stdio/FreeBSD/ftell.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Chris Torek.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 static char sccsid[] = "@(#)ftell.c     8.2 (Berkeley) 5/4/95";
  39 #endif /* LIBC_SCCS and not lint */
  40 #include <sys/cdefs.h>
  41 __FBSDID("$FreeBSD: src/lib/libc/stdio/ftell.c,v 1.26 2002/03/22 21:53:04 obrien Exp $");
  42
  43 #include "namespace.h"
  44 #include <sys/types.h>
  45 #include <errno.h>
  46 #include <limits.h>
  47 #include <stdio.h>
  48 #include "un-namespace.h"
  49 #include "local.h"
  50 #include "libc_private.h"
  51
  52 /*
  53  * standard ftell function.
  54  */
  55 long
  56 ftell(fp)
  57         FILE *fp;
  58 {
  59         off_t rv;
  60
  61         rv = ftello(fp);
  62         if (rv > LONG_MAX) {
  63                 errno = EOVERFLOW;
  64                 return (-1);
  65         }
  66         return (rv);
  67 }
  68
  69 /*
  70  * ftello: return current offset.
  71  */
  72 off_t
  73 ftello(fp)
  74         FILE *fp;
  75 {
  76         fpos_t rv;
  77         int ret;
  78
  79         FLOCKFILE(fp);
  80         ret = _ftello(fp, &rv);
  81         FUNLOCKFILE(fp);
  82         if (ret)
  83                 return (-1);
  84         if (rv < 0) {   /* Unspecified value because of ungetc() at 0 */
  85                 errno = ESPIPE;
  86                 return (-1);
  87         }
  88         return (rv);
  89 }
  90
  91 int
  92 _ftello(fp, offset)
  93         FILE *fp;
  94         fpos_t *offset;
  95 {
  96         fpos_t pos;
  97         size_t n;
  98
  99         if (fp->_seek == NULL) {
 100                 errno = ESPIPE;                 /* historic practice */
 101                 return (1);
 102         }
 103
 104         /*
 105          * Find offset of underlying I/O object, then
 106          * adjust for buffered bytes.
 107          */
 108         if (fp->_flags & __SOFF)
 109                 pos = fp->_offset;
 110         else {
 111                 pos = _sseek(fp, (fpos_t)0, SEEK_CUR);
 112                 if (pos == -1)
 113                         return (1);
 114         }
 115         if (fp->_flags & __SRD) {
 116                 /*
 117                  * Reading.  Any unread characters (including
 118                  * those from ungetc) cause the position to be
 119                  * smaller than that in the underlying object.
 120                  */
 121                 if ((pos -= (HASUB(fp) ? fp->_ur : fp->_r)) < 0) {
 122                         fp->_flags |= __SERR;
 123                         errno = EIO;
 124                         return (1);
 125                 }
 126                 if (HASUB(fp))
 127                         pos -= fp->_r;  /* Can be negative at this point. */
 128         } else if ((fp->_flags & __SWR) && fp->_p != NULL) {
 129                 /*
 130                  * Writing.  Any buffered characters cause the
 131                  * position to be greater than that in the
 132                  * underlying object.
 133                  */
 134                 n = fp->_p - fp->_bf._base;
 135                 if (pos > OFF_MAX - n) {
 136                         errno = EOVERFLOW;
 137                         return (1);
 138                 }
 139                 pos += n;
 140         }
 141         *offset = pos;
 142         return (0);
 143 }