projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| c5395442 RG |
1 | /* |
| 2 | * Copyright (c) 1983 Regents of the University of California. | |
| 3 | * All rights reserved. The Berkeley software License Agreement | |
| 4 | * specifies the terms and conditions for redistribution. | |
| 5 | */ | |
| 6 | ||
| 7 | #ifndef lint | |
| 95f51977 | 8 | static char sccsid[] = "@(#)cksum.c 1.2 (Berkeley) 9/18/85"; |
| c5395442 RG |
9 | #endif not lint |
| 10 | ||
| dd9851ac | 11 | #include <sys/types.h> |
| c5395442 RG |
12 | |
| 13 | #define ADD asm("adwc (r9)+,r8;"); | |
| 14 | ||
| 15 | /* computes the checksum for ip packets for the VAX */ | |
| 16 | ||
| 17 | in_cksum(addr, len) | |
| 18 | u_short *addr; | |
| 19 | int len; | |
| 20 | { | |
| 21 | register int nleft = len; /* on vax, (user mode), r11 */ | |
| 22 | #ifndef lint | |
| 23 | register int xxx; /* on vax, (user mode), r10 */ | |
| 24 | #endif not lint | |
| 25 | register u_short *w = addr; /* on vax, known to be r9 */ | |
| 26 | register int sum = 0; /* on vax, known to be r8 */ | |
| 27 | ||
| 28 | if (((int)w&0x2) && nleft >= 2) { | |
| 29 | sum += *w++; | |
| 30 | nleft -= 2; | |
| 31 | } | |
| 32 | while ((nleft -= 32) >= 0) { | |
| 33 | asm("clrl r0"); /* clears carry */ | |
| 34 | ADD; ADD; ADD; ADD; ADD; ADD; ADD; ADD; | |
| 35 | asm("adwc $0,r8"); | |
| 36 | } | |
| 37 | nleft += 32; | |
| 38 | while ((nleft -= 8) >= 0) { | |
| 39 | asm("clrl r0"); | |
| 40 | ADD; ADD; | |
| 41 | asm("adwc $0,r8"); | |
| 42 | } | |
| 43 | nleft += 8; | |
| 44 | { asm("ashl $-16,r8,r0; addw2 r0,r8"); | |
| 45 | asm("adwc $0,r8; movzwl r8,r8"); } | |
| 46 | while ((nleft -= 2) >= 0) { | |
| 47 | asm("movzwl (r9)+,r0; addl2 r0,r8"); | |
| 48 | } | |
| 49 | if (nleft == -1) { | |
| 50 | sum += *(u_char *)w; | |
| 51 | } | |
| 52 | ||
| 53 | { asm("ashl $-16,r8,r0; addw2 r0,r8; adwc $0,r8"); | |
| 54 | asm("mcoml r8,r8; movzwl r8,r8"); } | |
| 55 | return (sum); | |
| 56 | } |