blok.c

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· C语言 代码 · 共 243 行

#ifndef lint
static CHTYPE *sccsid = "@(#)blok.c	4.1      7/17/90";
#endif lint

/************************************************************************
 *									*
 *			Copyright (c) 1986 by				*
 *		Digital Equipment Corporation, Maynard, MA		*
 *			All rights reserved.				*
 *									*
 *   This software is furnished under a license and may be used and	*
 *   copied  only  in accordance with the terms of such license and	*
 *   with the  inclusion  of  the  above  copyright  notice.   This	*
 *   software  or  any  other copies thereof may not be provided or	*
 *   otherwise made available to any other person.  No title to and	*
 *   ownership of the software is hereby transferred.			*
 *									*
 *   This software is  derived  from  software  received  from  the	*
 *   University    of   California,   Berkeley,   and   from   Bell	*
 *   Laboratories.  Use, duplication, or disclosure is  subject  to	*
 *   restrictions  under  license  agreements  with  University  of	*
 *   California and with AT&T.						*
 *									*
 *   The information in this software is subject to change  without	*
 *   notice  and should not be construed as a commitment by Digital	*
 *   Equipment Corporation.						*
 *									*
 *   Digital assumes no responsibility for the use  or  reliability	*
 *   of its software on equipment which is not supplied by Digital.	*
 *									*
 ************************************************************************/
/*
 *
 *   Modification History:
 *
 * 001 - Gary Gaudet for Andy Gadsby 09-mar-88
 *	i18n version of csh
 *
 *
 *
 */

/*
 *	UNIX shell
 *
 *	Bell Telephone Laboratories
 *
 */

#include	"defs.h"


/*
 *	storage allocator
 *	(circular first fit strategy)
 */

#define BUSY 01
#define busy(x)	(Rcheat((x)->word) & BUSY)

unsigned	brkincr = BRKINCR;
struct blk *blokp;			/*current search pointer*/
struct blk *bloktop;		/* top of arena (last blok) */

CHTYPE		*brkbegin;
CHTYPE		*setbrk();

CHTYPE *
alloc(nbytes)
	unsigned nbytes;
{
	register unsigned rbytes = round(nbytes + BYTESPERWORD, BYTESPERWORD);

	for (;;)
	{
		int	c = 0;
		register struct blk *p = blokp;
		register struct blk *q;

		do
		{
			if (!busy(p))
			{
				while (!busy(q = p->word))
					p->word = q->word;
				if ((char *)q - (char *)p >= rbytes)
				{
					blokp = (struct blk *)((char *)p + rbytes);
					if (q > blokp)
						blokp->word = p->word;
					p->word = (struct blk *)(Rcheat(blokp) | BUSY);
					return((CHTYPE *)(p + 1));
				}
			}
			q = p;
			p = (struct blk *)(Rcheat(p->word) & ~BUSY);
		} while (p > q || (c++) == 0);
		addblok(rbytes);
	}
}

addblok(reqd)
	unsigned reqd;
{
	if (stakbot == 0)
	{
		brkbegin = setbrk(3 * BRKINCR);
		bloktop = (struct blk *)brkbegin;
	}

	if (stakbas != staktop)
	{
		register CHTYPE *rndstak;
		register struct blk *blokstak;

		pushstak(0);
		rndstak = (CHTYPE *)round(staktop, BYTESPERWORD);
		blokstak = (struct blk *)(stakbas) - 1;
		blokstak->word = stakbsy;
		stakbsy = blokstak;
		bloktop->word = (struct blk *)(Rcheat(rndstak) | BUSY);
		bloktop = (struct blk *)(rndstak);
	}
	reqd += brkincr;
	reqd &= ~(brkincr - 1);
	blokp = bloktop;
	bloktop = bloktop->word = (struct blk *)(Rcheat(bloktop) + reqd);
	if ((CHTYPE *) bloktop >= brkend) {	/* GAG - error check  from MIPS */
		if (setbrk(brkincr) == (CHTYPE *)-1) {
			error(nospace);
		}
	}
	/* 
	 * the following expression sets the busy bit 
	 */
	bloktop->word = (struct blk *)((char *)brkbegin + 1);
	{
		register CHTYPE *stakadr = (CHTYPE *)(bloktop + 2);

		if (stakbot != staktop)
			staktop = movstr(stakbot, stakadr);
		else
			staktop = stakadr;

		stakbas = stakbot = stakadr;
	}
}

free(ap)
	struct blk *ap;
{
	register struct blk *p;

	if ((p = ap) && p < bloktop)
	{
#ifdef DEBUG
		chkbptr(p);
#endif
		--p;
		p->word = (struct blk *)(Rcheat(p->word) & ~BUSY);
	}


}


#ifdef DEBUG

chkbptr(ptr)
	struct blk *ptr;
{
	int	exf = 0;
	register struct blk *p = (struct blk *)brkbegin;
	register struct blk *q;
	int	us = 0, un = 0;

	for (;;)
	{
		q = (struct blk *)(Rcheat(p->word) & ~BUSY);

		if (p+1 == ptr)
			exf++;

		if (q < (struct blk *)brkbegin || q > bloktop)
			abort(3);

		if (p == bloktop)
			break;

		if (busy(p))
			us += q - p;
		else
			un += q - p;

		if (p >= q)
			abort(4);

		p = q;
	}
	if (exf == 0)
		abort(1);
}


chkmem()
{
	register struct blk *p = (struct blk *)brkbegin;
	register struct blk *q;
	int	us = 0, un = 0;

	for (;;)
	{
		q = (struct blk *)(Rcheat(p->word) & ~BUSY);

		if (q < (struct blk *)brkbegin || q > bloktop)
			abort(3);

		if (p == bloktop)
			break;

		if (busy(p))
			us += q - p;
		else
			un += q - p;

		if (p >= q)
			abort(4);

		p = q;
	}

	prs("un/used/avail ");
	prn(un);
	blank();
	prn(us);
	blank();
	prn((CHTYPE *)bloktop - brkbegin - (un + us));
	newline();

}

#endif