lib/libc/stdio/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  * @(#)ftell.c  8.2 (Berkeley) 5/4/95
  37  * $FreeBSD: src/lib/libc/stdio/ftell.c,v 1.11 1999/08/28 00:01:06 peter Exp $
  38  * $DragonFly: src/lib/libc/stdio/ftell.c,v 1.6 2005/07/23 20:23:06 joerg Exp $
  39  */
  40
  41 #include "namespace.h"
  42 #include <sys/types.h>
  43 #include <stdio.h>
  44 #include <errno.h>
  45 #include "un-namespace.h"
  46
  47 #include "local.h"
  48 #include "libc_private.h"
  49 #include "priv_stdio.h"
  50
  51 /*
  52  * standard ftell function.
  53  */
  54 long
  55 ftell(FILE *fp)
  56 {
  57         off_t rv;
  58         rv = ftello(fp);
  59         if ((long)rv != rv) {
  60                 errno = EOVERFLOW;
  61                 return (-1);
  62         }
  63         return (rv);
  64 }
  65
  66 /*
  67  * ftello: return current offset.
  68  */
  69 off_t
  70 ftello(FILE *fp)
  71 {
  72         fpos_t pos;
  73
  74         if (fp->_seek == NULL) {
  75                 errno = ESPIPE;                 /* historic practice */
  76                 return (-1L);
  77         }
  78
  79         FLOCKFILE(fp);
  80         /*
  81          * Find offset of underlying I/O object, then
  82          * adjust for buffered bytes.
  83          */
  84         if (fp->pub._flags & __SOFF)
  85                 pos = fp->_offset;
  86         else {
  87                 pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR);
  88                 if (pos == -1) {
  89                         FUNLOCKFILE(fp);
  90                         return (pos);
  91                 }
  92         }
  93         if (fp->pub._flags & __SRD) {
  94                 /*
  95                  * Reading.  Any unread characters (including
  96                  * those from ungetc) cause the position to be
  97                  * smaller than that in the underlying object.
  98                  */
  99                 pos -= fp->pub._r;
 100                 if (HASUB(fp))
 101                         pos -= fp->_ur;
 102         } else if (fp->pub._flags & __SWR && fp->pub._p != NULL) {
 103                 /*
 104                  * Writing.  Any buffered characters cause the
 105                  * position to be greater than that in the
 106                  * underlying object.
 107                  */
 108                 pos += fp->pub._p - fp->_bf._base;
 109         }
 110         FUNLOCKFILE(fp);
 111         return (pos);
 112 }