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. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #if defined(LIBC_SCCS) && !defined(lint) 38 #if 0 39 static char sccsid[] = "@(#)ftell.c 8.2 (Berkeley) 5/4/95"; 40 #endif 41 static const char rcsid[] = 42 "$Id: ftell.c,v 1.8 1997/03/11 11:40:40 peter Exp $"; 43 #endif /* LIBC_SCCS and not lint */ 44 45 #include <stdio.h> 46 #include <errno.h> 47 #include "local.h" 48 #include "libc_private.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 FLOCKFILE(fp); 65 /* 66 * Find offset of underlying I/O object, then 67 * adjust for buffered bytes. 68 */ 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 == -1) { 74 FUNLOCKFILE(fp); 75 return (pos); 76 } 77 } 78 if (fp->_flags & __SRD) { 79 /* 80 * Reading. Any unread characters (including 81 * those from ungetc) cause the position to be 82 * smaller than that in the underlying object. 83 */ 84 pos -= fp->_r; 85 if (HASUB(fp)) 86 pos -= fp->_ur; 87 } else if (fp->_flags & __SWR && fp->_p != NULL) { 88 /* 89 * Writing. Any buffered characters cause the 90 * position to be greater than that in the 91 * underlying object. 92 */ 93 pos += fp->_p - fp->_bf._base; 94 } 95 FUNLOCKFILE(fp); 96 return (pos); 97 } 98