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ftell.c revision 1.15 
      1 /*	$NetBSD: ftell.c,v 1.15 2003/08/07 16:43:25 agc Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1990, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Chris Torek.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  */
     34 
     35 #include <sys/cdefs.h>
     36 #if defined(LIBC_SCCS) && !defined(lint)
     37 #if 0
     38 static char sccsid[] = "@(#)ftell.c	8.2 (Berkeley) 5/4/95";
     39 #else
     40 __RCSID("$NetBSD: ftell.c,v 1.15 2003/08/07 16:43:25 agc Exp $");
     41 #endif
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 #include <assert.h>
     45 #include <errno.h>
     46 #include <stdio.h>
     47 #include "reentrant.h"
     48 #include "local.h"
     49 
     50 /*
     51  * ftell: return current offset.
     52  */
     53 long
     54 ftell(fp)
     55 	FILE *fp;
     56 {
     57 	fpos_t pos;
     58 
     59 
     60 	FLOCKFILE(fp);
     61 
     62 	if (fp->_seek == NULL) {
     63 		FUNLOCKFILE(fp);
     64 		errno = ESPIPE;			/* historic practice */
     65 		return (-1L);
     66 	}
     67 
     68 	/*
     69 	 * Find offset of underlying I/O object, then
     70 	 * adjust for buffered bytes.
     71 	 */
     72 	__sflush(fp);		/* may adjust seek offset on append stream */
     73 	if (fp->_flags & __SOFF)
     74 		pos = fp->_offset;
     75 	else {
     76 		pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR);
     77 		if (pos == -1L) {
     78 			FUNLOCKFILE(fp);
     79 			return (long)(pos);
     80 		}
     81 	}
     82 	if (fp->_flags & __SRD) {
     83 		/*
     84 		 * Reading.  Any unread characters (including
     85 		 * those from ungetc) cause the position to be
     86 		 * smaller than that in the underlying object.
     87 		 */
     88 		pos -= fp->_r;
     89 		if (HASUB(fp))
     90 			pos -= fp->_ur;
     91 	} else if (fp->_flags & __SWR && fp->_p != NULL) {
     92 		/*
     93 		 * Writing.  Any buffered characters cause the
     94 		 * position to be greater than that in the
     95 		 * underlying object.
     96 		 */
     97 		pos += fp->_p - fp->_bf._base;
     98 	}
     99 	FUNLOCKFILE(fp);
    100 	return (long)(pos);
    101 }
    102