/*  fsbuf.c - buffer mgmt for file system				*/


/*
**  mods
**     date     who mod 		fix/change/note
**  ----------- --  ------------------	-------------------------------
**  27 May 1986 ktb M01.01.0527.02	moved makbuf to fsdir, as it was
**					only called from there and really had
**					nothing to do with cache buffers
*/


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


/*
**  flush -
**
**	Last modified	SCC	10 Apr 85
**
**	NOTE:	rwabs() is a macro that includes a longjmp() which is executed 
**		if the BIOS returns an error, therefore flush() does not need 
**		to return any error codes.
*/

flush(b)
REG BCB *b;
{
	int n,d;
	DMD *dm;

	/* if buffer not in use or not dirty, no work to do */

	if ((b->b_bufdrv == -1) || (!b->b_dirty))
	{
		b->b_bufdrv = -1;
		return;
	}

	dm = (DMD*) b->b_dm;		/*  media descr for buffer	*/
	n = b->b_buftyp;
	d = b->b_bufdrv;
	b->b_bufdrv = -1;		/* invalidate in case of error */

	rwabs(1,b->b_bufr,1,b->b_bufrec+dm->m_recoff[n],d);

	/* flush to both fats */

	if (n == 0) 
		rwabs(1,b->b_bufr,1,b->b_bufrec+dm->m_recoff[0]-dm->m_fsiz,d);

	b->b_bufdrv = d;			/* re-validate */
	b->b_dirty = 0;
}


/*
**  getrec -
**	return the ptr to the buffer containing the desired record
*/

char	*getrec(recn,dm,wrtflg)
	int	recn;
	int	wrtflg;
	REG DMD	*dm;
{
	REG BCB	*b;
	BCB	*p,*mtbuf,**q,**phdr;
	int n,cl,err;

	/* put bcb management here */

	cl = recn >> dm->m_clrlog;	/*  calculate cluster nbr	*/

	if (cl < dm->m_dtl->d_strtcl)
		n = 0;					/* FAT operat'n	*/
	else if (recn < 0)
		n = 1;					/*  DIR (?)	*/
	else
		n = 2;					/*  DATA (?)	*/

	mtbuf = 0;
	phdr = &bufl[(n != 0)];

	/*
	**  see if the desired record for the desired drive is in memory.
	**	if it is, we will use it.  Otherwise we will use
	**		the last invalid (available) buffer,  or
	**		the last (least recently) used buffer.
	*/

	for (b = *(q = phdr); b; b = *(q = &b->b_link))
	{
		if ((b->b_bufdrv == dm->m_drvnum) && (b->b_bufrec == recn))
			break;
		/*  
		**  keep track of the last invalid buffer
		*/
		if (b->b_bufdrv == -1)		/*  if buffer not valid	*/
			mtbuf = b;		/*    then it's 'empty'	*/
	}


	if (!b)
	{	/* 
		**  not in memory.  If there was an 'empty; buffer, use it.
		*/
		if (mtbuf)
			b = mtbuf;

		/*
		**  find predecessor of mtbuf, or last guy in list, which
		**  is the least recently used.
		*/

doio:		for (p = *(q = phdr); p->b_link; p = *(q = &p->b_link))
			if (b == p)
				break;
		b = p;

		/*
		**  flush the current contents of the buffer, and read in the 
		**	new record.
		*/

		flush(b);
		rwabs(0,b->b_bufr,1,recn+dm->m_recoff[n],dm->m_drvnum);

		/*
		**  make the new buffer current
		*/

		b->b_bufrec = recn;
		b->b_dirty = 0;
		b->b_buftyp = n;
		b->b_bufdrv = dm->m_drvnum;
		b->b_dm = (long) dm;
	}
	else
	{	/* use a buffer, but first validate media */
		if (err = trap13(9,b->b_bufdrv))
			if (err == 1)
				goto doio; /* media may be changed */
			else if (err == 2)
			{ /* media definitely changed */
				errdrv = b->b_bufdrv;
				rwerr = E_CHNG; /* media change */
				longjmp(errbuf,rwerr);
			}
	}

	/*
	**  now put the current buffer at the head of the list
	*/

	*q = b->b_link;
	b->b_link = *phdr;
	*phdr = b;

	/*
	**  if we are writing to the buffer, dirty it.
	*/

	if (wrtflg)
		b->b_dirty = 1;

	return(b->b_bufr);
}


/*
**  packit - pack into user buffer
*/

char	*packit(s,d)
	REG char *s,*d;
{ 
	char *s0;
	REG int i;

	if (!(*s))
		goto pakok;

	s0 = s;
	for (i=0; (i < 8) && (*s) && (*s != ' '); i++)
		*d++ = *s++;

	if (*s0 == '.')
		goto pakok;

	s = s0 + 8; /* ext */

	if (*s != ' ')
		*d++ = '.';
	else
		goto pakok;

	for (i=0; (i < 3) && (*s) && (*s != ' '); i++)
		*d++ = *s++;
pakok:	*d = 0;
	return(d);
}