dtview.c

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#include        "dthdr.h"

/*      Set a view path from dict to view.
**
**      Written by Kiem-Phong Vo (5/25/96)
*/


static void* dtvsearch(Dt_t* dt, reg void* obj, reg int type)
{
        Dt_t            *d, *p;
        void            *o, *n, *ok, *nk;
        int             cmp, lk, sz, ky;
        Dtcompar_f      cmpf;

        /* these operations only happen at the top level */
        if(type&(DT_INSERT|DT_DELETE|DT_CLEAR|DT_RENEW))
                return (*(dt->meth->searchf))(dt,obj,type);

        if((type&(DT_MATCH|DT_SEARCH)) || /* order sets first/last done below */
           ((type&(DT_FIRST|DT_LAST)) && !(dt->meth->type&(DT_OBAG|DT_OSET)) ) )
        {       for(d = dt; d; d = d->view)
                        if((o = (*(d->meth->searchf))(d,obj,type)) )
                                break;
                dt->walk = d;
                return o;
        }

        if(dt->meth->type & (DT_OBAG|DT_OSET) )
        {       if(!(type & (DT_FIRST|DT_LAST|DT_NEXT|DT_PREV)) )
                        return NIL(void*);

                n = nk = NIL(void*); p = NIL(Dt_t*);
                for(d = dt; d; d = d->view)
                {       if(!(o = (*d->meth->searchf)(d, obj, type)) )
                                continue;
                        _DTDSC(d->disc,ky,sz,lk,cmpf);
                        ok = _DTKEY(o,ky,sz);

                        if(n) /* get the right one among all dictionaries */
                        {       cmp = _DTCMP(d,ok,nk,d->disc,cmpf,sz);
                                if(((type & (DT_NEXT|DT_FIRST)) && cmp < 0) ||
                                   ((type & (DT_PREV|DT_LAST)) && cmp > 0) )
                                        goto a_dj;
                        }
                        else /* looks good for now */
                        { a_dj: p  = d;
                                n  = o;
                                nk = ok;
                        }
                }

                dt->walk = p;
                return n;
        }

        /* non-ordered methods */
        if(!(type & (DT_NEXT|DT_PREV)) )
                return NIL(void*);

        if(!dt->walk || obj != _DTOBJ(dt->walk->data->here, dt->walk->disc->link) )
        {       for(d = dt; d; d = d->view)
                        if((o = (*(d->meth->searchf))(d, obj, DT_SEARCH)) )
                                break;
                dt->walk = d;
                if(!(obj = o) )
                        return NIL(void*);
        }

        for(d = dt->walk, obj = (*d->meth->searchf)(d, obj, type);; )
        {       while(obj) /* keep moving until finding an uncovered object */
                {       for(p = dt; ; p = p->view)
                        {       if(p == d) /* adjacent object is uncovered */   
                                        return obj;
                                if((*(p->meth->searchf))(p, obj, DT_SEARCH) )
                                        break;
                        }
                        obj = (*d->meth->searchf)(d, obj, type);
                }

                if(!(d = dt->walk = d->view) ) /* move on to next dictionary */
                        return NIL(void*);
                else if(type&DT_NEXT)
                        obj = (*(d->meth->searchf))(d,NIL(void*),DT_FIRST);
                else    obj = (*(d->meth->searchf))(d,NIL(void*),DT_LAST);
        }
}

Dt_t* dtview(reg Dt_t* dt, reg Dt_t* view)
{
        reg Dt_t*       d;

        UNFLATTEN(dt);
        if(view)
        {       UNFLATTEN(view);
                if(view->meth != dt->meth) /* must use the same method */
                        return NIL(Dt_t*);
        }

        /* make sure there won't be a cycle */
        for(d = view; d; d = d->view)
                if(d == dt)
                        return NIL(Dt_t*);

        /* no more viewing lower dictionary */
        if((d = dt->view) )
                d->nview -= 1;
        dt->view = dt->walk = NIL(Dt_t*);

        if(!view)
        {       dt->searchf = dt->meth->searchf;
                return d;
        }

        /* ok */
        dt->view = view;
        dt->searchf = dtvsearch;
        view->nview += 1;

        return view;
}