stdio/ftell.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * Copyright (c) 1990, 1993
  27  *      The Regents of the University of California.  All rights reserved.
  28  *
  29  * This code is derived from software contributed to Berkeley by
  30  * Chris Torek.
  31  *
  32  * Redistribution and use in source and binary forms, with or without
  33  * modification, are permitted provided that the following conditions
  34  * are met:
  35  * 1. Redistributions of source code must retain the above copyright
  36  *    notice, this list of conditions and the following disclaimer.
  37  * 2. Redistributions in binary form must reproduce the above copyright
  38  *    notice, this list of conditions and the following disclaimer in the
  39  *    documentation and/or other materials provided with the distribution.
  40  * 3. All advertising materials mentioning features or use of this software
  41  *    must display the following acknowledgement:
  42  *      This product includes software developed by the University of
  43  *      California, Berkeley and its contributors.
  44  * 4. Neither the name of the University nor the names of its contributors
  45  *    may be used to endorse or promote products derived from this software
  46  *    without specific prior written permission.
  47  *
  48  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  49  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  50  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  51  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  52  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  53  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  54  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  55  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  56  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  57  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  58  * SUCH DAMAGE.
  59  */
  60
  61
  62 #include <sys/types.h>
  63 #include <stdio.h>
  64 #include <errno.h>
  65 #include "local.h"
  66
  67 /*
  68  * ftello: return current offset.
  69  */
  70 off_t
  71 ftello(fp)
  72         register FILE *fp;
  73 {
  74         register fpos_t pos;
  75
  76         if (fp->_seek == NULL) {
  77                 errno = ESPIPE;                 /* historic practice */
  78                 return (-1L);
  79         }
  80
  81         /* FLOCKFILE(fp); */
  82         /*
  83          * Find offset of underlying I/O object, then
  84          * adjust for buffered bytes.
  85          */
  86         if (fp->_flags & __SOFF)
  87                 pos = fp->_offset;
  88         else {
  89                 pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR);
  90                 if (pos == -1) {
  91                         /* FUNLOCKFILE(fp); */
  92                         return (pos);
  93                 }
  94         }
  95         if (fp->_flags & __SRD) {
  96                 /*
  97                  * Reading.  Any unread characters (including
  98                  * those from ungetc) cause the position to be
  99                  * smaller than that in the underlying object.
 100                  */
 101                 pos -= fp->_r;
 102                 if (HASUB(fp))
 103                         pos -= fp->_ur;
 104         } else if (fp->_flags & __SWR && fp->_p != NULL) {
 105                 /*
 106                  * Writing.  Any buffered characters cause the
 107                  * position to be greater than that in the
 108                  * underlying object.
 109                  */
 110                 pos += fp->_p - fp->_bf._base;
 111         }
 112         /* FUNLOCKFILE(fp); */
 113         return (pos);
 114 }
 115
 116 /*
 117  * standard ftell function.
 118  */
 119 long
 120 ftell(fp)
 121         register FILE *fp;
 122 {
 123         register off_t rv;
 124         rv = ftello(fp);
 125         if ((long)rv != rv) {
 126                 errno = EOVERFLOW;
 127                 return (-1);
 128         }
 129         return (rv);
 130 }