core: modify interface (#194)

* Add a new method to notify full node about round cutting.
* Modify interface to return error when preparing block

1 files changed, 4 insertions, 4 deletions

diff --git a/simulation/app.go b/simulation/app.go
index 0e3e184..0ca65c9 100644
--- a/simulation/app.go
+++ b/simulation/app.go
@@ -98,18 +98,18 @@ func (a *simApp) getAckedBlocks(ackHash common.Hash) (output common.Hashes) {
 }
 
 // PreparePayload implements core.Application.
-func (a *simApp) PreparePayload(position types.Position) []byte {
-	return []byte{}
+func (a *simApp) PreparePayload(position types.Position) ([]byte, error) {
+	return []byte{}, nil
 }
 
 // PrepareWitness implements core.Application.
-func (a *simApp) PrepareWitness(height uint64) types.Witness {
+func (a *simApp) PrepareWitness(height uint64) (types.Witness, error) {
 	a.latestWitnessReady.L.Lock()
 	defer a.latestWitnessReady.L.Unlock()
 	for a.latestWitness.Height < height {
 		a.latestWitnessReady.Wait()
 	}
-	return a.latestWitness
+	return a.latestWitness, nil
 }
 
 // StronglyAcked is called when a block is strongly acked by DEXON