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// Copyright 2014 The Bazel Authors. 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 java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
/**
* An {@link OutErr} specialization that supports subscribing / removing
* sinks, using {@link #addSink(OutErr)} and {@link #removeSink(OutErr)}.
* A sink is a destination to which the {@link DelegatingOutErr} will write.
*
* Also, we can hook up {@link System#out} / {@link System#err} as sources.
*/
public final class DelegatingOutErr extends OutErr {
/**
* Create a new instance to which no sinks have subscribed (basically just
* like a {@code /dev/null}.
*/
public DelegatingOutErr() {
super(new DelegatingOutputStream(), new DelegatingOutputStream());
}
private final DelegatingOutputStream outSink() {
return (DelegatingOutputStream) getOutputStream();
}
private final DelegatingOutputStream errSink() {
return (DelegatingOutputStream) getErrorStream();
}
/**
* Add a sink, that is, after calling this method, {@code outErrSink} will
* receive all output / errors written to {@code this} object.
*/
public void addSink(OutErr outErrSink) {
outSink().addSink(outErrSink.getOutputStream());
errSink().addSink(outErrSink.getErrorStream());
}
/**
* Remove the sink, that is, after calling this method, {@code outErrSink}
* will no longer receive output / errors written to {@code this} object.
*/
public void removeSink(OutErr outErrSink) {
outSink().removeSink(outErrSink.getOutputStream());
errSink().removeSink(outErrSink.getErrorStream());
}
private static class DelegatingOutputStream extends OutputStream {
private final List<OutputStream> sinks = new ArrayList<>();
public void addSink(OutputStream sink) {
sinks.add(sink);
}
public void removeSink(OutputStream sink) {
sinks.remove(sink);
}
@Override
public void write(int b) throws IOException {
for (OutputStream sink : sinks) {
sink.write(b);
}
}
@Override
public void close() throws IOException {
for (OutputStream sink : sinks) {
sink.close();
}
}
@Override
public void flush() throws IOException {
for (OutputStream sink : sinks) {
sink.flush();
}
}
@Override
public void write(byte[] b, int off, int len) throws IOException {
for (OutputStream sink : sinks) {
sink.write(b, off, len);
}
}
@Override
public void write(byte[] b) throws IOException {
for (OutputStream sink : sinks) {
sink.write(b);
}
}
}
}
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