/*
* Copyright (C) 2007 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 java.lang;
import java.io.File;
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.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.HashMap;
import java.util.Map;
import java.util.Arrays;
import java.util.logging.Logger;
import java.util.logging.Level;
/**
* Manages child processes.
*
* <p>Harmony's native implementation (for comparison purposes):
* http://tinyurl.com/3ytwuq
*/
final class ProcessManager {
/**
* constant communicated from native code indicating that a
* child died, but it was unable to determine the status
*/
private static final int WAIT_STATUS_UNKNOWN = -1;
/**
* constant communicated from native code indicating that there
* are currently no children to wait for
*/
private static final int WAIT_STATUS_NO_CHILDREN = -2;
/**
* constant communicated from native code indicating that a wait()
* call returned -1 and set an undocumented (and hence unexpected) errno
*/
private static final int WAIT_STATUS_STRANGE_ERRNO = -3;
/**
* Initializes native static state.
*/
static native void staticInitialize();
static {
staticInitialize();
}
/**
* Map from pid to Process. We keep weak references to the Process objects
* and clean up the entries when no more external references are left. The
* process objects themselves don't require much memory, but file
* descriptors (associated with stdin/out/err in this case) can be
* a scarce resource.
*/
private final Map<Integer, ProcessReference> processReferences
= new HashMap<Integer, ProcessReference>();
/** Keeps track of garbage-collected Processes. */
private final ProcessReferenceQueue referenceQueue
= new ProcessReferenceQueue();
private ProcessManager() {
// Spawn a thread to listen for signals from child processes.
Thread processThread = new Thread(ProcessManager.class.getName()) {
@Override
public void run() {
watchChildren();
}
};
processThread.setDaemon(true);
processThread.start();
}
/**
* Kills the process with the given ID.
*
* @parm pid ID of process to kill
*/
private static native void kill(int pid) throws IOException;
/**
* Cleans up after garbage collected processes. Requires the lock on the
* map.
*/
void cleanUp() {
ProcessReference reference;
while ((reference = referenceQueue.poll()) != null) {
synchronized (processReferences) {
processReferences.remove(reference.processId);
}
}
}
/**
* Listens for signals from processes and calls back to
* {@link #onExit(int,int)}.
*/
native void watchChildren();
/**
* Called by {@link #watchChildren()} when a child process exits.
*
* @param pid ID of process that exited
* @param exitValue value the process returned upon exit
*/
void onExit(int pid, int exitValue) {
ProcessReference processReference = null;
synchronized (processReferences) {
cleanUp();
if (pid >= 0) {
processReference = processReferences.remove(pid);
} else if (exitValue == WAIT_STATUS_NO_CHILDREN) {
if (processReferences.isEmpty()) {
/*
* There are no eligible children; wait for one to be
* added. The wait() will return due to the
* notifyAll() call below.
*/
try {
processReferences.wait();
} catch (InterruptedException ex) {
// This should never happen.
throw new AssertionError("unexpected interrupt");
}
} else {
/*
* A new child was spawned just before we entered
* the synchronized block. We can just fall through
* without doing anything special and land back in
* the native wait().
*/
}
} else {
// Something weird is happening; abort!
throw new AssertionError("unexpected wait() behavior");
}
}
if (processReference != null) {
ProcessImpl process = processReference.get();
if (process != null) {
process.setExitValue(exitValue);
}
}
}
/**
* Executes a native process. Fills in in, out, and err and returns the
* new process ID upon success.
*/
static native int exec(String[] commands, String[] environment,
String workingDirectory, FileDescriptor in, FileDescriptor out,
FileDescriptor err) throws IOException;
/**
* Executes a process and returns an object representing it.
*/
Process exec(String[] commands, String[] environment,
File workingDirectory) throws IOException {
FileDescriptor in = new FileDescriptor();
FileDescriptor out = new FileDescriptor();
FileDescriptor err = new FileDescriptor();
String workingPath = (workingDirectory == null)
? null
: workingDirectory.getPath();
// Ensure onExit() doesn't access the process map before we add our
// entry.
synchronized (processReferences) {
int pid;
try {
pid = exec(commands, environment, workingPath, in, out, err);
} catch (IOException e) {
IOException wrapper = new IOException("Error running exec()."
+ " Commands: " + Arrays.toString(commands)
+ " Working Directory: " + workingDirectory
+ " Environment: " + Arrays.toString(environment));
wrapper.initCause(e);
throw wrapper;
}
ProcessImpl process = new ProcessImpl(pid, in, out, err);
ProcessReference processReference
= new ProcessReference(process, referenceQueue);
processReferences.put(pid, processReference);
/*
* This will wake up the child monitor thread in case there
* weren't previously any children to wait on.
*/
processReferences.notifyAll();
return process;
}
}
static class ProcessImpl extends Process {
/** Process ID. */
final int id;
final InputStream errorStream;
/** Reads output from process. */
final InputStream inputStream;
/** Sends output to process. */
final OutputStream outputStream;
/** The process's exit value. */
Integer exitValue = null;
final Object exitValueMutex = new Object();
ProcessImpl(int id, FileDescriptor in, FileDescriptor out,
FileDescriptor err) {
this.id = id;
this.errorStream = new ProcessInputStream(err);
this.inputStream = new ProcessInputStream(in);
this.outputStream = new ProcessOutputStream(out);
}
public void destroy() {
try {
kill(this.id);
} catch (IOException e) {
Logger.getLogger(Runtime.class.getName()).log(Level.FINE,
"Failed to destroy process " + id + ".", e);
}
}
public int exitValue() {
synchronized (exitValueMutex) {
if (exitValue == null) {
throw new IllegalThreadStateException(
"Process has not yet terminated.");
}
return exitValue;
}
}
public InputStream getErrorStream() {
return this.errorStream;
}
public InputStream getInputStream() {
return this.inputStream;
}
public OutputStream getOutputStream() {
return this.outputStream;
}
public int waitFor() throws InterruptedException {
synchronized (exitValueMutex) {
while (exitValue == null) {
exitValueMutex.wait();
}
return exitValue;
}
}
void setExitValue(int exitValue) {
synchronized (exitValueMutex) {
this.exitValue = exitValue;
exitValueMutex.notifyAll();
}
}
@Override
public String toString() {
return "Process[id=" + id + "]";
}
}
static class ProcessReference extends WeakReference<ProcessImpl> {
final int processId;
public ProcessReference(ProcessImpl referent,
ProcessReferenceQueue referenceQueue) {
super(referent, referenceQueue);
this.processId = referent.id;
}
}
static class ProcessReferenceQueue extends ReferenceQueue<ProcessImpl> {
@Override
public ProcessReference poll() {
// Why couldn't they get the generics right on ReferenceQueue? :(
Object reference = super.poll();
return (ProcessReference) reference;
}
}
static final ProcessManager instance = new ProcessManager();
/** Gets the process manager. */
static ProcessManager getInstance() {
return instance;
}
/** Automatically closes fd when collected. */
private static class ProcessInputStream extends FileInputStream {
private FileDescriptor fd;
private ProcessInputStream(FileDescriptor fd) {
super(fd);
this.fd = fd;
}
@Override
public void close() throws IOException {
try {
super.close();
} finally {
synchronized (this) {
if (fd != null && fd.valid()) {
try {
ProcessManager.close(fd);
} finally {
fd = null;
}
}
}
}
}
}
/** Automatically closes fd when collected. */
private static class ProcessOutputStream extends FileOutputStream {
private FileDescriptor fd;
private ProcessOutputStream(FileDescriptor fd) {
super(fd);
this.fd = fd;
}
@Override
public void close() throws IOException {
try {
super.close();
} finally {
synchronized (this) {
if (fd != null && fd.valid()) {
try {
ProcessManager.close(fd);
} finally {
fd = null;
}
}
}
}
}
}
/** Closes the given file descriptor. */
private static native void close(FileDescriptor fd) throws IOException;
}
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