tango.io.selector.EpollSelector

License:

Author:

Juan Jose Comellas <juanjo@comellas.com.ar>

class EpollSelector : AbstractSelector [public] ¶

Selector that uses the Linux epoll* family of system calls.

This selector is the best option when dealing with large amounts of conduits under Linux. It will scale much better than any of the other options (PollSelector, SelectSelector). For small amounts of conduits (n < 20) the PollSelector will probably be more performant.

See Also:

ISelector, AbstractSelector

Examples:

import tango.io.selector.EpollSelector;
import tango.net.device.Socket;
import tango.io.Stdout;

SocketConduit conduit1;
SocketConduit conduit2;
EpollSelector selector = new EpollSelector();
MyClass object1 = new MyClass();
MyClass object2 = new MyClass();
uint eventCount;

// Initialize the selector assuming that it will deal with 10 conduits and
// will receive 3 events per invocation to the select() method.
selector.open(10, 3);

selector.register(conduit1, Event.Read, object1);
selector.register(conduit2, Event.Write, object2);

eventCount = selector.select();

if (eventCount > 0)
{
    char[16] buffer;
    int count;

    foreach (SelectionKey key; selector.selectedSet())
    {
        if (key.isReadable())
        {
            count = (cast(SocketConduit) key.conduit).read(buffer);
            if (count != IConduit.Eof)
            {
                Stdout.format("Received '{0}' from peer\n", buffer[0..count]);
                selector.register(key.conduit, Event.Write, key.attachment);
            }
            else
            {
                selector.unregister(key.conduit);
                key.conduit.close();
            }
        }

        if (key.isWritable())
        {
            count = (cast(SocketConduit) key.conduit).write("MESSAGE");
            if (count != IConduit.Eof)
            {
                Stdout("Sent 'MESSAGE' to peer");
                selector.register(key.conduit, Event.Read, key.attachment);
            }
            else
            {
                selector.unregister(key.conduit);
                key.conduit.close();
            }
        }

        if (key.isError() || key.isHangup() || key.isInvalidHandle())
        {
            selector.unregister(key.conduit);
            key.conduit.close();
        }
    }
}

selector.close();

alias AbstractSelector.select select ¶

Alias for the select() method as we're not reimplementing it in this class.

uint DefaultSize [public, const] ¶

Default number of SelectionKey's that will be handled by the EpollSelector.

uint DefaultMaxEvents [public, const] ¶

Default maximum number of events that will be received per invocation to select().

~this() ¶

Destructor

void open(uint size = DefaultSize, uint maxEvents = DefaultMaxEvents) [public, override] ¶

Open the epoll selector, makes a call to epoll_create()

Parameters:

size	maximum amount of conduits that will be registered; it will grow dynamically if needed.
maxEvents	maximum amount of conduit events that will be returned in the selection set per call to select(); this limit is enforced by this selector.

Throws:

SelectorException if there are not enough resources to open the selector (e.g. not enough file handles or memory available).

void close() [public, override] ¶

Close the selector, releasing the file descriptor that had been created in the previous call to open().

Remarks:

It can be called multiple times without harmful side-effects.

size_t count() [public, override] ¶

Return the number of keys resulting from the registration of a conduit to the selector.

void register(ISelectable conduit, Event events, Object attachment = null) [public, override] ¶

Associate a conduit to the selector and track specific I/O events. If a conduit is already associated, changes the events and attachment.

Parameters:

conduit	conduit that will be associated to the selector; must be a valid conduit (i.e. not null and open).
events	bit mask of Event values that represent the events that will be tracked for the conduit.
attachment	optional object with application-specific data that will be available when an event is triggered for the conduit

Throws:

RegisteredConduitException if the conduit had already been registered to the selector; SelectorException if there are not enough resources to add the conduit to the selector.

Examples:

1	selector.register(conduit, Event.Read \| Event.Write, object);

void unregister(ISelectable conduit) [public, override] ¶

Remove a conduit from the selector.

Parameters:

conduit

conduit that had been previously associated to the selector; it can be null.

Remarks:

Unregistering a null conduit is allowed and no exception is thrown if this happens.

Throws:

UnregisteredConduitException if the conduit had not been previously registered to the selector; SelectorException if there are not enough resources to remove the conduit registration.

int select(TimeSpan timeout) [public, override] ¶

Wait for I/O events from the registered conduits for a specified amount of time.

Parameters:

timeout

TimeSpan with the maximum amount of time that the selector will wait for events from the conduits; the amount of time is relative to the current system time (i.e. just the number of milliseconds that the selector has to wait for the events).

Returns:

The amount of conduits that have received events; 0 if no conduits have received events within the specified timeout; and -1 if the wakeup() method has been called from another thread.

Throws:

InterruptedSystemCallException if the underlying system call was interrupted by a signal and the 'restartInterruptedSystemCall' property was set to false; SelectorException if there were no resources available to wait for events from the conduits.

class EpollSelectionSet : ISelectionSet [protected] ¶

Class used to hold the list of Conduits that have received events.