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

1.1     ! root        1: /* Copyright (c) 1982, Regents, University of California */
        !             2: struct sdot    { long I; struct sdot *CDR; };
        !             3: struct vl      { long high; long low; };
        !             4: 
        !             5: struct sdot *adbig(a,b)
        !             6: struct sdot *a, *b;
        !             7: {
        !             8:        int la = 1, lb = 1;
        !             9:        long *sa, *sb, *sc, *base, *alloca();
        !            10:        struct sdot *export();
        !            11:        register struct sdot *p;
        !            12:        register int *q, *r, *s;
        !            13:        register carry = 0;
        !            14: 
        !            15:        /* compute lengths */
        !            16:        
        !            17:        for(p = a; p->CDR; p = p->CDR) la++;
        !            18:        for(p = b; p->CDR; p = p->CDR) lb++;
        !            19:        if(lb > la) la = lb;
        !            20: 
        !            21:        /* allocate storage areas on the stack */
        !            22: 
        !            23:        base = alloca((3*la+1)*sizeof(long));
        !            24:        sc = base + la +1;
        !            25:        sb = sc + la;
        !            26:        sa = sb + la;
        !            27:        q  = sa;
        !            28: 
        !            29:        /* copy sdots onto stack */
        !            30:        p = a;
        !            31:        do { *--q = p->I; p = p->CDR; } while (p);
        !            32:        while(q > sb) *--q = 0;
        !            33:        p = b;
        !            34:        do { *--q = p->I; p = p->CDR; } while (p);
        !            35:        while(q > sc) *--q = 0;
        !            36: 
        !            37:        /* perform the addition */
        !            38:        for(q = sa, r = sb, s = sc; q > sb;)
        !            39:        {
        !            40:                carry += *--q + *--r;
        !            41:                *--s = carry & 0x3fffffff;
        !            42:                carry >>= 30;
        !            43:        }
        !            44:        *--s = carry;
        !            45: 
        !            46:        return(export(sc,base));
        !            47: }

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