projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| d34e2139 SL |
1 | /* |
| 2 | * Copyright (c) 1986 Regents of the University of California. | |
| 26b5a830 KB |
3 | * All rights reserved. |
| 4 | * | |
| 5 | * Redistribution and use in source and binary forms are permitted | |
| b8c620d6 KB |
6 | * provided that the above copyright notice and this paragraph are |
| 7 | * duplicated in all such forms and that any documentation, | |
| 8 | * advertising materials, and other materials related to such | |
| 9 | * distribution and use acknowledge that the software was developed | |
| 10 | * by the University of California, Berkeley. The name of the | |
| 11 | * University may not be used to endorse or promote products derived | |
| 12 | * from this software without specific prior written permission. | |
| 13 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR | |
| 14 | * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED | |
| 15 | * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. | |
| d34e2139 SL |
16 | */ |
| 17 | ||
| 18 | #ifndef lint | |
| ca67e7b4 | 19 | static char sccsid[] = "@(#)cksum.tahoe.c 2.3 (Berkeley) 6/18/88"; |
| 26b5a830 | 20 | #endif /* not lint */ |
| d34e2139 SL |
21 | |
| 22 | #include <sys/types.h> | |
| 23 | ||
| 24 | /* | |
| 25 | * Checksum routine for Internet Protocol family headers. | |
| 26 | * | |
| 27 | * This routine is very heavily used in the network | |
| 28 | * code and should be modified for each CPU to be as fast as possible. | |
| 29 | * | |
| 30 | * This implementation is TAHOE version. | |
| 31 | */ | |
| 32 | ||
| 33 | #undef ADDCARRY | |
| 34 | #define ADDCARRY(sum) { \ | |
| 35 | if (sum & 0xffff0000) { \ | |
| 36 | sum &= 0xffff; \ | |
| 37 | sum++; \ | |
| 38 | } \ | |
| 39 | } | |
| 40 | ||
| 41 | in_cksum(addr, len) | |
| 42 | register u_short *addr; | |
| 43 | register int len; | |
| 44 | { | |
| 45 | union word { | |
| 46 | char c[2]; | |
| 47 | u_short s; | |
| 48 | } u; | |
| 49 | register int sum = 0; | |
| 50 | ||
| 51 | while (len > 0) { | |
| 52 | /* | |
| 53 | * add by words. | |
| 54 | */ | |
| 55 | while ((len -= 2) >= 0) { | |
| 56 | if ((int)addr & 0x1) { | |
| 57 | /* word is not aligned */ | |
| 58 | u.c[0] = *(char *)addr; | |
| 59 | u.c[1] = *((char *)addr+1); | |
| 60 | sum += u.s; | |
| 61 | addr++; | |
| 62 | } else | |
| 63 | sum += *addr++; | |
| 64 | ADDCARRY(sum); | |
| 65 | } | |
| 66 | if (len == -1) | |
| 67 | /* | |
| 68 | * Odd number of bytes. | |
| 69 | */ | |
| 70 | u.c[0] = *(u_char *)addr; | |
| 71 | } | |
| 72 | if (len == -1) { | |
| 73 | /* The last mbuf has odd # of bytes. Follow the | |
| 74 | standard (the odd byte is shifted left by 8 bits) */ | |
| 75 | u.c[1] = 0; | |
| 76 | sum += u.s; | |
| 77 | ADDCARRY(sum); | |
| 78 | } | |
| 79 | return (~sum & 0xffff); | |
| 80 | } |