Add a StateDecodeParams method

node/impl/full/state.go

@@ -491,6 +491,24 @@ func (a *StateAPI) StateReadState(ctx context.Context, actor address.Address, ts
 	}, nil
 }
 
+func (a *StateAPI) StateDecodeParams(ctx context.Context, toAddr address.Address, method abi.MethodNum, params []byte, tsk types.TipSetKey) (interface{}, error) {
+	act, err := a.StateGetActor(ctx, toAddr, tsk)
+	if err != nil {
+		return nil, xerrors.Errorf("getting actor: %w", err)
+	}
+
+	paramType, err := stmgr.GetParamType(act.Code, method)
+	if err != nil {
+		return nil, xerrors.Errorf("getting params type: %w", err)
+	}
+
+	if err = paramType.UnmarshalCBOR(bytes.NewReader(params)); err != nil {
+		return nil, err
+	}
+
+	return paramType, nil
+}
+
 // This is on StateAPI because miner.Miner requires this, and MinerAPI requires miner.Miner
 func (a *StateAPI) MinerGetBaseInfo(ctx context.Context, maddr address.Address, epoch abi.ChainEpoch, tsk types.TipSetKey) (*api.MiningBaseInfo, error) {
 	return stmgr.MinerGetBaseInfo(ctx, a.StateManager, a.Beacon, tsk, epoch, maddr, a.ProofVerifier)