consensus: get Validators from genesis instead of triedb in v1 consortium. (#624)

In snap sync, we will disable accessing/mark stale to triedb when enabling path scheme for protecting the persistent storing, so the data of validators only used for checking in some first blocks which we can return hardcore list from genesis data for following the flow of snap-sync  from go-eth team.

Author: huyngopt1994

consensus/consortium/v1/consortium.go

@@ -338,11 +338,10 @@ func (c *Consortium) snapshot(chain consensus.ChainHeaderReader, number uint64,
 			if cpHeader != nil {
 				hash := cpHeader.Hash()
 
-				validators, err := c.getValidatorsFromContract(chain, number)
+				validators, err := c.getValidatorsFromGenesis()
 				if err != nil {
 					return nil, err
 				}
-
 				snap = newSnapshot(c.config, c.signatures, number, hash, validators)
 				if err := snap.store(c.db); err != nil {
 					return nil, err
@@ -756,6 +755,31 @@ func (c *Consortium) doCalcDifficulty(signer common.Address, number uint64, vali
 	return new(big.Int).Set(diffNoTurn)
 }
 
+// getValidatorsFromGenesis gets the list of validators from the genesis block support backward compatibility in v1, only used with Snap Sync.
+func (c *Consortium) getValidatorsFromGenesis() ([]common.Address, error) {
+	var validatorSet []string
+	switch {
+	case c.chainConfig.ChainID.Cmp(big.NewInt(2020)) == 0:
+		validatorSet = []string{
+			"0x000000000000000000000000f224beff587362a88d859e899d0d80c080e1e812",
+			"0x00000000000000000000000011360eacdedd59bc433afad4fc8f0417d1fbebab",
+			"0x00000000000000000000000070bb1fb41c8c42f6ddd53a708e2b82209495e455",
+		}
+	case c.chainConfig.ChainID.Cmp(big.NewInt(2021)) == 0:
+		validatorSet = []string{
+			"0x0000000000000000000000004a4bc674a97737376cfe990ae2fe0d2b6e738393",
+			"0x000000000000000000000000b6bc5bc0410773a3f86b1537ce7495c52e38f88b",
+		}
+	default:
+		return nil, errors.New("no validator set for this chain only support Mainnet & Testnet")
+	}
+	var addresses []common.Address
+	for _, str := range validatorSet {
+		addresses = append(addresses, common.HexToAddress(str))
+	}
+	return addresses, nil
+}
+
 // Read the validator list from contract
 func (c *Consortium) getValidatorsFromContract(chain consensus.ChainHeaderReader, number uint64) ([]common.Address, error) {
 	if chain.Config().IsFenix(big.NewInt(int64(number))) {
@@ -779,7 +803,7 @@ func (c *Consortium) getValidatorsFromLastCheckpoint(chain consensus.ChainHeader
 
 	if lastCheckpoint == 0 {
 		// TODO(andy): Review if we should put validators in genesis block's extra data
-		return c.getValidatorsFromContract(chain, number)
+		return c.getValidatorsFromGenesis()
 	}
 
 	var header *types.Header