afc5abc48571ed1510e91b56ba13d9d7151a8819
[lttng-tools.git] / src / common / fs-handle.h
1 /*
2 * Copyright (C) 2020 Jérémie Galarneau <jeremie.galarneau@efficios.com>
3 *
4 * SPDX-License-Identifier: LGPL-2.1-only
5 *
6 */
7
8 #ifndef FS_HANDLE_H
9 #define FS_HANDLE_H
10
11 #include <common/macros.h>
12 #include <stdio.h>
13
14 #ifdef __cplusplus
15 extern "C" {
16 #endif
17
18 struct fs_handle;
19
20 /*
21 * Marks the handle as the most recently used and marks the 'fd' as
22 * "in-use". This prevents the tracker from recycling the underlying
23 * file descriptor while it is actively being used by a thread.
24 *
25 * Don't forget that the tracker may be initiating an fd 'suspension'
26 * from another thread as the need to free an fd slot may arise from any
27 * thread within the daemon.
28 *
29 * Note that a restorable fd should never be held for longer than
30 * strictly necessary (e.g. the duration of a syscall()).
31 *
32 * Returns the fd on success, otherwise a negative value may be returned
33 * if the restoration of the fd failed.
34 */
35 int fs_handle_get_fd(struct fs_handle *handle);
36
37 /*
38 * Used by the caller to signal that it is no longer using the underlying fd and
39 * that it may be safely suspended.
40 */
41 void fs_handle_put_fd(struct fs_handle *handle);
42
43 /*
44 * Unlink the file associated to an fs_handle. Note that the unlink
45 * operation will not be performed immediately. It will only be performed
46 * once all references to the underlying file (through other fs_handle objects)
47 * have been released.
48 *
49 * However, note that the file will be renamed so as to provide the observable
50 * effect of an unlink(), that is removing a name from the filesystem.
51 *
52 * Returns 0 on success, otherwise a negative value will be returned
53 * if the operation failed.
54 */
55 int fs_handle_unlink(struct fs_handle *handle);
56
57 /*
58 * Frees the handle and discards the underlying fd.
59 */
60 int fs_handle_close(struct fs_handle *handle);
61
62 ssize_t fs_handle_read(struct fs_handle *handle, void *buf, size_t count);
63
64 ssize_t fs_handle_write(struct fs_handle *handle, const void *buf, size_t count);
65
66 int fs_handle_truncate(struct fs_handle *handle, off_t offset);
67
68 off_t fs_handle_seek(struct fs_handle *handle, off_t offset, int whence);
69
70 #ifdef __cplusplus
71 }
72 #endif
73
74 #endif /* FS_HANDLE_H */
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