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att
GitHub Repository: att/ast
 Path: blob/master/src/cmd/dsslib/ip_t/ptdifference.c
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/***********************************************************************

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*                                                                      *

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*               This software is part of the ast package               *

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*          Copyright (c) 2000-2011 AT&T Intellectual Property          *

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*                      and is licensed under the                       *

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*                 Eclipse Public License, Version 1.0                  *

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*                    by AT&T Intellectual Property                     *

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*                                                                      *

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*                A copy of the License is available at                 *

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*          http://www.eclipse.org/org/documents/epl-v10.html           *

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*         (with md5 checksum b35adb5213ca9657e911e9befb180842)         *

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*                                                                      *

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*              Information and Software Systems Research               *

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*                            AT&T Research                             *

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*                           Florham Park NJ                            *

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*                                                                      *

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*                 Glenn Fowler <[email protected]>                  *

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*                   Phong Vo <[email protected]>                    *

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*                                                                      *

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***********************************************************************/

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#pragma prototyped

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#include "ptlib.h"

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/*

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 * return the table difference of a and b

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 */

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Pt_t*

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ptdifference(Pt_t* a, Pt_t* b)

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{

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	Pt_t*	t;

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	Ptprefix_t*	ap;

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	Ptprefix_t*	bp;

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	Ptaddr_t	m;

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	if (!(t = ptopen(a->disc)))

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		return 0;

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	m = 0;

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	ap = (Ptprefix_t*)dtfirst(a->dict);

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	bp = (Ptprefix_t*)dtfirst(b->dict);

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	while (ap)

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	{

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		if (!bp || ap->max < bp->min)

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		{

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			if (!ptinsert(t, ap->min, ap->max))

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				break;

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			ap = (Ptprefix_t*)dtnext(a->dict, ap);

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		}

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		else if (ap->min > bp->max)

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			bp = (Ptprefix_t*)dtnext(b->dict, bp);

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		else

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		{

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			if (ap->min < bp->min && !ptinsert(t, ap->min, bp->min - 1))

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				break;

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			if (ap->max < bp->max)

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				ap = (Ptprefix_t*)dtnext(a->dict, ap);

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			else if (ap->max == bp->max)

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			{

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				ap = (Ptprefix_t*)dtnext(a->dict, ap);

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				bp = (Ptprefix_t*)dtnext(b->dict, bp);

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			}

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			else

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			{

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				while (ap->max > bp->max)

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				{

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					m = bp->max + 1;

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					if (!(bp = (Ptprefix_t*)dtnext(b->dict, bp)) || bp->min > ap->max)

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					{

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						if (!ptinsert(t, m, ap->max))

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							goto done;

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						break;

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					}

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					if (bp->min > m && !ptinsert(t, m, bp->min - 1))

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						goto done;

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				}

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				ap = (Ptprefix_t*)dtnext(a->dict, ap);

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			}

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		}

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	}

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 done:

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	return t;

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}

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