2017-10-31 15:24:11 -07:00
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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 backend
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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/consensus/istanbul"
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2018-01-30 18:27:08 -08:00
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"github.com/ethereum/go-ethereum/consensus/istanbul/validator"
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2017-10-31 15:24:11 -07:00
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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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)
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const (
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dbKeySnapshotPrefix = "istanbul-snapshot"
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)
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// Vote represents a single vote that an authorized validator made to modify the
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// list of authorizations.
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type Vote struct {
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Validator common.Address `json:"validator"` // Authorized validator 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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Epoch uint64 // The number of blocks after which to checkpoint and reset the pending votes
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2018-01-30 18:27:08 -08:00
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Number uint64 // Block number where the snapshot was created
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Hash common.Hash // Block hash where the snapshot was created
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Votes []*Vote // List of votes cast in chronological order
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Tally map[common.Address]Tally // Current vote tally to avoid recalculating
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ValSet istanbul.ValidatorSet // Set of authorized validators at this moment
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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 validators, so only ever use if for
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// the genesis block.
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func newSnapshot(epoch uint64, number uint64, hash common.Hash, valSet istanbul.ValidatorSet) *Snapshot {
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snap := &Snapshot{
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Epoch: epoch,
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Number: number,
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Hash: hash,
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ValSet: valSet,
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Tally: make(map[common.Address]Tally),
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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(epoch uint64, db ethdb.Database, hash common.Hash) (*Snapshot, error) {
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blob, err := db.Get(append([]byte(dbKeySnapshotPrefix), 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.Epoch = epoch
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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(dbKeySnapshotPrefix), 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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Epoch: s.Epoch,
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Number: s.Number,
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Hash: s.Hash,
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ValSet: s.ValSet.Copy(),
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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 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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// checkVote return whether it's a valid vote
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func (s *Snapshot) checkVote(address common.Address, authorize bool) bool {
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_, validator := s.ValSet.GetByAddress(address)
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return (validator != nil && !authorize) || (validator == nil && authorize)
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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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if !s.checkVote(address, 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.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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// Resolve the authorization key and check against validators
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validator, 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 _, v := snap.ValSet.GetByAddress(validator); v == nil {
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return nil, errUnauthorized
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}
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// Header authorized, discard any previous votes from the validator
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for i, vote := range snap.Votes {
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if vote.Validator == validator && 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 validator
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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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Validator: validator,
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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 validators
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if tally := snap.Tally[header.Coinbase]; tally.Votes > snap.ValSet.Size()/2 {
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if tally.Authorize {
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snap.ValSet.AddValidator(header.Coinbase)
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} else {
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snap.ValSet.RemoveValidator(header.Coinbase)
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// Discard any previous votes the deauthorized validator cast
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for i := 0; i < len(snap.Votes); i++ {
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if snap.Votes[i].Validator == 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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// validators retrieves the list of authorized validators in ascending order.
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func (s *Snapshot) validators() []common.Address {
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validators := make([]common.Address, 0, s.ValSet.Size())
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for _, validator := range s.ValSet.List() {
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validators = append(validators, validator.Address())
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}
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for i := 0; i < len(validators); i++ {
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for j := i + 1; j < len(validators); j++ {
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if bytes.Compare(validators[i][:], validators[j][:]) > 0 {
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validators[i], validators[j] = validators[j], validators[i]
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}
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}
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}
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return validators
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}
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2018-01-30 18:27:08 -08:00
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type snapshotJSON struct {
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Epoch uint64 `json:"epoch"`
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Number uint64 `json:"number"`
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Hash common.Hash `json:"hash"`
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Votes []*Vote `json:"votes"`
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Tally map[common.Address]Tally `json:"tally"`
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// for validator set
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Validators []common.Address `json:"validators"`
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Policy istanbul.ProposerPolicy `json:"policy"`
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}
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func (s *Snapshot) toJSONStruct() *snapshotJSON {
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return &snapshotJSON{
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Epoch: s.Epoch,
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Number: s.Number,
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Hash: s.Hash,
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Votes: s.Votes,
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Tally: s.Tally,
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Validators: s.validators(),
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Policy: s.ValSet.Policy(),
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}
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}
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// Unmarshal from a json byte array
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func (s *Snapshot) UnmarshalJSON(b []byte) error {
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var j snapshotJSON
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if err := json.Unmarshal(b, &j); err != nil {
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return err
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}
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s.Epoch = j.Epoch
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s.Number = j.Number
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s.Hash = j.Hash
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s.Votes = j.Votes
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s.Tally = j.Tally
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s.ValSet = validator.NewSet(j.Validators, j.Policy)
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return nil
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}
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// Marshal to a json byte array
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func (s *Snapshot) MarshalJSON() ([]byte, error) {
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j := s.toJSONStruct()
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return json.Marshal(j)
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}
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