X-Git-Url: https://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/01b7a6a898cac0c20dccace8da6df8f60086a43a..32da0a464e03b39f894ecfe04cee0da114ff0c9a:/common/crc16.c

diff --git a/common/crc16.c b/common/crc16.c
index a37f1d7e..21310b79 100644
--- a/common/crc16.c
+++ b/common/crc16.c
@@ -7,55 +7,44 @@
 //-----------------------------------------------------------------------------
 
 #include "crc16.h"
+#define CRC16_POLY_CCITT 0x1021
+#define CRC16_POLY 0x8408
 
-unsigned short update_crc16( unsigned short crc, unsigned char c )
-{
-	unsigned short i, v, tcrc = 0;
+uint16_t update_crc16( uint16_t crc, unsigned char c ) {
+  uint16_t i, v, tcrc = 0;
 
-	v = (crc ^ c) & 0xff;
-	for (i = 0; i < 8; i++) {
-		tcrc = ( (tcrc ^ v) & 1 ) ? ( tcrc >> 1 ) ^ 0x8408 : tcrc >> 1;
-		v >>= 1;
-	}
+  v = (crc ^ c) & 0xff;
+  for (i = 0; i < 8; i++) {
+      tcrc = ( (tcrc ^ v) & 1 ) ? ( tcrc >> 1 ) ^ CRC16_POLY : tcrc >> 1;
+      v >>= 1;
+  }
 
-	return ((crc >> 8) ^ tcrc)&0xffff;
+  return ((crc >> 8) ^ tcrc) & 0xffff;
 }
 
 uint16_t crc16(uint8_t const *message, int length, uint16_t remainder, uint16_t polynomial) {
-
-	if (length == 0) return (~remainder);
-
-	for (int byte = 0; byte < length; ++byte) {
-		remainder ^= (message[byte] << 8);
-		for (uint8_t bit = 8; bit > 0; --bit) {
-			if (remainder & 0x8000) {
-				remainder = (remainder << 1) ^ polynomial;
-			} else {
-				remainder = (remainder << 1);
-			}
-		}
-	}
-	return remainder;
+    
+	if (length == 0)
+        return (~remainder);
+			
+    for (uint32_t i = 0; i < length; ++i) {
+        remainder ^= (message[i] << 8);
+        for (uint8_t bit = 8; bit > 0; --bit) {
+            if (remainder & 0x8000) {
+                remainder = (remainder << 1) ^ polynomial;
+            } else {
+                remainder = (remainder << 1);
+            }
+        }
+    }
+    return remainder;
 }
 
 uint16_t crc16_ccitt(uint8_t const *message, int length) {
-	return crc16(message, length, 0xffff, 0x1021);
+    return crc16(message, length, 0xffff, CRC16_POLY_CCITT);
 }
 
 uint16_t crc16_ccitt_kermit(uint8_t const *message, int length) {
-	return bit_reverse_uint16(crc16(message, length, 0x0000, 0x1021));
-}
-
-uint16_t bit_reverse_uint16 (uint16_t value) {
-	const uint16_t mask0 = 0x5555;
-	const uint16_t mask1 = 0x3333;
-	const uint16_t mask2 = 0x0F0F;
-	const uint16_t mask3 = 0x00FF;
-
-	value = (((~mask0) & value) >> 1) | ((mask0 & value) << 1);
-	value = (((~mask1) & value) >> 2) | ((mask1 & value) << 2);
-	value = (((~mask2) & value) >> 4) | ((mask2 & value) << 4);
-	value = (((~mask3) & value) >> 8) | ((mask3 & value) << 8);
-
-	return value;
+	uint16_t val = crc16(message, length, 0x0000, CRC16_POLY_CCITT);
+    return SwapBits(val, 16);
 }