projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| da7c5cc6 KM |
1 | /* |
| 2 | * Copyright (c) 1982 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 | * @(#)pup_cksum.c 6.3 (Berkeley) %G% | |
| 7 | */ | |
| 135f78ff | 8 | |
| 1884f3f6 JB |
9 | #include "types.h" |
| 10 | #include "mbuf.h" | |
| 135f78ff SL |
11 | |
| 12 | /* | |
| 13 | * Checksum routine for PUP-I Protocol family (VAX Version). | |
| 14 | */ | |
| 15 | pup_cksum(m, len) | |
| 16 | register struct mbuf *m; | |
| 17 | register int len; | |
| 18 | { | |
| 19 | register u_short *w; | |
| 20 | register int sum = 0; /* known to be r8 */ | |
| 21 | register int mlen = 0; | |
| 22 | ||
| 23 | for (;;) { | |
| 24 | /* | |
| 25 | * Each trip around loop adds in | |
| 26 | * words from one mbuf segment. | |
| 27 | */ | |
| 28 | w = mtod(m, u_short *); | |
| 29 | if (mlen == -1) { | |
| 30 | /* | |
| 31 | * There is a byte left from the last segment; | |
| 32 | * add it into the checksum. | |
| 33 | */ | |
| 34 | sum += *(u_char *)w << 8; | |
| 35 | asm("rotl $1,r8,r8"); | |
| 36 | w = (u_short *)((char *)w + 1); | |
| 37 | mlen = m->m_len - 1; | |
| 38 | len--; | |
| 39 | } else | |
| 40 | mlen = m->m_len; | |
| 41 | m = m->m_next; | |
| 42 | if (len < mlen) | |
| 43 | mlen = len; | |
| 44 | len -= mlen; | |
| 45 | while ((mlen -= 2) >= 0) { | |
| 46 | asm("addw2 (r9)+,r8; rotl $1,r8,r8;"); | |
| 47 | } | |
| 48 | if (mlen == -1) | |
| 49 | sum += *(u_char *)w; | |
| 50 | if (len == 0) | |
| 51 | break; | |
| 52 | /* | |
| 53 | * Locate the next block with some data. | |
| 54 | * If there is a word split across a boundary we | |
| 55 | * will wrap to the top with mlen == -1 and | |
| 56 | * then add it in shifted appropriately. | |
| 57 | */ | |
| 58 | for (;;) { | |
| 59 | if (m == 0) { | |
| 60 | printf("pup_cksum: out of data\n"); | |
| 61 | goto done; | |
| 62 | } | |
| 63 | if (m->m_len) | |
| 64 | break; | |
| 65 | m = m->m_next; | |
| 66 | } | |
| 67 | } | |
| 68 | done: | |
| 69 | return (sum); | |
| 70 | } |