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dtview.c

/***********************************************************************
*                                                                      *
*               This software is part of the ast package               *
*                  Copyright (c) 1985-2006 AT&T Corp.                  *
*                      and is licensed under the                       *
*                  Common Public License, Version 1.0                  *
*                            by AT&T Corp.                             *
*                                                                      *
*                A copy of the License is available at                 *
*            http://www.opensource.org/licenses/cpl1.0.txt             *
*         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
*                                                                      *
*              Information and Software Systems Research               *
*                            AT&T Research                             *
*                           Florham Park NJ                            *
*                                                                      *
*                 Glenn Fowler <gsf@research.att.com>                  *
*                  David Korn <dgk@research.att.com>                   *
*                   Phong Vo <kpv@research.att.com>                    *
*                                                                      *
***********************************************************************/
#include    "dthdr.h"

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


#if __STD_C
static Void_t* dtvsearch(Dt_t* dt, reg Void_t* obj, reg int type)
#else
static Void_t* dtvsearch(dt,obj,type)
Dt_t*       dt;
reg Void_t* obj;
reg int           type;
#endif
{
      reg Dt_t    *d, *p;
      reg Void_t* o;
      reg Dtdisc_t*     disc;
      reg Dtlink_t*     here;

      /* 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(!obj && !(type&(DT_FIRST|DT_LAST)) )
            return NIL(Void_t*);

      if(type&(DT_MATCH|DT_SEARCH|DT_FIRST|DT_LAST))
      {     for(d = dt; d; d = d->view)
            {     if((o = (*(d->meth->searchf))(d,obj,type)) )
                  {     dt->walk = d;
                        return o;
                  }
            }

            dt->walk = NIL(Dt_t*);
            return NIL(Void_t*);
      }

      /* must be (DT_NEXT|DT_PREV) */
      if(!dt->walk || !(here = dt->walk->data->here) ||
         obj != _DTOBJ(here,dt->walk->disc->link) )
      {     for(d = dt; d; d = d->view)
            {     if((o = (*(d->meth->searchf))(d,obj,DT_SEARCH)) )
                  {     dt->walk = d;
                        goto do_adj;
                  }
            }

            dt->walk = NIL(Dt_t*);
            return NIL(Void_t*);
      }

do_adj: for(d = dt->walk, o = (*(d->meth->searchf))(d,obj,type); ; )
      {     while(o)
            {     disc = d->disc;
                  here = (d->meth->type&(DT_SET|DT_BAG)) ?
                              d->data->here : NIL(Dtlink_t*);

                  for(p = dt; ; p = p->view)
                  {     reg Dtdisc_t*     dc;

                        if(p == d) /* this object is uncovered */ 
                              return o;

                        /* see if it is covered */
                        if(here && (p->meth->type&(DT_SET|DT_BAG)) &&
                           (disc == (dc = p->disc) ||
                            (disc->key == dc->key && disc->size == dc->size &&
                             disc->link == dc->link && disc->hashf == dc->hashf)))
                        {     if((*(p->meth->searchf))(p,here,DT_VSEARCH) )
                                    break;
                        }
                        else
                        {     if((*(p->meth->searchf))(p,o,DT_SEARCH) )
                                    break;
                        }
                  }

                  o = (*(d->meth->searchf))(d,o,type);
            }

            if(!(d = dt->walk = d->view) )
                  return NIL(Void_t*);

            if(type&DT_NEXT)
                  o = (*(d->meth->searchf))(d,NIL(Void_t*),DT_FIRST);
            else /* if(type&DT_PREV) */
                  o = (*(d->meth->searchf))(d,NIL(Void_t*),DT_LAST);
      }
}

#if __STD_C
Dt_t* dtview(reg Dt_t* dt, reg Dt_t* view)
#else
Dt_t* dtview(dt,view)
reg Dt_t*   dt;
reg Dt_t*   view;
#endif
{
      reg Dt_t*   d;

      UNFLATTEN(dt);
      if(view)
            UNFLATTEN(view);

      /* 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;
}

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