ftell.c revision 14840
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) 38static char sccsid[] = "@(#)ftell.c 8.1 (Berkeley) 6/4/93"; 39#endif /* LIBC_SCCS and not lint */ 40 41#include <stdio.h> 42#include <errno.h> 43#include "local.h" 44#ifdef _THREAD_SAFE 45#include <pthread.h> 46#include "pthread_private.h" 47#endif 48 49/* 50 * ftell: return current offset. 51 */ 52long 53ftell(fp) 54 register FILE *fp; 55{ 56 register fpos_t pos; 57 58 if (fp->_seek == NULL) { 59 errno = ESPIPE; /* historic practice */ 60 return (-1L); 61 } 62 63#ifdef _THREAD_SAFE 64 _thread_flockfile(fp, __FILE__, __LINE__); 65#endif 66 /* 67 * Find offset of underlying I/O object, then 68 * adjust for buffered bytes. 69 */ 70 if (fp->_flags & __SOFF) 71 pos = fp->_offset; 72 else { 73 pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR); 74 if (pos == -1) { 75#ifdef _THREAD_SAFE 76 _thread_funlockfile(fp); 77#endif 78 return (pos); 79 } 80 } 81 if (fp->_flags & __SRD) { 82 /* 83 * Reading. Any unread characters (including 84 * those from ungetc) cause the position to be 85 * smaller than that in the underlying object. 86 */ 87 pos -= fp->_r; 88 if (HASUB(fp)) 89 pos -= fp->_ur; 90 } else if (fp->_flags & __SWR && fp->_p != NULL) { 91 /* 92 * Writing. Any buffered characters cause the 93 * position to be greater than that in the 94 * underlying object. 95 */ 96 pos += fp->_p - fp->_bf._base; 97 } 98#ifdef _THREAD_SAFE 99 _thread_funlockfile(fp); 100#endif 101 return (pos); 102} 103