1 /* $NetBSD: ftello.c,v 1.7 2012/03/27 15:05:42 christos Exp $ */ 2 3 /*- 4 * Copyright (c) 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Chris Torek. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #include <sys/cdefs.h> 36 #if defined(LIBC_SCCS) && !defined(lint) 37 __RCSID("$NetBSD: ftello.c,v 1.7 2012/03/27 15:05:42 christos Exp $"); 38 #endif /* LIBC_SCCS and not lint */ 39 40 #include "namespace.h" 41 #include <assert.h> 42 #include <errno.h> 43 #include <stdio.h> 44 #include "reentrant.h" 45 #include "local.h" 46 47 #ifdef __weak_alias 48 __weak_alias(ftello, _ftello) 49 #endif 50 51 /* 52 * ftell: return current offset. 53 */ 54 off_t 55 ftello(FILE *fp) 56 { 57 off_t pos; 58 59 60 FLOCKFILE(fp); 61 62 if (fp->_seek == NULL) { 63 FUNLOCKFILE(fp); 64 errno = ESPIPE; /* historic practice */ 65 return (off_t)-1; 66 } 67 68 /* 69 * Find offset of underlying I/O object, then 70 * adjust for buffered bytes. 71 */ 72 (void)__sflush(fp); /* may adjust seek offset on append stream */ 73 if (fp->_flags & __SOFF) 74 pos = fp->_offset; 75 else { 76 pos = (*fp->_seek)(fp->_cookie, (off_t)0, SEEK_CUR); 77 if (pos == (off_t)-1) { 78 FUNLOCKFILE(fp); 79 return pos; 80 } 81 } 82 if (fp->_flags & __SRD) { 83 /* 84 * Reading. Any unread characters (including 85 * those from ungetc) cause the position to be 86 * smaller than that in the underlying object. 87 */ 88 pos -= fp->_r; 89 if (HASUB(fp)) 90 pos -= fp->_ur; 91 } else if (fp->_flags & __SWR && fp->_p != NULL) { 92 /* 93 * Writing. Any buffered characters cause the 94 * position to be greater than that in the 95 * underlying object. 96 */ 97 pos += fp->_p - fp->_bf._base; 98 } 99 FUNLOCKFILE(fp); 100 return pos; 101 } 102