added SymbolString(SymbolString), optimized

src/lib/ebus/symbol.cpp

@@ -48,7 +48,7 @@ static const unsigned char CRC_LOOKUP_TABLE[] =
 };
 
 
-SymbolString::SymbolString(const string str)
+SymbolString::SymbolString(const string& str)
 	: m_unescapeState(0), m_crc(0)
 {
 	// parse + escape
@@ -60,7 +60,18 @@ SymbolString::SymbolString(const string str)
 	push_back(m_crc, false, false);
 }
 
-SymbolString::SymbolString(const string str, bool isEscaped)
+SymbolString::SymbolString(const SymbolString& str)
+	: m_unescapeState(0), m_crc(0)
+{
+	// escape
+	for (size_t i = 0; i < str.size(); i++) {
+		push_back(str[i], false, true);
+	}
+	// add CRC + escape
+	push_back(m_crc, false, false);
+}
+
+SymbolString::SymbolString(const string& str, bool isEscaped)
 	: m_unescapeState(1), m_crc(0)
 {
 	// parse + optionally unescape

src/lib/ebus/symbol.h

@@ -50,13 +50,18 @@ public:
 	 * @brief Creates a new escaped instance from an unescaped hex string and adds the calculated CRC.
 	 * @param str the unescaped hex string.
 	 */
-	SymbolString(const string str);
+	SymbolString(const string& str);
+	/**
+	 * @brief Creates a new escaped instance from an unescaped @a SymbolString and adds the calculated CRC.
+	 * @param str the unescaped SymbolString.
+	 */
+	SymbolString(const SymbolString& str);
 	/**
 	 * @brief Creates a new unescaped instance from a hex string.
 	 * @param isEscaped whether the hex string is escaped and shall be unescaped.
 	 * @param str the hex string.
 	 */
-	SymbolString(const string str, const bool isEscaped);
+	SymbolString(const string& str, const bool isEscaped);
 	/**
 	 * @brief Returns the symbols as hex string.
 	 * @param unescape whether to unescape an escaped instance.