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Class nodeos.FlowHandle

java.lang.Object
   |
   +----nodeos.Linkable
           |
           +----nodeos.FlowHandle

public abstract class FlowHandle

extends Linkable

implements FlowDispatcher

Flow handles serve three purposes, each of which is optional.

• Packet buffering. Every flow is associated with a queue of free buffers and a queue of already received, but undelivered packets. Packets cannot be buffered unless free buffers are available. It is the responsibility of the user of the handle to provide it with buffers beforehand.

• Payload dispatch. A flow handle may be associated with a dispatcher. In this case, the payload of all packets dispatched to the handle will be dispatched to that dispatcher as well. This is used to implement protocol layering. Before dispatching, the flow handle will add its own header length to the dispatch offset.

• Packet identification. A flow handle may be used to determine whether a certain packet belongs to a certain flow. This is done by analyzing the packet data.

Uses Linkable for convenience. (XXX)

See Also:

FlowDispatcher

lastHeaderLength

will contain the number of bytes to skip to get to the payload.

addBuffer(Buffer)

Adds a buffer to the handle's free list.

addBuffers(Buffer[])

Adds an array of buffers to the handle's free list.

addBuffers(int, int)

Allocates buffers and adds them to the free list.

addBufferToReceiveQueue(Buffer)

Adds a buffer to the handle's receive queue.

checkBuffer(Buffer, int)

Checks data in buffer.

dispatchBuffer(Buffer, int)

Dispatch a given buffer.

getName()

getQueueLength()

Return number of packets in receive queue.

merge(FlowHandle)

Merge two flow handles into one This function appends the other flow handle's receive queue to our receive queue.

receive()

Receives a packet from that flow.

reclaimBuffer()

Reclaims a buffer from the free queue.

setName(String)

setPayloadDispatcher(FlowDispatcher)

Sets a dispatcher for that flow.

toString()

Convert to a String.

 public int lastHeaderLength

will contain the number of bytes to skip to get to the payload.
This must be set by checkBuffer. This is a hack to avoid having checkBuffer return a pair (boolean, int).

 public abstract boolean checkBuffer(Buffer b,
                                     int offset)

Checks data in buffer.

Checks whether the data in that buffer, starting at offset, may be identified as belonging to that flow.

Sets lastHeaderLength to the number of bytes in the header needed for identification.

 public String getName()

 public void setName(String name)

 public int getQueueLength()

Return number of packets in receive queue.

 public void setPayloadDispatcher(FlowDispatcher flowDispatcher)

Sets a dispatcher for that flow.

This has the effect that all packets presented to that flow handle will be presented to the payload dispatcher for dispatch.

Parameters:

flowDispatcher - new payload dispatcher for that flow.

 public Buffer dispatchBuffer(Buffer buf,
                              int offset)

Dispatch a given buffer.

If free buffers are available, a free buffer is taken from the free queue. If buf.exchanged is false, this buffer is returned and the buffer that is passed in is enqueued in the receive queue.

Otherwise, the free buffer is made a dependent of the buffer passed in, and it is enqueued in the receive queue.

If a payload dispatcher is given, the packet is dispatched to it, adding lastHeaderLength to the offset.

See FlowDispatch for a description of the parameters.

See Also:

dispatchBuffer

 public void addBufferToReceiveQueue(Buffer p)

Adds a buffer to the handle's receive queue.

 public void addBuffer(Buffer p)

Adds a buffer to the handle's free list.

 public void addBuffers(Buffer p[])

Adds an array of buffers to the handle's free list.

 public void addBuffers(int packets,
                        int size)

Allocates buffers and adds them to the free list.

Parameters:

packets - number of packets to be allocated

size - size of each packet in bytes

 public Buffer reclaimBuffer()

Reclaims a buffer from the free queue. This removes a buffer from the free queue of the handle, effectively reducing the flow handle's capacity.

Returns:

free buffer

 public Buffer receive()

Receives a packet from that flow.

The buffer in which the packet is contained is made independent. (XXX) let the application do that, unless there's security concerns.

 public void merge(FlowHandle other)

Merge two flow handles into one This function appends the other flow handle's receive queue to our receive queue.

 public String toString()

Convert to a String.

Returns:

statistics about that flow handle

Overrides:

toString in class Object

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