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Annotation of 42BSD/ucb/lisp/franz/68k/calqhat.c, revision 1.1

1.1     ! root        1: /* Copyright (c) 1982, Regents, University of California */
        !             2: struct vl      { long high; long low; };
        !             3: calqhat(uj,v1)
        !             4: register long *uj, *v1;
        !             5: {
        !             6:        struct vl work1, work2;
        !             7:        register handy, handy2;
        !             8:        register qhat, rhat;
        !             9:        char err;
        !            10:        if(*v1==*uj) {
        !            11:                /* set qhat to b-1
        !            12:                 * rhat is easily calculated since if we substite b-1
        !            13:                 * for qhat in the formula below, one gets (u[j+1] + v[1])
        !            14:                 */
        !            15:                 qhat = 0x3fffffff;
        !            16:                 rhat = uj[1] + *v1;
        !            17:        } else {
        !            18:                /* work1 = u[j]b + u[j+1]; */
        !            19:                handy2 = uj[1];
        !            20:                handy = *uj;
        !            21:                if(handy & 1) handy2 |= 0x40000000;
        !            22:                if(handy & 2) handy2 |= 0x80000000;
        !            23:                handy >>= 2;
        !            24:                work1.low = handy2; work1.high = handy;
        !            25:                qhat = ediv(&work1,*v1,&err);
        !            26:                /* rhat = work1 - qhat*v[1]; */
        !            27:                rhat = work1.high;
        !            28:        }
        !            29: again:
        !            30:        /* check if v[2]*qhat > rhat*b+u[j+2] */
        !            31:        emul(qhat,v1[1],0,&work1);
        !            32:        /* work2 = rhat*b+u[j+2]; */
        !            33:        { handy2 = uj[2]; handy = rhat;
        !            34:        if(handy & 1) handy2 |= 0x40000000;
        !            35:        if(handy & 2) handy2 |= 0x80000000;
        !            36:        handy >>= 2; work2.low = handy2; work2.high = handy; }
        !            37:        vlsub(&work1,&work2);
        !            38:        if(work1.high <= 0) return(qhat);
        !            39:        qhat--; rhat += *v1;
        !            40:        goto again;
        !            41: }

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