ftell.c (3093B)
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 37 #if defined(LIBC_SCCS) && !defined(lint) 38 static char rcsid[] = "$OpenBSD: ftell.c,v 1.2 1996/08/19 08:32:47 tholo Exp $"; 39 #endif /* LIBC_SCCS and not lint */ 40 41 #include <stdio.h> 42 #include <errno.h> 43 #include "local.h" 44 45 /* 46 * ftell: return current offset. 47 */ 48 long 49 ftell(fp) 50 register FILE *fp; 51 { 52 register fpos_t pos; 53 54 if (fp->_seek == NULL) { 55 errno = ESPIPE; /* historic practice */ 56 return (-1L); 57 } 58 59 /* 60 * Find offset of underlying I/O object, then 61 * adjust for buffered bytes. 62 */ 63 __sflush(fp); /* may adjust seek offset on append stream */ 64 if (fp->_flags & __SOFF) 65 pos = fp->_offset; 66 else { 67 pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR); 68 if (pos == -1L) 69 return (pos); 70 } 71 if (fp->_flags & __SRD) { 72 /* 73 * Reading. Any unread characters (including 74 * those from ungetc) cause the position to be 75 * smaller than that in the underlying object. 76 */ 77 pos -= fp->_r; 78 if (HASUB(fp)) 79 pos -= fp->_ur; 80 } else if (fp->_flags & __SWR && fp->_p != NULL) { 81 /* 82 * Writing. Any buffered characters cause the 83 * position to be greater than that in the 84 * underlying object. 85 */ 86 pos += fp->_p - fp->_bf._base; 87 } 88 return (pos); 89 }