INCLUDE(<experimental/string_view>) && __cplusplus > 201402L)
+#  include <experimental/string_view>
+#  define FMT_HAS_EXPERIMENTAL_STRING_VIEW 1
+# else
+#  define FMT_HAS_EXPERIMENTAL_STRING_VIEW 0
+# endif
 #endif
 
 #if defined _SECURE_SCL && _SECURE_SCL
@@ -582,6 +589,26 @@ class BasicStringRef {
   }
 #endif
 
+#if FMT_HAS_EXPERIMENTAL_STRING_VIEW
+  /**
+  \rst
+  Constructs a string reference from a ``std::experimental::basic_string_view`` object.
+  \endrst
+  */
+  BasicStringRef(
+	  const std::experimental::basic_string_view<Char, std::char_traits<Char>> &s)
+	  : data_(s.data()), size_(s.size()) {}
+
+  /**
+  \rst
+  Converts a string reference to an ``std::string_view`` object.
+  \endrst
+  */
+  explicit operator std::experimental::basic_string_view<Char>() const FMT_NOEXCEPT {
+	  return std::experimental::basic_string_view<Char>(data_, size_);
+  }
+#endif
+
   /**
     \rst
     Converts a string reference to an ``std::string`` object.
@@ -1367,6 +1394,9 @@ class MakeValue : public Arg {
   MakeValue(typename WCharHelper<const std::wstring &, Char>::Unsupported);
 #if FMT_HAS_STRING_VIEW
   MakeValue(typename WCharHelper<const std::wstring_view &, Char>::Unsupported);
+#endif
+#if FMT_HAS_EXPERIMENTAL_STRING_VIEW
+  MakeValue(typename WCharHelper<const std::experimental::wstring_view &, Char>::Unsupported);
 #endif
   MakeValue(typename WCharHelper<WStringRef, Char>::Unsupported);
 
@@ -1471,6 +1501,9 @@ class MakeValue : public Arg {
   FMT_MAKE_STR_VALUE(const std::string &, STRING)
 #if FMT_HAS_STRING_VIEW
   FMT_MAKE_STR_VALUE(const std::string_view &, STRING)
+#endif
+#if FMT_HAS_EXPERIMENTAL_STRING_VIEW
+  FMT_MAKE_STR_VALUE(const std::experimental::string_view &, STRING)
 #endif
   FMT_MAKE_STR_VALUE(StringRef, STRING)
   FMT_MAKE_VALUE_(CStringRef, string.value, CSTRING, value.c_str())
@@ -1486,6 +1519,9 @@ class MakeValue : public Arg {
   FMT_MAKE_WSTR_VALUE(const std::wstring &, WSTRING)
 #if FMT_HAS_STRING_VIEW
   FMT_MAKE_WSTR_VALUE(const std::wstring_view &, WSTRING)
+#endif
+#if FMT_HAS_EXPERIMENTAL_STRING_VIEW
+  FMT_MAKE_WSTR_VALUE(const std::experimental::wstring_view &, WSTRING)
 #endif
   FMT_MAKE_WSTR_VALUE(WStringRef, WSTRING)
 

test/CMakeLists.txt

@@ -11,6 +11,12 @@ target_compile_options(gmock PUBLIC ${CPP11_FLAG})
 target_compile_definitions(gmock PUBLIC GTEST_HAS_STD_WSTRING=1)
 target_include_directories(gmock PUBLIC .)
 
+# Workaround for Cygwin to make google-tests compile and run because the macro
+# _POSIX_C_SOURCE must be defined to allow fileno(), strdup(), fdopen() calls.
+if (CYGWIN)
+  target_compile_definitions(gmock PUBLIC _POSIX_C_SOURCE=200809)
+endif ()
+
 find_package(Threads)
 if (Threads_FOUND)
   target_link_libraries(gmock ${CMAKE_THREAD_LIBS_INIT})

test/format-test.cc

@@ -156,6 +156,11 @@ TEST(StringRefTest, Ctor) {
   EXPECT_STREQ("hijk", StringRef(std::string_view("hijk")).data());
   EXPECT_EQ(4u, StringRef(std::string_view("hijk")).size());
 #endif
+
+#if FMT_HAS_EXPERIMENTAL_STRING_VIEW
+  EXPECT_STREQ("hijk", StringRef(std::experimental::string_view("hijk")).data());
+  EXPECT_EQ(4u, StringRef(std::experimental::string_view("hijk")).size());
+#endif
 }
 
 TEST(StringRefTest, ConvertToString) {
@@ -167,6 +172,12 @@ TEST(StringRefTest, ConvertToString) {
   std::string_view sv = static_cast<std::string_view>(str_ref);
   EXPECT_EQ("defg", sv);
 #endif
+
+#if FMT_HAS_EXPERIMENTAL_STRING_VIEW
+  StringRef str_ref("defg");
+  std::experimental::string_view sv = static_cast<std::experimental::string_view>(str_ref);
+  EXPECT_EQ("defg", sv);
+#endif
 }
 
 TEST(CStringRefTest, Ctor) {
@@ -176,6 +187,10 @@ TEST(CStringRefTest, Ctor) {
 #if FMT_HAS_STRING_VIEW
   EXPECT_STREQ("hijk", CStringRef(std::string_view("hijk")).c_str());
 #endif
+
+#if FMT_HAS_EXPERIMENTAL_STRING_VIEW
+  EXPECT_STREQ("hijk", CStringRef(std::experimental::string_view("hijk")).c_str());
+#endif
 }
 
 #if FMT_USE_TYPE_TRAITS
@@ -1399,6 +1414,12 @@ TEST(FormatterTest, FormatStringView) {
 }
 #endif
 
+#if FMT_HAS_EXPERIMENTAL_STRING_VIEW
+TEST(FormatterTest, FormatExperimentalStringView) {
+	EXPECT_EQ("test", format("{0}", std::experimental::string_view("test")));
+}
+#endif
+
 void format_arg(fmt::BasicFormatter<char> &f, const char *, const Date &d) {
   f.writer() << d.year() << '-' << d.month() << '-' << d.day();
 }