bricks: Add an utf-8b decoder and use it in from_string for std::u32string. (4b49b6b2) · Commits · Adam Matoušek / tiny

bricks/brick-string

+73 −9

Original line number	Diff line number	Diff line
		@@ -506,6 +506,77 @@ namespace brq
		return rv;
		}

		[[gnu::pure]] static std::pair< char32_t, std::string_view >
		decode_utf8( std::string_view f, bool report_partial = true )
		{
		auto get = [&]( int i ) -> uint8_t { return f[ i ]; };
		uint32_t a = get( 0 ), b, c, d;
		auto error = std::make_pair( a \| 0xdc80, f.substr( 1 ) );
		auto partial = std::make_pair( 0xffffu, f );

		if ( a < 0x80 )
		return { a, f.substr( 1 ) };

		if ( a < 0xC2 )
		return error;

		if ( a < 0xE0 )
		{
		if ( f.size() < 2 )
		return report_partial ? partial : error;

		b = get( 1 );

		if ( ( b & 0xC0 ) != 0x80 )
		return error;

		return { ( ( a & 0x1f ) << 6 ) \| ( b & 0x3f ), f.substr( 2 ) };
		}

		if ( a < 0xF0 )
		{
		if ( f.size() < 3 )
		return report_partial ? partial : error;

		b = get( 1 ), c = get( 2 );

		switch ( a )
		{
		case 0xE0: if ( ( b & 0xe0 ) != 0xa0 ) return error; else break;
		case 0xED: if ( ( b & 0xe0 ) != 0x80 ) return error; else break;
		default: if ( ( b & 0xc0 ) != 0x80 ) return error; else break;
		}

		if ( ( c & 0xc0 ) != 0x80 )
		return error;

		return { ( ( a & 0x0f ) << 12 ) \| ( ( b & 0x3f ) << 6 ) \| ( c & 0x3f ), f.substr( 3 ) };
		}

		if ( a < 0xF5 )
		{
		if ( f.size() < 4 )
		return report_partial ? partial : error;

		b = get( 1 ), c = get( 2 ), d = get( 3 );

		switch ( a )
		{
		case 0xF0: if ( b < 0x90 \|\| b > 0xBF ) return error; else break;
		case 0xF4: if ( ( b & 0xf0 ) != 0x80 ) return error; else break;
		default: if ( ( b & 0xc0 ) != 0x80 ) return error; else break;
		}

		if ( ( c & 0xc0 ) != 0x80 \|\| ( d & 0xc0 ) != 0x80 )
		return error;

		return { ( ( a & 0x07 ) << 18 ) \| ( ( b & 0x3F ) << 12 ) \|
		( ( c & 0x3F ) << 6 ) \| ( d & 0x3F ), f.substr( 4 ) };
		}

		return error;
		}

		struct parse_result
		{
		std::string _err_str;
		@@ -573,15 +644,8 @@ namespace brq

		inline parse_result from_string( std::string_view s, std::u32string &v )
		{
		v.clear();

		while ( !s.empty() )
		{
		auto [ ch, next ] = brq::decode_utf8( s );
		v += ch;
		s = next;
		}

		std::wstring_convert< std::codecvt_utf8< char32_t >, char32_t > conv;
		v = conv.from_bytes( &s.begin(), &s.end() );
		return {};
		}