1 /* $NetBSD: ftell.c,v 1.6 1995/03/22 18:19:51 jtc 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. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #if defined(LIBC_SCCS) && !defined(lint) 40 #if 0 41 static char sccsid[] = "@(#)ftell.c 8.1 (Berkeley) 6/4/93"; 42 #endif 43 static char rcsid[] = "$NetBSD: ftell.c,v 1.6 1995/03/22 18:19:51 jtc Exp $"; 44 #endif /* LIBC_SCCS and not lint */ 45 46 #include <stdio.h> 47 #include <errno.h> 48 #include "local.h" 49 50 /* 51 * ftell: return current offset. 52 */ 53 long 54 ftell(fp) 55 register FILE *fp; 56 { 57 register fpos_t pos; 58 59 if (fp->_seek == NULL) { 60 errno = ESPIPE; /* historic practice */ 61 return (-1L); 62 } 63 64 /* 65 * Find offset of underlying I/O object, then 66 * adjust for buffered bytes. 67 */ 68 __sflush(fp); /* may adjust seek offset on append stream */ 69 if (fp->_flags & __SOFF) 70 pos = fp->_offset; 71 else { 72 pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR); 73 if (pos == -1L) 74 return (pos); 75 } 76 if (fp->_flags & __SRD) { 77 /* 78 * Reading. Any unread characters (including 79 * those from ungetc) cause the position to be 80 * smaller than that in the underlying object. 81 */ 82 pos -= fp->_r; 83 if (HASUB(fp)) 84 pos -= fp->_ur; 85 } else if (fp->_flags & __SWR && fp->_p != NULL) { 86 /* 87 * Writing. Any buffered characters cause the 88 * position to be greater than that in the 89 * underlying object. 90 */ 91 pos += fp->_p - fp->_bf._base; 92 } 93 return (pos); 94 } 95