unittrunc.c

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/*

  Copyright (C) 2000, 2001, Silicon Graphics, Inc.  All Rights Reserved.

  This program is free software; you can redistribute it and/or modify it
  under the terms of version 2.1 of the GNU Lesser General Public License 
  as published by the Free Software Foundation.

  This program is distributed in the hope that it would be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  

  Further, this software is distributed without any warranty that it is
  free of the rightful claim of any third person regarding infringement 
  or the like.  Any license provided herein, whether implied or 
  otherwise, applies only to this software file.  Patent licenses, if
  any, provided herein do not apply to combinations of this program with 
  other software, or any other product whatsoever.  

  You should have received a copy of the GNU Lesser General Public 
  License along with this program; if not, write the Free Software 
  Foundation, Inc., 59 Temple Place - Suite 330, Boston MA 02111-1307, 
  USA.

  Contact information:  Silicon Graphics, Inc., 1600 Amphitheatre Pky,
  Mountain View, CA 94043, or:

  http://www.sgi.com

  For further information regarding this notice, see:

  http://oss.sgi.com/projects/GenInfo/NoticeExplan

*/



#pragma ident "@(#) libf/fio/unittrunc.c        92.1    06/18/99 18:38:26"
 
#include <errno.h>
#include <liberrno.h>
#include <foreign.h>
#include <sys/types.h> 
#include <sys/stat.h> 
#include <unistd.h>
#include "fio.h"
#if     defined(__mips) || (defined(_LITTLE_ENDIAN) && defined(__sv2))
typedef long long _ftelltype;
#define LIBFSEEK fseek64 
#define LIBFTELL ftell64 
#define LIBFTRUNC ftruncate64
#else
typedef long _ftelltype;
#define LIBFSEEK fseek
#define LIBFTELL ftell
#define LIBFTRUNC ftruncate
#endif
/*
 *      _unit_trunc()
 *
 *              Truncate a file at its current position. 
 *
 *      Return value
 *
 *              0 for OK
 *              error code if an error is encountered
 */
int
_unit_trunc(unit *cup) 
{
        _ftelltype flength;
        FILE    *iop;
        
        if (cup->useq == 0)     /* If direct access file */ 
                return(0);      /* Don't truncate direct access files */

        switch(cup->ufs) {

        case FS_TEXT:
        case STD:

/*
 *              Truncate the file with trunc(2) if the file is a a regular 
 *              file.  The trunc(2) system call is not allowed on terminal 
 *              files, FIFO piped files, "/dev/null", or sockets.
 */
                if (cup->useek) {
                        iop = cup->ufp.std;

                        /*
                         * If stream is in O_APPEND mode (as when 'a.out>>ofil')
                         * we call fseek to current position.  Turns out that on
                         * SysV systems, ftell does not flush the buffer.  Thus
                         * the file offset does not get bumped to EOF as the
                         * result of the flush.
                         */
                        if (LIBFSEEK(iop, 0, SEEK_CUR) != 0)
                                return(errno);

                        flength = LIBFTELL(iop);        /* get current position */

                        /* position fd to the location of the truncation */
                        if (LIBFSEEK(iop, flength, SEEK_SET) != 0)
                                return(errno);
#ifdef  _UNICOS
                        if (trunc(fileno(iop)) == -1L) 
#else
                        if (LIBFTRUNC(fileno(iop), flength) == -1) 
#endif
                                return(errno);
                }
                break;

        case FS_FDC:
                if (XRCALL(cup->ufp.fdc, weodrtn)cup->ufp.fdc,
                        &cup->uffsw) < 0)
                        return(cup->uffsw.sw_error);
                break;

        default:
                return(FEINTFST);
        }

        return(0);
}