X-Git-Url: https://git.kernelconcepts.de/?p=metawatch.git;a=blobdiff_plain;f=crc16ccitt.c;h=ae0efe375645491829f2f3314169ace239bb5c33;hp=d468c80f5ea40425c23ec82e59c1268ba5876730;hb=a32e1e3a9f9e81bbf05beac619d1feb4941efc46;hpb=8de8db41a66bc0305400d92471596258ab58e9ad

diff --git a/crc16ccitt.c b/crc16ccitt.c
index d468c80..ae0efe3 100644
--- a/crc16ccitt.c
+++ b/crc16ccitt.c
@@ -1,5 +1,5 @@
 /*
- * derived from crctester.c
+ * derived from crctester.c 2011 by Nils Faerber <nils.faerber@kernelconcepts.de>
  * original header:
  * ----------------------------------------------------------------------------
  * CRC tester v1.3 written on 4th of February 2003 by Sven Reifegerste (zorc/reflex)
@@ -100,12 +100,19 @@ static unsigned long crctablefast (unsigned char* p, unsigned long len)
 
 	unsigned long crc = crcinit_direct;
 
-	if (refin) crc = reflect(crc, order);
+	if (refin)
+		crc = reflect(crc, order);
+
+	if (!refin)
+		while (len--)
+			crc = (crc << 8) ^ crctab[ ((crc >> (order-8)) & 0xff) ^ *p++];
+	else
+		while (len--)
+			crc = (crc >> 8) ^ crctab[ (crc & 0xff) ^ *p++];
 
-	if (!refin) while (len--) crc = (crc << 8) ^ crctab[ ((crc >> (order-8)) & 0xff) ^ *p++];
-	else while (len--) crc = (crc >> 8) ^ crctab[ (crc & 0xff) ^ *p++];
+	if (refout^refin)
+		crc = reflect(crc, order);
 
-	if (refout^refin) crc = reflect(crc, order);
 	crc^= crcxor;
 	crc&= crcmask;
 
@@ -114,8 +121,8 @@ static unsigned long crctablefast (unsigned char* p, unsigned long len)
 
 static unsigned long crctable (unsigned char* p, unsigned long len)
 {
-	// normal lookup table algorithm with augmented zero bytes.
-	// only usable with polynom orders of 8, 16, 24 or 32.
+	/* normal lookup table algorithm with augmented zero bytes. */
+	/* only usable with polynom orders of 8, 16, 24 or 32. */
 
 	unsigned long crc = crcinit_nondirect;
 
@@ -138,6 +145,7 @@ static unsigned long crctable (unsigned char* p, unsigned long len)
 
 	if (refout^refin)
 		crc = reflect(crc, order);
+
 	crc^= crcxor;
 	crc&= crcmask;
 
@@ -148,8 +156,8 @@ static unsigned long crctable (unsigned char* p, unsigned long len)
 
 unsigned long crcbitbybit(unsigned char* p, unsigned long len) {
 
-	// bit by bit algorithm with augmented zero bytes.
-	// does not use lookup table, suited for polynom orders between 1...32.
+	/* bit by bit algorithm with augmented zero bytes. */
+	/* does not use lookup table, suited for polynom orders between 1...32. */
 
 	unsigned long i, j, c, bit;
 	unsigned long crc = crcinit_nondirect;
@@ -179,6 +187,7 @@ unsigned long crcbitbybit(unsigned char* p, unsigned long len) {
 
 	if (refout)
 		crc=reflect(crc, order);
+
 	crc ^= crcxor;
 	crc &= crcmask;
 
@@ -365,3 +374,4 @@ int main() {
 	return(0);
 }
 #endif
+