ftell.c revision 82734
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#if 0 39static char sccsid[] = "@(#)ftell.c 8.2 (Berkeley) 5/4/95"; 40#endif 41static const char rcsid[] = 42 "$FreeBSD: head/lib/libc/stdio/ftell.c 82734 2001-09-01 11:18:53Z ache $"; 43#endif /* LIBC_SCCS and not lint */ 44 45#include "namespace.h" 46#include <sys/types.h> 47#include <errno.h> 48#include <limits.h> 49#include <stdio.h> 50#include "un-namespace.h" 51#include "local.h" 52#include "libc_private.h" 53 54/* 55 * standard ftell function. 56 */ 57long 58ftell(fp) 59 register FILE *fp; 60{ 61 register off_t rv; 62 63 rv = ftello(fp); 64 if (rv > LONG_MAX) { 65 errno = EOVERFLOW; 66 return (-1); 67 } 68 return (rv); 69} 70 71/* 72 * ftello: return current offset. 73 */ 74off_t 75ftello(fp) 76 register FILE *fp; 77{ 78 fpos_t rv; 79 int ret; 80 81 /* make sure stdio is set up */ 82 if (!__sdidinit) 83 __sinit(); 84 85 FLOCKFILE(fp); 86 ret = _ftello(fp, &rv); 87 FUNLOCKFILE(fp); 88 if (ret) 89 return (-1); 90 if (rv < 0) /* Unspecified value because of ungetc() at 0 */ 91 rv = 0; 92 return (rv); 93} 94 95int 96_ftello(fp, offset) 97 register FILE *fp; 98 fpos_t *offset; 99{ 100 register fpos_t pos; 101 size_t n; 102 103 if (fp->_seek == NULL) { 104 errno = ESPIPE; /* historic practice */ 105 return (1); 106 } 107 108 /* 109 * Find offset of underlying I/O object, then 110 * adjust for buffered bytes. 111 */ 112 if (fp->_flags & __SOFF) 113 pos = fp->_offset; 114 else { 115 pos = (*fp->_seek)(fp->_cookie, (fpos_t)0, SEEK_CUR); 116 if (pos == -1) 117 return (1); 118 } 119 if (fp->_flags & __SRD) { 120 /* 121 * Reading. Any unread characters (including 122 * those from ungetc) cause the position to be 123 * smaller than that in the underlying object. 124 */ 125 if ((pos -= (HASUB(fp) ? fp->_ur : fp->_r)) < 0) { 126 fp->_flags |= __SERR; 127 errno = EIO; 128 return (1); 129 } 130 if (HASUB(fp)) 131 pos -= fp->_r; /* Can be negative at this point. */ 132 } else if ((fp->_flags & __SWR) && fp->_p != NULL) { 133 /* 134 * Writing. Any buffered characters cause the 135 * position to be greater than that in the 136 * underlying object. 137 */ 138 n = fp->_p - fp->_bf._base; 139 if (pos > OFF_MAX - n) { 140 errno = EOVERFLOW; 141 return (1); 142 } 143 pos += n; 144 } 145 *offset = pos; 146 return (0); 147} 148