* ISO checksum related routines
*
* Copyright (C) 2001,2002 Sampo Saaristo
- * Tampere University of Technology
+ * Tampere University of Technology
* Institute of Communications Engineering
*
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public Licenseas published by the Free
- * Software Foundation; either version 2 of the License, or (at your option)
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public Licenseas published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
- * This program is distributed in the hope that it will be useful,but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * This program is distributed in the hope that it will be useful,but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along
* sum a (mod 255) = 0
* 1 i
*
- * L
+ * L
* sum (L-i+1)a (mod 255) = 0
* 1 i
*
* Based on Annex C.4 of ISO/IEC 8473
*/
-int
-iso_csum_verify (u_char * buffer, int len, uint16_t * csum)
+int iso_csum_verify(uint8_t *buffer, int len, uint16_t csum, int offset)
{
- u_int16_t checksum;
- u_int32_t c0;
- u_int32_t c1;
-
- c0 = *csum & 0xff00;
- c1 = *csum & 0x00ff;
+ uint16_t checksum;
+ uint32_t c0;
+ uint32_t c1;
- /*
- * If both are zero return correct
- */
- if (c0 == 0 && c1 == 0)
- return 0;
+ c0 = csum & 0xff00;
+ c1 = csum & 0x00ff;
- /*
- * If either, but not both are zero return incorrect
- */
- if (c0 == 0 || c1 == 0)
- return 1;
+ /*
+ * If both are zero return correct
+ */
+ if (c0 == 0 && c1 == 0)
+ return 0;
- /* Offset of checksum from the start of the buffer */
- int offset = (u_char *) csum - buffer;
+ /*
+ * If either, but not both are zero return incorrect
+ */
+ if (c0 == 0 || c1 == 0)
+ return 1;
- checksum = fletcher_checksum(buffer, len, offset);
- if (checksum == *csum)
- return 0;
- return 1;
+ checksum = fletcher_checksum(buffer, len, offset);
+ if (checksum == htons(csum))
+ return 0;
+ return 1;
}