1 /* Read symbolic links into a buffer without size limitation, relative to fd.
2
3 Copyright (C) 2011-2023 Free Software Foundation, Inc.
4
5 This file is free software: you can redistribute it and/or modify
6 it under the terms of the GNU Lesser General Public License as
7 published by the Free Software Foundation; either version 2.1 of the
8 License, or (at your option) any later version.
9
10 This file is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public License
16 along with this program. If not, see <https://www.gnu.org/licenses/>. */
17
18 /* Written by Paul Eggert, Bruno Haible, and Jim Meyering. */
19
20 #ifndef _GL_CAREADLINKAT_H
21 #define _GL_CAREADLINKAT_H
22
23 #include <fcntl.h>
24 #include <unistd.h>
25
26 struct allocator;
27
28 /* Assuming the current directory is FD, get the symbolic link value
29 of FILENAME as a null-terminated string and put it into a buffer.
30 If FD is AT_FDCWD, FILENAME is interpreted relative to the current
31 working directory, as in openat.
32
33 If the link is small enough to fit into BUFFER put it there.
34 BUFFER's size is BUFFER_SIZE, and BUFFER can be null
35 if BUFFER_SIZE is zero.
36
37 If the link is not small, put it into a dynamically allocated
38 buffer managed by ALLOC. It is the caller's responsibility to free
39 the returned value if it is nonnull and is not BUFFER.
40
41 The PREADLINKAT function specifies how to read links. It operates
42 like POSIX readlinkat()
43 <https://pubs.opengroup.org/onlinepubs/9699919799/functions/readlink.html>
44 but can assume that its first argument is the same as FD.
45
46 If successful, return the buffer address; otherwise return NULL and
47 set errno. */
48
49 char *careadlinkat (int fd, char const *filename,
50 char *restrict buffer, size_t buffer_size,
51 struct allocator const *alloc,
52 ssize_t (*preadlinkat) (int, char const *,
53 char *, size_t));
54
55 /* Suitable value for careadlinkat's FD argument. */
56 #if HAVE_READLINKAT
57 /* AT_FDCWD is declared in <fcntl.h>. */
58 #else
59 /* Define AT_FDCWD independently, so that the careadlinkat module does
60 not depend on the fcntl-h module. We might as well use the same value
61 as fcntl-h. */
62 # ifndef AT_FDCWD
63 # define AT_FDCWD (-3041965)
64 # endif
65 #endif
66
67 #endif /* _GL_CAREADLINKAT_H */