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	/*
	* Copyright (c) 1995, 2017, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.lang;

	import java.io.*;
	import java.lang.ProcessBuilder.Redirect;
	import java.util.concurrent.CompletableFuture;
	import java.util.concurrent.ForkJoinPool;
	import java.util.concurrent.TimeUnit;
	import java.util.stream.Stream;

	/**
	* {@code Process} provides control of native processes started by
	* ProcessBuilder.start and Runtime.exec.
	* The class provides methods for performing input from the process, performing
	* output to the process, waiting for the process to complete,
	* checking the exit status of the process, and destroying (killing)
	* the process.
	* The {@link ProcessBuilder#start()} and
	* {@link Runtime#exec(String[],String[],File) Runtime.exec}
	* methods create a native process and return an instance of a
	* subclass of {@code Process} that can be used to control the process
	* and obtain information about it.
	*
	* <p>The methods that create processes may not work well for special
	* processes on certain native platforms, such as native windowing
	* processes, daemon processes, Win16/DOS processes on Microsoft
	* Windows, or shell scripts.
	*
	* <p>By default, the created process does not have its own terminal
	* or console. All its standard I/O (i.e. stdin, stdout, stderr)
	* operations will be redirected to the parent process, where they can
	* be accessed via the streams obtained using the methods
	* {@link #getOutputStream()},
	* {@link #getInputStream()}, and
	* {@link #getErrorStream()}.
	* The parent process uses these streams to feed input to and get output
	* from the process. Because some native platforms only provide
	* limited buffer size for standard input and output streams, failure
	* to promptly write the input stream or read the output stream of
	* the process may cause the process to block, or even deadlock.
	*
	* <p>Where desired, <a href="ProcessBuilder.html#redirect-input">
	* process I/O can also be redirected</a>
	* using methods of the {@link ProcessBuilder} class.
	*
	* <p>The process is not killed when there are no more references to
	* the {@code Process} object, but rather the process
	* continues executing asynchronously.
	*
	* <p>There is no requirement that the process represented by a {@code
	* Process} object execute asynchronously or concurrently with respect
	* to the Java process that owns the {@code Process} object.
	*
	* <p>As of 1.5, {@link ProcessBuilder#start()} is the preferred way
	* to create a {@code Process}.
	*
	* <p>Subclasses of Process should override the {@link #onExit()} and
	* {@link #toHandle()} methods to provide a fully functional Process including the
	* {@linkplain #pid() process id},
	* {@linkplain #info() information about the process},
	* {@linkplain #children() direct children}, and
	* {@linkplain #descendants() direct children plus descendants of those children} of the process.
	* Delegating to the underlying Process or ProcessHandle is typically
	* easiest and most efficient.
	*
	* @since 1.0
	*/
	public abstract class Process {
	/**
	* Default constructor for Process.
	*/
	public Process() {}

	/**
	* Returns the output stream connected to the normal input of the
	* process. Output to the stream is piped into the standard
	* input of the process represented by this {@code Process} object.
	*
	* <p>If the standard input of the process has been redirected using
	* {@link ProcessBuilder#redirectInput(Redirect)
	* ProcessBuilder.redirectInput}
	* then this method will return a
	* <a href="ProcessBuilder.html#redirect-input">null output stream</a>.
	*
	* <p>Implementation note: It is a good idea for the returned
	* output stream to be buffered.
	*
	* @return the output stream connected to the normal input of the
	* process
	*/
	public abstract OutputStream getOutputStream();

	/**
	* Returns the input stream connected to the normal output of the
	* process. The stream obtains data piped from the standard
	* output of the process represented by this {@code Process} object.
	*
	* <p>If the standard output of the process has been redirected using
	* {@link ProcessBuilder#redirectOutput(Redirect)
	* ProcessBuilder.redirectOutput}
	* then this method will return a
	* <a href="ProcessBuilder.html#redirect-output">null input stream</a>.
	*
	* <p>Otherwise, if the standard error of the process has been
	* redirected using
	* {@link ProcessBuilder#redirectErrorStream(boolean)
	* ProcessBuilder.redirectErrorStream}
	* then the input stream returned by this method will receive the
	* merged standard output and the standard error of the process.
	*
	* <p>Implementation note: It is a good idea for the returned
	* input stream to be buffered.
	*
	* @return the input stream connected to the normal output of the
	* process
	*/
	public abstract InputStream getInputStream();

	/**
	* Returns the input stream connected to the error output of the
	* process. The stream obtains data piped from the error output
	* of the process represented by this {@code Process} object.
	*
	* <p>If the standard error of the process has been redirected using
	* {@link ProcessBuilder#redirectError(Redirect)
	* ProcessBuilder.redirectError} or
	* {@link ProcessBuilder#redirectErrorStream(boolean)
	* ProcessBuilder.redirectErrorStream}
	* then this method will return a
	* <a href="ProcessBuilder.html#redirect-output">null input stream</a>.
	*
	* <p>Implementation note: It is a good idea for the returned
	* input stream to be buffered.
	*
	* @return the input stream connected to the error output of
	* the process
	*/
	public abstract InputStream getErrorStream();

	/**
	* Causes the current thread to wait, if necessary, until the
	* process represented by this {@code Process} object has
	* terminated. This method returns immediately if the process
	* has already terminated. If the process has not yet
	* terminated, the calling thread will be blocked until the
	* process exits.
	*
	* @return the exit value of the process represented by this
	* {@code Process} object. By convention, the value
	* {@code 0} indicates normal termination.
	* @throws InterruptedException if the current thread is
	* {@linkplain Thread#interrupt() interrupted} by another
	* thread while it is waiting, then the wait is ended and
	* an {@link InterruptedException} is thrown.
	*/
	public abstract int waitFor() throws InterruptedException;

	/**
	* Causes the current thread to wait, if necessary, until the
	* process represented by this {@code Process} object has
	* terminated, or the specified waiting time elapses.
	*
	* <p>If the process has already terminated then this method returns
	* immediately with the value {@code true}. If the process has not
	* terminated and the timeout value is less than, or equal to, zero, then
	* this method returns immediately with the value {@code false}.
	*
	* <p>The default implementation of this methods polls the {@code exitValue}
	* to check if the process has terminated. Concrete implementations of this
	* class are strongly encouraged to override this method with a more
	* efficient implementation.
	*
	* @param timeout the maximum time to wait
	* @param unit the time unit of the {@code timeout} argument
	* @return {@code true} if the process has exited and {@code false} if
	* the waiting time elapsed before the process has exited.
	* @throws InterruptedException if the current thread is interrupted
	* while waiting.
	* @throws NullPointerException if unit is null
	* @since 1.8
	*/
	public boolean waitFor(long timeout, TimeUnit unit)
	throws InterruptedException
	{
	long startTime = System.nanoTime();
	long rem = unit.toNanos(timeout);

	do {
	try {
	exitValue();
	return true;
	} catch(IllegalThreadStateException ex) {
	if (rem > 0)
	Thread.sleep(
	Math.min(TimeUnit.NANOSECONDS.toMillis(rem) + 1, 100));
	}
	rem = unit.toNanos(timeout) - (System.nanoTime() - startTime);
	} while (rem > 0);
	return false;
	}

	/**
	* Returns the exit value for the process.
	*
	* @return the exit value of the process represented by this
	* {@code Process} object. By convention, the value
	* {@code 0} indicates normal termination.
	* @throws IllegalThreadStateException if the process represented
	* by this {@code Process} object has not yet terminated
	*/
	public abstract int exitValue();

	/**
	* Kills the process.
	* Whether the process represented by this {@code Process} object is
	* {@linkplain #supportsNormalTermination normally terminated} or not is
	* implementation dependent.
	* Forcible process destruction is defined as the immediate termination of a
	* process, whereas normal termination allows the process to shut down cleanly.
	* If the process is not alive, no action is taken.
	* <p>
	* The {@link java.util.concurrent.CompletableFuture} from {@link #onExit} is
	* {@linkplain java.util.concurrent.CompletableFuture#complete completed}
	* when the process has terminated.
	*/
	public abstract void destroy();

	/**
	* Kills the process forcibly. The process represented by this
	* {@code Process} object is forcibly terminated.
	* Forcible process destruction is defined as the immediate termination of a
	* process, whereas normal termination allows the process to shut down cleanly.
	* If the process is not alive, no action is taken.
	* <p>
	* The {@link java.util.concurrent.CompletableFuture} from {@link #onExit} is
	* {@linkplain java.util.concurrent.CompletableFuture#complete completed}
	* when the process has terminated.
	* <p>
	* Invoking this method on {@code Process} objects returned by
	* {@link ProcessBuilder#start} and {@link Runtime#exec} forcibly terminate
	* the process.
	*
	* @implSpec
	* The default implementation of this method invokes {@link #destroy}
	* and so may not forcibly terminate the process.
	* @implNote
	* Concrete implementations of this class are strongly encouraged to override
	* this method with a compliant implementation.
	* @apiNote
	* The process may not terminate immediately.
	* i.e. {@code isAlive()} may return true for a brief period
	* after {@code destroyForcibly()} is called. This method
	* may be chained to {@code waitFor()} if needed.
	*
	* @return the {@code Process} object representing the
	* process forcibly destroyed
	* @since 1.8
	*/
	public Process destroyForcibly() {
	destroy();
	return this;
	}

	/**
	* Returns {@code true} if the implementation of {@link #destroy} is to
	* normally terminate the process,
	* Returns {@code false} if the implementation of {@code destroy}
	* forcibly and immediately terminates the process.
	* <p>
	* Invoking this method on {@code Process} objects returned by
	* {@link ProcessBuilder#start} and {@link Runtime#exec} return
	* {@code true} or {@code false} depending on the platform implementation.
	*
	* @implSpec
	* This implementation throws an instance of
	* {@link java.lang.UnsupportedOperationException} and performs no other action.
	*
	* @return {@code true} if the implementation of {@link #destroy} is to
	* normally terminate the process;
	* otherwise, {@link #destroy} forcibly terminates the process
	* @throws UnsupportedOperationException if the Process implementation
	* does not support this operation
	* @since 9
	*/
	public boolean supportsNormalTermination() {
	throw new UnsupportedOperationException(this.getClass()
	+ ".supportsNormalTermination() not supported" );
	}

	/**
	* Tests whether the process represented by this {@code Process} is
	* alive.
	*
	* @return {@code true} if the process represented by this
	* {@code Process} object has not yet terminated.
	* @since 1.8
	*/
	public boolean isAlive() {
	try {
	exitValue();
	return false;
	} catch(IllegalThreadStateException e) {
	return true;
	}
	}

	/**
	* Returns the native process ID of the process.
	* The native process ID is an identification number that the operating
	* system assigns to the process.
	*
	* @implSpec
	* The implementation of this method returns the process id as:
	* {@link #toHandle toHandle().pid()}.
	*
	* @return the native process id of the process
	* @throws UnsupportedOperationException if the Process implementation
	* does not support this operation
	* @since 9
	*/
	public long pid() {
	return toHandle().pid();
	}

	/**
	* Returns a {@code CompletableFuture<Process>} for the termination of the Process.
	* The {@link java.util.concurrent.CompletableFuture} provides the ability
	* to trigger dependent functions or actions that may be run synchronously
	* or asynchronously upon process termination.
	* When the process has terminated the CompletableFuture is
	* {@link java.util.concurrent.CompletableFuture#complete completed} regardless
	* of the exit status of the process.
	* <p>
	* Calling {@code onExit().get()} waits for the process to terminate and returns
	* the Process. The future can be used to check if the process is
	* {@linkplain java.util.concurrent.CompletableFuture#isDone done} or to
	* {@linkplain java.util.concurrent.CompletableFuture#get() wait} for it to terminate.
	* {@linkplain java.util.concurrent.CompletableFuture#cancel(boolean) Cancelling}
	* the CompletableFuture does not affect the Process.
	* <p>
	* Processes returned from {@link ProcessBuilder#start} override the
	* default implementation to provide an efficient mechanism to wait
	* for process exit.
	*
	* @apiNote
	* Using {@link #onExit() onExit} is an alternative to
	* {@link #waitFor() waitFor} that enables both additional concurrency
	* and convenient access to the result of the Process.
	* Lambda expressions can be used to evaluate the result of the Process
	* execution.
	* If there is other processing to be done before the value is used
	* then {@linkplain #onExit onExit} is a convenient mechanism to
	* free the current thread and block only if and when the value is needed.
	* <br>
	* For example, launching a process to compare two files and get a boolean if they are identical:
	* <pre> {@code Process p = new ProcessBuilder("cmp", "f1", "f2").start();
	* Future<Boolean> identical = p.onExit().thenApply(p1 -> p1.exitValue() == 0);
	* ...
	* if (identical.get()) { ... }
	* }</pre>
	*
	* @implSpec
	* This implementation executes {@link #waitFor()} in a separate thread
	* repeatedly until it returns successfully. If the execution of
	* {@code waitFor} is interrupted, the thread's interrupt status is preserved.
	* <p>
	* When {@link #waitFor()} returns successfully the CompletableFuture is
	* {@linkplain java.util.concurrent.CompletableFuture#complete completed} regardless
	* of the exit status of the process.
	*
	* This implementation may consume a lot of memory for thread stacks if a
	* large number of processes are waited for concurrently.
	* <p>
	* External implementations should override this method and provide
	* a more efficient implementation. For example, to delegate to the underlying
	* process, it can do the following:
	* <pre>{@code
	* public CompletableFuture<Process> onExit() {
	* return delegate.onExit().thenApply(p -> this);
	* }
	* }</pre>
	* @apiNote
	* The process may be observed to have terminated with {@link #isAlive}
	* before the ComputableFuture is completed and dependent actions are invoked.
	*
	* @return a new {@code CompletableFuture<Process>} for the Process
	*
	* @since 9
	*/
	public CompletableFuture<Process> onExit() {
	return CompletableFuture.supplyAsync(this::waitForInternal);
	}

	/**
	* Wait for the process to exit by calling {@code waitFor}.
	* If the thread is interrupted, remember the interrupted state to
	* be restored before returning. Use ForkJoinPool.ManagedBlocker
	* so that the number of workers in case ForkJoinPool is used is
	* compensated when the thread blocks in waitFor().
	*
	* @return the Process
	*/
	private Process waitForInternal() {
	boolean interrupted = false;
	while (true) {
	try {
	ForkJoinPool.managedBlock(new ForkJoinPool.ManagedBlocker() {
	@Override
	public boolean block() throws InterruptedException {
	waitFor();
	return true;
	}

	@Override
	public boolean isReleasable() {
	return !isAlive();
	}
	});
	break;
	} catch (InterruptedException x) {
	interrupted = true;
	}
	}
	if (interrupted) {
	Thread.currentThread().interrupt();
	}
	return this;
	}

	/**
	* Returns a ProcessHandle for the Process.
	*
	* {@code Process} objects returned by {@link ProcessBuilder#start} and
	* {@link Runtime#exec} implement {@code toHandle} as the equivalent of
	* {@link ProcessHandle#of(long) ProcessHandle.of(pid)} including the
	* check for a SecurityManager and {@code RuntimePermission("manageProcess")}.
	*
	* @implSpec
	* This implementation throws an instance of
	* {@link java.lang.UnsupportedOperationException} and performs no other action.
	* Subclasses should override this method to provide a ProcessHandle for the
	* process. The methods {@link #pid}, {@link #info}, {@link #children},
	* and {@link #descendants}, unless overridden, operate on the ProcessHandle.
	*
	* @return Returns a ProcessHandle for the Process
	* @throws UnsupportedOperationException if the Process implementation
	* does not support this operation
	* @throws SecurityException if a security manager has been installed and
	* it denies RuntimePermission("manageProcess")
	* @since 9
	*/
	public ProcessHandle toHandle() {
	throw new UnsupportedOperationException(this.getClass()
	+ ".toHandle() not supported");
	}

	/**
	* Returns a snapshot of information about the process.
	*
	* <p> A {@link ProcessHandle.Info} instance has accessor methods
	* that return information about the process if it is available.
	*
	* @implSpec
	* This implementation returns information about the process as:
	* {@link #toHandle toHandle().info()}.
	*
	* @return a snapshot of information about the process, always non-null
	* @throws UnsupportedOperationException if the Process implementation
	* does not support this operation
	* @since 9
	*/
	public ProcessHandle.Info info() {
	return toHandle().info();
	}

	/**
	* Returns a snapshot of the direct children of the process.
	* The parent of a direct child process is the process.
	* Typically, a process that is {@linkplain #isAlive not alive} has no children.
	* <p>
	* <em>Note that processes are created and terminate asynchronously.
	* There is no guarantee that a process is {@linkplain #isAlive alive}.
	* </em>
	*
	* @implSpec
	* This implementation returns the direct children as:
	* {@link #toHandle toHandle().children()}.
	*
	* @return a sequential Stream of ProcessHandles for processes that are
	* direct children of the process
	* @throws UnsupportedOperationException if the Process implementation
	* does not support this operation
	* @throws SecurityException if a security manager has been installed and
	* it denies RuntimePermission("manageProcess")
	* @since 9
	*/
	public Stream<ProcessHandle> children() {
	return toHandle().children();
	}

	/**
	* Returns a snapshot of the descendants of the process.
	* The descendants of a process are the children of the process
	* plus the descendants of those children, recursively.
	* Typically, a process that is {@linkplain #isAlive not alive} has no children.
	* <p>
	* <em>Note that processes are created and terminate asynchronously.
	* There is no guarantee that a process is {@linkplain #isAlive alive}.
	* </em>
	*
	* @implSpec
	* This implementation returns all children as:
	* {@link #toHandle toHandle().descendants()}.
	*
	* @return a sequential Stream of ProcessHandles for processes that
	* are descendants of the process
	* @throws UnsupportedOperationException if the Process implementation
	* does not support this operation
	* @throws SecurityException if a security manager has been installed and
	* it denies RuntimePermission("manageProcess")
	* @since 9
	*/
	public Stream<ProcessHandle> descendants() {
	return toHandle().descendants();
	}

	/**
	* An input stream for a subprocess pipe that skips by reading bytes
	* instead of seeking, the underlying pipe does not support seek.
	*/
	static class PipeInputStream extends FileInputStream {

	PipeInputStream(FileDescriptor fd) {
	super(fd);
	}

	@Override
	public long skip(long n) throws IOException {
	long remaining = n;
	int nr;

	if (n <= 0) {
	return 0;
	}

	int size = (int)Math.min(2048, remaining);
	byte[] skipBuffer = new byte[size];
	while (remaining > 0) {
	nr = read(skipBuffer, 0, (int)Math.min(size, remaining));
	if (nr < 0) {
	break;
	}
	remaining -= nr;
	}

	return n - remaining;
	}
	}
	}

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