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 1.4 2004/06/07 20:35:41 hmp Exp $ 39 */ 40 41 #include <sys/types.h> 42 #include <stdio.h> 43 #include <errno.h> 44 #include "local.h" 45 #include "libc_private.h" 46 47 /* 48 * standard ftell function. 49 */ 50 long 51 ftell(FILE *fp) 52 { 53 off_t rv; 54 rv = ftello(fp); 55 if ((long)rv != rv) { 56 errno = EOVERFLOW; 57 return (-1); 58 } 59 return (rv); 60 } 61 62 /* 63 * ftello: return current offset. 64 */ 65 off_t 66 ftello(FILE *fp) 67 { 68 fpos_t pos; 69 70 if (fp->_seek == NULL) { 71 errno = ESPIPE; /* historic practice */ 72 return (-1L); 73 } 74 75 FLOCKFILE(fp); 76 /* 77 * Find offset of underlying I/O object, then 78 * adjust for buffered bytes. 79 */ 80 if (fp->_flags & __SOFF) 81 pos = fp->_offset; 82 else { 83 pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR); 84 if (pos == -1) { 85 FUNLOCKFILE(fp); 86 return (pos); 87 } 88 } 89 if (fp->_flags & __SRD) { 90 /* 91 * Reading. Any unread characters (including 92 * those from ungetc) cause the position to be 93 * smaller than that in the underlying object. 94 */ 95 pos -= fp->_r; 96 if (HASUB(fp)) 97 pos -= fp->_ur; 98 } else if (fp->_flags & __SWR && fp->_p != NULL) { 99 /* 100 * Writing. Any buffered characters cause the 101 * position to be greater than that in the 102 * underlying object. 103 */ 104 pos += fp->_p - fp->_bf._base; 105 } 106 FUNLOCKFILE(fp); 107 return (pos); 108 } 109