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dtview.c

/***********************************************************************
*                                                                      *
*               This software is part of the ast package               *
*          Copyright (c) 1985-2007 AT&T Intellectual Property          *
*                      and is licensed under the                       *
*                  Common Public License, Version 1.0                  *
*                    by AT&T Intellectual Property                     *
*                                                                      *
*                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
{
      Dt_t        *d, *p;
      Void_t            *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_t*);

            n = nk = NIL(Void_t*); 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_t*);

      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_t*);
      }

      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_t*);
            else if(type&DT_NEXT)
                  obj = (*(d->meth->searchf))(d,NIL(Void_t*),DT_FIRST);
            else  obj = (*(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);
            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;
}

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