// Copyright 2018 The dexon-consensus Authors
// This file is part of the dexon-consensus library.
//
// The dexon-consensus 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 dexon-consensus 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 dexon-consensus library. If not, see
// <http://www.gnu.org/licenses/>.
package core
import (
"fmt"
"github.com/dexon-foundation/dexon-consensus/common"
"github.com/dexon-foundation/dexon-consensus/core/types"
)
// Errors for agreement state module.
var (
ErrNoEnoughVoteInPrepareState = fmt.Errorf("no enough vote in prepare state")
ErrNoEnoughVoteInAckState = fmt.Errorf("no enough vote in ack state")
)
// agreementStateType is the state of agreement
type agreementStateType int
// agreementStateType enum.
const (
stateInitial agreementStateType = iota
statePreCommit
stateCommit
stateForward
statePullVote
)
var nullBlockHash = common.Hash{}
var skipBlockHash common.Hash
func init() {
for idx := range skipBlockHash {
skipBlockHash[idx] = 0xff
}
}
type agreementState interface {
state() agreementStateType
nextState() (agreementState, error)
clocks() int
}
//----- InitialState -----
type initialState struct {
a *agreementData
}
func newInitialState(a *agreementData) *initialState {
return &initialState{a: a}
}
func (s *initialState) state() agreementStateType { return stateInitial }
func (s *initialState) clocks() int { return 0 }
func (s *initialState) nextState() (agreementState, error) {
hash := s.a.recv.ProposeBlock()
s.a.lock.Lock()
defer s.a.lock.Unlock()
s.a.recv.ProposeVote(&types.Vote{
Type: types.VoteInit,
BlockHash: hash,
Period: s.a.period,
})
return newPreCommitState(s.a), nil
}
//----- PreCommitState -----
type preCommitState struct {
a *agreementData
}
func newPreCommitState(a *agreementData) *preCommitState {
return &preCommitState{a: a}
}
func (s *preCommitState) state() agreementStateType { return statePreCommit }
func (s *preCommitState) clocks() int { return 2 }
func (s *preCommitState) nextState() (agreementState, error) {
s.a.lock.RLock()
defer s.a.lock.RUnlock()
hash := s.a.lockValue
if hash == nullBlockHash {
hash = s.a.leader.leaderBlockHash()
}
s.a.recv.ProposeVote(&types.Vote{
Type: types.VotePreCom,
BlockHash: hash,
Period: s.a.period,
})
return newCommitState(s.a), nil
}
//----- CommitState -----
type commitState struct {
a *agreementData
}
func newCommitState(a *agreementData) *commitState {
return &commitState{a: a}
}
func (s *commitState) state() agreementStateType { return stateCommit }
func (s *commitState) clocks() int { return 2 }
func (s *commitState) nextState() (agreementState, error) {
hash, ok := s.a.countVote(s.a.period, types.VotePreCom)
s.a.lock.Lock()
defer s.a.lock.Unlock()
if ok && hash != skipBlockHash {
s.a.lockValue = hash
s.a.lockRound = s.a.period
} else {
hash = skipBlockHash
}
s.a.recv.ProposeVote(&types.Vote{
Type: types.VoteCom,
BlockHash: hash,
Period: s.a.period,
})
return newForwardState(s.a), nil
}
// ----- ForwardState -----
type forwardState struct {
a *agreementData
}
func newForwardState(a *agreementData) *forwardState {
return &forwardState{a: a}
}
func (s *forwardState) state() agreementStateType { return stateForward }
func (s *forwardState) clocks() int { return 4 }
func (s *forwardState) nextState() (agreementState, error) {
return newPullVoteState(s.a), nil
}
// ----- PullVoteState -----
// pullVoteState is a special state to ensure the assumption in the consensus
// algorithm that every vote will eventually arrive for all nodes.
type pullVoteState struct {
a *agreementData
}
func newPullVoteState(a *agreementData) *pullVoteState {
return &pullVoteState{a: a}
}
func (s *pullVoteState) state() agreementStateType { return statePullVote }
func (s *pullVoteState) clocks() int { return 4 }
func (s *pullVoteState) nextState() (agreementState, error) {
return s, nil
}
