1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of 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,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package dexfuzz;
18
19import java.io.BufferedReader;
20import java.io.InputStream;
21import java.io.InputStreamReader;
22import java.io.IOException;
23import java.util.ArrayList;
24import java.util.List;
25import java.util.concurrent.Semaphore;
26
27/**
28 * process.waitFor() can block if its output buffers are not drained.
29 * These threads are used to keep the buffers drained, and provide the final
30 * output once the command has finished executing. Each Executor has its own
31 * output and error StreamConsumers.
32 */
33public class StreamConsumer extends Thread {
34  private List<String> output;
35  private BufferedReader reader;
36
37  private State state;
38
39  private Semaphore workToBeDone;
40  private Semaphore outputIsReady;
41
42  enum State {
43    WAITING,
44    CONSUMING,
45    SHOULD_STOP_CONSUMING,
46    FINISHED,
47    ERROR
48  }
49
50  /**
51   * Create a StreamConsumer, will be immediately ready to start consuming.
52   */
53  public StreamConsumer() {
54    output = new ArrayList<String>();
55    workToBeDone = new Semaphore(0);
56    outputIsReady = new Semaphore(0);
57
58    state = State.WAITING;
59  }
60
61  /**
62   * Executor should call this to provide its StreamConsumers with the Streams
63   * for a Process it is about to call waitFor() on.
64   */
65  public void giveStreamAndStartConsuming(InputStream stream) {
66    output.clear();
67
68    reader = new BufferedReader(new InputStreamReader(stream));
69
70    changeState(State.CONSUMING, State.WAITING);
71
72    // Tell consumer there is work to be done.
73    workToBeDone.release();
74  }
75
76  /**
77   * Executor should call this once its call to waitFor() returns.
78   */
79  public void processFinished() {
80    changeState(State.SHOULD_STOP_CONSUMING, State.CONSUMING);
81  }
82
83  /**
84   * Executor should call this to get the captured output of this StreamConsumer.
85   */
86  public List<String> getOutput() {
87
88    try {
89      // Wait until the output is ready.
90      outputIsReady.acquire();
91    } catch (InterruptedException e) {
92      Log.error("Client of StreamConsumer was interrupted while waiting for output?");
93      return null;
94    }
95
96    // Take a copy of the Strings, so when we call output.clear(), we don't
97    // clear the ExecutionResult's list.
98    List<String> copy = new ArrayList<String>(output);
99    return copy;
100  }
101
102  /**
103   * Executor should call this when we're shutting down.
104   */
105  public void shutdown() {
106    changeState(State.FINISHED, State.WAITING);
107
108    // Tell Consumer there is work to be done (it will check first if FINISHED has been set.)
109    workToBeDone.release();
110  }
111
112  private void consume() {
113    try {
114
115      if (checkState(State.SHOULD_STOP_CONSUMING)) {
116        // Caller already called processFinished() before we even started
117        // consuming. Just get what we can and finish.
118        while (reader.ready()) {
119          output.add(reader.readLine());
120        }
121      } else {
122        // Caller's process is still executing, so just loop and consume.
123        while (checkState(State.CONSUMING)) {
124          Thread.sleep(50);
125          while (reader.ready()) {
126            output.add(reader.readLine());
127          }
128        }
129      }
130
131      if (checkState(State.SHOULD_STOP_CONSUMING)) {
132        changeState(State.WAITING, State.SHOULD_STOP_CONSUMING);
133      } else {
134        Log.error("StreamConsumer stopped consuming, but was not told to?");
135        setErrorState();
136      }
137
138      reader.close();
139
140    } catch (IOException e) {
141      Log.error("StreamConsumer caught IOException while consuming");
142      setErrorState();
143    } catch (InterruptedException e) {
144      Log.error("StreamConsumer caught InterruptedException while consuming");
145      setErrorState();
146    }
147
148    // Tell client of Consumer that the output is ready.
149    outputIsReady.release();
150  }
151
152  @Override
153  public void run() {
154    while (checkState(State.WAITING)) {
155      try {
156        // Wait until there is work to be done
157        workToBeDone.acquire();
158      } catch (InterruptedException e) {
159        Log.error("StreamConsumer caught InterruptedException while waiting for work");
160        setErrorState();
161        break;
162      }
163
164      // Check first if we're done
165      if (checkState(State.FINISHED)) {
166        break;
167      }
168
169      // Make sure we're either supposed to be consuming
170      // or supposed to be finishing up consuming
171      if (!(checkState(State.CONSUMING) || checkState(State.SHOULD_STOP_CONSUMING))) {
172        Log.error("invalid state: StreamConsumer told about work, but not CONSUMING?");
173        Log.error("state was: " + getCurrentState());
174        setErrorState();
175        break;
176      }
177
178      consume();
179    }
180  }
181
182  private synchronized boolean checkState(State expectedState) {
183    return (expectedState == state);
184  }
185
186  private synchronized void changeState(State newState, State previousState) {
187    if (state != previousState) {
188      Log.error("StreamConsumer Unexpected state: " + state + ", expected " + previousState);
189      state = State.ERROR;
190    } else {
191      state = newState;
192    }
193  }
194
195  private synchronized void setErrorState() {
196    state = State.ERROR;
197  }
198
199  private synchronized State getCurrentState() {
200    return state;
201  }
202}
203