1/*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
5 * use this file except in compliance with the License. You may obtain a copy of
6 * the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations under
14 * the License.
15 */
16package android.os;
17
18import android.annotation.NonNull;
19import android.annotation.Nullable;
20
21import java.util.concurrent.CompletableFuture;
22import java.util.concurrent.ExecutionException;
23import java.util.concurrent.TimeUnit;
24import java.util.concurrent.TimeoutException;
25
26/**
27 * Extends ResultReceiver to allow the server end of the ResultReceiver to synchronously wait
28 * on the response from the client. This enables an RPC like system but with the ability to
29 * timeout and discard late results.
30 *
31 * NOTE: Can only be used for one response. Subsequent responses on the same instance are ignored.
32 * {@hide}
33 */
34public class SynchronousResultReceiver extends ResultReceiver {
35    public static class Result {
36        public int resultCode;
37        @Nullable public Bundle bundle;
38
39        public Result(int resultCode, @Nullable Bundle bundle) {
40            this.resultCode = resultCode;
41            this.bundle = bundle;
42        }
43    }
44
45    private final CompletableFuture<Result> mFuture = new CompletableFuture<>();
46
47    public SynchronousResultReceiver() {
48        super((Handler) null);
49    }
50
51    @Override
52    final protected void onReceiveResult(int resultCode, Bundle resultData) {
53        super.onReceiveResult(resultCode, resultData);
54        mFuture.complete(new Result(resultCode, resultData));
55    }
56
57    /**
58     * Blocks waiting for the result from the remote client.
59     *
60     * @return the Result
61     * @throws TimeoutException if the timeout in milliseconds expired.
62     */
63    public @NonNull Result awaitResult(long timeoutMillis) throws TimeoutException {
64        final long deadline = System.currentTimeMillis() + timeoutMillis;
65        while (timeoutMillis >= 0) {
66            try {
67                return mFuture.get(timeoutMillis, TimeUnit.MILLISECONDS);
68            } catch (ExecutionException e) {
69                // This will NEVER happen.
70                throw new AssertionError("Error receiving response", e);
71            } catch (InterruptedException e) {
72                // The thread was interrupted, try and get the value again, this time
73                // with the remaining time until the deadline.
74                timeoutMillis -= deadline - System.currentTimeMillis();
75            }
76        }
77        throw new TimeoutException();
78    }
79
80}
81