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root/usr/lib/libc/stdio/ftell.c

DEFINITIONS

1. ftell

   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  */
  33 #include <stdio.h>
  34 #include <errno.h>
  35 #include "local.h"
  37 /*
  38  * ftell: return current offset.
  39  */
  40 long
ftell(fp)
FILE *fp;
  43 {
fpos_t pos;
  46         /*
  47          * Find offset of underlying I/O object, then
  48          * adjust for buffered bytes.
  49          */
pos = __sseek(fp, (fpos_t)0, SEEK_CUR);
  51         if (pos == -(fpos_t)1)
  52                 return (pos);
  54         if (fp->_flags & __SRD) {
  55                 /*
  56                  * Reading.  Any unread characters (including
  57                  * those from ungetc) cause the position to be
  58                  * smaller than that in the underlying object.
  59                  */
pos -= fp->_r;
  61                 if (HASUB(fp))
pos -= fp->_ur;
  63         } else if (fp->_flags & __SWR && fp->_p != NULL) {
  64                 /*
  65                  * Writing.  Any buffered characters cause the
  66                  * position to be greater than that in the
  67                  * underlying object.
  68                  */
pos += fp->_p - fp->_bf._base;
  70         }
  71         return (pos);
  72 }