demo.howto
Class DDHowto.Ping

java.lang.Object
  |
  +--dd.api.DDRouteMsg
        |
        +--demo.howto.DDHowto.Ping

All Implemented Interfaces:

QueueElementIF, QuickSerializable

Enclosing class:

DDHowto

public static class DDHowto.Ping

extends DDRouteMsg

One of two DD messages used in this test. I inherit from DDRouteMsg because I'm talking to a specific other node in the network. If I wanted to talk to any node holding an object with GUID g, I would use a DDLocateMsg instead. Other interesting DD message types are:

• DDMacRouteMsg -- cryptographically guarentees that the message is from the node it says it's from
• DDPrefixRouteMsg -- routes to the node with the GUID which most closely matches a given GUID. For example, DDPrefixRouteMsg is used by the OceanStore archive to find storage candidates for erasure coded fragments
• DDPublishReq -- advertise that your own node is storing a given object. A DDPublishResp will be returned indicating the success or failure of the DDPublishReq. Also, DDPublishReq.publish==false -- will stop advertising an object

Refer to the DD javadocs for more details about any of the above.

Since this class inherits from DDRouteMsg, it indirectly inherits from QuickSerializable, meaning that we have to define two main functions:

• A serialization function, QuickSerializable.serialize(ostore.util.OutputBuffer), which takes an OutputBuffer and serializes the object into that buffer.
• A deserialization constructor, which takes InputBuffer where the object can be extracted from bytes.
• Finally, TypeTable.type_code(ostore.util.QuickSerializable) will produce a unique type_code based on the wire form of the object.

See below for details.

Field Summary

int	seq sequence number to keep track of ping/pong.

Fields inherited from class dd.api.DDRouteMsg

dd_intermediate_upcall, hopCount, inbound, one_hop, peer, recursive_route, TTL

Constructor Summary

DDHowto.Ping(InputBuffer buffer)
A deserialization constructor.

DDHowto.Ping(SecureHash dest, boolean recursive, boolean dd_intermediate_upcall, boolean one_hop, int seq)
A constructor for messages I'm going to send to someone else.

Method Summary

void	serialize(OutputBuffer buffer) Specified by ostore.util.QuickSerializable A serialization function.
String	toString() Specified by java.lang.Object It's always nice for debugging to define one of these.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

seq

public int seq

sequence number to keep track of ping/pong.

Constructor Detail

DDHowto.Ping

public DDHowto.Ping(SecureHash dest,
                    boolean recursive,
                    boolean dd_intermediate_upcall,
                    boolean one_hop,
                    int seq)

A constructor for messages I'm going to send to someone else. Sets the destination node and sequence number.

DDHowto.Ping

public DDHowto.Ping(InputBuffer buffer)

A deserialization constructor. Used by DD on the receiving node to reproduce the message from its "on-the-wire" representation.

Method Detail

serialize

public void serialize(OutputBuffer buffer)

Specified by ostore.util.QuickSerializable A serialization function. Produces the "on-the-wire" representation of this object. Must be the inverse of the deserialization constructor, above, or bad things will happen.

Specified by:

serialize in interface QuickSerializable

Overrides:

serialize in class DDRouteMsg

toString

public String toString()

Specified by java.lang.Object It's always nice for debugging to define one of these.

Overrides:

toString in class Object