[lttng-tools.git] / src / common / fs-handle.h

/*
 * Copyright (C) 2020 Jérémie Galarneau <jeremie.galarneau@efficios.com>
 *
 * SPDX-License-Identifier: LGPL-2.1-only
 *
 */

#ifndef FS_HANDLE_H
#define FS_HANDLE_H

#include <common/macros.h>
#include <stdio.h>

#ifdef __cplusplus
extern "C" {
#endif

struct fs_handle;

/*
 * Marks the handle as the most recently used and marks the 'fd' as
 * "in-use". This prevents the tracker from recycling the underlying
 * file descriptor while it is actively being used by a thread.
 *
 * Don't forget that the tracker may be initiating an fd 'suspension'
 * from another thread as the need to free an fd slot may arise from any
 * thread within the daemon.
 *
 * Note that a restorable fd should never be held for longer than
 * strictly necessary (e.g. the duration of a syscall()).
 *
 * Returns the fd on success, otherwise a negative value may be returned
 * if the restoration of the fd failed.
 */
int fs_handle_get_fd(struct fs_handle *handle);

/*
 * Used by the caller to signal that it is no longer using the underlying fd and
 * that it may be safely suspended.
 */
void fs_handle_put_fd(struct fs_handle *handle);

/*
 * Unlink the file associated to an fs_handle. Note that the unlink
 * operation will not be performed immediately. It will only be performed
 * once all references to the underlying file (through other fs_handle objects)
 * have been released.
 *
 * However, note that the file will be renamed so as to provide the observable
 * effect of an unlink(), that is removing a name from the filesystem.
 *
 * Returns 0 on success, otherwise a negative value will be returned
 * if the operation failed.
 */
int fs_handle_unlink(struct fs_handle *handle);

/*
 * Frees the handle and discards the underlying fd.
 */
int fs_handle_close(struct fs_handle *handle);

ssize_t fs_handle_read(struct fs_handle *handle, void *buf, size_t count);

ssize_t fs_handle_write(struct fs_handle *handle, const void *buf, size_t count);

int fs_handle_truncate(struct fs_handle *handle, off_t offset);

off_t fs_handle_seek(struct fs_handle *handle, off_t offset, int whence);

#ifdef __cplusplus
}
#endif

#endif /* FS_HANDLE_H */
Commit	Line	Data
	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 */