/*
* Copyright (c) 2005, 2016, 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
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package sun.nio.ch;
import java.io.IOException;
import java.security.AccessController;
import java.util.BitSet;
import java.util.HashMap;
import java.util.Map;
import sun.security.action.GetIntegerAction;
/**
* Manipulates a native array of epoll_event structs on Linux:
*
* typedef union epoll_data {
* void *ptr;
* int fd;
* __uint32_t u32;
* __uint64_t u64;
* } epoll_data_t;
*
* struct epoll_event {
* __uint32_t events;
* epoll_data_t data;
* };
*
* The system call to wait for I/O events is epoll_wait(2). It populates an
* array of epoll_event structures that are passed to the call. The data
* member of the epoll_event structure contains the same data as was set
* when the file descriptor was registered to epoll via epoll_ctl(2). In
* this implementation we set data.fd to be the file descriptor that we
* register. That way, we have the file descriptor available when we
* process the events.
*/
class EPollArrayWrapper {
// EPOLL_EVENTS
private static final int EPOLLIN = 0x001;
// opcodes
private static final int EPOLL_CTL_ADD = 1;
private static final int EPOLL_CTL_DEL = 2;
private static final int EPOLL_CTL_MOD = 3;
// Miscellaneous constants
private static final int SIZE_EPOLLEVENT = sizeofEPollEvent();
private static final int EVENT_OFFSET = 0;
private static final int DATA_OFFSET = offsetofData();
private static final int FD_OFFSET = DATA_OFFSET;
private static final int OPEN_MAX = IOUtil.fdLimit();
private static final int NUM_EPOLLEVENTS = Math.min(OPEN_MAX, 8192);
// Special value to indicate that an update should be ignored
private static final byte KILLED = (byte)-1;
// Initial size of arrays for fd registration changes
private static final int INITIAL_PENDING_UPDATE_SIZE = 64;
// maximum size of updatesLow
private static final int MAX_UPDATE_ARRAY_SIZE = AccessController.doPrivileged(
new GetIntegerAction("sun.nio.ch.maxUpdateArraySize", Math.min(OPEN_MAX, 64*1024)));
// The fd of the epoll driver
private final int epfd;
// The epoll_event array for results from epoll_wait
private final AllocatedNativeObject pollArray;
// Base address of the epoll_event array
private final long pollArrayAddress;
// The fd of the interrupt line going out
private int outgoingInterruptFD;
// The fd of the interrupt line coming in
private int incomingInterruptFD;
// The index of the interrupt FD
private int interruptedIndex;
// Number of updated pollfd entries
int updated;
// object to synchronize fd registration changes
private final Object updateLock = new Object();
// number of file descriptors with registration changes pending
private int updateCount;
// file descriptors with registration changes pending
private int[] updateDescriptors = new int[INITIAL_PENDING_UPDATE_SIZE];
// events for file descriptors with registration changes pending, indexed
// by file descriptor and stored as bytes for efficiency reasons. For
// file descriptors higher than MAX_UPDATE_ARRAY_SIZE (unlimited case at
// least) then the update is stored in a map.
private final byte[] eventsLow = new byte[MAX_UPDATE_ARRAY_SIZE];
private final Map<Integer,Byte> eventsHigh = new HashMap<>();
// Used by release and updateRegistrations to track whether a file
// descriptor is registered with epoll.
private final BitSet registered = new BitSet();
EPollArrayWrapper() throws IOException {
// creates the epoll file descriptor
epfd = epollCreate();
// the epoll_event array passed to epoll_wait
int allocationSize = NUM_EPOLLEVENTS * SIZE_EPOLLEVENT;
pollArray = new AllocatedNativeObject(allocationSize, true);
pollArrayAddress = pollArray.address();
}
void initInterrupt(int fd0, int fd1) {
outgoingInterruptFD = fd1;
incomingInterruptFD = fd0;
epollCtl(epfd, EPOLL_CTL_ADD, fd0, EPOLLIN);
}
void putEventOps(int i, int event) {
int offset = SIZE_EPOLLEVENT * i + EVENT_OFFSET;
pollArray.putInt(offset, event);
}
void putDescriptor(int i, int fd) {
int offset = SIZE_EPOLLEVENT * i + FD_OFFSET;
pollArray.putInt(offset, fd);
}
int getEventOps(int i) {
int offset = SIZE_EPOLLEVENT * i + EVENT_OFFSET;
return pollArray.getInt(offset);
}
int getDescriptor(int i) {
int offset = SIZE_EPOLLEVENT * i + FD_OFFSET;
return pollArray.getInt(offset);
}
/**
* Returns {@code true} if updates for the given key (file
* descriptor) are killed.
*/
private boolean isEventsHighKilled(Integer key) {
assert key >= MAX_UPDATE_ARRAY_SIZE;
Byte value = eventsHigh.get(key);
return (value != null && value == KILLED);
}
/**
* Sets the pending update events for the given file descriptor. This
* method has no effect if the update events is already set to KILLED,
* unless {@code force} is {@code true}.
*/
private void setUpdateEvents(int fd, byte events, boolean force) {
if (fd < MAX_UPDATE_ARRAY_SIZE) {
if ((eventsLow[fd] != KILLED) || force) {
eventsLow[fd] = events;
}
} else {
Integer key = Integer.valueOf(fd);
if (!isEventsHighKilled(key) || force) {
eventsHigh.put(key, Byte.valueOf(events));
}
}
}
/**
* Returns the pending update events for the given file descriptor.
*/
private byte getUpdateEvents(int fd) {
if (fd < MAX_UPDATE_ARRAY_SIZE) {
return eventsLow[fd];
} else {
Byte result = eventsHigh.get(Integer.valueOf(fd));
// result should never be null
return result.byteValue();
}
}
/**
* Update the events for a given file descriptor
*/
void setInterest(int fd, int mask) {
synchronized (updateLock) {
// record the file descriptor and events
int oldCapacity = updateDescriptors.length;
if (updateCount == oldCapacity) {
int newCapacity = oldCapacity + INITIAL_PENDING_UPDATE_SIZE;
int[] newDescriptors = new int[newCapacity];
System.arraycopy(updateDescriptors, 0, newDescriptors, 0, oldCapacity);
updateDescriptors = newDescriptors;
}
updateDescriptors[updateCount++] = fd;
// events are stored as bytes for efficiency reasons
byte b = (byte)mask;
assert (b == mask) && (b != KILLED);
setUpdateEvents(fd, b, false);
}
}
/**
* Add a file descriptor
*/
void add(int fd) {
// force the initial update events to 0 as it may be KILLED by a
// previous registration.
synchronized (updateLock) {
assert !registered.get(fd);
setUpdateEvents(fd, (byte)0, true);
}
}
/**
* Remove a file descriptor
*/
void remove(int fd) {
synchronized (updateLock) {
// kill pending and future update for this file descriptor
setUpdateEvents(fd, KILLED, false);
// remove from epoll
if (registered.get(fd)) {
epollCtl(epfd, EPOLL_CTL_DEL, fd, 0);
registered.clear(fd);
}
}
}
/**
* Close epoll file descriptor and free poll array
*/
void closeEPollFD() throws IOException {
FileDispatcherImpl.closeIntFD(epfd);
pollArray.free();
}
int poll(long timeout) throws IOException {
updateRegistrations();
updated = epollWait(pollArrayAddress, NUM_EPOLLEVENTS, timeout, epfd);
for (int i=0; i<updated; i++) {
if (getDescriptor(i) == incomingInterruptFD) {
interruptedIndex = i;
interrupted = true;
break;
}
}
return updated;
}
/**
* Update the pending registrations.
*/
private void updateRegistrations() {
synchronized (updateLock) {
int j = 0;
while (j < updateCount) {
int fd = updateDescriptors[j];
short events = getUpdateEvents(fd);
boolean isRegistered = registered.get(fd);
int opcode = 0;
if (events != KILLED) {
if (isRegistered) {
opcode = (events != 0) ? EPOLL_CTL_MOD : EPOLL_CTL_DEL;
} else {
opcode = (events != 0) ? EPOLL_CTL_ADD : 0;
}
if (opcode != 0) {
epollCtl(epfd, opcode, fd, events);
if (opcode == EPOLL_CTL_ADD) {
registered.set(fd);
} else if (opcode == EPOLL_CTL_DEL) {
registered.clear(fd);
}
}
}
j++;
}
updateCount = 0;
}
}
// interrupt support
private boolean interrupted = false;
public void interrupt() {
interrupt(outgoingInterruptFD);
}
public int interruptedIndex() {
return interruptedIndex;
}
boolean interrupted() {
return interrupted;
}
void clearInterrupted() {
interrupted = false;
}
static {
IOUtil.load();
init();
}
private native int epollCreate();
private native void epollCtl(int epfd, int opcode, int fd, int events);
private native int epollWait(long pollAddress, int numfds, long timeout,
int epfd) throws IOException;
private static native int sizeofEPollEvent();
private static native int offsetofData();
private static native void interrupt(int fd);
private static native void init();
}