/* $Header: /cvsup/minix/src/lib/ack/libp/dis.c,v 1.1 2005/10/10 15:27:46 beng Exp $ *//* * (c) copyright 1983 by the Vrije Universiteit, Amsterdam, The Netherlands. * *          This product is part of the Amsterdam Compiler Kit. * * Permission to use, sell, duplicate or disclose this software must be * obtained in writing. Requests for such permissions may be sent to * *      Dr. Andrew S. Tanenbaum *      Wiskundig Seminarium *      Vrije Universiteit *      Postbox 7161 *      1007 MC Amsterdam *      The Netherlands * *//* Author: J.W. Stevenson */#include	<pc_err.h>#define assert()	/* nothing *//* * use circular list of free blocks from low to high addresses * _highp points to free block with highest address */struct adm {	struct adm	*next;	int		size;};extern struct adm	*_lastp;extern struct adm	*_highp;extern			_trp();static int merge(p1,p2) struct adm *p1,*p2; {	struct adm *p;	p = (struct adm *)((char *)p1 + p1->size);	if (p > p2)		_trp(EFREE);	if (p != p2)		return(0);	p1->size += p2->size;	p1->next = p2->next;	return(1);}_dis(n,pp) int n; struct adm **pp; {	struct adm *p1,*p2;	/*	 * NOTE: dispose only objects whose size is a multiple of sizeof(*pp).	 *       this is always true for objects allocated by _new()	 */	n = ((n+sizeof(*p1)-1) / sizeof(*p1)) * sizeof(*p1);	if (n == 0)		return;	if ((p1= *pp) == (struct adm *) 0)		_trp(EFREE);	p1->size = n;	if ((p2 = _highp) == 0)  /*p1 is the only free block*/		p1->next = p1;	else {		if (p2 > p1) {			/*search for the preceding free block*/			if (_lastp < p1)  /*reduce search*/				p2 = _lastp;			while (p2->next < p1)				p2 = p2->next;		}		/* if p2 preceeds p1 in the circular list,		 * try to merge them			*/		p1->next = p2->next; p2->next = p1;		if (p2 <= p1 && merge(p2,p1))			p1 = p2;		p2 = p1->next;		/* p1 preceeds p2 in the circular list */		if (p2 > p1) merge(p1,p2);	}	if (p1 >= p1->next)		_highp = p1;	_lastp = p1;	*pp = (struct adm *) 0;}