/* 
 * (c) The GRASP/AQUA Project, Glasgow University, 1994-1998
 *
 * $Id: filePosn.c,v 1.3 1998/12/02 13:27:27 simonm Exp $
 *
 * hGetPosn and hSetPosn Runtime Support
 */

#include "Rts.h"
#include "stgio.h"

StgInt
getFilePosn(ptr)
StgForeignPtr ptr;
{
    IOFileObject* fo = (IOFileObject*)ptr;
    StgInt posn;
   
    while ( (posn = lseek(fo->fd, 0, SEEK_CUR)) == -1) {
	if (errno != EINTR) {
	    cvtErrno();
	    stdErrno();
	    return -1;
	}
    }
    if (fo->flags & FILEOBJ_WRITE)  {
       posn += fo->bufWPtr;
    } else if (fo->flags & FILEOBJ_READ) {
       posn -= (fo->bufWPtr - fo->bufRPtr);
    }
    return posn;
}

/* The following is only called with a position that we've already visited 
   (this is ensured by making the Haskell file posn. type abstract.)
*/
StgInt
setFilePosn(ptr, posn)
StgForeignPtr ptr;
StgInt posn;
{
    IOFileObject* fo = (IOFileObject*)ptr;
    int rc;

    rc = flushBuffer(ptr);
    if (rc < 0) return rc;

    while (lseek(fo->fd, posn, SEEK_SET) == -1) {
	if (errno != EINTR) {
	    cvtErrno();
	    stdErrno();
	    return -1;
	}
    }
    FILEOBJ_CLEAR_EOF(fo);
    return 0;
}