message: Add doc comments for WASI FD associated constants
diff: @@ -122,16 +122,30 @@ pub struct Fd {
  pub rights_inheriting: __wasi_rights_t,
  pub flags: __wasi_fdflags_t,
  pub offset: u64,
  - /// Used when reopening the file on the host system
  + /// Flags that determine how the [`Fd`] can be used.
  + ///
  + /// Used when reopening a [`HostFile`] during [`WasiState`] deserialization.
  pub open_flags: u16,
  pub inode: Inode,
  }
  impl Fd {
  + /// This [`Fd`] can be used with read system calls.
  pub const READ: u16 = 1;
  + /// This [`Fd`] can be used with write system calls.
  pub const WRITE: u16 = 2;
  + /// This [`Fd`] can append in write system calls. Note that the append
  + /// permission implies the write permission.
  pub const APPEND: u16 = 4;
  + /// This [`Fd`] will delete everything before writing. Note that truncate
  + /// permissions require the write permission.
  + ///
  + /// This permission is currently unused when deserializing [`WasiState`].
  pub const TRUNCATE: u16 = 8;
  + /// This [`Fd`] may create a file before writing to it. Note that create
  + /// permissions require write permissions.
  + ///
  + /// This permission is currently unused when deserializing [`WasiState`].
  pub const CREATE: u16 = 16;
  }
  