usr/src/lib/libc/port/stdio/ftell.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1988 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"
  31
  32 /*
  33  * Return file offset.
  34  * Coordinates with buffering.
  35  */
  36 #pragma weak _ftell = ftell
  37
  38 #include "lint.h"
  39 #include "file64.h"
  40 #include "mtlib.h"
  41 #include <fcntl.h>
  42 #include <stdio.h>
  43 #include <thread.h>
  44 #include <synch.h>
  45 #include <errno.h>
  46 #include <unistd.h>
  47 #include <stddef.h>
  48 #include <limits.h>
  49 #include <sys/types.h>
  50 #include "stdiom.h"
  51
  52 long
  53 ftell(FILE *iop)
  54 {
  55         ptrdiff_t adjust;
  56         off64_t tres;
  57         rmutex_t *lk;
  58
  59         FLOCKFILE(lk, iop);
  60         if (iop->_cnt < 0)
  61                 iop->_cnt = 0;
  62         if (iop->_flag & _IOREAD)
  63                 adjust = (ptrdiff_t)-iop->_cnt;
  64         else if (iop->_flag & (_IOWRT | _IORW)) {
  65                 adjust = 0;
  66                 if (((iop->_flag & (_IOWRT | _IONBF)) == _IOWRT) &&
  67                     (iop->_base != 0))
  68                         adjust = iop->_ptr - iop->_base;
  69                 else if ((iop->_flag & _IORW) && (iop->_base != 0))
  70                         adjust = (ptrdiff_t)-iop->_cnt;
  71         } else {
  72                 errno = EBADF;  /* file descriptor refers to no open file */
  73                 FUNLOCKFILE(lk);
  74                 return (EOF);
  75         }
  76
  77         tres = lseek64(FILENO(iop), 0, SEEK_CUR);
  78         if (tres >= 0)
  79                 tres += adjust;
  80
  81         if (tres > LONG_MAX) {
  82                 errno = EOVERFLOW;
  83                 FUNLOCKFILE(lk);
  84                 return (EOF);
  85         }
  86
  87         FUNLOCKFILE(lk);
  88         return ((long)tres);
  89 }