/*  fsdrive.c - physical drive routines for file system			*/

/*
**    date      who     comment
**  ---------	---	-------
**  21 Mar 86	ktb	M01.01.20 - ckdrv() returns EINTRN if no slots
**			avail in dirtbl.
**
**  15 Sep 86	scc	M01.01.0915.02	ckdrv() now checks for negative error
**					return from BIOS
**
**   7 Oct 86	scc	M01.01.1007.01  cast several pointers to longs when
**			they are compared to 0.
**
**  31 Oct 86	scc	M01.01.1031.01  removed definition of drvmap.  It was used on
**			the assumption that the drive map would not change after boot
**			time, which is not the case in BNR land.  Also removed
**			ValidDrv(), which checked it.  Corresponding change made in
**			xgetdir() in FSDIR.C
**
*/


#include	"gportab.h"
#include	"fs.h"
#include	"bios.h"		/*  M01.01.01			*/
#include	"gemerror.h"

/*
**  globals
*/

	/*
	**  dirtbl - default directories.
	**	Each entry points to the DND for someone's default directory.
	**	They are linked to each process by the p_curdir entry in the PD.
	**	The first entry (dirtbl[0]) is not used, as p_curdir[i]==0
	**	means 'none set yet'.
	*/

	DND	*dirtbl[NCURDIR] ;

	/*
	**  diruse - use count 
	**  drvsel - mask of drives selected since power up
	*/

	char	diruse[NCURDIR] ;
	int	drvsel ;


/*
**  ckdrv - check the drive, see if it needs to be logged in.
**
**  returns:
**	ERR	if getbpb() failed
**	ENSMEM	if log() failed
**	EINTRN	if no room in dirtbl
**	drive nbr if success.
*/

long	ckdrv(d)
	int d; /* has this drive been accessed, or had a media change */
{
	int mask,i;
	BPB *b;

	mask = 1 << d;

	if (!(mask & drvsel))
	{	/*  drive has not been selected yet  */
		b = (BPB *) getbpb(d);

		if ( !(long)b )			/* M01.01.1007.01 */
			return(ERR);
		if ( (long)b < 0 ) /* M01.01.0915.02 */ /* M01.01.1007.01 */
			return( (long)b );

		if (log(b,d))
			return (ENSMEM);

		drvsel |= mask;
	}

	if ((!run->p_curdir[d]) || (!dirtbl[run->p_curdir[d]]))
	{	/* need to allocate current dir on this drv */

		for (i = 1; i < NCURDIR; i++)	/*  find unused slot	*/
			if (!diruse[i])
				break;

		if (i == NCURDIR)		/*  no slot available	*/
			return( EINTRN ) ; 	/*  M01.01.20		*/

		diruse[i]++;			/*  mark as used	*/
		dirtbl[i] = drvtbl[d]->m_dtl;	/*  link to DND		*/
		run->p_curdir[d] = i;		/*  link to process	*/
	}

	return(d);
}



/*
**  getdmd - allocate storage for and initialize a DMD
*/

DMD	*getdmd(drv)
	int drv;
{
	DMD *dm;

	if (!(drvtbl[drv] = dm = MGET(DMD)))
		return ( (DMD *) 0 );

	if (!(dm->m_dtl = MGET(DND)))
		goto fredm;

	if (!(dm->m_dtl->d_ofd = MGET(OFD)))
		goto fredtl;

	if (!(dm->m_fatofd = MGET(OFD)))
		goto freofd;

	return(dm);

freofd:	xmfreblk (dm->m_dtl->d_ofd);
fredtl:	xmfreblk (dm->m_dtl);
fredm:	xmfreblk (dm);

	return ( (DMD *) 0 );
}



/*
**  log -
**	log in media 'b' on drive 'drv'.
**
*/

long	log(b,drv) 
	BPB *b;			/*  bios parm block for drive		*/
	int drv;		/*  drive number			*/
{
	OFD *fo,*f;				/*  M01.01.03	*/
	DND *d;
	DMD *dm;
	int rsiz,cs,n,fs,ncl,fcl;

	rsiz = b->recsiz;
	cs = b->clsiz;
	n = b->rdlen;
	fs = b->fsiz;

	if (!(dm = getdmd(drv)))
		return (ENSMEM);

	d = dm->m_dtl;			/*  root DND for drive		*/
	dm->m_fsiz = fs;		/*  fat size 			*/
	f = d->d_ofd;			/*  root dir file 		*/
	dm->m_drvnum = drv;		/*  drv nbr into media descr	*/
	f->o_dmd = dm;			/*  link to OFD for rt dir file	*/

	d->d_drv = dm;			/*  link root DND with DMD	*/
	d->d_name[0] = 0;		/*  null out name of root	*/

	dm->m_16 = b->b_flags & B_16;	/*  set 12 or 16 bit fat flag	*/
	dm->m_clsiz = cs;		/*  set cluster size in sectors	*/
	dm->m_clsizb = b->clsizb;	/*    and in bytes		*/
	dm->m_recsiz = rsiz;		/*  set record (sector) size	*/
	dm->m_numcl = b->numcl;		/*  set cluster size in records	*/
	dm->m_clrlog = log2(cs);	/*    and log of it		*/
	dm->m_clrm = logmsk[dm->m_clrlog];	/*  and mask of it	*/
	dm->m_rblog = log2(rsiz);	/*  set log of bytes/record	*/
	dm->m_rbm = logmsk[dm->m_rblog];	/*  and mask of it	*/
	dm->m_clblog = log2(dm->m_clsizb);	/*  log of bytes/clus	*/

	f->o_fileln = n * rsiz;		/*  size of file (root dir)	*/


	ncl = (n + cs - 1)/cs;		/* number of "clusters" in root	*/
	d->d_strtcl = f->o_strtcl = -1 - ncl;	/*  root start clus	*/
	fcl = (fs + cs - 1)/cs;

	fo = dm->m_fatofd;		/*  OFD for 'fat file'		*/
	fo->o_strtcl = d->d_strtcl - fcl;	/*  start clus for fat	*/
	fo->o_dmd = dm;			/*  link with DMD		*/

	dm->m_recoff[0] = b->fatrec - (fo->o_strtcl * cs);
	dm->m_recoff[1] = (b->fatrec + fs) - (d->d_strtcl * cs);

	/* 2 is first data cluster */

	dm->m_recoff[2] = b->datrec - (2 * cs);

	fo->o_bytnum = 3;
	fo->o_curbyt = 3;
	fo->o_fileln = fs * rsiz;

	return (0L);
}


/*
**  log2 -
**	return log base 2 of n
*/

int	log2(n) 
	int n;
{
	int i;

	for (i = 0; n ; i++)
		n >>= 1;

	return(i-1);
}