refactor: Use RIOTs built-in crc16

Author: Teufelchen1

drivers/slipdev/Makefile.dep

@@ -8,6 +8,7 @@ ifneq (,$(filter slipdev_stdio,$(USEMODULE)))
   USEMODULE += isrpipe
 endif
 ifneq (,$(filter slipdev_config,$(USEMODULE)))
+  USEMODULE += checksum
   USEMODULE += sock_udp
   USEMODULE += gnrc_ipv6
   USEMODULE += nanocoap_sock

drivers/slipdev/slipdev.c

@@ -33,6 +33,7 @@
 #include "isrpipe.h"
 #include "mutex.h"
 #if IS_USED(MODULE_SLIPDEV_CONFIG)
+#include "checksum/crc16_ccitt.h"
 #include "net/nanocoap.h"
 #endif
 #include "stdio_uart.h"
@@ -43,38 +44,9 @@ mutex_t slipdev_mutex = MUTEX_INIT;
 #endif
 
 #if IS_USED(MODULE_SLIPDEV_CONFIG)
-#define COAP_STACKSIZE (1024)
-
-/* Magic values for the fcs */
 /* The special init is the result of normal fcs init combined with slipmux config start (0xa9) */
 #define SPECIAL_INIT_FCS (0x374cU)
-#define INIT_FCS (0xffffU)
-#define GOOD_FCS (0xf0b8U)
-
-static const uint16_t FCS_LOOKUP[256] = {
-    0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf, 0x8c48, 0x9dc1, 0xaf5a, 0xbed3,
-    0xca6c, 0xdbe5, 0xe97e, 0xf8f7, 0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
-    0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876, 0x2102, 0x308b, 0x0210, 0x1399,
-    0x6726, 0x76af, 0x4434, 0x55bd, 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
-    0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c, 0xbdcb, 0xac42, 0x9ed9, 0x8f50,
-    0xfbef, 0xea66, 0xd8fd, 0xc974, 0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
-    0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3, 0x5285, 0x430c, 0x7197, 0x601e,
-    0x14a1, 0x0528, 0x37b3, 0x263a, 0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
-    0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9, 0xef4e, 0xfec7, 0xcc5c, 0xddd5,
-    0xa96a, 0xb8e3, 0x8a78, 0x9bf1, 0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
-    0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70, 0x8408, 0x9581, 0xa71a, 0xb693,
-    0xc22c, 0xd3a5, 0xe13e, 0xf0b7, 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
-    0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036, 0x18c1, 0x0948, 0x3bd3, 0x2a5a,
-    0x5ee5, 0x4f6c, 0x7df7, 0x6c7e, 0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
-    0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd, 0xb58b, 0xa402, 0x9699, 0x8710,
-    0xf3af, 0xe226, 0xd0bd, 0xc134, 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
-    0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3, 0x4a44, 0x5bcd, 0x6956, 0x78df,
-    0x0c60, 0x1de9, 0x2f72, 0x3efb, 0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
-    0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a, 0xe70e, 0xf687, 0xc41c, 0xd595,
-    0xa12a, 0xb0a3, 0x8238, 0x93b1, 0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
-    0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330, 0x7bc7, 0x6a4e, 0x58d5, 0x495c,
-    0x3de3, 0x2c6a, 0x1ef1, 0x0f78
-};
+#define COAP_STACKSIZE (1024)
 
 static char coap_stack[COAP_STACKSIZE];
 #endif /* IS_USED(MODULE_SLIPDEV_CONFIG) */
@@ -460,26 +432,6 @@ static const netdev_driver_t slip_driver = {
 };
 
 #if IS_USED(MODULE_SLIPDEV_CONFIG)
-static uint16_t _fcs_part(const uint8_t * data, size_t len) {
-    uint16_t fcs = SPECIAL_INIT_FCS;
-    for (size_t i = 0; i < len; ++i)
-    {
-        fcs = (fcs >> 8) ^ FCS_LOOKUP[(fcs ^ data[i]) & 0xff];
-    }
-    return fcs;
-}
-
-static int check_fcs(const uint8_t * data, size_t len) {
-    uint16_t trialfcs = _fcs_part(data, len);
-    return trialfcs == GOOD_FCS;
-}
-
-static uint16_t fcs(const uint8_t * data, size_t len) {
-    uint16_t trialfcs = _fcs_part(data, len);
-    uint16_t result = trialfcs ^ INIT_FCS;
-    return result;
-}
-
 static void *_coap_server_thread(void *arg)
 {
     static uint8_t buf[512];
@@ -490,11 +442,12 @@ static void *_coap_server_thread(void *arg)
         while (crb_get_chunk_size(&dev->rb_config, &len)) {
             crb_consume_chunk(&dev->rb_config, buf, len);
 
-            if (!check_fcs(buf, len)) {
+            /* Is crc correct via Residue test */
+            if (crc16_ccitt_fcs_update(SPECIAL_INIT_FCS, buf, len) != 0xF0B8) {
                 break;
             }
 
-            // cut off the FCS checksum at the end
+            /* cut off the FCS checksum at the end */
             size_t pktlen = len - 2;
 
             coap_pkt_t pkt;
@@ -510,7 +463,7 @@ static void *_coap_server_thread(void *arg)
                 break;
             }
 
-            uint16_t fcs_sum = fcs(buf, res);
+            uint16_t fcs_sum = crc16_ccitt_fcs_finish(SPECIAL_INIT_FCS, buf, res);
 
             slipdev_lock();
             slipdev_write_byte(dev->config.uart, SLIPDEV_CONFIG_START);

tests/unittests/tests-checksum/tests-checksum-crc16-ccitt-fcs.c

@@ -5,7 +5,6 @@
  * General Public License v2.1. See the file LICENSE in the top level
  * directory for more details.
  */
-#include <stdio.h>
 #include <stdint.h>
 
 #include "embUnit/embUnit.h"