source: trunk/minix/lib/stdio/fseek.c@ 15

/*
 * fseek.c - perform an fseek
 */
/* $Header: /cvsup/minix/src/lib/stdio/fseek.c,v 1.1.1.1 2005/04/21 14:56:35 beng Exp $ */

#include        <stdio.h>

#if     (SEEK_CUR != 1) || (SEEK_END != 2) || (SEEK_SET != 0)
#error SEEK_* values are wrong
#endif

#include        "loc_incl.h"

#include        <sys/types.h>

off_t _lseek(int fildes, off_t offset, int whence);

int
fseek(FILE *stream, long int offset, int whence)
{
        int adjust = 0;
        long pos;

        stream->_flags &= ~(_IOEOF | _IOERR);
        /* Clear both the end of file and error flags */

        if (io_testflag(stream, _IOREADING)) {
                if (whence == SEEK_CUR
                    && stream->_buf
                    && !io_testflag(stream,_IONBF))
                        adjust = stream->_count;
                stream->_count = 0;
        } else if (io_testflag(stream,_IOWRITING)) {
                fflush(stream);
        } else  /* neither reading nor writing. The buffer must be empty */
                /* EMPTY */ ;

        pos = _lseek(fileno(stream), offset - adjust, whence);
        if (io_testflag(stream, _IOREAD) && io_testflag(stream, _IOWRITE))
                stream->_flags &= ~(_IOREADING | _IOWRITING);

        stream->_ptr = stream->_buf;
        return ((pos == -1) ? -1 : 0);
}