sdk/fidl/fuchsia.io2/io2.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 Overview
///
library fuchsia.io2;

using zx;

/// The type for the name of a node, i.e. a single path component.
/// E.g. `foo`
///
/// ## Invariants
///
/// A valid node name must meet the following criteria:
///
/// * It cannot be longer than [`MAX_NAME_LENGTH`].
/// * It cannot be empty.
/// * It cannot be ".." (dot-dot).
/// * It cannot be "." (single dot).
/// * It cannot contain "/".
/// * It cannot contain embedded NUL.
alias Name = string:MAX_NAME_LENGTH;

/// The maximum length, in bytes, of a single filesystem component.
const uint64 MAX_NAME_LENGTH = 255;

/// A path is a string of one or more components, separated by "/".
/// E.g. `foo/bar/baz`
///
/// ## Invariants
///
/// A valid path must meet the following criteria:
///
/// * It cannot be empty.
/// * It cannot be longer than [`MAX_PATH_LENGTH`].
/// * It cannot have a leading "/".
/// * It cannot have a trailing "/".
/// * Each component must be a valid [`Name`].
///
/// Paths should be transformed into their canonical forms at client side.
/// For example, a client should convert `"foo/bar/.././baz/"` to `"foo/baz"`
/// before using it as a path.
alias Path = string:MAX_PATH_LENGTH;

/// The maximum length, in bytes, of a filesystem path.
const uint64 MAX_PATH_LENGTH = 4095;

/// The type to identify a connection to a node.
/// It represents a capability: a reference to a node with associated rights.
// TODO(fxb/65218): Replace with an alias.
using Token = zx.handle:EVENT;

/// The type to identify a node, if the implementation supports some notion of
/// unique node ID.
///
/// ## Uniqueness Guarantees
///
/// A client is usually presented with a directory tree that is the result
/// of composing together multiple backing implementation instances. An ID
/// would be unique within the corresponding instance only.
/// Their boundaries are rather implicit on Fuchsia, as a result of
/// transparently-forwarding directory proxies. It could be common for a client
/// to observe identical `Id`s when traversing a directory tree, when it
/// encounters nodes from different backing instances. Therefore, the ID is best
/// used for debugging and informational purposes.
///
/// If the implementation also supports [`fuchsia.fs/Query`], the
/// [`fuchsia.fs/FilesystemInfo.fs_id`] field may be used to disambiguate IDs
/// from different backing instances.
alias Id = uint64;