- added checksum algorithm binprot.c

- minor fix in ascon.c

binprot.c

@@ -53,18 +53,19 @@
  * modbus-crc: CRC-16-IBM, order: lo,hi
  * keller-crc: CRC-16-IBM, order: hi,lo
  * sycon-crc: sort of mod 256 checksum, byte stuffing included (no float allowed)
+ * chksum-crc: simple 8bit checksum
  */
 
 typedef enum {intType, hexType, floatType,
   skipType, codeType, crcType, dumpType, errorType} BinDataType;
 // dumpType, errorType must be the last items
 
-typedef enum {modbusCrc, kellerCrc, rsportCrc, syconCrc} CrcAlgorithm;
+typedef enum {modbusCrc, kellerCrc, rsportCrc, syconCrc, chksumCrc} CrcAlgorithm;
 
 typedef struct {
   CrcAlgorithm crcAlgorithm;
   pDynString inp;
-  char *nextFmt;
+  char *nextFmt; // position of next format token
   pDynString result;
   int expectedChars;
   BinDataType type;
@@ -135,6 +136,23 @@ static int calc_crc8(char *inp, int inpLen)
   }
   return crc;
 }
+/*----------------------------------------------------------------------------*/
+static int calc_chksum(char *inp, int inpLen)
+{
+/** simple 8bit checksum
+ */
+
+  unsigned char crc = 0;
+  unsigned char data;
+  int n;
+
+  while (inpLen--) {
+    data = *(unsigned char *) inp;
+    crc += data;
+    inp++;
+  }
+  return crc;
+}
 
 /*----------------------------------------------------------------------------*/
 int BinReadItem(Ascon *a) {
@@ -154,7 +172,11 @@ int BinReadItem(Ascon *a) {
 
   if (strcasecmp(item, "crc") == 0) {
     p->type = crcType;
-    p->expectedChars = 2;
+    if (p->crcAlgorithm == chksumCrc) {
+      p->expectedChars = 1;
+    } else {
+      p->expectedChars = 2;
+    }
     p->nextFmt += valen;
     return 1;
   } else if (strncasecmp(item, "int", 3) == 0) {
@@ -281,6 +303,10 @@ int BinHandler(Ascon *a) {
           DynStringConcatChar(dyn, crc % 256);
           DynStringConcatChar(dyn, crc / 256);
           break;
+        case chksumCrc:
+          crc = calc_chksum(GetCharArray(dyn), l);
+          DynStringConcatChar(dyn, crc % 256);
+          break;
         case rsportCrc:
           crc = calc_crc8(GetCharArray(dyn), l);
           DynStringConcatChar(dyn, crc);
@@ -509,6 +535,11 @@ int BinHandler(Ascon *a) {
             DynStringConcat(p->result, "badCRC ");
           }
           break;
+        case chksumCrc:
+          if (calc_chksum(str, l-1) != (unsigned char)str[l-1]) {
+            DynStringConcat(p->result, "badCRC ");
+          }
+          break;
         case kellerCrc:
           i = str[l-2];
           str[l-2] = str[l-1];
@@ -560,6 +591,8 @@ static int BinInit(Ascon * a, SConnection * con, int argc, char *argv[])
       p->crcAlgorithm = syconCrc;
     } else if (strcasecmp(argv[2], "rsport-crc") == 0) {
       p->crcAlgorithm = rsportCrc;
+    } else if (strcasecmp(argv[2], "chksum-crc") == 0) {
+      p->crcAlgorithm = chksumCrc;
     } else if (strcasecmp(argv[2], "modbus-crc") != 0) {
       SCPrintf(con, eError, "ERROR: unknown crc-algorithm %s", argv[2]);
       a->private = NULL;