dtmethod.c

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#include        "dthdr.h"

/*      Change search method.
**
**      Written by Kiem-Phong Vo (05/25/96)
*/

Dtmethod_t* dtmethod(Dt_t* dt, Dtmethod_t* meth)
{
        reg Dtlink_t    *list, *r;
        reg Dtdisc_t*   disc = dt->disc;
        reg Dtmethod_t* oldmeth = dt->meth;

        if(!meth || meth->type == oldmeth->type)
                return oldmeth;

        if(disc->eventf &&
           (*disc->eventf)(dt,DT_METH,(void*)meth,disc) < 0)
                return NIL(Dtmethod_t*);

        dt->data->minp = 0;

        /* get the list of elements */
        list = dtflatten(dt);

        if(dt->data->type&(DT_LIST|DT_STACK|DT_QUEUE) )
                dt->data->head = NIL(Dtlink_t*);
        else if(dt->data->type&(DT_SET|DT_BAG) )
        {       if(dt->data->ntab > 0)
                        (*dt->memoryf)(dt,(void*)dt->data->htab,0,disc);
                dt->data->ntab = 0;
                dt->data->htab = NIL(Dtlink_t**);
        }

        dt->data->here = NIL(Dtlink_t*);
        dt->data->type = (dt->data->type&~(DT_METHODS|DT_FLATTEN)) | meth->type;
        dt->meth = meth;
        if(dt->searchf == oldmeth->searchf)
                dt->searchf = meth->searchf;

        if(meth->type&(DT_LIST|DT_STACK|DT_QUEUE) )
        {       if(!(oldmeth->type&(DT_LIST|DT_STACK|DT_QUEUE)) )
                {       if((r = list) )
                        {       reg Dtlink_t*   t;
                                for(t = r->right; t; r = t, t = t->right )
                                        t->left = r;
                                list->left = r;
                        }
                }
                dt->data->head = list;
        }
        else if(meth->type&(DT_OSET|DT_OBAG))
        {       dt->data->size = 0;
                while(list)
                {       r = list->right;
                        (*meth->searchf)(dt,(void*)list,DT_RENEW);
                        list = r;
                }
        }
        else if(!((meth->type&DT_BAG) && (oldmeth->type&DT_SET)) )
        {       int     rehash;
                if((meth->type&(DT_SET|DT_BAG)) && !(oldmeth->type&(DT_SET|DT_BAG)))
                        rehash = 1;
                else    rehash = 0;

                dt->data->size = dt->data->loop = 0;
                while(list)
                {       r = list->right;
                        if(rehash)
                        {       reg void* key = _DTOBJ(list,disc->link);
                                key = _DTKEY(key,disc->key,disc->size);
                                list->hash = _DTHSH(dt,key,disc,disc->size);
                        }
                        (void)(*meth->searchf)(dt,(void*)list,DT_RENEW);
                        list = r;
                }
        }

        return oldmeth;
}