source: buchla-68k/libcio/posit.c@ bc11fc1

/*
   =============================================================================
        posit.c -- position a file to a specific relative sector
        Version 4 -- 1987-06-29 -- D.N. Lynx Crowe
   =============================================================================
*/

#include "biosdefs.h"
#include "io.h"
#include "errno.h"
#include "stddefs.h"

extern  int16_t _seek(struct fcb *fcp);

/*
   =============================================================================
        posit(fd, pos) -- position file 'fd' at sector 'pos'.
   =============================================================================
*/

int16_t posit(int16_t fd, uint16_t pos)
{
        register struct fcb *fp;

        if ((fd < 0) OR (fd > MAXCHAN)) {

                errno = EBADF;
                return(FAILURE);
        }

        fp = chantab[fd].c_arg;

        if ((chantab[fd].c_seek EQ 0)
            OR ((pos << FILESHFT) > fp->curlen)) {

                errno = EINVAL;
                fp->modefl |= FC_ERR;
                return(FAILURE);
        }

        fp->curlsn = pos;
        fp->offset = 0;

        if (_seek(fp) < 0) {

                errno = EIO;
                fp->modefl |= FC_ERR;
                return(FAILURE);
        }

        return(SUCCESS);
}