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 */