创建Selector

Selector selector = Selector.open();

selector.select()

select() = select(0) = lockAndDoSelect(-1) = doSelect(-1)

public int select() throws IOException {return this.select(0L);
}

public int select(long var1) throws IOException {if (var1 < 0L) {throw new IllegalArgumentException("Negative timeout");} else {return this.lockAndDoSelect(var1 == 0L ? -1L : var1);}
}

selectNow()

selectNow = lockAndDoSelect(0L) = doSelect(0)

其他超时

假设是select(5) = lockAndDoSelect(5) = doSelect(5)

在这里插入代码片

SelectorImpl

最终调用doSelect(timeout)

private int lockAndDoSelect(long timeout) throws IOException {synchronized (this) {if (!isOpen())throw new ClosedSelectorException();synchronized (publicKeys) {synchronized (publicSelectedKeys) {return doSelect(timeout);}}}
}

EPollSelectorImpl

doSelect

protected int doSelect(long timeout) throws IOException { // select(0)=-1   selectNow():0if (closed)throw new ClosedSelectorException();processDeregisterQueue();try {begin();pollWrapper.poll(timeout);} finally {end();}processDeregisterQueue();int numKeysUpdated = updateSelectedKeys();if (pollWrapper.interrupted()) {// Clear the wakeup pipepollWrapper.putEventOps(pollWrapper.interruptedIndex(), 0);synchronized (interruptLock) {pollWrapper.clearInterrupted();IOUtil.drain(fd0);interruptTriggered = false;}}return numKeysUpdated;
}

processDeregisterQueue

处理cancel的事件

# SelectorImpl
void processDeregisterQueue() throws IOException { // 处理cancelledKeys// Precondition: Synchronized on this, keys, and selectedKeysSet<SelectionKey> cks = cancelledKeys();synchronized (cks) {if (!cks.isEmpty()) {Iterator<SelectionKey> i = cks.iterator();while (i.hasNext()) {SelectionKeyImpl ski = (SelectionKeyImpl)i.next();try {implDereg(ski); //取消注册} catch (SocketException se) {throw new IOException("Error deregistering key", se);} finally {i.remove();}}}}
}

EPollSelectorImpl.implDereg

protected void implDereg(SelectionKeyImpl ski) throws IOException {assert (ski.getIndex() >= 0);SelChImpl ch = ski.channel; // 得到channelint fd = ch.getFDVal(); // 得到fdfdToKey.remove(Integer.valueOf(fd)); // 从map删除文件描述符和的SelectionKey的映射关系pollWrapper.remove(fd); // EPOLL_CTL_DEL remove from epollski.setIndex(-1);keys.remove(ski); //从注册的Selector删除本SelectionKeyselectedKeys.remove(ski); // 从已就绪的事件列表中删除本SelectionKeyderegister((AbstractSelectionKey)ski);  // AbstractSelector.deregister调用 最终((AbstractSelectableChannel)key.channel()).removeKey(key) 从Channel删除该SelectionKeySelectableChannel selch = ski.channel();if (!selch.isOpen() && !selch.isRegistered())((SelChImpl)selch).kill();
}

EPollArrayWrapper

/*** Remove a file descriptor*/
void remove(int fd) {synchronized (updateLock) {// kill pending and future update for this file descriptorsetUpdateEvents(fd, KILLED, false);// remove from epollif (registered.get(fd)) {epollCtl(epfd, EPOLL_CTL_DEL, fd, 0);registered.clear(fd);}}
}

poll

int poll(long timeout) throws IOException {updateRegistrations();// int epoll_wait(int epfd, struct epoll_event * events, intmaxevents, int timeout);// timeout是超时时间（毫秒，0:立即返回，-1:一直阻塞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;}

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Selector.select

创建Selector

selector.select()

selectNow()

其他超时

SelectorImpl

EPollSelectorImpl

doSelect

processDeregisterQueue

EPollSelectorImpl.implDereg

EPollArrayWrapper

poll

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