stdio.subproj/ftell.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * Copyright (c) 1990, 1993
  24  *      The Regents of the University of California.  All rights reserved.
  25  *
  26  * This code is derived from software contributed to Berkeley by
  27  * Chris Torek.
  28  *
  29  * Redistribution and use in source and binary forms, with or without
  30  * modification, are permitted provided that the following conditions
  31  * are met:
  32  * 1. Redistributions of source code must retain the above copyright
  33  *    notice, this list of conditions and the following disclaimer.
  34  * 2. Redistributions in binary form must reproduce the above copyright
  35  *    notice, this list of conditions and the following disclaimer in the
  36  *    documentation and/or other materials provided with the distribution.
  37  * 3. All advertising materials mentioning features or use of this software
  38  *    must display the following acknowledgement:
  39  *      This product includes software developed by the University of
  40  *      California, Berkeley and its contributors.
  41  * 4. Neither the name of the University nor the names of its contributors
  42  *    may be used to endorse or promote products derived from this software
  43  *    without specific prior written permission.
  44  *
  45  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  46  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  47  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  48  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  49  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  50  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  51  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  52  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  53  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  54  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  55  * SUCH DAMAGE.
  56  */
  57
  58
  59 #include <sys/types.h>
  60 #include <stdio.h>
  61 #include <errno.h>
  62 #include "local.h"
  63
  64 /*
  65  * ftello: return current offset.
  66  */
  67 off_t
  68 ftello(fp)
  69         register FILE *fp;
  70 {
  71         register fpos_t pos;
  72
  73         if (fp->_seek == NULL) {
  74                 errno = ESPIPE;                 /* historic practice */
  75                 return (-1L);
  76         }
  77
  78         /* FLOCKFILE(fp); */
  79         /*
  80          * Find offset of underlying I/O object, then
  81          * adjust for buffered bytes.
  82          */
  83         if (fp->_flags & __SOFF)
  84                 pos = fp->_offset;
  85         else {
  86                 pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR);
  87                 if (pos == -1) {
  88                         /* FUNLOCKFILE(fp); */
  89                         return (pos);
  90                 }
  91         }
  92         if (fp->_flags & __SRD) {
  93                 /*
  94                  * Reading.  Any unread characters (including
  95                  * those from ungetc) cause the position to be
  96                  * smaller than that in the underlying object.
  97                  */
  98                 pos -= fp->_r;
  99                 if (HASUB(fp))
 100                         pos -= fp->_ur;
 101         } else if (fp->_flags & __SWR && fp->_p != NULL) {
 102                 /*
 103                  * Writing.  Any buffered characters cause the
 104                  * position to be greater than that in the
 105                  * underlying object.
 106                  */
 107                 pos += fp->_p - fp->_bf._base;
 108         }
 109         /* FUNLOCKFILE(fp); */
 110         return (pos);
 111 }
 112
 113 /*
 114  * standard ftell function.
 115  */
 116 long
 117 ftell(fp)
 118         register FILE *fp;
 119 {
 120         register off_t rv;
 121         rv = ftello(fp);
 122         if ((long)rv != rv) {
 123                 errno = EOVERFLOW;
 124                 return (-1);
 125         }
 126         return (rv);
 127 }