--- libelwix/src/crc.c	2019/12/18 20:00:18	1.5.28.1
+++ libelwix/src/crc.c	2019/12/30 18:11:16	1.6
@@ -3,7 +3,7 @@
 *  by Michael Pounov <misho@openbsd-bg.org>
 *
 * $Author: misho $
-* $Id: crc.c,v 1.5.28.1 2019/12/18 20:00:18 misho Exp $
+* $Id: crc.c,v 1.6 2019/12/30 18:11:16 misho Exp $
 *
 **************************************************************************
 The ELWIX and AITNET software is distributed under the following
@@ -190,14 +190,14 @@ crcCalc(u_char * __restrict psBuf, u_int bufLen, u_cha
 
 
 /*
- * crc16() - Checksum in X/Y modem communication
+ * crc16_ext() - Checksum ver.2 calculation in X/Y modem communication
  *
  * @buf = Data for calculation
  * @bufLen = Length of data
  * return: Checksum
  */
 u_short
-crc16(u_char * __restrict buf, int bufLen)
+crc16_ext(u_char * __restrict buf, int bufLen)
 {
 	u_short crc, x;
 	register u_short i;
@@ -221,6 +221,31 @@ crc16(u_char * __restrict buf, int bufLen)
 
 		if (x)
 			crc ^= crc_16poly;
+	}
+
+	return crc;
+}
+
+/*
+ * crc16() - Checksum calculation in X/Y modem communication
+ *
+ * @buf = Data for calculation
+ * @bufLen = Length of data
+ * return: Checksum
+ */
+u_short
+crc16(u_char * __restrict buf, int bufLen)
+{
+	u_short crc;
+	register u_char i;
+
+	for (crc = 0; bufLen > 0; bufLen--, buf++) {
+		crc ^= (u_short) *buf << 8;
+		for (i = 0x80; i; i >>= 1)
+			if (crc & 0x8000)
+				crc = crc << 1 ^ crc_16poly;
+			else
+				crc <<= 1;
 	}
 
 	return crc;