src/common/fs-handle.hpp

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