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// Copyright 2014 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.devtools.build.lib.util.io;
import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
import com.google.devtools.build.lib.vfs.Path;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
/**
* The FileWatcher dumps the contents of a files into an OutErr.
* It then stays active and dumps any content to the OutErr that is
* added to the file, until it is told to stop and all output has
* been dumped.
*
* This is useful to emulate streaming test output.
*/
@ThreadSafe
public class FileWatcher extends Thread {
// How often we check for updates in the file we watch. (in ms)
private static final int WATCH_INTERVAL = 100;
private final Path outputFile;
private final OutErr output;
private volatile boolean finishPumping;
private long toSkip = 0;
/**
* Creates a FileWatcher that will dump any output that is appended to
* outputFile onto output. If skipExisting is true, the watcher will not dump
* any output that is in outputFile when we construct the watcher. If
* skipExisting is false, already existing output will be dumped, too.
*
* @param outputFile the File to watch
* @param output the outErr to dump the files contents to
* @param skipExisting whether to dump already existing output or not.
*/
public FileWatcher(Path outputFile, OutErr output, boolean skipExisting) throws IOException {
super("Streaming Test Output Pump");
this.outputFile = outputFile;
this.output = output;
finishPumping = false;
if (outputFile.exists() && skipExisting) {
toSkip = outputFile.getFileSize();
}
}
/**
* Tells the FileWatcher to stop pumping output and finish.
* The FileWatcher will only finish until there is no data left to display.
* This means that it is rarely a good idea to unconditionally wait for the
* FileWatcher thread to terminate -- Instead, it is better to have a timeout.
*/
@ThreadSafe
public void stopPumping() {
finishPumping = true;
}
@Override
public void run() {
try {
// Wait until the file exists, or we have to abort.
while (!outputFile.exists() && !finishPumping) {
Thread.sleep(WATCH_INTERVAL);
}
// Check that we did not have abort before the file was created.
if (outputFile.exists()) {
try (InputStream inputStream = outputFile.getInputStream();
OutputStream outputStream = output.getOutputStream();) {
byte[] buffer = new byte[1024];
while (!finishPumping || (inputStream.available() != 0)) {
if (inputStream.available() != 0) {
if (toSkip > 0) {
toSkip -= inputStream.skip(toSkip);
} else {
int read = inputStream.read(buffer);
if (read > 0) {
outputStream.write(buffer, 0, read);
}
}
} else {
Thread.sleep(WATCH_INTERVAL);
}
}
}
}
} catch (IOException ex) {
output.printOutLn("Failure reading or writing: " + ex.getMessage());
} catch (InterruptedException ex) {
// Don't do anything.
}
}
}
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