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Annotation of 43BSDReno/sys/hp300/ns_cksum.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1985, 1986 Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * Redistribution is only permitted until one year after the first shipment
        !             6:  * of 4.4BSD by the Regents.  Otherwise, redistribution and use in source and
        !             7:  * binary forms are permitted provided that: (1) source distributions retain
        !             8:  * this entire copyright notice and comment, and (2) distributions including
        !             9:  * binaries display the following acknowledgement:  This product includes
        !            10:  * software developed by the University of California, Berkeley and its
        !            11:  * contributors'' in the documentation or other materials provided with the
        !            12:  * distribution and in all advertising materials mentioning features or use
        !            13:  * of this software.  Neither the name of the University nor the names of
        !            14:  * its contributors may be used to endorse or promote products derived from
        !            15:  * this software without specific prior written permission.
        !            16:  * THIS SOFTWARE IS PROVIDED AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
        !            17:  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
        !            18:  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            19:  *
        !            20:  *     @(#)ns_cksum.c  7.1 (Berkeley) 5/8/90
        !            21:  */
        !            22: 
        !            23: #include "types.h"
        !            24: #include "mbuf.h"
        !            25: 
        !            26: 
        !            27: /*
        !            28:  * Checksum routine for Network Systems Protocol Packets (SUN Version).
        !            29:  *
        !            30:  * This routine is very heavily used in the network
        !            31:  * code and should be modified for each CPU to be as fast as possible.
        !            32:  */
        !            33: 
        !            34: u_short
        !            35: ns_cksum(m, len)
        !            36:        register struct mbuf *m;
        !            37:        register int len;
        !            38: {
        !            39:        register u_short *w;            /* on sun, known to be a4 */
        !            40:        register int sum = 0;           /* on sun, known to be d6 */
        !            41:        register int low = 0;           /* on sun, known to be d5 */
        !            42:        register int mlen = low;        /* want 0, shuts lint up about low */
        !            43:        register int zero = mlen;       /* handy for fold */
        !            44:        register int sumH = mlen;       /* handy for fold2 */
        !            45: #undef ADD
        !            46: #define ADD asm("addw a4@+,d6; addxw d3,d6; rolw #1,d6")
        !            47: #define FOLD asm("movw d6,d5; swap d6; addw d6,d5; addxw d3,d5;  movl d5,d6");
        !            48: #define ADDH asm("movb a4@+,d5; addl d5,d2; addl d2,d2")
        !            49: #define ADDL asm("movb a4@+,d5; addl d5,d6; addl d6,d6")
        !            50: #define FOLDH asm("movw d2,d5; swap d2; addw d2,d5; addxw d3,d5; movl d5,d2");
        !            51: 
        !            52:        for (;;) {
        !            53:                /*
        !            54:                 * Each trip around loop adds in
        !            55:                 * word from one mbuf segment.
        !            56:                 */
        !            57:                w = mtod(m, u_short *);
        !            58:                if (mlen == -1) {
        !            59:                        /*
        !            60:                         * There is a byte left from the last segment;
        !            61:                         * ones-complement add it into the checksum.
        !            62:                         */
        !            63:                        low = *(u_char *)w;
        !            64:                        asm("addw d5,d6; addxw d3,d6; rolw #1,d6");
        !            65:                        w = (u_short *)((char *)w + 1);
        !            66:                        mlen = m->m_len - 1;
        !            67:                        len--;
        !            68:                } else
        !            69:                        mlen = m->m_len;
        !            70:                m = m->m_next;
        !            71:                if (len < mlen)
        !            72:                        mlen = len;
        !            73:                len -= mlen;
        !            74:                /*
        !            75:                 *
        !            76:                 * We can do a 16 bit ones complement sum using
        !            77:                 * 32 bit arithmetic registers for adding,
        !            78:                 * with carries from the low added
        !            79:                 * into the high (by normal carry-chaining)
        !            80:                 * so long as we fold back before 16 carries have occured.
        !            81:                 *
        !            82:                 */
        !            83: #ifndef OKTOODDWORD
        !            84:                if (((int) w & 1)==0) goto easycase;
        !            85:                while ((mlen -= 32) >= 0) {
        !            86:                        ADDH; ADDL; ADDH; ADDL; ADDH; ADDL; ADDH; ADDL;
        !            87:                        ADDH; ADDL; ADDH; ADDL; ADDH; ADDL; ADDH; ADDL;
        !            88:                        FOLD;
        !            89:                        FOLDH;
        !            90:                        ADDH; ADDL; ADDH; ADDL; ADDH; ADDL; ADDH; ADDL;
        !            91:                        ADDH; ADDL; ADDH; ADDL; ADDH; ADDL; ADDH; ADDL;
        !            92:                        FOLD;
        !            93:                        FOLDH;
        !            94:                }
        !            95:                mlen += 32;
        !            96:                while ((mlen -= 8) >= 0) {
        !            97:                        ADDH; ADDL; ADDH; ADDL; ADDH; ADDL; ADDH; ADDL;
        !            98:                        FOLD;
        !            99:                        FOLDH;
        !           100:                }
        !           101:                mlen += 8;
        !           102:                while ((mlen -= 2) >= 0) {
        !           103:                        ADDH; ADDL;
        !           104:                }
        !           105:                FOLDH;
        !           106:                sum = (sumH << 8) + sum;
        !           107:                FOLD;
        !           108:                sumH = 0;
        !           109:                goto commoncase;
        !           110: easycase:
        !           111: #endif
        !           112:                /* In this sequence there will be no carries out of
        !           113:                 * the lower 16 bits.
        !           114:                 */
        !           115:                while ((mlen -= 32) >= 0) {
        !           116:                        ADD; ADD; ADD; ADD; ADD; ADD; ADD; ADD;
        !           117:                        ADD; ADD; ADD; ADD; ADD; ADD; ADD; ADD;
        !           118:                }
        !           119:                mlen += 32;
        !           120:                while ((mlen -= 8) >= 0) {
        !           121:                        ADD; ADD; ADD; ADD;
        !           122:                }
        !           123:                mlen += 8;
        !           124:                while ((mlen -= 2) >= 0) {
        !           125:                        ADD;
        !           126:                }
        !           127: commoncase:
        !           128:                if (mlen == -1) {
        !           129:                        /*sum += *(u_char *)w << 8; FOLD*/
        !           130:                        low = *(u_char *)w << 8;
        !           131:                        asm("addw d5,d6; addxw d3,d6");
        !           132:                }
        !           133:                if (len == 0) 
        !           134:                        break;
        !           135:                /*
        !           136:                 * Locate the next block with some data.
        !           137:                 * If there is a word split across a boundary we
        !           138:                 * will wrap to the top with mlen == -1 and
        !           139:                 * then add it in shifted appropriately.
        !           140:                 */
        !           141:                for (;;) {
        !           142:                        if (m == 0) {
        !           143:                                printf("idpcksum: out of data\n");
        !           144:                                goto done;
        !           145:                        }
        !           146:                        if (m->m_len)
        !           147:                                break;
        !           148:                        m = m->m_next;
        !           149:                }
        !           150:        }
        !           151: done:
        !           152:        /*
        !           153:         * sum has already been kept to low sixteen bits.
        !           154:         * just examine result and exit.
        !           155:         */
        !           156:        
        !           157:        if(sum==0xffff) sum = 0;
        !           158:        return (sum);
        !           159: }

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