1/* Copyright (C) 1993-2024 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>.
17
18 As a special exception, if you link the code in this file with
19 files compiled with a GNU compiler to produce an executable,
20 that does not cause the resulting executable to be covered by
21 the GNU Lesser General Public License. This exception does not
22 however invalidate any other reasons why the executable file
23 might be covered by the GNU Lesser General Public License.
24 This exception applies to code released by its copyright holders
25 in files containing the exception. */
26
27#include <stdlib.h>
28#include "libioP.h"
29#include <fcntl.h>
30
31#include <shlib-compat.h>
32
33FILE *
34_IO_new_fdopen (int fd, const char *mode)
35{
36 int read_write;
37 struct locked_FILE
38 {
39 struct _IO_FILE_plus fp;
40#ifdef _IO_MTSAFE_IO
41 _IO_lock_t lock;
42#endif
43 struct _IO_wide_data wd;
44 } *new_f;
45 int i;
46 int use_mmap = 0;
47
48 /* Decide whether we modify the offset of the file we attach to and seek to
49 the end of file. We only do this if the mode is 'a' and if the file
50 descriptor did not have O_APPEND in its flags already. */
51 bool do_seek = false;
52
53 switch (*mode)
54 {
55 case 'r':
56 read_write = _IO_NO_WRITES;
57 break;
58 case 'w':
59 read_write = _IO_NO_READS;
60 break;
61 case 'a':
62 read_write = _IO_NO_READS|_IO_IS_APPENDING;
63 break;
64 default:
65 __set_errno (EINVAL);
66 return NULL;
67 }
68 for (i = 1; i < 5; ++i)
69 {
70 switch (*++mode)
71 {
72 case '\0':
73 break;
74 case '+':
75 read_write &= _IO_IS_APPENDING;
76 break;
77 case 'm':
78 use_mmap = 1;
79 continue;
80 case 'x':
81 case 'b':
82 default:
83 /* Ignore */
84 continue;
85 }
86 break;
87 }
88 int fd_flags = __fcntl (fd, F_GETFL);
89 if (fd_flags == -1)
90 return NULL;
91
92 if (((fd_flags & O_ACCMODE) == O_RDONLY && !(read_write & _IO_NO_WRITES))
93 || ((fd_flags & O_ACCMODE) == O_WRONLY && !(read_write & _IO_NO_READS)))
94 {
95 __set_errno (EINVAL);
96 return NULL;
97 }
98
99 /* The May 93 draft of P1003.4/D14.1 (redesignated as 1003.1b)
100 [System Application Program Interface (API) Amendment 1:
101 Realtime Extensions], Rationale B.8.3.3
102 Open a Stream on a File Descriptor says:
103
104 Although not explicitly required by POSIX.1, a good
105 implementation of append ("a") mode would cause the
106 O_APPEND flag to be set.
107
108 (Historical implementations [such as Solaris2] do a one-time
109 seek in fdopen.)
110
111 However, we do not turn O_APPEND off if the mode is "w" (even
112 though that would seem consistent) because that would be more
113 likely to break historical programs.
114 */
115 if ((read_write & _IO_IS_APPENDING) && !(fd_flags & O_APPEND))
116 {
117 do_seek = true;
118 if (__fcntl (fd, F_SETFL, fd_flags | O_APPEND) == -1)
119 return NULL;
120 }
121
122 new_f = (struct locked_FILE *) malloc (size: sizeof (struct locked_FILE));
123 if (new_f == NULL)
124 return NULL;
125#ifdef _IO_MTSAFE_IO
126 new_f->fp.file._lock = &new_f->lock;
127#endif
128 _IO_no_init (&new_f->fp.file, 0, 0, &new_f->wd,
129#if _G_HAVE_MMAP
130 (use_mmap && (read_write & _IO_NO_WRITES))
131 ? &_IO_wfile_jumps_maybe_mmap :
132#endif
133 &_IO_wfile_jumps);
134 _IO_JUMPS (&new_f->fp) =
135#if _G_HAVE_MMAP
136 (use_mmap && (read_write & _IO_NO_WRITES)) ? &_IO_file_jumps_maybe_mmap :
137#endif
138 &_IO_file_jumps;
139 _IO_new_file_init_internal (&new_f->fp);
140 /* We only need to record the fd because _IO_file_init_internal will
141 have unset the offset. It is important to unset the cached
142 offset because the real offset in the file could change between
143 now and when the handle is activated and we would then mislead
144 ftell into believing that we have a valid offset. */
145 new_f->fp.file._fileno = fd;
146 new_f->fp.file._flags &= ~_IO_DELETE_DONT_CLOSE;
147
148 _IO_mask_flags (&new_f->fp.file, read_write,
149 _IO_NO_READS+_IO_NO_WRITES+_IO_IS_APPENDING);
150
151 /* For append mode, set the file offset to the end of the file if we added
152 O_APPEND to the file descriptor flags. Don't update the offset cache
153 though, since the file handle is not active. */
154 if (do_seek && ((read_write & (_IO_IS_APPENDING | _IO_NO_READS))
155 == (_IO_IS_APPENDING | _IO_NO_READS)))
156 {
157 off64_t new_pos = _IO_SYSSEEK (&new_f->fp.file, 0, _IO_seek_end);
158 if (new_pos == _IO_pos_BAD && errno != ESPIPE)
159 return NULL;
160 }
161 return &new_f->fp.file;
162}
163libc_hidden_ver (_IO_new_fdopen, _IO_fdopen)
164
165strong_alias (_IO_new_fdopen, __new_fdopen)
166versioned_symbol (libc, _IO_new_fdopen, _IO_fdopen, GLIBC_2_1);
167versioned_symbol (libc, __new_fdopen, fdopen, GLIBC_2_1);
168

source code of glibc/libio/iofdopen.c