source: buchla-68k/orig/IOLIB/READRN.C@ a838f5b

/*
   =============================================================================
        readrn.c -- read a random sector from a file
        Version 8 -- 1987-12-15 -- D.N. Lynx Crowe

        int
        ReadRN(fcp, buf)
        struct fcb *fcp;
        char *buf;

                Reads a sector from file 'fcp' into 'buf'.  Seeks as needed.
                Returns 0 if OK, -1 for errors, 1 for EOF (no data returned).
   =============================================================================
*/

#define DEBUGIT         0

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

#if     DEBUGIT
extern  short   fsdebug;
#endif

#if     TBUFFER
extern  long    _secrd();
#endif

extern  long    _berrno;
extern  int     _seek();

/* 

*/

/*
   =============================================================================
        ReadRN(fcp, buf) -- Reads a sector from file 'fcp' into 'buf'.
        Seeks as needed.  Returns SUCCESS (0) if OK,  FAILURE (-1) for errors.
   =============================================================================
*/

int
ReadRN(fcp, buf)
struct fcb *fcp;
char *buf;
{
        int     sv;             /* seek return code */
        long    brc;            /* bios return code */

        if (sv = _seek(fcp))            /* try to find the sector we want */
                if (sv < 0) {

                        errno = EIO;            /* I/O error */
                        return(-1);             /* return:  ERROR */

                } else {

                        errno = EINVAL;         /* invalid argument */
                        return(1);              /* return:  EOF */
                }

#if     DEBUGIT
        if (fsdebug)
                printf("ReadRN():  curlsn=%ld, curdsn=%ld, offset=%u\n",
                        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;                    /* ... as an I/O error */
                return(FAILURE);                /* return:  ERROR */
        }

        return(SUCCESS);                /* return:  SUCCESS */
}