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Annotation of 42BSD/ucb/lisp/franz/68k/calqhat.c, revision 1.1.1.1

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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