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  * 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
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 static char sccsid[] = "@(#)ftell.c     8.2 (Berkeley) 5/4/95";
  35 #endif /* LIBC_SCCS and not lint */
  36 #include <sys/cdefs.h>
  37 __FBSDID("$FreeBSD: src/lib/libc/stdio/ftell.c,v 1.27 2007/01/09 00:28:06 imp Exp $");
  38
  39 #include "namespace.h"
  40 #include <sys/types.h>
  41 #include <errno.h>
  42 #include <limits.h>
  43 #include <stdio.h>
  44 #include "un-namespace.h"
  45 #include "local.h"
  46 #include "libc_private.h"
  47
  48 /*
  49  * standard ftell function.
  50  */
  51 long
  52 ftell(fp)
  53         FILE *fp;
  54 {
  55         off_t rv;
  56
  57         rv = ftello(fp);
  58         if (rv > LONG_MAX) {
  59                 errno = EOVERFLOW;
  60                 return (-1);
  61         }
  62         return (rv);
  63 }
  64
  65 /*
  66  * ftello: return current offset.
  67  */
  68 off_t
  69 ftello(fp)
  70         FILE *fp;
  71 {
  72         fpos_t rv;
  73         int ret;
  74
  75         FLOCKFILE(fp);
  76         ret = _ftello(fp, &rv);
  77         FUNLOCKFILE(fp);
  78         if (ret)
  79                 return (-1);
  80         if (rv < 0) {   /* Unspecified value because of ungetc() at 0 */
  81                 errno = ESPIPE;
  82                 return (-1);
  83         }
  84         return (rv);
  85 }
  86
  87 int
  88 _ftello(fp, offset)
  89         FILE *fp;
  90         fpos_t *offset;
  91 {
  92         fpos_t pos;
  93         size_t n;
  94
  95         if (fp->_seek == NULL) {
  96                 errno = ESPIPE;                 /* historic practice */
  97                 return (1);
  98         }
  99
 100         /*
 101          * Find offset of underlying I/O object, then
 102          * adjust for buffered bytes.
 103          */
 104         if (__sflush(fp))               /* may adjust seek offset on append stream */
 105                 return (1);
 106         if (fp->_flags & __SOFF)
 107                 pos = fp->_offset;
 108         else {
 109                 pos = _sseek(fp, (fpos_t)0, SEEK_CUR);
 110                 if (pos == -1)
 111                         return (1);
 112         }
 113         if (fp->_flags & __SRD) {
 114                 /*
 115                  * Reading.  Any unread characters (including
 116                  * those from ungetc) cause the position to be
 117                  * smaller than that in the underlying object.
 118                  */
 119                 if ((pos -= (HASUB(fp) ? fp->_ur : fp->_r)) < 0) {
 120                         fp->_flags |= __SERR;
 121                         errno = EIO;
 122                         return (1);
 123                 }
 124                 if (HASUB(fp))
 125                         pos -= fp->_r;  /* Can be negative at this point. */
 126         } else if ((fp->_flags & __SWR) && fp->_p != NULL) {
 127                 /*
 128                  * Writing.  Any buffered characters cause the
 129                  * position to be greater than that in the
 130                  * underlying object.
 131                  */
 132                 n = fp->_p - fp->_bf._base;
 133                 if (pos > OFF_MAX - n) {
 134                         errno = EOVERFLOW;
 135                         return (1);
 136                 }
 137                 pos += n;
 138         }
 139         *offset = pos;
 140         return (0);
 141 }