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  * 4. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)ftell.c  8.2 (Berkeley) 5/4/95
  33  * $FreeBSD: src/lib/libc/stdio/ftell.c,v 1.27 2007/01/09 00:28:06 imp Exp $
  34  * $DragonFly: src/lib/libc/stdio/ftell.c,v 1.6 2005/07/23 20:23:06 joerg Exp $
  35  */
  36
  37 #include "namespace.h"
  38 #include <sys/types.h>
  39 #include <errno.h>
  40 #include <limits.h>
  41 #include <stdio.h>
  42 #include "un-namespace.h"
  43 #include "local.h"
  44 #include "libc_private.h"
  45 #include "priv_stdio.h"
  46
  47 /*
  48  * standard ftell function.
  49  */
  50 long
  51 ftell(FILE *fp)
  52 {
  53         off_t rv;
  54
  55         rv = ftello(fp);
  56         if (rv > LONG_MAX) {
  57                 errno = EOVERFLOW;
  58                 return (-1);
  59         }
  60         return (rv);
  61 }
  62
  63 /*
  64  * ftello: return current offset.
  65  */
  66 off_t
  67 ftello(FILE *fp)
  68 {
  69         fpos_t rv;
  70         int ret;
  71
  72         FLOCKFILE(fp);
  73         ret = _ftello(fp, &rv);
  74         FUNLOCKFILE(fp);
  75         if (ret)
  76                 return (-1);
  77         if (rv < 0) {   /* Unspecified value because of ungetc() at 0 */
  78                 errno = ESPIPE;
  79                 return (-1);
  80         }
  81         return (rv);
  82 }
  83
  84 int
  85 _ftello(FILE *fp, fpos_t *offset)
  86 {
  87         fpos_t pos;
  88         size_t n;
  89
  90         if (fp->_seek == NULL) {
  91                 errno = ESPIPE;                 /* historic practice */
  92                 return (1);
  93         }
  94
  95         /*
  96          * Find offset of underlying I/O object, then
  97          * adjust for buffered bytes.
  98          */
  99         if (fp->pub._flags & __SOFF)
 100                 pos = fp->_offset;
 101         else {
 102                 pos = _sseek(fp, (fpos_t)0, SEEK_CUR);
 103                 if (pos == -1)
 104                         return (1);
 105         }
 106         if (fp->pub._flags & __SRD) {
 107                 /*
 108                  * Reading.  Any unread characters (including
 109                  * those from ungetc) cause the position to be
 110                  * smaller than that in the underlying object.
 111                  */
 112                 if ((pos -= (HASUB(fp) ? fp->_ur : fp->pub._r)) < 0) {
 113                         fp->pub._flags |= __SERR;
 114                         errno = EIO;
 115                         return (1);
 116                 }
 117                 if (HASUB(fp))
 118                         pos -= fp->pub._r;  /* Can be negative at this point. */
 119         } else if ((fp->pub._flags & __SWR) && fp->pub._p != NULL) {
 120                 /*
 121                  * Writing.  Any buffered characters cause the
 122                  * position to be greater than that in the
 123                  * underlying object.
 124                  */
 125                 n = fp->pub._p - fp->_bf._base;
 126                 if (pos > OFF_MAX - n) {
 127                         errno = EOVERFLOW;
 128                         return (1);
 129                 }
 130                 pos += n;
 131         }
 132         *offset = pos;
 133         return (0);
 134 }