1 /* $NetBSD: ftello.c,v 1.4 2003/08/07 16:43:26 agc 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 1.4 2003/08/07 16:43:26 agc 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(fp) 56 FILE *fp; 57 { 58 fpos_t pos; 59 60 61 FLOCKFILE(fp); 62 63 if (fp->_seek == NULL) { 64 FUNLOCKFILE(fp); 65 errno = ESPIPE; /* historic practice */ 66 return ((off_t)-1); 67 } 68 69 /* 70 * Find offset of underlying I/O object, then 71 * adjust for buffered bytes. 72 */ 73 __sflush(fp); /* may adjust seek offset on append stream */ 74 if (fp->_flags & __SOFF) 75 pos = fp->_offset; 76 else { 77 pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR); 78 if (pos == (fpos_t)-1) { 79 FUNLOCKFILE(fp); 80 return (pos); 81 } 82 } 83 if (fp->_flags & __SRD) { 84 /* 85 * Reading. Any unread characters (including 86 * those from ungetc) cause the position to be 87 * smaller than that in the underlying object. 88 */ 89 pos -= fp->_r; 90 if (HASUB(fp)) 91 pos -= fp->_ur; 92 } else if (fp->_flags & __SWR && fp->_p != NULL) { 93 /* 94 * Writing. Any buffered characters cause the 95 * position to be greater than that in the 96 * underlying object. 97 */ 98 pos += fp->_p - fp->_bf._base; 99 } 100 FUNLOCKFILE(fp); 101 return (pos); 102 } 103