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// Copyright 2017 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.modular;
using fuchsia.mem;
/// A multi-typed data entity.
protocol Entity {
/// Returns the types associated with this entity. Each entry in `types`
/// references a well-known content type.
GetTypes() -> (vector<string> types);
/// Given one of the types returned from `GetTypes()` above, returns
/// associated short-form data, or null if the type is absent from
/// `GetTypes()`.
GetData(string type) -> (fuchsia.mem.Buffer? data);
/// Sets the data for a particular type. This will precipitate an `OnUpdated`
/// event with the associated type.
WriteData(string type, fuchsia.mem.Buffer data)
-> (EntityWriteStatus status);
/// Gets the entity reference for this entity, which can be persisted and
/// then later used to locate this entity. These references are weak
/// references and are not sufficient to keep the entity alive.
GetReference() -> (string entity_reference);
/// Begins watching for data changes on a particular type. The watcher
/// immediately fires `OnUpdated` with the current value for the requested
/// type (or null if the type is not present). Closing the `Entity` interface
/// does not close the watcher.
Watch(string type, EntityWatcher watcher);
protocol EntityWatcher {
/// Fires on data updates for a particular type. If the type is initially not
/// present, a null `data` pointer is produced. The type may only transition
/// from absent to present at most once, as there is no deletion.
/// No deduplication is performed.
OnUpdated(fuchsia.mem.Buffer? data);
enum EntityWriteStatus {
OK = 0;
/// Indicates a failure of the entity provider to write the update.
ERROR = 1;
/// Entity providers are not necessarily required to support entity mutation.