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// Copyright 2017 The DEXON Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package dexcon
import (
"math/big"
"github.com/dexon-foundation/dexon/common"
"github.com/dexon-foundation/dexon/consensus"
"github.com/dexon-foundation/dexon/core/state"
"github.com/dexon-foundation/dexon/core/types"
"github.com/dexon-foundation/dexon/core/vm"
"github.com/dexon-foundation/dexon/rpc"
)
type GovernanceStateFetcher interface {
GetStateForConfigAtRound(round uint64) *vm.GovernanceState
}
// Dexcon is a delegated proof-of-stake consensus engine.
type Dexcon struct {
govStateFetcer GovernanceStateFetcher
}
// New creates a Clique proof-of-authority consensus engine with the initial
// signers set to the ones provided by the user.
func New() *Dexcon {
return &Dexcon{}
}
// SetGovStateFetcher sets the config fetcher for Dexcon. The reason this is not
// passed in the New() method is to bypass cycle dependencies when initializing
// dex backend.
func (d *Dexcon) SetGovStateFetcher(fetcher GovernanceStateFetcher) {
d.govStateFetcer = fetcher
}
// Author implements consensus.Engine, returning the Ethereum address recovered
// from the signature in the header's extra-data section.
func (d *Dexcon) Author(header *types.Header) (common.Address, error) {
return common.Address{}, nil
}
// VerifyHeader checks whether a header conforms to the consensus rules.
func (d *Dexcon) VerifyHeader(chain consensus.ChainReader, header *types.Header, seal bool) error {
return nil
}
// VerifyHeaders is similar to VerifyHeader, but verifies a batch of headers. The
// method returns a quit channel to abort the operations and a results channel to
// retrieve the async verifications (the order is that of the input slice).
func (d *Dexcon) VerifyHeaders(chain consensus.ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error) {
abort, results := make(chan struct{}), make(chan error)
go func() {
for range headers {
results <- nil
}
}()
return abort, results
}
// verifyHeader checks whether a header conforms to the consensus rules.The
// caller may optionally pass in a batch of parents (ascending order) to avoid
// looking those up from the database. This is useful for concurrently verifying
// a batch of new headers.
func (d *Dexcon) verifyHeader(chain consensus.ChainReader, header *types.Header, parents []*types.Header) error {
return nil
}
// verifyCascadingFields verifies all the header fields that are not standalone,
// rather depend on a batch of previous headers. The caller may optionally pass
// in a batch of parents (ascending order) to avoid looking those up from the
// database. This is useful for concurrently verifying a batch of new headers.
func (d *Dexcon) verifyCascadingFields(chain consensus.ChainReader, header *types.Header, parents []*types.Header) error {
return nil
}
// VerifyUncles implements consensus.Engine, always returning an error for any
// uncles as this consensus mechanism doesn't permit uncles.
func (d *Dexcon) VerifyUncles(chain consensus.ChainReader, block *types.Block) error {
return nil
}
// VerifySeal implements consensus.Engine, checking whether the signature contained
// in the header satisfies the consensus protocol requirements.
func (d *Dexcon) VerifySeal(chain consensus.ChainReader, header *types.Header) error {
return nil
}
// Prepare implements consensus.Engine, preparing all the consensus fields of the
// header for running the transactions on top.
func (d *Dexcon) Prepare(chain consensus.ChainReader, header *types.Header) error {
return nil
}
func (d *Dexcon) calculateBlockReward(round int64, state *state.StateDB) *big.Int {
gs := d.govStateFetcer.GetStateForConfigAtRound(uint64(round))
config := gs.Configuration()
blocksPerRound := config.RoundLength
roundInterval := new(big.Float).Mul(
big.NewFloat(float64(blocksPerRound)),
big.NewFloat(float64(config.MinBlockInterval)))
// blockReard = miningVelocity * totalStaked * roundInterval / aYear / numBlocksInCurRound
numerator, _ := new(big.Float).Mul(
new(big.Float).Mul(
big.NewFloat(float64(config.MiningVelocity)),
new(big.Float).SetInt(gs.TotalStaked())),
roundInterval).Int(nil)
reward := new(big.Int).Div(numerator,
new(big.Int).Mul(
big.NewInt(86400*1000*365),
big.NewInt(int64(blocksPerRound))))
return reward
}
// Finalize implements consensus.Engine, ensuring no uncles are set, nor block
// rewards given, and returns the final block.
func (d *Dexcon) Finalize(chain consensus.ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction, uncles []*types.Header, receipts []*types.Receipt) (*types.Block, error) {
gs := vm.GovernanceState{state}
height := gs.RoundHeight(new(big.Int).SetUint64(header.Round))
if header.Round > 0 && height.Uint64() == 0 {
gs.PushRoundHeight(header.Number)
}
// Distribute block reward and halving condition.
if header.Coinbase == (common.Address{}) {
header.Reward = new(big.Int)
} else {
reward := d.calculateBlockReward(int64(header.Round), state)
state.AddBalance(header.Coinbase, reward)
gs.IncTotalSupply(reward)
config := gs.Configuration()
// Check if halving checkpoint reached.
if gs.TotalSupply().Cmp(config.NextHalvingSupply) >= 0 {
gs.MiningHalved()
}
header.Reward = reward
}
header.Root = state.IntermediateRoot(true)
return types.NewBlock(header, txs, uncles, receipts), nil
}
// Seal implements consensus.Engine, attempting to create a sealed block using
// the local signing credentials.
func (d *Dexcon) Seal(chain consensus.ChainReader, block *types.Block, results chan<- *types.Block, stop <-chan struct{}) error {
return nil
}
// SealHash returns the hash of a block prior to it being sealed.
func (d *Dexcon) SealHash(header *types.Header) (hash common.Hash) {
return common.Hash{}
}
// CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty
// that a new block should have based on the previous blocks in the chain and the
// current signer.
func (d *Dexcon) CalcDifficulty(chain consensus.ChainReader, time uint64, parent *types.Header) *big.Int {
return big.NewInt(0)
}
// Close implements consensus.Engine. It's a noop for clique as there is are no background threads.
func (d *Dexcon) Close() error {
return nil
}
// APIs implements consensus.Engine, returning the user facing RPC API to allow
// controlling the signer voting.
func (d *Dexcon) APIs(chain consensus.ChainReader) []rpc.API {
return []rpc.API{}
}
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