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// 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 (
"errors"
"time"
"github.com/dexon-foundation/dexon-consensus/core/types"
)
// consensusTimestamp is for Concensus Timestamp Algorithm.
type consensusTimestamp struct {
chainTimestamps []time.Time
// This part keeps configs for each round.
numChainsOfRounds []uint32
numChainsBase uint64
// dMoment represents the genesis time.
dMoment time.Time
// lastTimestamp represents previous assigned consensus timestamp.
lastTimestamp time.Time
}
var (
// ErrTimestampNotIncrease would be reported if the timestamp is not strickly
// increasing on the same chain.
ErrTimestampNotIncrease = errors.New("timestamp is not increasing")
// ErrNoRoundConfig for no round config found.
ErrNoRoundConfig = errors.New("no round config found")
// ErrConsensusTimestampRewind would be reported if the generated timestamp
// is rewinded.
ErrConsensusTimestampRewind = errors.New("consensus timestamp rewind")
)
// newConsensusTimestamp creates timestamper object.
func newConsensusTimestamp(
dMoment time.Time, round uint64, numChains uint32) *consensusTimestamp {
ts := make([]time.Time, numChains)
for i := range ts {
ts[i] = dMoment
}
return &consensusTimestamp{
numChainsOfRounds: []uint32{numChains},
numChainsBase: round,
dMoment: dMoment,
chainTimestamps: ts,
}
}
// appendConfig appends a configuration for upcoming round. When you append
// a config for round R, next time you can only append the config for round R+1.
func (ct *consensusTimestamp) appendConfig(
round uint64, config *types.Config) error {
if round != uint64(len(ct.numChainsOfRounds))+ct.numChainsBase {
return ErrRoundNotIncreasing
}
ct.numChainsOfRounds = append(ct.numChainsOfRounds, config.NumChains)
return nil
}
func (ct *consensusTimestamp) resizeChainTimetamps(numChain uint32) {
l := uint32(len(ct.chainTimestamps))
if numChain > l {
for i := l; i < numChain; i++ {
ct.chainTimestamps = append(ct.chainTimestamps, ct.dMoment)
}
} else if numChain < l {
ct.chainTimestamps = ct.chainTimestamps[:numChain]
}
}
// ProcessBlocks is the entry function.
func (ct *consensusTimestamp) processBlocks(blocks []*types.Block) (err error) {
for _, block := range blocks {
// Rounds might interleave within rounds if no configuration change
// occurs. And it is limited to one round, that is, round r can only
// interleave with r-1 and r+1.
round := block.Position.Round
if ct.numChainsBase == round || ct.numChainsBase+1 == round {
// Normal case, no need to modify chainTimestamps.
} else if ct.numChainsBase+2 == round {
if len(ct.numChainsOfRounds) < 2 {
return ErrNoRoundConfig
}
ct.numChainsBase++
ct.numChainsOfRounds = ct.numChainsOfRounds[1:]
if ct.numChainsOfRounds[0] > ct.numChainsOfRounds[1] {
ct.resizeChainTimetamps(ct.numChainsOfRounds[0])
} else {
ct.resizeChainTimetamps(ct.numChainsOfRounds[1])
}
} else {
// Error if round < base or round > base + 2.
return ErrInvalidRoundID
}
ts := ct.chainTimestamps[:ct.numChainsOfRounds[round-ct.numChainsBase]]
if block.Finalization.Timestamp, err = getMedianTime(ts); err != nil {
return
}
if block.Timestamp.Before(ct.chainTimestamps[block.Position.ChainID]) {
return ErrTimestampNotIncrease
}
ct.chainTimestamps[block.Position.ChainID] = block.Timestamp
if block.Finalization.Timestamp.Before(ct.lastTimestamp) {
block.Finalization.Timestamp = ct.lastTimestamp
} else {
ct.lastTimestamp = block.Finalization.Timestamp
}
}
return
}
func (ct *consensusTimestamp) isSynced() bool {
numChain := ct.numChainsOfRounds[0]
for i := uint32(0); i < numChain; i++ {
if ct.chainTimestamps[i].Equal(ct.dMoment) {
return false
}
}
return true
}
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