Tron Architecture

MsgBuffer and Buffer Manager

The protocl stack uses a buffer manager to allocate all of its message buffers. It uses the cMsgBuffer object to hold msg data. When the protocol stack is composed, the cLayerInfo class gathers information about the MTS and header sizes required by each layer. When a new message buffer is allocated by the protocol stack (through the buffer manager), the total sum of the header sizes of all of the layers are reserved within the buffer along with the expected message size. In this manner, when the cMsgBuffer is passed down through the layers, each layer can tack its own header on the front without having to realloc or copy the payload. If the application preallocates its buffers, then zero copy send and receive can be accomplished. The cMsgBuffer uses its own reference counting so that on receive, if a layer wants to keep a copy of a cMsgBuffer it merely has to add a reference. The cMsgBuffer provides the following set of methods:

Method	Description
AddRef	Increases the reference count on this buffer.
Release	Decreases the reference count on this buffer. If the reference count is equal to or less than zero then the buffer is freed.
Init	Initializes the buffer, optionally reserving the given amount of space for headers.
AddHeader	Copies the given header onto the front of the buffer, decreasing the amt of free header space.
RemoveHeader	Removes the given amount of header from the front of the buffer, increasing the amt of free header space.
SetPayload	Copies the given byte buffer into the msg buffer and sets the payload size.
GetPayload	Gets a pointer to the byte buffer that is the potential payload for this buffer, along with its size.
SetPayloadSize GetPayloadSize	Sets and gets the size of the payload, respectively.
Clone	Allocates and creates an exact clone of this message buffer (including amt of header reserve space).

Groups

The cObject interface provides a common base class that all Tron classes can derive from.

The cLayer interface provides the glue that holds layers together in the protocol stack. It consists of the following members:

Method	Description
Init	Initializes the layer with the given cParam.
Cleanup	Cleans up the layer. The layer should be able to handle another Init() call after cleanup.
Send	Sends the given message. Will pass the msg down the stack if necessary.
RegisterDeliverCallback UnregisterDeliverCallback	Used to set up cDeliver callback.
RegisterViewCallback UnregisterViewCallback	Used to set up the cView callback.
RegisterErrorCallback UnregisterErrorCallback	Used to set up cErrorCallback, the asynchronous error handler.
Schedule	Called on the layer by the protocol stack. This will be called regularly and gives the layer a reasonable, but small, timeslice in which to do some extra work.
GetLayerInfo	Returns the layer info (usually to be propagated up the stack).

This provides an interface for the parameter set to be used on a layer in its cLayer::Init() method. cParam's single method, cParam::ResetToDefault(), should reset all of the parameters to their default values.

This provides the callback for message delivery. It will be called whenever there is a message ready for delivery. An observer registers for a deliver callback either through the top of the protocol stack or through a layer directly. A layer will usually register itself for delivery with the layer below.

This provides the callback for view membership information. An observer registers for a view callback either through the top of the protocol stack or through a layer directly.

This provides the callback for an asynchronous error handler. An observer registers for an error callback either through the top of the protocol stack or through a layer directly.

This provides a generic callback method. Currently it is used so that an event can be added to the protocol stack and the given callback will be called when the event is triggered.