8154231: Simplify access to System properties from JDK code
Reviewed-by: rriggs, chegar, weijun
/*
* Copyright (c) 2003, 2015, 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.lang.ProcessBuilder.Redirect;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.ByteArrayInputStream;
import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.EnumSet;
import java.util.Locale;
import java.util.Set;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.TimeUnit;
import java.security.AccessController;
import static java.security.AccessController.doPrivileged;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Properties;
import jdk.internal.misc.JavaIOFileDescriptorAccess;
import jdk.internal.misc.SharedSecrets;
import sun.security.action.GetPropertyAction;
/**
* java.lang.Process subclass in the UNIX environment.
*
* @author Mario Wolczko and Ross Knippel.
* @author Konstantin Kladko (ported to Linux and Bsd)
* @author Martin Buchholz
* @author Volker Simonis (ported to AIX)
* @since 1.5
*/
final class ProcessImpl extends Process {
private static final JavaIOFileDescriptorAccess fdAccess
= SharedSecrets.getJavaIOFileDescriptorAccess();
// Linux platforms support a normal (non-forcible) kill signal.
static final boolean SUPPORTS_NORMAL_TERMINATION = true;
private final int pid;
private final ProcessHandleImpl processHandle;
private int exitcode;
private boolean hasExited;
private /* final */ OutputStream stdin;
private /* final */ InputStream stdout;
private /* final */ InputStream stderr;
// only used on Solaris
private /* final */ DeferredCloseInputStream stdout_inner_stream;
private static enum LaunchMechanism {
// order IS important!
FORK,
POSIX_SPAWN,
VFORK
}
private static enum Platform {
LINUX(LaunchMechanism.VFORK, LaunchMechanism.FORK),
BSD(LaunchMechanism.POSIX_SPAWN, LaunchMechanism.FORK),
SOLARIS(LaunchMechanism.POSIX_SPAWN, LaunchMechanism.FORK),
AIX(LaunchMechanism.POSIX_SPAWN, LaunchMechanism.FORK);
final LaunchMechanism defaultLaunchMechanism;
final Set<LaunchMechanism> validLaunchMechanisms;
Platform(LaunchMechanism ... launchMechanisms) {
this.defaultLaunchMechanism = launchMechanisms[0];
this.validLaunchMechanisms =
EnumSet.copyOf(Arrays.asList(launchMechanisms));
}
@SuppressWarnings("fallthrough")
private String helperPath(String javahome, String osArch) {
switch (this) {
case SOLARIS:
if (osArch.equals("x86")) { osArch = "i386"; }
else if (osArch.equals("x86_64")) { osArch = "amd64"; }
// fall through...
case LINUX:
case AIX:
return javahome + "/lib/" + osArch + "/jspawnhelper";
case BSD:
return javahome + "/lib/jspawnhelper";
default:
throw new AssertionError("Unsupported platform: " + this);
}
}
String helperPath() {
Properties props = GetPropertyAction.getProperties();
return helperPath(props.getProperty("java.home"),
props.getProperty("os.arch"));
}
LaunchMechanism launchMechanism() {
return AccessController.doPrivileged(
(PrivilegedAction<LaunchMechanism>) () -> {
String s = System.getProperty(
"jdk.lang.Process.launchMechanism");
LaunchMechanism lm;
if (s == null) {
lm = defaultLaunchMechanism;
s = lm.name().toLowerCase(Locale.ENGLISH);
} else {
try {
lm = LaunchMechanism.valueOf(
s.toUpperCase(Locale.ENGLISH));
} catch (IllegalArgumentException e) {
lm = null;
}
}
if (lm == null || !validLaunchMechanisms.contains(lm)) {
throw new Error(
s + " is not a supported " +
"process launch mechanism on this platform."
);
}
return lm;
}
);
}
static Platform get() {
String osName = GetPropertyAction.getProperty("os.name");
if (osName.equals("Linux")) { return LINUX; }
if (osName.contains("OS X")) { return BSD; }
if (osName.equals("SunOS")) { return SOLARIS; }
if (osName.equals("AIX")) { return AIX; }
throw new Error(osName + " is not a supported OS platform.");
}
}
private static final Platform platform = Platform.get();
private static final LaunchMechanism launchMechanism = platform.launchMechanism();
private static final byte[] helperpath = toCString(platform.helperPath());
private static byte[] toCString(String s) {
if (s == null)
return null;
byte[] bytes = s.getBytes();
byte[] result = new byte[bytes.length + 1];
System.arraycopy(bytes, 0,
result, 0,
bytes.length);
result[result.length-1] = (byte)0;
return result;
}
// Only for use by ProcessBuilder.start()
static Process start(String[] cmdarray,
java.util.Map<String,String> environment,
String dir,
ProcessBuilder.Redirect[] redirects,
boolean redirectErrorStream)
throws IOException
{
assert cmdarray != null && cmdarray.length > 0;
// Convert arguments to a contiguous block; it's easier to do
// memory management in Java than in C.
byte[][] args = new byte[cmdarray.length-1][];
int size = args.length; // For added NUL bytes
for (int i = 0; i < args.length; i++) {
args[i] = cmdarray[i+1].getBytes();
size += args[i].length;
}
byte[] argBlock = new byte[size];
int i = 0;
for (byte[] arg : args) {
System.arraycopy(arg, 0, argBlock, i, arg.length);
i += arg.length + 1;
// No need to write NUL bytes explicitly
}
int[] envc = new int[1];
byte[] envBlock = ProcessEnvironment.toEnvironmentBlock(environment, envc);
int[] std_fds;
FileInputStream f0 = null;
FileOutputStream f1 = null;
FileOutputStream f2 = null;
try {
boolean forceNullOutputStream = false;
if (redirects == null) {
std_fds = new int[] { -1, -1, -1 };
} else {
std_fds = new int[3];
if (redirects[0] == Redirect.PIPE) {
std_fds[0] = -1;
} else if (redirects[0] == Redirect.INHERIT) {
std_fds[0] = 0;
} else if (redirects[0] instanceof ProcessBuilder.RedirectPipeImpl) {
std_fds[0] = fdAccess.get(((ProcessBuilder.RedirectPipeImpl) redirects[0]).getFd());
} else {
f0 = new FileInputStream(redirects[0].file());
std_fds[0] = fdAccess.get(f0.getFD());
}
if (redirects[1] == Redirect.PIPE) {
std_fds[1] = -1;
} else if (redirects[1] == Redirect.INHERIT) {
std_fds[1] = 1;
} else if (redirects[1] instanceof ProcessBuilder.RedirectPipeImpl) {
std_fds[1] = fdAccess.get(((ProcessBuilder.RedirectPipeImpl) redirects[1]).getFd());
// Force getInputStream to return a null stream,
// the fd is directly assigned to the next process.
forceNullOutputStream = true;
} else {
f1 = new FileOutputStream(redirects[1].file(),
redirects[1].append());
std_fds[1] = fdAccess.get(f1.getFD());
}
if (redirects[2] == Redirect.PIPE) {
std_fds[2] = -1;
} else if (redirects[2] == Redirect.INHERIT) {
std_fds[2] = 2;
} else if (redirects[2] instanceof ProcessBuilder.RedirectPipeImpl) {
std_fds[2] = fdAccess.get(((ProcessBuilder.RedirectPipeImpl) redirects[2]).getFd());
} else {
f2 = new FileOutputStream(redirects[2].file(),
redirects[2].append());
std_fds[2] = fdAccess.get(f2.getFD());
}
}
Process p = new ProcessImpl
(toCString(cmdarray[0]),
argBlock, args.length,
envBlock, envc[0],
toCString(dir),
std_fds,
forceNullOutputStream,
redirectErrorStream);
if (redirects != null) {
// Copy the fd's if they are to be redirected to another process
if (std_fds[0] >= 0 &&
redirects[0] instanceof ProcessBuilder.RedirectPipeImpl) {
fdAccess.set(((ProcessBuilder.RedirectPipeImpl) redirects[0]).getFd(), std_fds[0]);
}
if (std_fds[1] >= 0 &&
redirects[1] instanceof ProcessBuilder.RedirectPipeImpl) {
fdAccess.set(((ProcessBuilder.RedirectPipeImpl) redirects[1]).getFd(), std_fds[1]);
}
if (std_fds[2] >= 0 &&
redirects[2] instanceof ProcessBuilder.RedirectPipeImpl) {
fdAccess.set(((ProcessBuilder.RedirectPipeImpl) redirects[2]).getFd(), std_fds[2]);
}
}
return p;
} finally {
// In theory, close() can throw IOException
// (although it is rather unlikely to happen here)
try { if (f0 != null) f0.close(); }
finally {
try { if (f1 != null) f1.close(); }
finally { if (f2 != null) f2.close(); }
}
}
}
/**
* Creates a process. Depending on the {@code mode} flag, this is done by
* one of the following mechanisms:
* <pre>
* 1 - fork(2) and exec(2)
* 2 - posix_spawn(3P)
* 3 - vfork(2) and exec(2)
* </pre>
* @param fds an array of three file descriptors.
* Indexes 0, 1, and 2 correspond to standard input,
* standard output and standard error, respectively. On
* input, a value of -1 means to create a pipe to connect
* child and parent processes. On output, a value which
* is not -1 is the parent pipe fd corresponding to the
* pipe which has been created. An element of this array
* is -1 on input if and only if it is <em>not</em> -1 on
* output.
* @return the pid of the subprocess
*/
private native int forkAndExec(int mode, byte[] helperpath,
byte[] prog,
byte[] argBlock, int argc,
byte[] envBlock, int envc,
byte[] dir,
int[] fds,
boolean redirectErrorStream)
throws IOException;
private ProcessImpl(final byte[] prog,
final byte[] argBlock, final int argc,
final byte[] envBlock, final int envc,
final byte[] dir,
final int[] fds,
final boolean forceNullOutputStream,
final boolean redirectErrorStream)
throws IOException {
pid = forkAndExec(launchMechanism.ordinal() + 1,
helperpath,
prog,
argBlock, argc,
envBlock, envc,
dir,
fds,
redirectErrorStream);
processHandle = ProcessHandleImpl.getInternal(pid);
try {
doPrivileged((PrivilegedExceptionAction<Void>) () -> {
initStreams(fds, forceNullOutputStream);
return null;
});
} catch (PrivilegedActionException ex) {
throw (IOException) ex.getException();
}
}
static FileDescriptor newFileDescriptor(int fd) {
FileDescriptor fileDescriptor = new FileDescriptor();
fdAccess.set(fileDescriptor, fd);
return fileDescriptor;
}
/**
* Initialize the streams from the file descriptors.
* @param fds array of stdin, stdout, stderr fds
* @param forceNullOutputStream true if the stdout is being directed to
* a subsequent process. The stdout stream should be a null output stream .
* @throws IOException
*/
void initStreams(int[] fds, boolean forceNullOutputStream) throws IOException {
switch (platform) {
case LINUX:
case BSD:
stdin = (fds[0] == -1) ?
ProcessBuilder.NullOutputStream.INSTANCE :
new ProcessPipeOutputStream(fds[0]);
stdout = (fds[1] == -1 || forceNullOutputStream) ?
ProcessBuilder.NullInputStream.INSTANCE :
new ProcessPipeInputStream(fds[1]);
stderr = (fds[2] == -1) ?
ProcessBuilder.NullInputStream.INSTANCE :
new ProcessPipeInputStream(fds[2]);
ProcessHandleImpl.completion(pid, true).handle((exitcode, throwable) -> {
synchronized (this) {
this.exitcode = (exitcode == null) ? -1 : exitcode.intValue();
this.hasExited = true;
this.notifyAll();
}
if (stdout instanceof ProcessPipeInputStream)
((ProcessPipeInputStream) stdout).processExited();
if (stderr instanceof ProcessPipeInputStream)
((ProcessPipeInputStream) stderr).processExited();
if (stdin instanceof ProcessPipeOutputStream)
((ProcessPipeOutputStream) stdin).processExited();
return null;
});
break;
case SOLARIS:
stdin = (fds[0] == -1) ?
ProcessBuilder.NullOutputStream.INSTANCE :
new BufferedOutputStream(
new FileOutputStream(newFileDescriptor(fds[0])));
stdout = (fds[1] == -1) ?
ProcessBuilder.NullInputStream.INSTANCE :
new BufferedInputStream(
stdout_inner_stream =
new DeferredCloseInputStream(
newFileDescriptor(fds[1])));
stderr = (fds[2] == -1) ?
ProcessBuilder.NullInputStream.INSTANCE :
new DeferredCloseInputStream(newFileDescriptor(fds[2]));
/*
* For each subprocess forked a corresponding reaper task
* is submitted. That task is the only thread which waits
* for the subprocess to terminate and it doesn't hold any
* locks while doing so. This design allows waitFor() and
* exitStatus() to be safely executed in parallel (and they
* need no native code).
*/
ProcessHandleImpl.completion(pid, true).handle((exitcode, throwable) -> {
synchronized (this) {
this.exitcode = (exitcode == null) ? -1 : exitcode.intValue();
this.hasExited = true;
this.notifyAll();
}
return null;
});
break;
case AIX:
stdin = (fds[0] == -1) ?
ProcessBuilder.NullOutputStream.INSTANCE :
new ProcessPipeOutputStream(fds[0]);
stdout = (fds[1] == -1) ?
ProcessBuilder.NullInputStream.INSTANCE :
new DeferredCloseProcessPipeInputStream(fds[1]);
stderr = (fds[2] == -1) ?
ProcessBuilder.NullInputStream.INSTANCE :
new DeferredCloseProcessPipeInputStream(fds[2]);
ProcessHandleImpl.completion(pid, true).handle((exitcode, throwable) -> {
synchronized (this) {
this.exitcode = (exitcode == null) ? -1 : exitcode.intValue();
this.hasExited = true;
this.notifyAll();
}
if (stdout instanceof DeferredCloseProcessPipeInputStream)
((DeferredCloseProcessPipeInputStream) stdout).processExited();
if (stderr instanceof DeferredCloseProcessPipeInputStream)
((DeferredCloseProcessPipeInputStream) stderr).processExited();
if (stdin instanceof ProcessPipeOutputStream)
((ProcessPipeOutputStream) stdin).processExited();
return null;
});
break;
default: throw new AssertionError("Unsupported platform: " + platform);
}
}
public OutputStream getOutputStream() {
return stdin;
}
public InputStream getInputStream() {
return stdout;
}
public InputStream getErrorStream() {
return stderr;
}
public synchronized int waitFor() throws InterruptedException {
while (!hasExited) {
wait();
}
return exitcode;
}
@Override
public synchronized boolean waitFor(long timeout, TimeUnit unit)
throws InterruptedException
{
long remainingNanos = unit.toNanos(timeout); // throw NPE before other conditions
if (hasExited) return true;
if (timeout <= 0) return false;
long deadline = System.nanoTime() + remainingNanos;
do {
// Round up to next millisecond
wait(TimeUnit.NANOSECONDS.toMillis(remainingNanos + 999_999L));
if (hasExited) {
return true;
}
remainingNanos = deadline - System.nanoTime();
} while (remainingNanos > 0);
return hasExited;
}
public synchronized int exitValue() {
if (!hasExited) {
throw new IllegalThreadStateException("process hasn't exited");
}
return exitcode;
}
private void destroy(boolean force) {
switch (platform) {
case LINUX:
case BSD:
case AIX:
// There is a risk that pid will be recycled, causing us to
// kill the wrong process! So we only terminate processes
// that appear to still be running. Even with this check,
// there is an unavoidable race condition here, but the window
// is very small, and OSes try hard to not recycle pids too
// soon, so this is quite safe.
synchronized (this) {
if (!hasExited)
processHandle.destroyProcess(force);
}
try { stdin.close(); } catch (IOException ignored) {}
try { stdout.close(); } catch (IOException ignored) {}
try { stderr.close(); } catch (IOException ignored) {}
break;
case SOLARIS:
// There is a risk that pid will be recycled, causing us to
// kill the wrong process! So we only terminate processes
// that appear to still be running. Even with this check,
// there is an unavoidable race condition here, but the window
// is very small, and OSes try hard to not recycle pids too
// soon, so this is quite safe.
synchronized (this) {
if (!hasExited)
processHandle.destroyProcess(force);
try {
stdin.close();
if (stdout_inner_stream != null)
stdout_inner_stream.closeDeferred(stdout);
if (stderr instanceof DeferredCloseInputStream)
((DeferredCloseInputStream) stderr)
.closeDeferred(stderr);
} catch (IOException e) {
// ignore
}
}
break;
default: throw new AssertionError("Unsupported platform: " + platform);
}
}
@Override
public CompletableFuture<Process> onExit() {
return ProcessHandleImpl.completion(pid, false)
.handleAsync((unusedExitStatus, unusedThrowable) -> {
boolean interrupted = false;
while (true) {
// Ensure that the concurrent task setting the exit status has completed
try {
waitFor();
break;
} catch (InterruptedException ie) {
interrupted = true;
}
}
if (interrupted) {
Thread.currentThread().interrupt();
}
return this;
});
}
@Override
public ProcessHandle toHandle() {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(new RuntimePermission("manageProcess"));
}
return processHandle;
}
@Override
public boolean supportsNormalTermination() {
return ProcessImpl.SUPPORTS_NORMAL_TERMINATION;
}
@Override
public void destroy() {
destroy(false);
}
@Override
public Process destroyForcibly() {
destroy(true);
return this;
}
@Override
public long getPid() {
return pid;
}
@Override
public synchronized boolean isAlive() {
return !hasExited;
}
private static native void init();
static {
init();
}
/**
* A buffered input stream for a subprocess pipe file descriptor
* that allows the underlying file descriptor to be reclaimed when
* the process exits, via the processExited hook.
*
* This is tricky because we do not want the user-level InputStream to be
* closed until the user invokes close(), and we need to continue to be
* able to read any buffered data lingering in the OS pipe buffer.
*/
private static class ProcessPipeInputStream extends BufferedInputStream {
private final Object closeLock = new Object();
ProcessPipeInputStream(int fd) {
super(new FileInputStream(newFileDescriptor(fd)));
}
private static byte[] drainInputStream(InputStream in)
throws IOException {
int n = 0;
int j;
byte[] a = null;
while ((j = in.available()) > 0) {
a = (a == null) ? new byte[j] : Arrays.copyOf(a, n + j);
n += in.read(a, n, j);
}
return (a == null || n == a.length) ? a : Arrays.copyOf(a, n);
}
/** Called by the process reaper thread when the process exits. */
synchronized void processExited() {
synchronized (closeLock) {
try {
InputStream in = this.in;
// this stream is closed if and only if: in == null
if (in != null) {
byte[] stragglers = drainInputStream(in);
in.close();
this.in = (stragglers == null) ?
ProcessBuilder.NullInputStream.INSTANCE :
new ByteArrayInputStream(stragglers);
}
} catch (IOException ignored) {}
}
}
@Override
public void close() throws IOException {
// BufferedInputStream#close() is not synchronized unlike most other
// methods. Synchronizing helps avoid race with processExited().
synchronized (closeLock) {
super.close();
}
}
}
/**
* A buffered output stream for a subprocess pipe file descriptor
* that allows the underlying file descriptor to be reclaimed when
* the process exits, via the processExited hook.
*/
private static class ProcessPipeOutputStream extends BufferedOutputStream {
ProcessPipeOutputStream(int fd) {
super(new FileOutputStream(newFileDescriptor(fd)));
}
/** Called by the process reaper thread when the process exits. */
synchronized void processExited() {
OutputStream out = this.out;
if (out != null) {
try {
out.close();
} catch (IOException ignored) {
// We know of no reason to get an IOException, but if
// we do, there's nothing else to do but carry on.
}
this.out = ProcessBuilder.NullOutputStream.INSTANCE;
}
}
}
// A FileInputStream that supports the deferment of the actual close
// operation until the last pending I/O operation on the stream has
// finished. This is required on Solaris because we must close the stdin
// and stdout streams in the destroy method in order to reclaim the
// underlying file descriptors. Doing so, however, causes any thread
// currently blocked in a read on one of those streams to receive an
// IOException("Bad file number"), which is incompatible with historical
// behavior. By deferring the close we allow any pending reads to see -1
// (EOF) as they did before.
//
private static class DeferredCloseInputStream extends FileInputStream
{
DeferredCloseInputStream(FileDescriptor fd) {
super(fd);
}
private Object lock = new Object(); // For the following fields
private boolean closePending = false;
private int useCount = 0;
private InputStream streamToClose;
private void raise() {
synchronized (lock) {
useCount++;
}
}
private void lower() throws IOException {
synchronized (lock) {
useCount--;
if (useCount == 0 && closePending) {
streamToClose.close();
}
}
}
// stc is the actual stream to be closed; it might be this object, or
// it might be an upstream object for which this object is downstream.
//
private void closeDeferred(InputStream stc) throws IOException {
synchronized (lock) {
if (useCount == 0) {
stc.close();
} else {
closePending = true;
streamToClose = stc;
}
}
}
public void close() throws IOException {
synchronized (lock) {
useCount = 0;
closePending = false;
}
super.close();
}
public int read() throws IOException {
raise();
try {
return super.read();
} finally {
lower();
}
}
public int read(byte[] b) throws IOException {
raise();
try {
return super.read(b);
} finally {
lower();
}
}
public int read(byte[] b, int off, int len) throws IOException {
raise();
try {
return super.read(b, off, len);
} finally {
lower();
}
}
public long skip(long n) throws IOException {
raise();
try {
return super.skip(n);
} finally {
lower();
}
}
public int available() throws IOException {
raise();
try {
return super.available();
} finally {
lower();
}
}
}
/**
* A buffered input stream for a subprocess pipe file descriptor
* that allows the underlying file descriptor to be reclaimed when
* the process exits, via the processExited hook.
*
* This is tricky because we do not want the user-level InputStream to be
* closed until the user invokes close(), and we need to continue to be
* able to read any buffered data lingering in the OS pipe buffer.
*
* On AIX this is especially tricky, because the 'close()' system call
* will block if another thread is at the same time blocked in a file
* operation (e.g. 'read()') on the same file descriptor. We therefore
* combine 'ProcessPipeInputStream' approach used on Linux and Bsd
* with the DeferredCloseInputStream approach used on Solaris. This means
* that every potentially blocking operation on the file descriptor
* increments a counter before it is executed and decrements it once it
* finishes. The 'close()' operation will only be executed if there are
* no pending operations. Otherwise it is deferred after the last pending
* operation has finished.
*
*/
private static class DeferredCloseProcessPipeInputStream
extends BufferedInputStream {
private final Object closeLock = new Object();
private int useCount = 0;
private boolean closePending = false;
DeferredCloseProcessPipeInputStream(int fd) {
super(new FileInputStream(newFileDescriptor(fd)));
}
private InputStream drainInputStream(InputStream in)
throws IOException {
int n = 0;
int j;
byte[] a = null;
synchronized (closeLock) {
if (buf == null) // asynchronous close()?
return null; // discard
j = in.available();
}
while (j > 0) {
a = (a == null) ? new byte[j] : Arrays.copyOf(a, n + j);
synchronized (closeLock) {
if (buf == null) // asynchronous close()?
return null; // discard
n += in.read(a, n, j);
j = in.available();
}
}
return (a == null) ?
ProcessBuilder.NullInputStream.INSTANCE :
new ByteArrayInputStream(n == a.length ? a : Arrays.copyOf(a, n));
}
/** Called by the process reaper thread when the process exits. */
synchronized void processExited() {
try {
InputStream in = this.in;
if (in != null) {
InputStream stragglers = drainInputStream(in);
in.close();
this.in = stragglers;
}
} catch (IOException ignored) { }
}
private void raise() {
synchronized (closeLock) {
useCount++;
}
}
private void lower() throws IOException {
synchronized (closeLock) {
useCount--;
if (useCount == 0 && closePending) {
closePending = false;
super.close();
}
}
}
@Override
public int read() throws IOException {
raise();
try {
return super.read();
} finally {
lower();
}
}
@Override
public int read(byte[] b) throws IOException {
raise();
try {
return super.read(b);
} finally {
lower();
}
}
@Override
public int read(byte[] b, int off, int len) throws IOException {
raise();
try {
return super.read(b, off, len);
} finally {
lower();
}
}
@Override
public long skip(long n) throws IOException {
raise();
try {
return super.skip(n);
} finally {
lower();
}
}
@Override
public int available() throws IOException {
raise();
try {
return super.available();
} finally {
lower();
}
}
@Override
public void close() throws IOException {
// BufferedInputStream#close() is not synchronized unlike most other
// methods. Synchronizing helps avoid racing with drainInputStream().
synchronized (closeLock) {
if (useCount == 0) {
super.close();
}
else {
closePending = true;
}
}
}
}
}