1 /*-
2 * Copyright (c) 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * %sccs.include.redist.c%
6 */
7
8 #ifndef lint
9 static char sccsid[] = "@(#)sum2.c 8.1 (Berkeley) 06/06/93";
10 #endif /* not lint */
11
12 #include <sys/types.h>
13 #include <unistd.h>
14
15 int
csum2(fd,cval,clen)16 csum2(fd, cval, clen)
17 register int fd;
18 u_long *cval, *clen;
19 {
20 register u_long crc, total;
21 register int nr;
22 register u_char *p;
23 u_char buf[8192];
24
25 /*
26 * Draft 8 POSIX 1003.2:
27 *
28 * s = sum of all bytes
29 * r = s % 2^16 + (s % 2^32) / 2^16
30 * crc = (r % 2^16) + r / 2^16
31 */
32 crc = total = 0;
33 while ((nr = read(fd, buf, sizeof(buf))) > 0)
34 for (total += nr, p = buf; nr--; ++p)
35 crc += *p;
36 if (nr < 0)
37 return(1);
38
39 crc = (crc & 0xffff) + (crc >> 16);
40 crc = (crc & 0xffff) + (crc >> 16);
41
42 *cval = crc;
43 *clen = total;
44 return(0);
45 }
46