ostore.apps.test
Class TapestryHowto.Ping

java.lang.Object
  |
  +--dd.api.DDRouteMsg
        |
        +--ostore.apps.test.TapestryHowto.Ping

All Implemented Interfaces:

QueueElementIF, QuickSerializable

Enclosing class:

TapestryHowto

public static class TapestryHowto.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 OceanStore. 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; used by the OceanStore archive to find storage candidates for erasure coded fragments
• DDPublishMsg -- advertise that your own node is storing a given object
• DDUnpublishMsg -- 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 and QuickSerializable, meaning that we have to define three main functions:

• A serialization function, to_bytes, which takes a byte array and an offset and returns the resulting offset (number of bytes written plus the original offset)
• A deserialization constructor, which takes a byte array and an offset and returns the resulting offset (number of bytes read plus the original offset)
• A digest function, add_to_digest, which works like the serialization function, but rather than writing everything into a new array, just passes it on to a digest object. This is used to compute the hash of messages for use inside DD.
• Finally, there is a legacy function, type_code, which must be defined but need not be implemented.

See below for details.

Field Summary

int

seq

Fields inherited from class dd.api.DDRouteMsg

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

Constructor Summary

TapestryHowto.Ping(InputBuffer buffer)
A deserialization constructor.

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

Method Summary

void	serialize(OutputBuffer buffer) A serialization function.
String	toString() 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

Constructor Detail

TapestryHowto.Ping

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

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

TapestryHowto.Ping

public TapestryHowto.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)

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

Parameters:

buffer - the output buffer to add the object to

toString

public String toString()

It's always nice for debugging to define one of these.

Overrides:

toString in class Object