consensus, core: move CalcDifficulty to Engine interface

consensus/clique/clique.go

@@ -510,7 +510,6 @@ func (c *Clique) Prepare(chain consensus.ChainReader, header *types.Header) erro
 	header.Nonce = types.BlockNonce{}
 
 	number := header.Number.Uint64()
-
 	// Assemble the voting snapshot to check which votes make sense
 	snap, err := c.snapshot(chain, number-1, header.ParentHash, nil)
 	if err != nil {
@@ -538,10 +537,8 @@ func (c *Clique) Prepare(chain consensus.ChainReader, header *types.Header) erro
 		c.lock.RUnlock()
 	}
 	// Set the correct difficulty
-	header.Difficulty = diffNoTurn
-	if snap.inturn(header.Number.Uint64(), c.signer) {
-		header.Difficulty = diffInTurn
-	}
+	header.Difficulty = CalcDifficulty(snap, c.signer)
+
 	// Ensure the extra data has all it's components
 	if len(header.Extra) < extraVanity {
 		header.Extra = append(header.Extra, bytes.Repeat([]byte{0x00}, extraVanity-len(header.Extra))...)
@@ -655,6 +652,22 @@ func (c *Clique) Seal(chain consensus.ChainReader, block *types.Block, stop <-ch
 	return block.WithSeal(header), nil
 }
 
+// CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty that a new block should have.
+func (c *Clique) CalcDifficulty(chain consensus.ChainReader, time uint64, parent *types.Header) *big.Int {
+	snap, err := c.snapshot(chain, parent.Number.Uint64(), parent.Hash(), nil)
+	if err != nil {
+		return nil
+	}
+	return CalcDifficulty(snap, c.signer)
+}
+
+func CalcDifficulty(snap *Snapshot, signer common.Address) *big.Int {
+	if snap.inturn(snap.Number+1, signer) {
+		return new(big.Int).Set(diffInTurn)
+	}
+	return new(big.Int).Set(diffNoTurn)
+}
+
 // APIs implements consensus.Engine, returning the user facing RPC API to allow
 // controlling the signer voting.
 func (c *Clique) APIs(chain consensus.ChainReader) []rpc.API {

consensus/consensus.go

@@ -89,6 +89,10 @@ type Engine interface {
 	// seal place on top.
 	Seal(chain ChainReader, block *types.Block, stop <-chan struct{}) (*types.Block, error)
 
+	// CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty
+	// that a new block should have.
+	CalcDifficulty(chain ChainReader, time uint64, parent *types.Header) *big.Int
+
 	// APIs returns the RPC APIs this consensus engine provides.
 	APIs(chain ChainReader) []rpc.API
 }
@@ -99,13 +103,4 @@ type PoW interface {
 
 	// Hashrate returns the current mining hashrate of a PoW consensus engine.
 	Hashrate() float64
-
-	// CalcDifficulty returns the difficulty that a new block should have when created at time
-	// given the parent block's time and difficulty.
-	CalcDifficulty(*params.ChainConfig, uint64, *types.Header) *big.Int
-
-	// AccumulateRewards credits the coinbase of the given block with the mining
-	// reward. The total reward consists of the static block reward and rewards for
-	// included uncles. The coinbase of each uncle block is also rewarded.
-	AccumulateRewards(*params.ChainConfig, *state.StateDB, *types.Header, []*types.Header)
 }

consensus/ethash/consensus.go

@@ -239,7 +239,8 @@ func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, parent *
 		return errZeroBlockTime
 	}
 	// Verify the block's difficulty based in it's timestamp and parent's difficulty
-	expected := ethash.CalcDifficulty(chain.Config(), header.Time.Uint64(), parent)
+	expected := ethash.CalcDifficulty(chain, header.Time.Uint64(), parent)
+
 	if expected.Cmp(header.Difficulty) != 0 {
 		return fmt.Errorf("invalid difficulty: have %v, want %v", header.Difficulty, expected)
 	}
@@ -286,7 +287,11 @@ func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, parent *
 // CalcDifficulty is the difficulty adjustment algorithm. It returns
 // the difficulty that a new block should have when created at time
 // given the parent block's time and difficulty.
-func (ethash *Ethash) CalcDifficulty(config *params.ChainConfig, time uint64, parent *types.Header) *big.Int {
+func (ethash *Ethash) CalcDifficulty(chain consensus.ChainReader, time uint64, parent *types.Header) *big.Int {
+	return CalcDifficulty(chain.Config(), time, parent)
+}
+
+func CalcDifficulty(config *params.ChainConfig, time uint64, parent *types.Header) *big.Int {
 	next := new(big.Int).Add(parent.Number, big1)
 	switch {
 	case config.IsByzantium(next):
@@ -500,8 +505,7 @@ func (ethash *Ethash) Prepare(chain consensus.ChainReader, header *types.Header)
 	if parent == nil {
 		return consensus.ErrUnknownAncestor
 	}
-	header.Difficulty = ethash.CalcDifficulty(chain.Config(), header.Time.Uint64(), parent)
-
+	header.Difficulty = ethash.CalcDifficulty(chain, header.Time.Uint64(), parent)
 	return nil
 }
 
@@ -509,7 +513,7 @@ func (ethash *Ethash) Prepare(chain consensus.ChainReader, header *types.Header)
 // setting the final state and assembling the block.
 func (ethash *Ethash) Finalize(chain consensus.ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction, uncles []*types.Header, receipts []*types.Receipt) (*types.Block, error) {
 	// Accumulate any block and uncle rewards and commit the final state root
-	ethash.AccumulateRewards(chain.Config(), state, header, uncles)
+	accumulateRewards(chain.Config(), state, header, uncles)
 	header.Root = state.IntermediateRoot(chain.Config().IsEIP158(header.Number))
 
 	// Header seems complete, assemble into a block and return
@@ -525,7 +529,7 @@ var (
 // AccumulateRewards credits the coinbase of the given block with the mining
 // reward. The total reward consists of the static block reward and rewards for
 // included uncles. The coinbase of each uncle block is also rewarded.
-func (ethash *Ethash) AccumulateRewards(config *params.ChainConfig, state *state.StateDB, header *types.Header, uncles []*types.Header) {
+func accumulateRewards(config *params.ChainConfig, state *state.StateDB, header *types.Header, uncles []*types.Header) {
 	// Select the correct block reward based on chain progression
 	blockReward := frontierBlockReward
 	if config.IsByzantium(header.Number) {

consensus/ethash/consensus_test.go

@@ -71,9 +71,10 @@ func TestCalcDifficulty(t *testing.T) {
 	}
 
 	config := &params.ChainConfig{HomesteadBlock: big.NewInt(1150000)}
+
 	for name, test := range tests {
 		number := new(big.Int).Sub(test.CurrentBlocknumber, big.NewInt(1))
-		diff := NewFaker().CalcDifficulty(config, test.CurrentTimestamp, &types.Header{
+		diff := CalcDifficulty(config, test.CurrentTimestamp, &types.Header{
 			Number:     number,
 			Time:       new(big.Int).SetUint64(test.ParentTimestamp),
 			Difficulty: test.ParentDifficulty,

core/chain_makers.go

@@ -42,6 +42,7 @@ type BlockGen struct {
 	i           int
 	parent      *types.Block
 	chain       []*types.Block
+	chainReader consensus.ChainReader
 	header      *types.Header
 	statedb     *state.StateDB
 
@@ -142,9 +143,7 @@ func (b *BlockGen) OffsetTime(seconds int64) {
 	if b.header.Time.Cmp(b.parent.Header().Time) <= 0 {
 		panic("block time out of range")
 	}
-	if pow, ok := b.engine.(consensus.PoW); ok {
-		b.header.Difficulty = pow.CalcDifficulty(b.config, b.header.Time.Uint64(), b.parent.Header())
-	}
+	b.header.Difficulty = b.engine.CalcDifficulty(b.chainReader, b.header.Time.Uint64(), b.parent.Header())
 }
 
 // GenerateChain creates a chain of n blocks. The first block's
@@ -165,8 +164,10 @@ func GenerateChain(config *params.ChainConfig, parent *types.Block, engine conse
 	}
 	blocks, receipts := make(types.Blocks, n), make([]types.Receipts, n)
 	genblock := func(i int, parent *types.Block, statedb *state.StateDB) (*types.Block, types.Receipts) {
-		b := &BlockGen{i: i, parent: parent, chain: blocks, statedb: statedb, config: config, engine: engine}
-		b.header = makeHeader(config, parent, statedb, b.engine)
+		blockchain, _ := NewBlockChain(db, config, engine, vm.Config{})
+		defer blockchain.Stop()
+		b := &BlockGen{i: i, parent: parent, chain: blocks, chainReader: blockchain, statedb: statedb, config: config, engine: engine}
+		b.header = makeHeader(b.chainReader, parent, statedb, b.engine)
 
 		// Mutate the state and block according to any hard-fork specs
 		if daoBlock := config.DAOForkBlock; daoBlock != nil {
@@ -185,16 +186,16 @@ func GenerateChain(config *params.ChainConfig, parent *types.Block, engine conse
 			gen(i, b)
 		}
 
-		if pow, ok := b.engine.(consensus.PoW); ok {
-			pow.AccumulateRewards(config, statedb, b.header, b.uncles)
-		}
-
-		root, err := statedb.CommitTo(db, config.IsEIP158(b.header.Number))
+		if b.engine != nil {
+			block, _ := b.engine.Finalize(b.chainReader, b.header, statedb, b.txs, b.uncles, b.receipts)
+			// Write state changes to db
+			_, err := statedb.CommitTo(db, config.IsEIP158(b.header.Number))
 			if err != nil {
 				panic(fmt.Sprintf("state write error: %v", err))
 			}
-		b.header.Root = root
-		return types.NewBlock(b.header, b.txs, b.uncles, b.receipts), b.receipts
+			return block, b.receipts
+		}
+		return nil, nil
 	}
 	for i := 0; i < n; i++ {
 		statedb, err := state.New(parent.Root(), state.NewDatabase(db))
@@ -209,7 +210,7 @@ func GenerateChain(config *params.ChainConfig, parent *types.Block, engine conse
 	return blocks, receipts
 }
 
-func makeHeader(config *params.ChainConfig, parent *types.Block, state *state.StateDB, engine consensus.Engine) *types.Header {
+func makeHeader(chain consensus.ChainReader, parent *types.Block, state *state.StateDB, engine consensus.Engine) *types.Header {
 	var time *big.Int
 	if parent.Time() == nil {
 		time = big.NewInt(10)
@@ -217,26 +218,21 @@ func makeHeader(config *params.ChainConfig, parent *types.Block, state *state.St
 		time = new(big.Int).Add(parent.Time(), big.NewInt(10)) // block time is fixed at 10 seconds
 	}
 
-	header := &types.Header{
-		Root:       state.IntermediateRoot(config.IsEIP158(parent.Number())),
+	return &types.Header{
+		Root:       state.IntermediateRoot(chain.Config().IsEIP158(parent.Number())),
 		ParentHash: parent.Hash(),
 		Coinbase:   parent.Coinbase(),
+		Difficulty: engine.CalcDifficulty(chain, time.Uint64(), &types.Header{
+			Number:     parent.Number(),
+			Time:       new(big.Int).Sub(time, big.NewInt(10)),
+			Difficulty: parent.Difficulty(),
+			UncleHash:  parent.UncleHash(),
+		}),
 		GasLimit: CalcGasLimit(parent),
 		GasUsed:  new(big.Int),
 		Number:   new(big.Int).Add(parent.Number(), common.Big1),
 		Time:     time,
 	}
-
-	if pow, ok := engine.(consensus.PoW); ok {
-		header.Difficulty = pow.CalcDifficulty(config, time.Uint64(), &types.Header{
-			Number:     parent.Number(),
-			Time:       new(big.Int).Sub(time, big.NewInt(10)),
-			Difficulty: parent.Difficulty(),
-			UncleHash:  parent.UncleHash(),
-		})
-	}
-
-	return header
 }
 
 // newCanonical creates a chain database, and injects a deterministic canonical

tests/difficulty_test_util.go

@@ -57,7 +57,7 @@ func (test *DifficultyTest) Run(config *params.ChainConfig) error {
 		UncleHash:  test.UncleHash,
 	}
 
-	actual := ethash.NewFaker().CalcDifficulty(config, test.CurrentTimestamp.Uint64(), parent)
+	actual := ethash.CalcDifficulty(config, test.CurrentTimestamp.Uint64(), parent)
 	exp := test.CurrentDifficulty
 
 	if actual.Cmp(exp) != 0 {