dtrenew.c

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#include        "dthdr.h"


/*      Renew the object at the current finger.
**
**      Written by Kiem-Phong Vo (5/25/96)
*/

void* dtrenew(Dt_t* dt, reg void* obj)
{
        reg void*       key;
        reg Dtlink_t    *e, *t, **s;
        reg Dtdisc_t*   disc = dt->disc;

        UNFLATTEN(dt);

        if(!(e = dt->data->here) || _DTOBJ(e,disc->link) != obj)
                return NIL(void*);

        if(dt->data->type&(DT_STACK|DT_QUEUE|DT_LIST))
                return obj;
        else if(dt->data->type&(DT_OSET|DT_OBAG) )
        {       if(!e->right )  /* make left child the new root */
                        dt->data->here = e->left;
                else            /* make right child the new root */
                {       dt->data->here = e->right;

                        /* merge left subtree to right subtree */
                        if(e->left)
                        {       for(t = e->right; t->left; t = t->left)
                                        ;
                                t->left = e->left;
                        }
                }
        }
        else /*if(dt->data->type&(DT_SET|DT_BAG))*/
        {       s = dt->data->htab + HINDEX(dt->data->ntab,e->hash);
                if((t = *s) == e)
                        *s = e->right;
                else
                {       for(; t->right != e; t = t->right)
                                ;
                        t->right = e->right;
                }
                key = _DTKEY(obj,disc->key,disc->size);
                e->hash = _DTHSH(dt,key,disc,disc->size);
                dt->data->here = NIL(Dtlink_t*);
        }

        dt->data->size -= 1;
        return (*dt->meth->searchf)(dt,(void*)e,DT_RENEW) ? obj : NIL(void*);
}