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 1.2 2003/06/17 04:26:46 dillon 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(fp) 52 register FILE *fp; 53 { 54 register off_t rv; 55 rv = ftello(fp); 56 if ((long)rv != rv) { 57 errno = EOVERFLOW; 58 return (-1); 59 } 60 return (rv); 61 } 62 63 /* 64 * ftello: return current offset. 65 */ 66 off_t 67 ftello(fp) 68 register FILE *fp; 69 { 70 register fpos_t pos; 71 72 if (fp->_seek == NULL) { 73 errno = ESPIPE; /* historic practice */ 74 return (-1L); 75 } 76 77 FLOCKFILE(fp); 78 /* 79 * Find offset of underlying I/O object, then 80 * adjust for buffered bytes. 81 */ 82 if (fp->_flags & __SOFF) 83 pos = fp->_offset; 84 else { 85 pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR); 86 if (pos == -1) { 87 FUNLOCKFILE(fp); 88 return (pos); 89 } 90 } 91 if (fp->_flags & __SRD) { 92 /* 93 * Reading. Any unread characters (including 94 * those from ungetc) cause the position to be 95 * smaller than that in the underlying object. 96 */ 97 pos -= fp->_r; 98 if (HASUB(fp)) 99 pos -= fp->_ur; 100 } else if (fp->_flags & __SWR && fp->_p != NULL) { 101 /* 102 * Writing. Any buffered characters cause the 103 * position to be greater than that in the 104 * underlying object. 105 */ 106 pos += fp->_p - fp->_bf._base; 107 } 108 FUNLOCKFILE(fp); 109 return (pos); 110 } 111