consensus/clique: Proof of Authority (#3753)
This PR is a prototype implementation of plugable consensus engines and the Clique PoA protocol ethereum/EIPs#225
This commit is contained in:
Péter Szilágyi
committed by
Felix Lange
Felix Lange
parent
bfe5eb7f8c
commit
feeccdf4ec
299
consensus/clique/snapshot.go
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299
consensus/clique/snapshot.go
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// Copyright 2017 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package clique
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import (
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"bytes"
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"encoding/json"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/core/types"
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"github.com/ethereum/go-ethereum/ethdb"
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"github.com/ethereum/go-ethereum/params"
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)
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// vote represents a single vote that an authorized signer made to modify the
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// list of authorizations.
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type vote struct {
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Signer common.Address `json:"signer"` // Authorized signer that cast this vote
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Block uint64 `json:"block"` // Block number the vote was cast in (expire old votes)
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Address common.Address `json:"address"` // Account being voted on to change its authorization
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Authorize bool `json:"authorize"` // Whether to authorize or deauthorize the voted account
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}
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// tally is a simple vote tally to keep the current score of votes. Votes that
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// go against the proposal aren't counted since it's equivalent to not voting.
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type tally struct {
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Authorize bool `json:"authorize"` // Whether the vote it about authorizing or kicking someone
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Votes int `json:"votes"` // Number of votes until now wanting to pass the proposal
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}
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// snapshot is the state of the authorization voting at a given point in time.
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type snapshot struct {
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config *params.CliqueConfig // Consensus engine parameters to fine tune behavior
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Number uint64 `json:"number"` // Block number where the snapshot was created
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Hash common.Hash `json:"hash"` // Block hash where the snapshot was created
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Signers map[common.Address]struct{} `json:"signers"` // Set of authorized signers at this moment
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Recents map[uint64]common.Address `json:"recents"` // Set of recent signers for spam protections
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Votes []*vote `json:"votes"` // List of votes cast in chronological order
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Tally map[common.Address]tally `json:"tally"` // Current vote tally to avoid recalculating
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}
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// newSnapshot create a new snapshot with the specified startup parameters. This
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// method does not initialize the set of recent signers, so only ever use if for
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// the genesis block.
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func newSnapshot(config *params.CliqueConfig, number uint64, hash common.Hash, signers []common.Address) *snapshot {
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snap := &snapshot{
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config: config,
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Number: number,
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Hash: hash,
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Signers: make(map[common.Address]struct{}),
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Recents: make(map[uint64]common.Address),
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Tally: make(map[common.Address]tally),
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}
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for _, signer := range signers {
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snap.Signers[signer] = struct{}{}
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}
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return snap
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}
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// loadSnapshot loads an existing snapshot from the database.
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func loadSnapshot(config *params.CliqueConfig, db ethdb.Database, hash common.Hash) (*snapshot, error) {
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blob, err := db.Get(append([]byte("clique-"), hash[:]...))
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if err != nil {
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return nil, err
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}
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snap := new(snapshot)
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if err := json.Unmarshal(blob, snap); err != nil {
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return nil, err
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}
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snap.config = config
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return snap, nil
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}
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// store inserts the snapshot into the database.
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func (s *snapshot) store(db ethdb.Database) error {
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blob, err := json.Marshal(s)
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if err != nil {
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return err
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}
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return db.Put(append([]byte("clique-"), s.Hash[:]...), blob)
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}
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// copy creates a deep copy of the snapshot, though not the individual votes.
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func (s *snapshot) copy() *snapshot {
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cpy := &snapshot{
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config: s.config,
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Number: s.Number,
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Hash: s.Hash,
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Signers: make(map[common.Address]struct{}),
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Recents: make(map[uint64]common.Address),
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Votes: make([]*vote, len(s.Votes)),
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Tally: make(map[common.Address]tally),
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}
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for signer := range s.Signers {
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cpy.Signers[signer] = struct{}{}
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}
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for block, signer := range s.Recents {
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cpy.Recents[block] = signer
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}
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for address, tally := range s.Tally {
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cpy.Tally[address] = tally
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}
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copy(cpy.Votes, s.Votes)
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return cpy
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}
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// cast adds a new vote into the tally.
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func (s *snapshot) cast(address common.Address, authorize bool) bool {
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// Ensure the vote is meaningful
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_, signer := s.Signers[address]
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if (signer && authorize) || (!signer && !authorize) {
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return false
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}
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// Cast the vote into an existing or new tally
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if old, ok := s.Tally[address]; ok {
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old.Votes++
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s.Tally[address] = old
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} else {
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s.Tally[address] = tally{Authorize: authorize, Votes: 1}
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}
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return true
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}
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// uncast removes a previously cast vote from the tally.
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func (s *snapshot) uncast(address common.Address, authorize bool) bool {
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// If there's no tally, it's a dangling vote, just drop
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tally, ok := s.Tally[address]
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if !ok {
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return false
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}
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// Ensure we only revert counted votes
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if tally.Authorize != authorize {
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return false
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}
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// Otherwise revert the vote
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if tally.Votes > 1 {
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tally.Votes--
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s.Tally[address] = tally
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} else {
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delete(s.Tally, address)
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}
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return true
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}
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// apply creates a new authorization snapshot by applying the given headers to
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// the original one.
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func (s *snapshot) apply(headers []*types.Header) (*snapshot, error) {
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// Allow passing in no headers for cleaner code
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if len(headers) == 0 {
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return s, nil
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}
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// Sanity check that the headers can be applied
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for i := 0; i < len(headers)-1; i++ {
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if headers[i+1].Number.Uint64() != headers[i].Number.Uint64()+1 {
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return nil, errInvalidVotingChain
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}
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}
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if headers[0].Number.Uint64() != s.Number+1 {
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return nil, errInvalidVotingChain
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}
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// Iterate through the headers and create a new snapshot
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snap := s.copy()
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for _, header := range headers {
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// Remove any votes on checkpoint blocks
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number := header.Number.Uint64()
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if number%s.config.Epoch == 0 {
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snap.Votes = nil
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snap.Tally = make(map[common.Address]tally)
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}
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// Delete the oldest signer from the recent list to allow it signing again
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if limit := uint64(len(snap.Signers)/2 + 1); number >= limit {
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delete(snap.Recents, number-limit)
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}
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// Resolve the authorization key and check against signers
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signer, err := ecrecover(header)
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if err != nil {
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return nil, err
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}
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if _, ok := snap.Signers[signer]; !ok {
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return nil, errUnauthorized
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}
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for _, recent := range snap.Recents {
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if recent == signer {
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return nil, errUnauthorized
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}
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}
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snap.Recents[number] = signer
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// Header authorized, discard any previous votes from the signer
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for i, vote := range snap.Votes {
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if vote.Signer == signer && vote.Address == header.Coinbase {
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// Uncast the vote from the cached tally
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snap.uncast(vote.Address, vote.Authorize)
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// Uncast the vote from the chronological list
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snap.Votes = append(snap.Votes[:i], snap.Votes[i+1:]...)
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break // only one vote allowed
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}
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}
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// Tally up the new vote from the signer
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var authorize bool
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switch {
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case bytes.Compare(header.Nonce[:], nonceAuthVote) == 0:
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authorize = true
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case bytes.Compare(header.Nonce[:], nonceDropVote) == 0:
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authorize = false
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default:
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return nil, errInvalidVote
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}
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if snap.cast(header.Coinbase, authorize) {
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snap.Votes = append(snap.Votes, &vote{
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Signer: signer,
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Block: number,
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Address: header.Coinbase,
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Authorize: authorize,
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})
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}
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// If the vote passed, update the list of signers
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if tally := snap.Tally[header.Coinbase]; tally.Votes > len(snap.Signers)/2 {
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if tally.Authorize {
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snap.Signers[header.Coinbase] = struct{}{}
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} else {
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delete(snap.Signers, header.Coinbase)
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// Signer list shrunk, delete any leftover recent caches
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if limit := uint64(len(snap.Signers)/2 + 1); number >= limit {
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delete(snap.Recents, number-limit)
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}
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// Discard any previous votes the deauthorized signer cast
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for i := 0; i < len(snap.Votes); i++ {
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if snap.Votes[i].Signer == header.Coinbase {
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// Uncast the vote from the cached tally
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snap.uncast(snap.Votes[i].Address, snap.Votes[i].Authorize)
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// Uncast the vote from the chronological list
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snap.Votes = append(snap.Votes[:i], snap.Votes[i+1:]...)
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i--
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}
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}
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}
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// Discard any previous votes around the just changed account
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for i := 0; i < len(snap.Votes); i++ {
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if snap.Votes[i].Address == header.Coinbase {
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snap.Votes = append(snap.Votes[:i], snap.Votes[i+1:]...)
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i--
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}
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}
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delete(snap.Tally, header.Coinbase)
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}
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}
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snap.Number += uint64(len(headers))
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snap.Hash = headers[len(headers)-1].Hash()
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return snap, nil
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}
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// signers retrieves the list of authorized signers in ascending order.
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func (s *snapshot) signers() []common.Address {
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signers := make([]common.Address, 0, len(s.Signers))
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for signer := range s.Signers {
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signers = append(signers, signer)
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}
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for i := 0; i < len(signers); i++ {
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for j := i + 1; j < len(signers); j++ {
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if bytes.Compare(signers[i][:], signers[j][:]) > 0 {
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signers[i], signers[j] = signers[j], signers[i]
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}
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}
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}
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return signers
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}
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// inturn returns if a signer at a given block height is in-turn or not.
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func (s *snapshot) inturn(number uint64, signer common.Address) bool {
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signers, offset := s.signers(), 0
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for offset < len(signers) && signers[offset] != signer {
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offset++
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}
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return (number % uint64(len(signers))) == uint64(offset)
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}
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