add class nfc_string

src/nfc.cc

@@ -683,6 +683,12 @@ size_t UTF<char16_t>::utf_length(std::u32string_view s)
 }
 
 
+template<class CharT>
+UTF<CharT>::nfc_string::nfc_string(std::basic_string_view<CharT> src)
+: s{ UTF<CharT>::toNFC(src) }
+{}
+
+
 // convenience function to avoid ::strdup(pEp::toNFC<char>(text).c_str());
 // and unecessary temporary std::string etc.
 char* strdup_NFC(std::string_view s)

src/nfc.hh

@@ -75,11 +75,63 @@ public:
 	/// creates an NFD u32string from UTF-8/UTF-16 input string s
 	static
 	std::u32string fromUtf_decompose(std::basic_string_view<CharT> s);
+	
+	
+	/// class holding a NFC-conform Unicode string.
+	/// content is mostly read-only, because arbitrary modifications might destroy NFC conformacy.
+	class nfc_string
+	{
+	public:
+		typedef std::basic_string<CharT> String;
+		
+		/// only const_reference is supported.
+		typedef typename String::const_reference const_reference;
+		typedef typename String::const_pointer   const_pointer;
+		
+		/// only forward iterator. Does a backward_iterator make sense in UTF-encoded strings?
+		typedef typename String::const_iterator  const_iterator;
+		
+		
+		explicit nfc_string(std::basic_string_view<CharT>   src);
+		explicit nfc_string(std::basic_string     <CharT>&& src);
+		
+		/// construct from a NUL-terminated src
+		explicit nfc_string(const CharT* src);
+		
+		nfc_string(const CharT* src, size_t length);
+		
+		nfc_string(const nfc_string&  src) = default;
+		nfc_string(      nfc_string&& src) = default;
+		
+		nfc_string& operator=(const nfc_string&  src) = default;
+		nfc_string& operator=(      nfc_string&& src) = default;
+		
+		nfc_string& assign(String&& src);
+		nfc_string& assign(std::basic_string_view<CharT> src);
+		
+		
+		/// read-only: shares representation
+		operator const String&() const noexcept { return s; }
+		
+		/// read write: copy content
+		operator String() const { return s; }
+		
+		const CharT* c_str() const noexcept { return s.c_str(); }
+		const CharT* data()  const noexcept { return s.data();  }
+		std::size_t  size()  const noexcept { return s.size();  }
+		bool         empty() const noexcept { return s.empty(); }
+		
+	private:
+		std::basic_string<CharT> s;
+	};
 };
 
+/// convenient alias names:
 using UTF8 = UTF<char>;
 using UTF16 = UTF<char16_t>;
 
+using nfc_string = UTF8::nfc_string;
+using nfc_u16string = UTF16::nfc_string;
 
 // throws illegal_utf8 exception if s is not valid UTF-8
 void assert_utf8(std::string_view s);