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sdk-common library used by other Android tools libraries.
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/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * 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.android.ide.common.process;

import com.android.annotations.NonNull;
import com.android.utils.ILogger;
import com.google.common.base.Joiner;
import com.google.common.collect.Lists;
import com.google.common.io.ByteStreams;
import com.google.common.io.Closeables;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.List;
import java.util.Map;

/**
 * Simple implementation of ProcessExecutor, using the standard Java Process(Builder) API.
 */
public class DefaultProcessExecutor implements ProcessExecutor {

    private final ILogger mLogger;

    public DefaultProcessExecutor(ILogger logger) {
        mLogger = logger;
    }

    @NonNull
    @Override
    public ProcessResult execute(
            @NonNull ProcessInfo processInfo,
            @NonNull ProcessOutputHandler processOutputHandler) {

        List command = Lists.newArrayList();
        command.add(processInfo.getExecutable());
        command.addAll(processInfo.getArgs());

        String commandString = Joiner.on(' ').join(command);
        mLogger.info("command: " + commandString);

        try {
            // launch the command line process
            ProcessBuilder processBuilder = new ProcessBuilder(command);

            Map envVariableMap = processInfo.getEnvironment();

            if (!envVariableMap.isEmpty()) {
                Map env = processBuilder.environment();
                for (Map.Entry entry : envVariableMap.entrySet()) {
                    env.put(entry.getKey(), entry.getValue().toString());
                }
            }

            // start the process
            Process process = processBuilder.start();
            // and grab the output, and the exit code
            ProcessOutput output = processOutputHandler.createOutput();
            int exitCode = grabProcessOutput(process, output);

            processOutputHandler.handleOutput(output);

            return new ProcessResultImpl(commandString, exitCode);
        } catch (IOException e) {
            return new ProcessResultImpl(commandString, e);
        } catch (InterruptedException e) {
            // Restore the interrupted status
            Thread.currentThread().interrupt();
            return new ProcessResultImpl(commandString, e);
        } catch (ProcessException e) {
            return new ProcessResultImpl(commandString, e);
        }
    }

    /**
     * Get the stderr/stdout outputs of a process and return when the process is done.
     * Both must be read or the process will block on windows.
     *
     * @param process The process to get the output from.
     * @param output The processOutput containing where to send the output.
     *      Note that on Windows capturing the output is not optional. If output is null
     *      the stdout/stderr will be captured and discarded.
     * @return the process return code.
     * @throws InterruptedException if {@link Process#waitFor()} was interrupted.
     */
    private static int grabProcessOutput(
            @NonNull final Process process,
            @NonNull final ProcessOutput output) throws InterruptedException {
        Thread threadErr = new Thread("stderr") {
            @Override
            public void run() {
                InputStream stderr = process.getErrorStream();
                OutputStream stream = output.getErrorOutput();

                try {
                    ByteStreams.copy(stderr, stream);
                    stream.flush();
                } catch (IOException e) {
                    // ignore?
                } finally {
                    try {
                        Closeables.close(stderr, true /* swallowIOException */);
                    } catch (IOException e) {
                        // cannot happen
                    }
                    try {
                        Closeables.close(stream, true /* swallowIOException */);
                    } catch (IOException e) {
                        // cannot happen
                    }

                }
            }
        };

        Thread threadOut = new Thread("stdout") {
            @Override
            public void run() {
                InputStream stdout = process.getInputStream();
                OutputStream stream = output.getStandardOutput();

                try {
                    ByteStreams.copy(stdout, stream);
                    stream.flush();
                } catch (IOException e) {
                    // ignore?
                } finally {
                    try {
                        Closeables.close(stdout, true /* swallowIOException */);
                    } catch (IOException e) {
                        // cannot happen
                    }
                    try {
                        Closeables.close(stream, true /* swallowIOException */);
                    } catch (IOException e) {
                        // cannot happen
                    }

                }
            }
        };

        threadErr.start();
        threadOut.start();

        // it looks like on windows process#waitFor() can return
        // before the thread have filled the arrays, so we wait for both threads and the
        // process itself.
        threadErr.join();
        threadOut.join();

        // get the return code from the process
        return process.waitFor();
    }
}