1 /* $OpenBSD: ftell.c,v 1.10 2012/05/21 22:24:19 matthew Exp $ */ 2 /*- 3 * Copyright (c) 1990, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * This code is derived from software contributed to Berkeley by 7 * Chris Torek. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 #include <stdio.h> 35 #include <errno.h> 36 #include <limits.h> 37 #include "local.h" 38 39 /* 40 * ftello: return current offset. 41 */ 42 off_t 43 ftello(FILE *fp) 44 { 45 fpos_t pos; 46 47 if (fp->_seek == NULL) { 48 errno = ESPIPE; /* historic practice */ 49 pos = -1; 50 goto out; 51 } 52 53 /* 54 * Find offset of underlying I/O object, then 55 * adjust for buffered bytes. 56 */ 57 FLOCKFILE(fp); 58 __sflush(fp); /* may adjust seek offset on append stream */ 59 if (fp->_flags & __SOFF) 60 pos = fp->_offset; 61 else { 62 pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR); 63 if (pos == -1) 64 goto out; 65 } 66 if (fp->_flags & __SRD) { 67 /* 68 * Reading. Any unread characters (including 69 * those from ungetc) cause the position to be 70 * smaller than that in the underlying object. 71 */ 72 pos -= fp->_r; 73 if (HASUB(fp)) 74 pos -= fp->_ur; 75 } else if (fp->_flags & __SWR && fp->_p != NULL) { 76 /* 77 * Writing. Any buffered characters cause the 78 * position to be greater than that in the 79 * underlying object. 80 */ 81 pos += fp->_p - fp->_bf._base; 82 } 83 out: FUNLOCKFILE(fp); 84 return (pos); 85 } 86 87 long 88 ftell(FILE *fp) 89 { 90 off_t offset = ftello(fp); 91 if (offset > LONG_MAX) { 92 errno = EOVERFLOW; 93 return (-1); 94 } 95 return ((long)offset); 96 } 97