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git.saurik.com Git - apple/libc.git/blob - stdio/FreeBSD/fseek.c
2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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.
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
37 #if defined(LIBC_SCCS) && !defined(lint)
38 static char sccsid
[] = "@(#)fseek.c 8.3 (Berkeley) 1/2/94";
39 #endif /* LIBC_SCCS and not lint */
40 #include <sys/cdefs.h>
41 __FBSDID("$FreeBSD: src/lib/libc/stdio/fseek.c,v 1.41 2004/05/22 15:19:41 tjr Exp $");
43 #include "namespace.h"
44 #include <sys/types.h>
51 #include "un-namespace.h"
53 #include "libc_private.h"
55 #define POS_ERR (-(fpos_t)1)
58 fseek(fp
, offset
, whence
)
66 /* make sure stdio is set up */
71 ret
= _fseeko(fp
, (off_t
)offset
, whence
, 1);
79 fseeko(fp
, offset
, whence
)
87 /* make sure stdio is set up */
92 ret
= _fseeko(fp
, offset
, whence
, 0);
100 * Seek the given file to the given offset.
101 * `Whence' must be one of the three SEEK_* macros.
104 _fseeko(fp
, offset
, whence
, ltest
)
110 fpos_t (*seekfn
)(void *, fpos_t, int);
111 fpos_t target
, curoff
, ret
;
117 * Have to be able to seek.
119 if ((seekfn
= fp
->_seek
) == NULL
) {
120 errno
= ESPIPE
; /* historic practice */
125 * Change any SEEK_CUR to SEEK_SET, and check `whence' argument.
126 * After this, whence is either SEEK_SET or SEEK_END.
132 * In order to seek relative to the current stream offset,
133 * we have to first find the current stream offset via
134 * ftell (see ftell for details).
136 if (_ftello(fp
, &curoff
))
139 /* Unspecified position because of ungetc() at 0 */
143 if (offset
> 0 && curoff
> OFF_MAX
- offset
) {
152 if (ltest
&& offset
> LONG_MAX
) {
166 curoff
= 0; /* XXX just to keep gcc quiet */
176 * Can only optimise if:
177 * reading (and not reading-and-writing);
178 * not unbuffered; and
179 * this is a `regular' Unix file (and hence seekfn==__sseek).
180 * We must check __NBF first, because it is possible to have __NBF
181 * and __SOPT both set.
183 if (fp
->_bf
._base
== NULL
)
185 if (fp
->_flags
& (__SWR
| __SRW
| __SNBF
| __SNPT
))
187 if ((fp
->_flags
& __SOPT
) == 0) {
188 if (seekfn
!= __sseek
||
189 fp
->_file
< 0 || _fstat(fp
->_file
, &st
) ||
190 (st
.st_mode
& S_IFMT
) != S_IFREG
) {
191 fp
->_flags
|= __SNPT
;
194 fp
->_blksize
= st
.st_blksize
;
195 fp
->_flags
|= __SOPT
;
199 * We are reading; we can try to optimise.
200 * Figure out where we are going and where we are now.
202 if (whence
== SEEK_SET
)
205 if (_fstat(fp
->_file
, &st
))
207 if (offset
> 0 && st
.st_size
> OFF_MAX
- offset
) {
211 target
= st
.st_size
+ offset
;
212 if ((off_t
)target
< 0) {
216 if (ltest
&& (off_t
)target
> LONG_MAX
) {
222 if (!havepos
&& _ftello(fp
, &curoff
))
226 * (If the buffer was modified, we have to
227 * skip this; see fgetln.c.)
229 if (fp
->_flags
& __SMOD
)
233 * Compute the number of bytes in the input buffer (pretending
234 * that any ungetc() input has been discarded). Adjust current
235 * offset backwards by this count so that it represents the
236 * file offset for the first byte in the current input buffer.
239 curoff
+= fp
->_r
; /* kill off ungetc */
240 n
= fp
->_extra
->_up
- fp
->_bf
._base
;
244 n
= fp
->_p
- fp
->_bf
._base
;
250 * If the target offset is within the current buffer,
251 * simply adjust the pointers, clear EOF, undo ungetc(),
254 if (target
>= curoff
&& target
< curoff
+ n
) {
255 size_t o
= target
- curoff
;
257 fp
->_p
= fp
->_bf
._base
+ o
;
261 fp
->_flags
&= ~__SEOF
;
262 memset(&fp
->_extra
->mbstate
, 0, sizeof(mbstate_t));
268 * The place we want to get to is not within the current buffer,
269 * but we can still be kind to the kernel copyout mechanism.
270 * By aligning the file offset to a block boundary, we can let
271 * the kernel use the VM hardware to map pages instead of
272 * copying bytes laboriously. Using a block boundary also
273 * ensures that we only read one block, rather than two.
275 curoff
= target
& ~(fp
->_blksize
- 1);
276 if (_sseek(fp
, curoff
, SEEK_SET
) == POS_ERR
)
279 fp
->_p
= fp
->_bf
._base
;
284 if (__srefill(fp
) || fp
->_r
< n
)
289 fp
->_flags
&= ~__SEOF
;
293 * We get here if we cannot optimise the seek ... just
294 * do it. Allow the seek function to change fp->_bf._base.
298 (ret
= _sseek(fp
, (fpos_t)offset
, whence
)) == POS_ERR
)
300 /* success: clear EOF indicator and discard ungetc() data */
303 fp
->_p
= fp
->_bf
._base
;
305 /* fp->_w = 0; */ /* unnecessary (I think...) */
306 fp
->_flags
&= ~__SEOF
;
307 memset(&fp
->_extra
->mbstate
, 0, sizeof(mbstate_t));
308 if (ltest
&& ret
> LONG_MAX
) {
309 fp
->_flags
|= __SERR
;