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/*
* ActionSelector.java February 2013
*
* Copyright (C) 2013, Niall Gallagher <niallg@users.sf.net>
*
* 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 org.simpleframework.transport.reactor;
import java.io.IOException;
import java.nio.channels.SelectableChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;
/**
* The <code>ActionSelector</code> object is used to perform socket
* based selection with the help of the <code>ActionSet</code> object.
* All registered channels have an associated action set. The action
* set contains a set of actions that should be executed when the
* selector selects the channel.
*
* @author Niall Gallagher
*/
class ActionSelector {
/**
* This is the selector used to perform the select operations.
*/
private final Selector selector;
/**
* Constructor for the <code>ActionSelector</code> object. This is
* used to create a selector that can register socket channels
* with an associated <code>ActionSet</code>. The set can then be
* used to store actions to be executed upon selection.
*/
public ActionSelector() throws IOException {
this.selector = Selector.open();
}
/**
* This is used to perform a select on the selector. This returns
* the number of channels that have been selected. If this returns
* a number greater than zero the <code>ready</code> method can
* be used to acquire the actions that are ready for execution.
*
* @param timeout this is the timeout associated with the select
*
* @return this returns the number of channels that are ready
*/
public int select(long timeout) throws IOException {
return selector.select(timeout);
}
/**
* This performs the actual registration of the channel for selection
* based on the provided interest bitmask. When the channel has been
* registered for selection this returns an <code>ActionSet</code>
* for the selection key. The set can then be used to register the
* actions that should be executed when selection succeeds.
*
* @param channel this is the channel to register for selection
* @param interest this is the interested operations bitmask
*
* @return this is the action set associated with the registration
*/
public ActionSet register(SelectableChannel channel, int interest) throws IOException {
SelectionKey key = channel.register(selector, interest);
Object value = key.attachment();
if(value == null) {
value = new ActionSet(key);
key.attach(value);
}
return (ActionSet)value;
}
/**
* This is used to acquire all the action sets that are associated
* with this selector. Only action sets that have a valid selection
* key are returned. Modification of the list will not affect the
* associated selector instance.
*
* @return this returns all the associated action sets for this
*/
public List<ActionSet> registeredSets() {
Set<SelectionKey> keys = selector.keys();
Iterator<SelectionKey> ready = keys.iterator();
return registeredSets(ready);
}
/**
* This is used to acquire all the action sets that are associated
* with this selector. Only action sets that have a valid selection
* key are returned. Modification of the list will not affect the
* associated selector instance.
*
* @param keys the selection keys to get the associated sets from
*
* @return this returns all the associated action sets for this
*/
private List<ActionSet> registeredSets(Iterator<SelectionKey> keys) {
List<ActionSet> sets = new LinkedList<ActionSet>();
while(keys.hasNext()) {
SelectionKey key = keys.next();
ActionSet actions = (ActionSet)key.attachment();
if(!key.isValid()) {
key.cancel();
} else {
sets.add(actions);
}
}
return sets;
}
/**
* This is used to acquire all the action sets that are selected
* by this selector. All action sets returned are unregistered from
* the selector and must be registered again to hear about further
* I/O events that occur on the associated channel.
*
* @return this returns all the selected action sets for this
*/
public List<ActionSet> selectedSets() throws IOException {
Set<SelectionKey> keys = selector.selectedKeys();
Iterator<SelectionKey> ready = keys.iterator();
return selectedSets(ready);
}
/**
* This is used to acquire all the action sets that are selected
* by this selector. All action sets returned are unregistered from
* the selector and must be registered again to hear about further
* I/O events that occur on the associated channel.
*
* @param keys the selection keys to get the associated sets from
*
* @return this returns all the selected action sets for this
*/
private List<ActionSet> selectedSets(Iterator<SelectionKey> keys) {
List<ActionSet> ready = new LinkedList<ActionSet>();
while(keys.hasNext()) {
SelectionKey key = keys.next();
ActionSet actions = (ActionSet)key.attachment();
if(key != null) {
keys.remove();
}
if(key != null) {
ready.add(actions);
}
}
return ready;
}
/**
* This is used to wake the selector if it is in the middle of a
* select operation. Waking up the selector in this manner is
* useful if further actions are to be registered with it.
*/
public void wake() throws IOException {
selector.wakeup();
}
/**
* This is used to close the associated selector. Further attempts
* to register a channel with the selector will fail. All actions
* should be cancelled before closing the selector in this way.
*/
public void close() throws IOException {
selector.close();
}
}
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