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 <time.h>
64 #include <stdio.h>
65 #include <string.h>
66 #include <errno.h>
67 #include <fcntl.h>
68 #include <stdlib.h>
69 #include <sys/lock.h>
70 #include "local.h"
71
72 /*
73 * Re-direct an existing, open (probably) file to some other file.
74 */
75
76 FILE *
freopen(const char * __restrict file,const char * __restrict mode,register FILE * __restrict fp)77 freopen (
78 const char *__restrict file,
79 const char *__restrict mode,
80 register FILE *__restrict fp)
81 {
82 register int f;
83 int flags, oflags, oflags2;
84 int e = 0;
85
86 CHECK_INIT (ptr, fp);
87
88 /* We can't use the _newlib_flockfile_XXX macros here due to the
89 interlocked locking with the sfp_lock. */
90 #ifdef _STDIO_WITH_THREAD_CANCELLATION_SUPPORT
91 int __oldcancel;
92 pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &__oldcancel);
93 #endif
94 oflags2 = fp->_flags2;
95 if (!(oflags2 & __SNLK))
96 _flockfile (fp);
97
98 if ((flags = __sflags (mode, &oflags)) == 0)
99 {
100 if (!(oflags2 & __SNLK))
101 _funlockfile (fp);
102 #ifdef _STDIO_WITH_THREAD_CANCELLATION_SUPPORT
103 pthread_setcancelstate (__oldcancel, &__oldcancel);
104 #endif
105 fclose ( fp);
106 return NULL;
107 }
108
109 /*
110 * Remember whether the stream was open to begin with, and
111 * which file descriptor (if any) was associated with it.
112 * If it was attached to a descriptor, defer closing it,
113 * so that, e.g., freopen("/dev/stdin", "r", stdin) works.
114 * This is unnecessary if it was not a Unix file.
115 */
116
117 if (fp->_flags == 0)
118 fp->_flags = __SEOF; /* hold on to it */
119 else
120 {
121 if (fp->_flags & __SWR)
122 fflush ( fp);
123 /*
124 * If close is NULL, closing is a no-op, hence pointless.
125 * If file is NULL, the file should not be closed.
126 */
127 if (fp->_close != NULL && file != NULL)
128 fp->_close (fp->_cookie);
129 }
130
131 /*
132 * Now get a new descriptor to refer to the new file, or reuse the
133 * existing file descriptor if file is NULL.
134 */
135
136 if (file != NULL)
137 {
138 f = open ((char *) file, oflags, 0666);
139 e = _REENT_ERRNO(ptr);
140 }
141 else
142 {
143 #ifdef _HAVE_FCNTL
144 int oldflags;
145 /*
146 * Reuse the file descriptor, but only if the new access mode is
147 * equal or less permissive than the old. F_SETFL correctly
148 * ignores creation flags.
149 */
150 f = fp->_file;
151 if ((oldflags = fcntl (f, F_GETFL, 0)) == -1
152 || ! ((oldflags & O_ACCMODE) == O_RDWR
153 || ((oldflags ^ oflags) & O_ACCMODE) == 0)
154 || fcntl (f, F_SETFL, oflags) == -1)
155 f = -1;
156 #else
157 /* We cannot modify without fcntl support. */
158 f = -1;
159 #endif
160
161 #ifdef __SCLE
162 /*
163 * F_SETFL doesn't change textmode. Don't mess with modes of ttys.
164 */
165 if (0 <= f && ! isatty ( f)
166 && setmode (f, oflags & (O_BINARY | O_TEXT)) == -1)
167 f = -1;
168 #endif
169
170 if (f < 0)
171 {
172 e = EBADF;
173 if (fp->_close != NULL)
174 fp->_close (fp->_cookie);
175 }
176 }
177
178 /*
179 * Finish closing fp. Even if the open succeeded above,
180 * we cannot keep fp->_base: it may be the wrong size.
181 * This loses the effect of any setbuffer calls,
182 * but stdio has always done this before.
183 */
184
185 if (fp->_flags & __SMBF)
186 free ((char *) fp->_bf._base);
187 fp->_w = 0;
188 fp->_r = 0;
189 fp->_p = NULL;
190 fp->_bf._base = NULL;
191 fp->_bf._size = 0;
192 fp->_lbfsize = 0;
193 if (HASUB (fp))
194 FREEUB (ptr, fp);
195 fp->_ub._size = 0;
196 if (HASLB (fp))
197 FREELB (ptr, fp);
198 fp->_lb._size = 0;
199 fp->_flags &= ~__SORD;
200 fp->_flags2 &= ~__SWID;
201 memset (&fp->_mbstate, 0, sizeof (_mbstate_t));
202
203 if (f < 0)
204 { /* did not get it after all */
205 __sfp_lock_acquire ();
206 fp->_flags = 0; /* set it free */
207 _REENT_ERRNO(ptr) = e; /* restore in case _close clobbered */
208 if (!(oflags2 & __SNLK))
209 _funlockfile (fp);
210 #ifndef __SINGLE_THREAD__
211 __lock_close_recursive (fp->_lock);
212 #endif
213 __sfp_lock_release ();
214 #ifdef _STDIO_WITH_THREAD_CANCELLATION_SUPPORT
215 pthread_setcancelstate (__oldcancel, &__oldcancel);
216 #endif
217 return NULL;
218 }
219
220 fp->_flags = flags;
221 fp->_file = f;
222 fp->_cookie = (void *) fp;
223 fp->_read = __sread;
224 fp->_write = __swrite;
225 fp->_seek = __sseek;
226 fp->_close = __sclose;
227
228 #ifdef __SCLE
229 if (__stextmode (fp->_file))
230 fp->_flags |= __SCLE;
231 #endif
232
233 if (!(oflags2 & __SNLK))
234 _funlockfile (fp);
235 #ifdef _STDIO_WITH_THREAD_CANCELLATION_SUPPORT
236 pthread_setcancelstate (__oldcancel, &__oldcancel);
237 #endif
238 return fp;
239 }
240
