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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
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*
* 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).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
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package sun.nio.ch;
import java.io.IOException;
import java.nio.channels.ClosedSelectorException;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.spi.SelectorProvider;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.function.Consumer;
import jdk.internal.misc.Unsafe;
/**
* Selector implementation based on poll
*/
public class PollSelectorImpl extends SelectorImpl {
// initial capacity of poll array
private static final int INITIAL_CAPACITY = 16;
// poll array, grows as needed
private int pollArrayCapacity = INITIAL_CAPACITY;
private int pollArraySize;
private AllocatedNativeObject pollArray;
// file descriptors used for interrupt
private final int fd0;
private final int fd1;
// keys for file descriptors in poll array, synchronize on selector
private final List<SelectionKeyImpl> pollKeys = new ArrayList<>();
// pending updates, queued by putEventOps
private final Object updateLock = new Object();
private final Deque<SelectionKeyImpl> updateKeys = new ArrayDeque<>();
// interrupt triggering and clearing
private final Object interruptLock = new Object();
private boolean interruptTriggered;
protected PollSelectorImpl(SelectorProvider sp) throws IOException {
super(sp);
int size = pollArrayCapacity * SIZE_POLLFD;
this.pollArray = new AllocatedNativeObject(size, false);
try {
long fds = IOUtil.makePipe(false);
this.fd0 = (int) (fds >>> 32);
this.fd1 = (int) fds;
} catch (IOException ioe) {
pollArray.free();
throw ioe;
}
// wakeup support
synchronized (this) {
setFirst(fd0, Net.POLLIN);
}
}
private void ensureOpen() {
if (!isOpen())
throw new ClosedSelectorException();
}
@Override
protected int doSelect(Consumer<SelectionKey> action, long timeout)
throws IOException
{
assert Thread.holdsLock(this);
int to = (int) Math.min(timeout, Integer.MAX_VALUE); // max poll timeout
boolean blocking = (to != 0);
boolean timedPoll = (to > 0);
processUpdateQueue();
processDeregisterQueue();
try {
begin(blocking);
int numPolled;
do {
long startTime = timedPoll ? System.nanoTime() : 0;
numPolled = poll(pollArray.address(), pollArraySize, to);
if (numPolled == IOStatus.INTERRUPTED && timedPoll) {
// timed poll interrupted so need to adjust timeout
long adjust = System.nanoTime() - startTime;
to -= TimeUnit.MILLISECONDS.convert(adjust, TimeUnit.NANOSECONDS);
if (to <= 0) {
// timeout expired so no retry
numPolled = 0;
}
}
} while (numPolled == IOStatus.INTERRUPTED);
assert numPolled <= pollArraySize;
} finally {
end(blocking);
}
processDeregisterQueue();
return processEvents(action);
}
/**
* Protected poll method allows different platform-specific
* native implementations
*/
protected int poll(long pollAddress, int numfds, int timeout) {
return poll0(pollAddress, numfds, timeout);
}
/**
* Process changes to the interest ops.
*/
private void processUpdateQueue() {
assert Thread.holdsLock(this);
synchronized (updateLock) {
SelectionKeyImpl ski;
while ((ski = updateKeys.pollFirst()) != null) {
int newEvents = ski.translateInterestOps();
if (ski.isValid()) {
int index = ski.getIndex();
assert index >= 0 && index < pollArraySize;
if (index > 0) {
assert pollKeys.get(index) == ski;
if (newEvents == 0) {
remove(ski);
} else {
update(ski, newEvents);
}
} else if (newEvents != 0) {
add(ski, newEvents);
}
}
}
}
}
/**
* Process the polled events.
* If the interrupt fd has been selected, drain it and clear the interrupt.
*/
private int processEvents(Consumer<SelectionKey> action)
throws IOException
{
assert Thread.holdsLock(this);
assert pollArraySize > 0 && pollArraySize == pollKeys.size();
int numKeysUpdated = 0;
for (int i = 1; i < pollArraySize; i++) {
int rOps = getReventOps(i);
if (rOps != 0) {
SelectionKeyImpl ski = pollKeys.get(i);
assert ski.getFDVal() == getDescriptor(i);
if (ski.isValid()) {
numKeysUpdated += processReadyEvents(rOps, ski, action);
}
}
}
// check for interrupt
if (getReventOps(0) != 0) {
assert getDescriptor(0) == fd0;
clearInterrupt();
}
return numKeysUpdated;
}
@Override
protected void implClose() throws IOException {
assert !isOpen();
assert Thread.holdsLock(this);
// prevent further wakeup
synchronized (interruptLock) {
interruptTriggered = true;
}
pollArray.free();
FileDispatcherImpl.closeIntFD(fd0);
FileDispatcherImpl.closeIntFD(fd1);
}
@Override
protected void implRegister(SelectionKeyImpl ski) {
assert ski.getIndex() == 0;
ensureOpen();
}
@Override
protected void implDereg(SelectionKeyImpl ski) throws IOException {
assert !ski.isValid();
assert Thread.holdsLock(this);
// remove from poll array
int index = ski.getIndex();
if (index > 0) {
remove(ski);
}
}
@Override
public void setEventOps(SelectionKeyImpl ski) {
ensureOpen();
synchronized (updateLock) {
updateKeys.addLast(ski);
}
}
@Override
public Selector wakeup() {
synchronized (interruptLock) {
if (!interruptTriggered) {
try {
IOUtil.write1(fd1, (byte)0);
} catch (IOException ioe) {
throw new InternalError(ioe);
}
interruptTriggered = true;
}
}
return this;
}
private void clearInterrupt() throws IOException {
synchronized (interruptLock) {
IOUtil.drain(fd0);
interruptTriggered = false;
}
}
/**
* Sets the first pollfd enty in the poll array to the given fd
*/
private void setFirst(int fd, int ops) {
assert pollArraySize == 0;
assert pollKeys.isEmpty();
putDescriptor(0, fd);
putEventOps(0, ops);
pollArraySize = 1;
pollKeys.add(null); // dummy element
}
/**
* Adds a pollfd entry to the poll array, expanding the poll array if needed.
*/
private void add(SelectionKeyImpl ski, int ops) {
expandIfNeeded();
int index = pollArraySize;
assert index > 0;
putDescriptor(index, ski.getFDVal());
putEventOps(index, ops);
putReventOps(index, 0);
ski.setIndex(index);
pollArraySize++;
pollKeys.add(ski);
assert pollKeys.size() == pollArraySize;
}
/**
* Update the events of pollfd entry.
*/
private void update(SelectionKeyImpl ski, int ops) {
int index = ski.getIndex();
assert index > 0 && index < pollArraySize;
assert getDescriptor(index) == ski.getFDVal();
putEventOps(index, ops);
}
/**
* Removes a pollfd entry from the poll array
*/
private void remove(SelectionKeyImpl ski) {
int index = ski.getIndex();
assert index > 0 && index < pollArraySize;
assert getDescriptor(index) == ski.getFDVal();
// replace pollfd at index with the last pollfd in array
int lastIndex = pollArraySize - 1;
if (lastIndex != index) {
SelectionKeyImpl lastKey = pollKeys.get(lastIndex);
assert lastKey.getIndex() == lastIndex;
int lastFd = getDescriptor(lastIndex);
int lastOps = getEventOps(lastIndex);
int lastRevents = getReventOps(lastIndex);
assert lastKey.getFDVal() == lastFd;
putDescriptor(index, lastFd);
putEventOps(index, lastOps);
putReventOps(index, lastRevents);
pollKeys.set(index, lastKey);
lastKey.setIndex(index);
}
pollKeys.remove(lastIndex);
pollArraySize--;
assert pollKeys.size() == pollArraySize;
ski.setIndex(0);
}
/**
* Expand poll array if at capacity
*/
private void expandIfNeeded() {
if (pollArraySize == pollArrayCapacity) {
int oldSize = pollArrayCapacity * SIZE_POLLFD;
int newCapacity = pollArrayCapacity + INITIAL_CAPACITY;
int newSize = newCapacity * SIZE_POLLFD;
AllocatedNativeObject newPollArray = new AllocatedNativeObject(newSize, false);
Unsafe.getUnsafe().copyMemory(pollArray.address(), newPollArray.address(), oldSize);
pollArray.free();
pollArray = newPollArray;
pollArrayCapacity = newCapacity;
}
}
private static final short SIZE_POLLFD = 8;
private static final short FD_OFFSET = 0;
private static final short EVENT_OFFSET = 4;
private static final short REVENT_OFFSET = 6;
private void putDescriptor(int i, int fd) {
int offset = SIZE_POLLFD * i + FD_OFFSET;
pollArray.putInt(offset, fd);
}
private int getDescriptor(int i) {
int offset = SIZE_POLLFD * i + FD_OFFSET;
return pollArray.getInt(offset);
}
private void putEventOps(int i, int event) {
int offset = SIZE_POLLFD * i + EVENT_OFFSET;
pollArray.putShort(offset, (short)event);
}
private int getEventOps(int i) {
int offset = SIZE_POLLFD * i + EVENT_OFFSET;
return pollArray.getShort(offset);
}
private void putReventOps(int i, int revent) {
int offset = SIZE_POLLFD * i + REVENT_OFFSET;
pollArray.putShort(offset, (short)revent);
}
private int getReventOps(int i) {
int offset = SIZE_POLLFD * i + REVENT_OFFSET;
return pollArray.getShort(offset);
}
private static native int poll0(long pollAddress, int numfds, int timeout);
static {
IOUtil.load();
}
}