hashchain.md 3.4 KB
Structures
EventId
Hash of Event
type EventId = [u8; 32];
EventAction
The Event could have many actions according to the underlying data.
enum EventAction { ... };
Event
| Description | Data Type | Comments |
|---|---|---|
| previous_event_hash | EventId |
Hash of the previous Event |
| action | EventAction |
Event's action |
| timestamp | u64 | Event's timestamp |
EventNode
| Description | Data Type | Comments |
|---|---|---|
| parent | Option<EventId> |
Only current root has this set to None |
| event | Event |
The Event itself |
| children | Vec<EventId> |
The Events which has parent as this Event hash |
Model
The Model consist of chains(EventNodes) structured as a tree, each chain has Event-based
list. To maintain strict order in chain, Each Event dependent on the hash of the previous Event.
All the chains share a root Event to preserve the tree structure.
| Description | Data Type | Comments |
|---|---|---|
| current_root | EventId |
The root Event for the tree |
| orphans | HashMap<EventId, Event> |
Recently added Events |
| event_map | HashMap<EventId, EventNode> |
The actual tree |
| events_queue | EventsQueue |
Communication channel |
View
The View check the Model for new Events, then dispatch these Events to the clients.
Events are sorted according to the timestamp attached to each Event.
| Description | Data Type | Comments |
|---|---|---|
| seen | HashMap<EventId, Event> |
A list of Events |
EventsQueue
The EventsQueue used to transport the event from Model to View.
The Model fill The EventsQueue with the new Event, while the View keep
fetching Events from queue continuously.
Architecture
Tau using Model–view software architecture. All the operations, main data structures,
and handling messages from network protocol, happen in the Model side.
While keeping the View independent of the Model and focusing on getting update
from it continuously.
Add new Event
Once receiving new Event from the network protocol, the Event will be add to the
orphans list.
After the ancestor for the new orphan gets found, The orphan Event will be add to the chain
according to its ancestor.
For example, in the Example1 below, An Event add to the first chain if
its previous hash is Event-A1
Remove old leaves
Remove leaves which are too far from the head leaf(the leaf in the longest chain).
The depth difference from the common ancestor between a leaf to be removed and a head leaf
must be greater than MAX_DEPTH.
Update the root
Finding the highest common ancestor for the leaves and assign it as the root for the tree.
The highest common ancestor must have height greater than MAX_HEIGHT.
Example1