hashchain.md 3.6 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 consists of chains (EventNodes) structured as a tree;
whereby, each chain has an Event-based list. To maintain a strict
order of chains, each Event depends on the hash of the previous
Event. All of 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 checks the Model for new Events and then dispatches
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 fills the EventsQueue with the new Event, while the
View continuously fetches Events from queue.
Architecture
Tau uses Model–view software architecture. All of the operations, main
data structures, and message handling from the network protocol happen
on the Model side. Further, this keeps the View independent of the
Model and allows the View to focus on receiving continuous updates
from it.
Add new Event
Upon receiving a new Event from the network protocol, the Event
will be added to the orphans list.
After the ancestor of the new orphan is found, the orphan Event will
be added to the chain according to its ancestor.
For example: in Example1 below, an Event is added 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 a height greater than
MAX_HEIGHT.
Example1
