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 * @(#)ftell.c 8.2 (Berkeley) 5/4/95 37 * $FreeBSD: src/lib/libc/stdio/ftell.c,v 1.11 1999/08/28 00:01:06 peter Exp $ 38 * $DragonFly: src/lib/libc/stdio/ftell.c,v 1.6 2005/07/23 20:23:06 joerg Exp $ 39 */ 40 41 #include "namespace.h" 42 #include <sys/types.h> 43 #include <stdio.h> 44 #include <errno.h> 45 #include "un-namespace.h" 46 47 #include "local.h" 48 #include "libc_private.h" 49 #include "priv_stdio.h" 50 51 /* 52 * standard ftell function. 53 */ 54 long 55 ftell(FILE *fp) 56 { 57 off_t rv; 58 rv = ftello(fp); 59 if ((long)rv != rv) { 60 errno = EOVERFLOW; 61 return (-1); 62 } 63 return (rv); 64 } 65 66 /* 67 * ftello: return current offset. 68 */ 69 off_t 70 ftello(FILE *fp) 71 { 72 fpos_t pos; 73 74 if (fp->_seek == NULL) { 75 errno = ESPIPE; /* historic practice */ 76 return (-1L); 77 } 78 79 FLOCKFILE(fp); 80 /* 81 * Find offset of underlying I/O object, then 82 * adjust for buffered bytes. 83 */ 84 if (fp->pub._flags & __SOFF) 85 pos = fp->_offset; 86 else { 87 pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR); 88 if (pos == -1) { 89 FUNLOCKFILE(fp); 90 return (pos); 91 } 92 } 93 if (fp->pub._flags & __SRD) { 94 /* 95 * Reading. Any unread characters (including 96 * those from ungetc) cause the position to be 97 * smaller than that in the underlying object. 98 */ 99 pos -= fp->pub._r; 100 if (HASUB(fp)) 101 pos -= fp->_ur; 102 } else if (fp->pub._flags & __SWR && fp->pub._p != NULL) { 103 /* 104 * Writing. Any buffered characters cause the 105 * position to be greater than that in the 106 * underlying object. 107 */ 108 pos += fp->pub._p - fp->_bf._base; 109 } 110 FUNLOCKFILE(fp); 111 return (pos); 112 } 113