Don't break IRC control characters in some encodings

Fix #577

include/znc/Client.h

@@ -82,9 +82,9 @@ protected:
 	CClient* m_pClient;
 };
 
-class CClient : public CZNCSock {
+class CClient : public CIRCSocket {
 public:
-	CClient() : CZNCSock() {
+	CClient() : CIRCSocket() {
 		m_pUser = NULL;
 		m_pNetwork = NULL;
 		m_bGotPass = false;

include/znc/IRCSock.h

@@ -30,7 +30,8 @@ class CIRCNetwork;
 class CClient;
 // !Forward Declarations
 
-class CIRCSock : public CZNCSock {
+// TODO: This class needs new name
+class CIRCSock : public CIRCSocket {
 public:
 	CIRCSock(CIRCNetwork* pNetwork);
 	virtual ~CIRCSock();

include/znc/Socket.h

@@ -220,4 +220,37 @@ protected:
 	CModule*  m_pModule; //!< pointer to the module that this sock instance belongs to
 };
 
+/**
+ * @class CIRCSocket
+ * @brief Base IRC socket for client<->ZNC, and ZNC<->server
+ */
+class CIRCSocket : public CZNCSock {
+public:
+#ifdef HAVE_ICU
+	/**
+	 * @brief Allow IRC control characters to appear even if protocol encoding explicitly disallows them.
+	 *
+	 * E.g. ISO-2022-JP disallows 0x0F, which in IRC means "reset format",
+	 * so by default it gets replaced with U+FFFD ("replacement character").
+	 * https://code.google.com/p/chromium/issues/detail?id=277062#c3
+	 *
+	 * In case if protocol encoding uses these code points for something else, the encoding takes preference,
+	 * and they are not IRC control characters anymore.
+	 */
+	void IcuExtToUCallback(
+		UConverterToUnicodeArgs* toArgs,
+		const char* codeUnits,
+		int32_t length,
+		UConverterCallbackReason reason,
+		UErrorCode* err) override;
+	void IcuExtFromUCallback(
+		UConverterFromUnicodeArgs* fromArgs,
+		const UChar* codeUnits,
+		int32_t length,
+		UChar32 codePoint,
+		UConverterCallbackReason reason,
+		UErrorCode* err) override;
+#endif
+};
+
 #endif /* SOCKET_H */