1 files changed, 139 insertions, 0 deletions
diff --git a/vendor/github.com/dexon-foundation/dexon-consensus/core/consensus-timestamp.go b/vendor/github.com/dexon-foundation/dexon-consensus/core/consensus-timestamp.go
new file mode 100644
index 000000000..9750a74c3
--- /dev/null
+++ b/vendor/github.com/dexon-foundation/dexon-consensus/core/consensus-timestamp.go
@@ -0,0 +1,139 @@
+// 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, 0, numChains)
+	for i := uint32(0); i < numChains; i++ {
+		ts = append(ts, 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
+}