1 /*
2 * Copyright (c) 1990, 2007 The Regents of the University of California.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms are permitted
6 * provided that the above copyright notice and this paragraph are
7 * duplicated in all such forms and that any documentation,
8 * and/or other materials related to such
9 * distribution and use acknowledge that the software was developed
10 * by the University of California, Berkeley. The name of the
11 * University may not be used to endorse or promote products derived
12 * from this software without specific prior written permission.
13 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
15 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
16 */
17
18 /*
19 FUNCTION
20 <<freopen>>---open a file using an existing file descriptor
21
22 INDEX
23 freopen
24 INDEX
25 _freopen_r
26
27 SYNOPSIS
28 #include <stdio.h>
29 FILE *freopen(const char *restrict <[file]>, const char *restrict <[mode]>,
30 FILE *restrict <[fp]>);
31 FILE *freopen( const char *restrict <[file]>,
32 const char *restrict <[mode]>, FILE *restrict <[fp]>);
33
34 DESCRIPTION
35 Use this variant of <<fopen>> if you wish to specify a particular file
36 descriptor <[fp]> (notably <<stdin>>, <<stdout>>, or <<stderr>>) for
37 the file.
38
39 If <[fp]> was associated with another file or stream, <<freopen>>
40 closes that other file or stream (but ignores any errors while closing
41 it).
42
43 <[file]> and <[mode]> are used just as in <<fopen>>.
44
45 If <[file]> is <<NULL>>, the underlying stream is modified rather than
46 closed. The file cannot be given a more permissive access mode (for
47 example, a <[mode]> of "w" will fail on a read-only file descriptor),
48 but can change status such as append or binary mode. If modification
49 is not possible, failure occurs.
50
51 RETURNS
52 If successful, the result is the same as the argument <[fp]>. If the
53 file cannot be opened as specified, the result is <<NULL>>.
54
55 PORTABILITY
56 ANSI C requires <<freopen>>.
57
58 Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
59 <<lseek>>, <<open>>, <<read>>, <<sbrk>>, <<write>>.
60 */
61
62 #define _DEFAULT_SOURCE
63 #include <_ansi.h>
64 #include <time.h>
65 #include <stdio.h>
66 #include <string.h>
67 #include <errno.h>
68 #include <fcntl.h>
69 #include <stdlib.h>
70 #include <sys/lock.h>
71 #include "local.h"
72
73 /*
74 * Re-direct an existing, open (probably) file to some other file.
75 */
76
77 FILE *
freopen(const char * __restrict file,const char * __restrict mode,register FILE * __restrict fp)78 freopen (
79 const char *__restrict file,
80 const char *__restrict mode,
81 register FILE *__restrict fp)
82 {
83 register int f;
84 int flags, oflags, oflags2;
85 int e = 0;
86
87 CHECK_INIT (ptr, fp);
88
89 /* We can't use the _newlib_flockfile_XXX macros here due to the
90 interlocked locking with the sfp_lock. */
91 #ifdef _STDIO_WITH_THREAD_CANCELLATION_SUPPORT
92 int __oldcancel;
93 pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &__oldcancel);
94 #endif
95 oflags2 = fp->_flags2;
96 if (!(oflags2 & __SNLK))
97 _flockfile (fp);
98
99 if ((flags = __sflags (mode, &oflags)) == 0)
100 {
101 if (!(oflags2 & __SNLK))
102 _funlockfile (fp);
103 #ifdef _STDIO_WITH_THREAD_CANCELLATION_SUPPORT
104 pthread_setcancelstate (__oldcancel, &__oldcancel);
105 #endif
106 fclose ( fp);
107 return NULL;
108 }
109
110 /*
111 * Remember whether the stream was open to begin with, and
112 * which file descriptor (if any) was associated with it.
113 * If it was attached to a descriptor, defer closing it,
114 * so that, e.g., freopen("/dev/stdin", "r", stdin) works.
115 * This is unnecessary if it was not a Unix file.
116 */
117
118 if (fp->_flags == 0)
119 fp->_flags = __SEOF; /* hold on to it */
120 else
121 {
122 if (fp->_flags & __SWR)
123 fflush ( fp);
124 /*
125 * If close is NULL, closing is a no-op, hence pointless.
126 * If file is NULL, the file should not be closed.
127 */
128 if (fp->_close != NULL && file != NULL)
129 fp->_close (fp->_cookie);
130 }
131
132 /*
133 * Now get a new descriptor to refer to the new file, or reuse the
134 * existing file descriptor if file is NULL.
135 */
136
137 if (file != NULL)
138 {
139 f = open ((char *) file, oflags, 0666);
140 e = _REENT_ERRNO(ptr);
141 }
142 else
143 {
144 #ifdef _HAVE_FCNTL
145 int oldflags;
146 /*
147 * Reuse the file descriptor, but only if the new access mode is
148 * equal or less permissive than the old. F_SETFL correctly
149 * ignores creation flags.
150 */
151 f = fp->_file;
152 if ((oldflags = fcntl (f, F_GETFL, 0)) == -1
153 || ! ((oldflags & O_ACCMODE) == O_RDWR
154 || ((oldflags ^ oflags) & O_ACCMODE) == 0)
155 || fcntl (f, F_SETFL, oflags) == -1)
156 f = -1;
157 #else
158 /* We cannot modify without fcntl support. */
159 f = -1;
160 #endif
161
162 #ifdef __SCLE
163 /*
164 * F_SETFL doesn't change textmode. Don't mess with modes of ttys.
165 */
166 if (0 <= f && ! isatty ( f)
167 && setmode (f, oflags & (O_BINARY | O_TEXT)) == -1)
168 f = -1;
169 #endif
170
171 if (f < 0)
172 {
173 e = EBADF;
174 if (fp->_close != NULL)
175 fp->_close (fp->_cookie);
176 }
177 }
178
179 /*
180 * Finish closing fp. Even if the open succeeded above,
181 * we cannot keep fp->_base: it may be the wrong size.
182 * This loses the effect of any setbuffer calls,
183 * but stdio has always done this before.
184 */
185
186 if (fp->_flags & __SMBF)
187 free ((char *) fp->_bf._base);
188 fp->_w = 0;
189 fp->_r = 0;
190 fp->_p = NULL;
191 fp->_bf._base = NULL;
192 fp->_bf._size = 0;
193 fp->_lbfsize = 0;
194 if (HASUB (fp))
195 FREEUB (ptr, fp);
196 fp->_ub._size = 0;
197 if (HASLB (fp))
198 FREELB (ptr, fp);
199 fp->_lb._size = 0;
200 fp->_flags &= ~__SORD;
201 fp->_flags2 &= ~__SWID;
202 memset (&fp->_mbstate, 0, sizeof (_mbstate_t));
203
204 if (f < 0)
205 { /* did not get it after all */
206 __sfp_lock_acquire ();
207 fp->_flags = 0; /* set it free */
208 _REENT_ERRNO(ptr) = e; /* restore in case _close clobbered */
209 if (!(oflags2 & __SNLK))
210 _funlockfile (fp);
211 #ifndef __SINGLE_THREAD__
212 __lock_close_recursive (fp->_lock);
213 #endif
214 __sfp_lock_release ();
215 #ifdef _STDIO_WITH_THREAD_CANCELLATION_SUPPORT
216 pthread_setcancelstate (__oldcancel, &__oldcancel);
217 #endif
218 return NULL;
219 }
220
221 fp->_flags = flags;
222 fp->_file = f;
223 fp->_cookie = (void *) fp;
224 fp->_read = __sread;
225 fp->_write = __swrite;
226 fp->_seek = __sseek;
227 fp->_close = __sclose;
228
229 #ifdef __SCLE
230 if (__stextmode (fp->_file))
231 fp->_flags |= __SCLE;
232 #endif
233
234 if (!(oflags2 & __SNLK))
235 _funlockfile (fp);
236 #ifdef _STDIO_WITH_THREAD_CANCELLATION_SUPPORT
237 pthread_setcancelstate (__oldcancel, &__oldcancel);
238 #endif
239 return fp;
240 }
241
