source: buchla-68k/libcio/blkrd.c@ 109c83b

/*
   =============================================================================
        blkrd.c -- read a block of 0..32767 sectors
        Version 10 -- 1988-01-08 -- D.N. Lynx Crowe

        int
        blkrd(fcp, buf, ns)
        struct fcb *fcp;
        char *buf;
        int ns;

                Reads 'ns' sectors from file 'fcp' into 'buf'.
                Returns the number of unread sectors, or 0 if all were read.

        long
        _secrd(buf, rec)
        register char *buf;
        register short rec;

                Reads a logical sector via the track buffer.
                Functionally equivalent to the BIOS B_RDWR read function
                with the addition of transparent write-thru track buffering.
   =============================================================================
*/

#define DEBUGIT         0

#include "stddefs.h"
#include "biosdefs.h"
#include "errno.h"
#include "errdefs.h"
#include "fspars.h"

/* 

*/

#if     DEBUGIT
extern  short   fsdebug;                /* file system debug switch */
#endif

extern  int     _nsic();                /* next sector function */

extern  long    _berrno;                /* last file system bios error number */

extern  short   _thefat[];              /* current file allocation table */

extern  struct  bpb     *_thebpb;       /* current bios parameter block */

#if     TBUFFER

/* WARNING:  this ONLY works for 512 byte sectors, 9 sectors per track */

extern  short   _b_tbuf[9][256];        /* the track buffer */

extern  short   _b_trak;                /* current track */
extern  short   _b_side;                /* current side */
extern  short   _b_sect;                /* current sector */
extern  short   _b_tsec;                /* current base sector of current track */

#endif

/* 

*/

#if     TBUFFER

/*
   =============================================================================
        _secrd(buf, rec) -- read a logical sector via the track buffer
   =============================================================================
*/

long
_secrd(buf, rec)
register char *buf;
register short rec;
{
        register short  track, side, sector;
        long brc;

        if (_thebpb->dspt NE 9)                 /* make sure we can do this */
                return(ERR07);

        if (_thebpb->recsiz NE 512)
                return(ERR07);

        track = rec / _thebpb->dspc;            /* desired track */
        _b_tsec = track * _thebpb->dspc;        /* base sector of track */
        sector = rec - _b_tsec;                 /* logical sector in cylinder */

        if (sector GE _thebpb->dspt) {          /* adjust sector and side */

                sector -= _thebpb->dspt;        /* sector now in track */
                side = 1;
                _b_tsec += _thebpb->dspt;

        } else {

                side = 0;
        }

#if     DEBUGIT
        if (fsdebug)
                printf("_secrd($%08.8LX, %d):  track=%d, side=%d, sector=%d, _b_tsec=%d\n",
                        buf, rec, track, side, sector, _b_tsec);
#endif

        if ((track NE _b_trak) OR (side NE _b_side)) {  /* track in buffer ? */

                if (brc = BIOS(B_RDWR, 0, &_b_tbuf, _thebpb->dspt, _b_tsec, 0)) {

                        _b_trak = -1;
                        _b_side = -1;
                        return(brc);
                }

                _b_trak = track;
                _b_side = side;
        }

        memcpy(buf, (char *)_b_tbuf[sector], 512);
        return(0L);
}

#endif

/* 

*/

/*
   =============================================================================
        blkrd(fcp, buf, ns) -- read 'ns' sectors from file 'fcp' into 'buf'.
        Returns the number of unread sectors, or 0 if all were read.
   =============================================================================
*/

int
blkrd(fcp, buf, ns)
register struct fcb *fcp;
register char *buf;
register int ns;
{
        register long   brc;            /* bios return code */
        register int    rb;             /* _nsic return code */

        if (ns < 0)             /* can't read a negative number of sectors */
                return(ns);

        while (ns--) {          /* read a sector at a time */

#if     DEBUGIT
        if (fsdebug)
                printf("_blkrd():  ns=%d, buf=$%08.8lX, curlsn=%ld, curdsn=%ld, offset=%u\n",
                        ns, buf, fcp->curlsn, fcp->curdsn, fcp->offset);
#endif

#if     TBUFFER
                if (brc = _secrd(buf, (short)fcp->curdsn)) {
#else
                if (brc = BIOS(B_RDWR, 0, buf, 1, (short)fcp->curdsn, 0)) {
#endif

                        _berrno = brc;          /* log the error */
                        errno = EIO;
                        return(ns);             /* return unread sector count */
                }

                if (rb = _nsic(fcp, _thebpb, _thefat)) {  /* find next sector */

                        if (rb EQ -1)           /* see if we had an error */
                                errno = EIO;    /* set error number */

                        return(ns);     /* return unread sector count */
                }

                buf += _thebpb->recsiz;         /* advance buffer pointer */
        }

        return(0);      /* return -- all sectors read */
}