| // 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 com.google.common.base.Preconditions; |
| import java.io.Closeable; |
| import java.io.IOException; |
| import java.io.OutputStream; |
| import java.io.PrintStream; |
| import java.io.PrintWriter; |
| |
| /** |
| * A pair of output streams to be used for redirecting the output and error streams of a subprocess. |
| */ |
| public class OutErr implements Closeable { |
| |
| private final OutputStream out; |
| private final OutputStream err; |
| |
| public static final OutErr SYSTEM_OUT_ERR = create(System.out, System.err); |
| |
| /** Creates a new OutErr instance from the specified output and error streams. */ |
| public static OutErr create(OutputStream out, OutputStream err) { |
| return new OutErr(out, err); |
| } |
| |
| protected OutErr(OutputStream out, OutputStream err) { |
| this.out = Preconditions.checkNotNull(out); |
| this.err = Preconditions.checkNotNull(err); |
| } |
| |
| @Override |
| public void close() throws IOException { |
| // Ensure that we close both out and err even if one throws. |
| try { |
| out.close(); |
| } finally { |
| if (out != err) { |
| err.close(); |
| } |
| } |
| } |
| |
| /** Returns a {@link SystemPatcher} that uses this instance's out and err streams. */ |
| public final SystemPatcher getSystemPatcher() { |
| return new SystemPatcher(out, err); |
| } |
| |
| /** |
| * Temporarily patches {@link System#out} and {@link System#err} with custom streams. |
| * |
| * <p>{@link #start} is called to signal the beginning of the scope of the patch. {@link #close} |
| * ends the scope of the patch, returning {@link System#out} and {@link System#err} to what they |
| * were when this instance was instantiated. |
| */ |
| public static class SystemPatcher implements AutoCloseable { |
| private final PrintStream savedOut; |
| private final PrintStream savedErr; |
| private final SwitchingPrintStream outPatch; |
| private final SwitchingPrintStream errPatch; |
| |
| private SystemPatcher(OutputStream overrideOut, OutputStream overrideErr) { |
| this.savedOut = System.out; |
| this.savedErr = System.err; |
| this.outPatch = new SwitchingPrintStream(overrideOut); |
| this.errPatch = new SwitchingPrintStream(overrideErr); |
| } |
| |
| public void start() { |
| System.setOut(outPatch); |
| System.setErr(errPatch); |
| } |
| |
| @Override |
| public void close() { |
| System.setOut(savedOut); |
| System.setErr(savedErr); |
| outPatch.switchBackTo(savedOut); |
| errPatch.switchBackTo(savedErr); |
| } |
| } |
| |
| /** |
| * Starts by streaming to {@code override}, then switches back to {@code saved}. |
| * |
| * <p>The switching strategy is used to guard against memory leaks. For example, if {@code |
| * override} is passed directly to {@link System#setErr}, anyone may retain a reference to it via |
| * {@link System#err}. Instead, they will get a reference to this class, which frees up {@code |
| * override} in {@link #switchBackTo}. |
| */ |
| private static final class SwitchingPrintStream extends PrintStream { |
| |
| private SwitchingPrintStream(OutputStream override) { |
| super(override, /*autoFlush=*/ true); |
| } |
| |
| private void switchBackTo(OutputStream saved) { |
| out = saved; |
| } |
| } |
| |
| public OutputStream getOutputStream() { |
| return out; |
| } |
| |
| public OutputStream getErrorStream() { |
| return err; |
| } |
| |
| /** Writes the specified string to the output stream, and flushes. */ |
| public void printOut(String s) { |
| PrintWriter writer = new PrintWriter(out, true); |
| writer.print(s); |
| writer.flush(); |
| } |
| |
| public void printOutLn(String s) { |
| printOut(s + "\n"); |
| } |
| |
| /** Writes the specified string to the error stream, and flushes. */ |
| public void printErr(String s) { |
| PrintWriter writer = new PrintWriter(err, true); |
| writer.print(s); |
| writer.flush(); |
| } |
| |
| public void printErrLn(String s) { |
| printErr(s + "\n"); |
| } |
| } |