refactor: update encoding namespace

- add all essential functions prototypes in iconv encoding.
- add lost UTF convertion for windows encoding.

src/yycc/encoding/iconv.hpp

@@ -40,9 +40,9 @@ namespace yycc::encoding::iconv {
 
     /// @private
     enum class ConvError {
-        InvalidCd, ///< Given token is invalid.
-        NullPointer, ///< Some of essential pointer in argument is nullptr.
-        InvalidMbSeq, ///< An invalid multibyte sequence has been encountered in the input.
+        InvalidCd,       ///< Given token is invalid.
+        NullPointer,     ///< Some of essential pointer in argument is nullptr.
+        InvalidMbSeq,    ///< An invalid multibyte sequence has been encountered in the input.
         IncompleteMbSeq, ///< An incomplete multibyte sequence has been encountered in the input.
     };
 
@@ -50,6 +50,145 @@ namespace yycc::encoding::iconv {
     template<typename T>
     using ConvResult = NS_YYCC_PATCH_EXPECTED::Expected<T, ConvError>;
 
+    // TODO: 为下列类添加注释时，指明static开头的是一次性使用的，适用于转换一两次结束。
+    // 用实例类的适用于需要持续转换的。
+
+    // Char -> UTF8
+    class CharToUtf8 {
+    public:
+        CharToUtf8(const CodeName& code_name);
+        ~CharToUtf8();
+        YYCC_DELETE_COPY(CharToUtf8)
+        YYCC_DEFAULT_MOVE(CharToUtf8)
+
+    public:
+        ConvResult<NS_YYCC_STRING::u8string> priv_to_utf8(const std::string_view& src);
+        bool to_utf8(const std::string_view& src, NS_YYCC_STRING::u8string& dst);
+        NS_YYCC_STRING::u8string to_utf8(const std::string_view& src);
+
+    private:
+        Token token;
+    };
+
+    // UTF8 -> Char
+    class Utf8ToChar {
+    public:
+        Utf8ToChar(const CodeName& code_name);
+        ~Utf8ToChar();
+        YYCC_DELETE_COPY(Utf8ToChar)
+        YYCC_DEFAULT_MOVE(Utf8ToChar)
+
+    public:
+        ConvResult<std::string> priv_to_char(const NS_YYCC_STRING::u8string_view& src);
+        bool to_char(const NS_YYCC_STRING::u8string_view& src, std::string& dst);
+        std::string to_char(const NS_YYCC_STRING::u8string_view& src);
+
+    private:
+        Token token;
+    };
+
+    // WChar -> Char
+    class WcharToChar {
+    public:
+        WcharToChar(const CodeName& code_name);
+        ~WcharToChar();
+        YYCC_DELETE_COPY(WcharToChar)
+        YYCC_DEFAULT_MOVE(WcharToChar)
+
+    public:
+        ConvResult<std::string> priv_to_char(const std::wstring_view& src);
+        bool to_char(const std::wstring_view& src, std::string& dst);
+        std::string to_char(const std::wstring_view& src);
+
+    private:
+        Token token;
+    };
+
+    // Char -> WChar
+    class CharToWchar {
+    public:
+        CharToWchar(const CodeName& code_name);
+        ~CharToWchar();
+        YYCC_DELETE_COPY(CharToWchar)
+        YYCC_DEFAULT_MOVE(CharToWchar)
+
+    public:
+        ConvResult<std::wstring> priv_to_wchar(const std::string_view& src, const CodeName& code_name);
+        bool to_wchar(const std::string_view& src, std::wstring& dst, const CodeName& code_name);
+        std::wstring to_wchar(const std::string_view& src, const CodeName& code_name);
+
+    private:
+        Token token;
+    };
+
+    // UTF8 -> UTF16
+    class Utf8ToUtf16 {
+    public:
+        Utf8ToUtf16();
+        ~Utf8ToUtf16();
+        YYCC_DELETE_COPY(Utf8ToUtf16)
+        YYCC_DEFAULT_MOVE(Utf8ToUtf16)
+
+    public:
+        ConvResult<std::u16string> priv_to_utf16(const NS_YYCC_STRING::u8string_view& src);
+        bool to_utf16(const NS_YYCC_STRING::u8string_view& src, std::u16string& dst);
+        std::u16string to_utf16(const NS_YYCC_STRING::u8string_view& src);
+
+    private:
+        Token token;
+    };
+
+    // UTF16 -> UTF8
+    class Utf16ToUtf8 {
+    public:
+        Utf16ToUtf8();
+        ~Utf16ToUtf8();
+        YYCC_DELETE_COPY(Utf16ToUtf8)
+        YYCC_DEFAULT_MOVE(Utf16ToUtf8)
+
+    public:
+        ConvResult<NS_YYCC_STRING::u8string> priv_to_utf8(const std::u16string_view& src);
+        bool to_utf8(const std::u16string_view& src, NS_YYCC_STRING::u8string& dst);
+        NS_YYCC_STRING::u8string to_utf8(const std::u16string_view& src);
+
+    private:
+        Token token;
+    };
+
+    // UTF8 -> UTF32
+    class Utf8ToUtf32 {
+    public:
+        Utf8ToUtf32();
+        ~Utf8ToUtf32();
+        YYCC_DELETE_COPY(Utf8ToUtf32)
+        YYCC_DEFAULT_MOVE(Utf8ToUtf32)
+
+    public:
+        ConvResult<std::u32string> priv_to_utf32(const NS_YYCC_STRING::u8string_view& src);
+        bool to_utf32(const NS_YYCC_STRING::u8string_view& src, std::u32string& dst);
+        std::u32string to_utf32(const NS_YYCC_STRING::u8string_view& src);
+
+    private:
+        Token token;
+    };
+
+    // UTF32 -> UTF8
+    class Utf32ToUtf8 {
+    public:
+        Utf32ToUtf8();
+        ~Utf32ToUtf8();
+        YYCC_DELETE_COPY(Utf32ToUtf8)
+        YYCC_DEFAULT_MOVE(Utf32ToUtf8)
+
+    public:
+        ConvResult<NS_YYCC_STRING::u8string> priv_to_utf8(const std::u32string_view& src);
+        bool to_utf8(const std::u32string_view& src, NS_YYCC_STRING::u8string& dst);
+        NS_YYCC_STRING::u8string to_utf8(const std::u32string_view& src);
+
+    private:
+        Token token;
+    };
+
 } // namespace yycc::encoding::iconv
 
 #undef NS_YYCC_PATCH_EXPECTED