Element::Port Class Reference

An Element's ports. More...

Public Member Functions
bool	active () const
	Returns whether this port is active (a push output or a pull input).
Element *	element () const
	Returns the element connected to this active port.
int	port () const
	Returns the port number of the port connected to this active port.
void	push (Packet *p) const
	Push packet p over this port.
Packet *	pull () const
	Pull a packet over this port and return it.
void	assign_peer (bool isoutput, Element *e, int port, bool unstack=false)

Detailed Description

An Element's ports.

Each of an element's ports has an associated Port object, accessible via the Element::port(), Element::input(), and Element::output() functions. Each active port knows, and can transfer a packet with, the single complementary port to which it is connected. Thus, each push output knows its connected input, and can push a packet there; and each pull input can pull a packet from its connected output. Inactive ports – push inputs and pull outputs – can be connected multiple times. Their corresponding Port objects have very little functionality.

Element authors generally encounter Port objects only in two stylized formulations. First, to push a packet p out on push output port i:

output(i).push(p);

And second, to pull a packet p from pull input port i:

Packet *p = input(i).pull();

See also

Element::checked_output_push()

Member Function Documentation

active()

bool Element::Port::active ( ) const

inline

Returns whether this port is active (a push output or a pull input).

See also

Element::port_active

element()

Element * Element::Port::element ( ) const

inline

Returns the element connected to this active port.

Returns 0 if this port is not active().

port()

int Element::Port::port ( ) const

inline

Returns the port number of the port connected to this active port.

Returns < 0 if this port is not active().

push()

void Element::Port::push ( Packet *  p ) const

inline

Push packet p over this port.

Pushes packet p downstream through the router configuration by passing it to the next element's push() function. Returns when the rest of the router finishes processing p.

This port must be an active() push output port. Usually called from element code like output(i) .push(p).

When element code calls Element::Port::push(p), it relinquishes control of packet p. When push() returns, p may have been altered or even freed by downstream elements. Thus, you must not use p after pushing it downstream. To push a copy and keep a copy, see Packet::clone().

output(i).push(p) basically behaves like the following code, although it maintains additional statistics depending on how CLICK_STATS is defined:

output(i).element()->push(output(i).port(), p);

pull()

Packet * Element::Port::pull ( ) const

inline

Pull a packet over this port and return it.

Pulls a packet from upstream in the router configuration by calling the previous element's pull() function. When the router finishes processing, returns the result.

This port must be an active() pull input port. Usually called from element code like input(i) .pull().

input(i).pull() basically behaves like the following code, although it maintains additional statistics depending on how CLICK_STATS is defined:

input(i).element()->pull(input(i).port())

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The documentation for this class was generated from the following file:

• include/click/element.hh