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crdt-sync-state_based.md

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CRDT.Sync.State_Based

State-Based (CvRDT) sync engine. Replicas exchange full or delta-compressed state using Hybrid Logical Clock (HLC) timestamps for causal ordering. Network trait: Highly resilient to lossy/unstable topologies (UDP, peer-to-peer mesh, radio datalinks) because state merges are fully idempotent. Requirements traceability: - HLR-SYNC-STATE: State-based sync with vector clocks - HLR-SYNC-DELTA: Delta computation for partial state exchange

Note: 6 public item(s) shown below; 1 private internal item(s) are in the private section.

Types

type Replica_State

type Replica_State (Max_Replicas : Positive) is record
HLC_Clock : CRDT.HLC.Instance;
SV        : Core.VTime (1 .. Max_Replicas);
end record;

type Sync_Config

type Sync_Config is record
Max_Replicas : Positive := 32;
Delta_Sync   : Boolean := True;
HLC_Node     : Core.Replica_Id;
end record;

Functions

function Compute_Delta (Local : CRDT.Sync.State_Based.Replica_State; Remote_SV : CRDT.Core.VTime) return Standard.Natural [Post]

Parameter Description
Local Local replica state.
Remote_SV Remote state vector.

Returns: Count of replicas where local is ahead of remote.

function Create (Config : CRDT.Sync.State_Based.Sync_Config) return CRDT.Sync.State_Based.Replica_State

Parameter Description
Config Sync configuration.

Returns: Freshly initialised replica state.

function Is_Ahead (SV : CRDT.Core.VTime; TS : CRDT.Core.Lamport_Time) return Standard.Boolean [Post]

Parameter Description
SV State vector to check.
TS Lamport timestamp to compare against.

Returns: True if the SV has entry at or past TS.

Procedures

procedure Merge (Local : CRDT.Sync.State_Based.Replica_State; Remote : CRDT.Sync.State_Based.Replica_State) [Depends]

Parameter Description
Local Local state to update.
Remote Remote state to merge from.

Private Section

  • type Replica_State