sdk/fidl/fuchsia.io/node-protocols.fidl

// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
library fuchsia.io;

/// A node may have multiple supported representations when opening, even though
/// it may have a fixed underlying identity.
///
/// Today, a file is accessed via the [`File`] protocol, and sends a
/// [`Representation.FileInfo`] when opened with `GET_REPRESENTATION`. However,
/// in the future we might introduce a more sophisticated `FileV2` protocol, or
/// a more efficient `SuperFastFile` backed by a specialized kernel object. New
/// clients can request the more advanced representations by specifying the
/// corresponding bits in [`NodeProtocolKinds`], whereas existing clients would
/// continue to talk to the node via the old representation.
///
/// [`NodeProtocolKinds`] enables forward-compatibility through a form of protocol
/// negotiation.
///
/// The elements have one-to-one correspondence with the members of
/// [`Representation`].
type NodeProtocolKinds = flexible bits : uint64 {
    /// The connector representation of a node.
    ///
    /// The connection will speak either [`Node`] or the target protocol,
    /// depending on the flags used during opening.
    CONNECTOR = 0x1;

    /// The directory representation of a node.
    ///
    /// The connection will speak the [`Directory`] protocol.
    DIRECTORY = 0x2;

    /// The file representation of a node.
    ///
    /// The connection will speak the [`File`] protocol.
    FILE = 0x4;

    /// The symlink representation of a node.
    ///
    /// The connection will speak the [`Symlink`] protocol.
    @available(added=HEAD)
    SYMLINK = 0x8;
};