/*  iumem.c - internal user memory management routines			 */
/*  ffit, freeit */

#ifndef	DBGIUMEM
#define	DBGIUMEM	0
#endif

/*
**  mods
**
**  mod no.	date       who	comments
**  ---------	---------  ---	--------
**  
**
*/

#include	"gportab.h"
#include	"fs.h"
#include	"bios.h"				/*  M01.01.02	*/
#include	"mem.h"
#include	"gemerror.h"


/*
**  STATIUMEM - cond comp; set to true to count calls to these routines
*/

#define	STATIUMEM	TRUE


#if	STATIUMEM

long	ccffit = 0 ;
long	ccfreeit = 0 ;

#endif

/*
**  ffit - find first fit for requested memory in ospool
*/

MD	*ffit(amount,mp)
	MPB	*mp;
	long	amount;
{
					/*  M01.01.03  */
	MD	*p,*q,*p1;		/* free list is composed of MD's */
	BOOLEAN	maxflg;
	long	maxval;

#if	STATIUMEM
	++ccffit ;
#endif

	if( (q = mp->mp_rover) == 0  )	/*  get rotating pointer	*/
	{
#if	DBGIUMEM
		kprintf("ffit: null rover\n") ;
#endif
		return( 0 ) ;
	}

	maxval = 0;
	maxflg = (amount == -1 ? TRUE : FALSE) ;

	p = q->m_link;			/*  start with next MD		*/

	do /* search the list for an MD with enough space */
	{

		if( p == 0 )
		{	/*  at end of list, wrap back to start  */
			q = (MD *) &mp->mp_mfl ;	/*  q => mfl field  */
			p = q->m_link ;			/*  p => 1st MD     */
		}

		if ((!maxflg) && (p->m_length >= amount)) 
		{ 	
			/*  big enough  */

			if (p->m_length == amount)
				/* take the whole thing */
				q->m_link = p->m_link;
			else 
			{	/* break it up - 1st allocate a new
					MD to describe the remainder */

				/*********** TBD **********
				*  Nicer Handling of This *
				*         Situation       *
				**************************/
				if( (p1=MGET(MD)) == 0 )
				{
#if	DBGIUMEM
					kprintf("ffit: Null Mget\n") ;
#endif
					return(0);
				}

				/*  init new MD  */

				p1->m_length = p->m_length - amount;
				p1->m_start = p->m_start + amount;
				p1->m_link = p->m_link;

				/*  adjust allocated block  */

				p->m_length = amount;
				q->m_link = p1;
			}

			/*  link allocate block into allocated list,
				mark owner of block, & adjust rover  */

			p->m_link = mp->mp_mal;
			mp->mp_mal = p;

			p->m_own = run;

			mp->mp_rover = 
				(q == (MD *) &mp->mp_mfl ? q->m_link : q);

			return(p);	/* got some */
		}
		else if (p->m_length > maxval)
			maxval = p->m_length;

		p = ( q=p )->m_link;

	} while (q != mp->mp_rover);

	/*  return either the max, or 0 (error)  */

#if	DBGIUMEM
	if( !maxflg )
		kprintf("ffit: Not Enough Contiguous Memory\n") ;
#endif
	return( maxflg ? (MD *) maxval : 0 ) ;
}


/*
**  freeit - Free up a memory descriptor
*/

freeit(m,mp)
MD *m;
MPB *mp;
{
	MD *p, *q;

#if	STATIUMEM
	++ccfreeit ;
#endif

	q = 0;

	for (p = mp->mp_mfl; p ; p = (q=p) -> m_link)
		if (m->m_start <= p->m_start)
			break;

	m->m_link = p;

	if (q)
		q->m_link = m;
	else
		mp->mp_mfl = m;

	if (!mp->mp_rover)
		mp->mp_rover = m;

	if (p)
		if (m->m_start + m->m_length == p->m_start)
		{ /* join to higher neighbor */
			m->m_length += p->m_length;
			m->m_link = p->m_link;

			if (p == mp->mp_rover)
				mp->mp_rover = m;

			xmfreblk(p);
		}

	if (q)
		if (q->m_start + q->m_length == m->m_start)
		{ /* join to lower neighbor */
			q->m_length += m->m_length;
			q->m_link = m->m_link;

			if (m == mp->mp_rover)
				mp->mp_rover = q;

			xmfreblk(m);
		}
}