ftell.c revision 1573
11573Srgrimes/*- 21573Srgrimes * Copyright (c) 1990, 1993 31573Srgrimes * The Regents of the University of California. All rights reserved. 41573Srgrimes * 51573Srgrimes * This code is derived from software contributed to Berkeley by 61573Srgrimes * Chris Torek. 71573Srgrimes * 81573Srgrimes * Redistribution and use in source and binary forms, with or without 91573Srgrimes * modification, are permitted provided that the following conditions 101573Srgrimes * are met: 111573Srgrimes * 1. Redistributions of source code must retain the above copyright 121573Srgrimes * notice, this list of conditions and the following disclaimer. 131573Srgrimes * 2. Redistributions in binary form must reproduce the above copyright 141573Srgrimes * notice, this list of conditions and the following disclaimer in the 151573Srgrimes * documentation and/or other materials provided with the distribution. 161573Srgrimes * 3. All advertising materials mentioning features or use of this software 171573Srgrimes * must display the following acknowledgement: 181573Srgrimes * This product includes software developed by the University of 191573Srgrimes * California, Berkeley and its contributors. 201573Srgrimes * 4. Neither the name of the University nor the names of its contributors 211573Srgrimes * may be used to endorse or promote products derived from this software 221573Srgrimes * without specific prior written permission. 231573Srgrimes * 241573Srgrimes * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 251573Srgrimes * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 261573Srgrimes * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 271573Srgrimes * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 281573Srgrimes * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 291573Srgrimes * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 301573Srgrimes * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 311573Srgrimes * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 321573Srgrimes * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 331573Srgrimes * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 341573Srgrimes * SUCH DAMAGE. 351573Srgrimes */ 361573Srgrimes 371573Srgrimes#if defined(LIBC_SCCS) && !defined(lint) 381573Srgrimesstatic char sccsid[] = "@(#)ftell.c 8.1 (Berkeley) 6/4/93"; 391573Srgrimes#endif /* LIBC_SCCS and not lint */ 401573Srgrimes 411573Srgrimes#include <stdio.h> 421573Srgrimes#include <errno.h> 431573Srgrimes#include "local.h" 441573Srgrimes 451573Srgrimes/* 461573Srgrimes * ftell: return current offset. 471573Srgrimes */ 481573Srgrimeslong 491573Srgrimesftell(fp) 501573Srgrimes register const FILE *fp; 511573Srgrimes{ 521573Srgrimes register fpos_t pos; 531573Srgrimes 541573Srgrimes if (fp->_seek == NULL) { 551573Srgrimes errno = ESPIPE; /* historic practice */ 561573Srgrimes return (-1L); 571573Srgrimes } 581573Srgrimes 591573Srgrimes /* 601573Srgrimes * Find offset of underlying I/O object, then 611573Srgrimes * adjust for buffered bytes. 621573Srgrimes */ 631573Srgrimes if (fp->_flags & __SOFF) 641573Srgrimes pos = fp->_offset; 651573Srgrimes else { 661573Srgrimes pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR); 671573Srgrimes if (pos == -1L) 681573Srgrimes return (pos); 691573Srgrimes } 701573Srgrimes if (fp->_flags & __SRD) { 711573Srgrimes /* 721573Srgrimes * Reading. Any unread characters (including 731573Srgrimes * those from ungetc) cause the position to be 741573Srgrimes * smaller than that in the underlying object. 751573Srgrimes */ 761573Srgrimes pos -= fp->_r; 771573Srgrimes if (HASUB(fp)) 781573Srgrimes pos -= fp->_ur; 791573Srgrimes } else if (fp->_flags & __SWR && fp->_p != NULL) { 801573Srgrimes /* 811573Srgrimes * Writing. Any buffered characters cause the 821573Srgrimes * position to be greater than that in the 831573Srgrimes * underlying object. 841573Srgrimes */ 851573Srgrimes pos += fp->_p - fp->_bf._base; 861573Srgrimes } 871573Srgrimes return (pos); 881573Srgrimes} 89