1/* $NetBSD: ftell.c,v 1.19 2012/03/15 18:22:30 christos 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 38static char sccsid[] = "@(#)ftell.c 8.2 (Berkeley) 5/4/95"; 39#else 40__RCSID("$NetBSD: ftell.c,v 1.19 2012/03/15 18:22:30 christos 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 */ 53long 54ftell(FILE *fp) 55{ 56 off_t pos; 57 58 59 FLOCKFILE(fp); 60 61 if (fp->_seek == NULL) { 62 FUNLOCKFILE(fp); 63 errno = ESPIPE; /* historic practice */ 64 return -1L; 65 } 66 67 /* 68 * Find offset of underlying I/O object, then 69 * adjust for buffered bytes. 70 */ 71 (void)__sflush(fp); /* may adjust seek offset on append stream */ 72 if (fp->_flags & __SOFF) 73 pos = fp->_offset; 74 else { 75 pos = (*fp->_seek)(fp->_cookie, (off_t)0, SEEK_CUR); 76 if (pos == -1L) { 77 FUNLOCKFILE(fp); 78 return (long)pos; 79 } 80 } 81 if (fp->_flags & __SRD) { 82 /* 83 * Reading. Any unread characters (including 84 * those from ungetc) cause the position to be 85 * smaller than that in the underlying object. 86 */ 87 pos -= fp->_r; 88 if (HASUB(fp)) 89 pos -= fp->_ur; 90 } else if (fp->_flags & __SWR && fp->_p != NULL) { 91 /* 92 * Writing. Any buffered characters cause the 93 * position to be greater than that in the 94 * underlying object. 95 */ 96 pos += fp->_p - fp->_bf._base; 97 } 98 FUNLOCKFILE(fp); 99 100 if (__long_overflow(pos)) { 101 errno = EOVERFLOW; 102 return -1L; 103 } 104 105 return (long)pos; 106} 107