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