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. 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  */
  35
  36 #include "namespace.h"
  37 #include <sys/types.h>
  38 #include <errno.h>
  39 #include <limits.h>
  40 #include <stdio.h>
  41 #include "un-namespace.h"
  42 #include "local.h"
  43 #include "libc_private.h"
  44
  45 /*
  46  * standard ftell function.
  47  */
  48 long
  49 ftell(FILE *fp)
  50 {
  51         off_t rv;
  52
  53         rv = ftello(fp);
  54         if (rv > LONG_MAX) {
  55                 errno = EOVERFLOW;
  56                 return (-1);
  57         }
  58         return (rv);
  59 }
  60
  61 /*
  62  * ftello: return current offset.
  63  */
  64 off_t
  65 ftello(FILE *fp)
  66 {
  67         fpos_t rv;
  68         int ret;
  69
  70         FLOCKFILE(fp);
  71         ret = _ftello(fp, &rv);
  72         FUNLOCKFILE(fp);
  73         if (ret)
  74                 return (-1);
  75         if (rv < 0) {   /* Unspecified value because of ungetc() at 0 */
  76                 errno = ESPIPE;
  77                 return (-1);
  78         }
  79         return (rv);
  80 }
  81
  82 int
  83 _ftello(FILE *fp, fpos_t *offset)
  84 {
  85         fpos_t pos;
  86         size_t n;
  87
  88         if (fp->_seek == NULL) {
  89                 errno = ESPIPE;                 /* historic practice */
  90                 return (1);
  91         }
  92
  93         /*
  94          * Find offset of underlying I/O object, then
  95          * adjust for buffered bytes.
  96          */
  97         if (fp->pub._flags & __SOFF)
  98                 pos = fp->_offset;
  99         else {
 100                 pos = _sseek(fp, (fpos_t)0, SEEK_CUR);
 101                 if (pos == -1)
 102                         return (1);
 103         }
 104         if (fp->pub._flags & __SRD) {
 105                 /*
 106                  * Reading.  Any unread characters (including
 107                  * those from ungetc) cause the position to be
 108                  * smaller than that in the underlying object.
 109                  */
 110                 if ((pos -= (HASUB(fp) ? fp->_ur : fp->pub._r)) < 0) {
 111                         fp->pub._flags |= __SERR;
 112                         errno = EIO;
 113                         return (1);
 114                 }
 115                 if (HASUB(fp))
 116                         pos -= fp->pub._r;  /* Can be negative at this point. */
 117         } else if ((fp->pub._flags & __SWR) && fp->pub._p != NULL) {
 118                 /*
 119                  * Writing.  Any buffered characters cause the
 120                  * position to be greater than that in the
 121                  * underlying object.
 122                  */
 123                 n = fp->pub._p - fp->_bf._base;
 124                 if (pos > OFF_MAX - n) {
 125                         errno = EOVERFLOW;
 126                         return (1);
 127                 }
 128                 pos += n;
 129         }
 130         *offset = pos;
 131         return (0);
 132 }