refactor: bring utf8 patch for std::ostream back.

src/CMakeLists.txt

@@ -13,6 +13,7 @@ PRIVATE
     # Sources
     yycc/string/reinterpret.cpp
     yycc/string/op.cpp
+    yycc/string/stream.cpp
     yycc/patch/fopen.cpp
     yycc/rust/panic.cpp
     yycc/rust/env.cpp
@@ -45,6 +46,7 @@ FILES
     yycc/flag_enum.hpp
     yycc/string/reinterpret.hpp
     yycc/string/op.hpp
+    yycc/string/stream.hpp
     yycc/patch/ptr_pad.hpp
     yycc/patch/fopen.hpp
     yycc/num/parse.hpp

src/yycc/string/stream.cpp

@@ -0,0 +1,23 @@
+#include "stream.hpp"
+#include "reinterpret.hpp"
+
+#define REINTERPRET ::yycc::string::reinterpret
+
+namespace yycc::string::stream {
+
+    std::ostream& operator<<(std::ostream& os, const std::u8string_view& u8str) {
+        os << REINTERPRET::as_ordinary_view(u8str);
+        return os;
+    }
+
+    std::ostream& operator<<(std::ostream& os, const char8_t* u8str) {
+        os << REINTERPRET::as_ordinary(u8str);
+        return os;
+    }
+
+    std::ostream& operator<<(std::ostream& os, char8_t u8chr) {
+        os << static_cast<char>(u8chr);
+        return os;
+    }
+
+}

src/yycc/string/stream.hpp

@@ -0,0 +1,17 @@
+#pragma once
+#include <ostream>
+#include <string_view>
+
+/**
+ * @brief This namespace add UTF8 support for \c std::ostream.
+ * @details
+ * The operator overloads written in this namespace will give \c std::ostream ability to write UTF8 string and its char.
+ * For using this feature, please directly use <TT>using namespace yycc::string:stream;</TT> to import this namespace.
+ */
+namespace yycc::string::stream {
+
+    std::ostream& operator<<(std::ostream& os, const std::u8string_view& u8str);
+    std::ostream& operator<<(std::ostream& os, const char8_t* u8str);
+    std::ostream& operator<<(std::ostream& os, char8_t u8chr);
+
+}

testbench/CMakeLists.txt

@@ -19,8 +19,9 @@ PRIVATE
     yycc/patch/ptr_pad.cpp
     yycc/patch/fopen.cpp
     yycc/rust/env.cpp
-    yycc/string/op.cpp
     yycc/string/reinterpret.cpp
+    yycc/string/op.cpp
+    yycc/string/stream.cpp
     yycc/num/parse.cpp
     yycc/num/stringify.cpp
     yycc/num/op.cpp

testbench/yycc/string/stream.cpp

@@ -0,0 +1,31 @@
+#include <gtest/gtest.h>
+#include <yycc.hpp>
+#include <yycc/string/stream.hpp>
+#include <yycc/string/reinterpret.hpp>
+#include <sstream>
+
+#define REINTERPRET ::yycc::string::reinterpret
+using namespace std::literals::string_view_literals;
+using namespace ::yycc::string::stream;
+
+namespace yycctest::string::stream {
+    
+    TEST(StringStream, StringView) {
+        std::stringstream ss;
+        ss << u8"hello"sv;
+        EXPECT_EQ(REINTERPRET::as_utf8_view(ss.view()), u8"hello"sv);
+    }
+
+    TEST(StringStream, CStrPtr) {
+        std::stringstream ss;
+        ss << u8"hello";
+        EXPECT_EQ(REINTERPRET::as_utf8_view(ss.view()), u8"hello");
+    }
+
+    TEST(StringStream, Character) {
+        std::stringstream ss;
+        ss << u8'y';
+        EXPECT_EQ(REINTERPRET::as_utf8_view(ss.view()), u8"y");
+    }
+
+}