X-Git-Url: http://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/bd20f8f47847787e1f3e933043933272908c5beb..c2c7f6c271b33c6d95aa47f339fe6d47c433d8d5:/common/crc16.c

diff --git a/common/crc16.c b/common/crc16.c
index d181bb2a..d48df3b2 100644
--- a/common/crc16.c
+++ b/common/crc16.c
@@ -8,15 +8,52 @@
 
 #include "crc16.h"
 
+
 unsigned short update_crc16( unsigned short crc, unsigned char c )
 {
-  unsigned short i, v, tcrc = 0;
+	unsigned short 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;
+	}
+
+	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;
+}
+
+uint16_t crc16_ccitt(uint8_t const *message, int length) {
+	return crc16(message, length, 0xffff, 0x1021);
+}
 
-  v = (crc ^ c) & 0xff;
-  for (i = 0; i < 8; i++) {
-      tcrc = ( (tcrc ^ v) & 1 ) ? ( tcrc >> 1 ) ^ 0x8408 : tcrc >> 1;
-      v >>= 1;
-  }
+uint16_t crc16_ccitt_kermit(uint8_t const *message, int length) {
+	if (length == 0) return 0;
+	uint32_t crc = 0, q = 0;
+	uint8_t c;
 
-  return ((crc >> 8) ^ tcrc)&0xffff;
+	for (int i = 0; i < length; i++){
+		c = message[i];
+		q = (crc ^ c ) & 0xF;
+		crc = (crc >> 4) ^ (q * 0x1081);
+		q = (crc ^ (c >> 4)) & 0xF;
+		crc = (crc >> 4) ^ (q * 0x1081);
+	}
+	return crc;
 }