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// Copyright 2018 The dexon-consensus-core Authors
// This file is part of the dexon-consensus-core library.
//
// The dexon-consensus-core 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-core 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-core library. If not, see
// <http://www.gnu.org/licenses/>.
package core
import (
"errors"
"github.com/dexon-foundation/dexon-consensus-core/core/types"
)
// consensusTimestamp is for Concensus Timestamp Algorithm.
type consensusTimestamp struct {
lastMainChainBlock *types.Block
blocksNotInMainChain []*types.Block
}
var (
// ErrInvalidMainChain would be reported if the invalid result from
// main chain selection algorithm is detected.
ErrInvalidMainChain = errors.New("invalid main chain")
)
// newConsensusTimestamp create timestamper object.
func newConsensusTimestamp() *consensusTimestamp {
return &consensusTimestamp{}
}
// ProcessBlocks is the entry function.
func (ct *consensusTimestamp) processBlocks(blocks []*types.Block) (
blocksWithTimestamp []*types.Block, mainChain []*types.Block, err error) {
if len(blocks) == 0 {
// TODO (jimmy-dexon): Remove this panic before release.
panic("Unexpected empty block list.")
}
outputFirstBlock := true
blocks = append(ct.blocksNotInMainChain, blocks...)
if ct.lastMainChainBlock != nil {
// TODO (jimmy-dexon): The performance here can be optimized.
blocks = append([]*types.Block{ct.lastMainChainBlock}, blocks...)
outputFirstBlock = false
}
mainChain, nonMainChain := ct.selectMainChain(blocks)
ct.blocksNotInMainChain = nonMainChain
ct.lastMainChainBlock = mainChain[len(mainChain)-1]
blocksWithTimestamp = blocks[:len(blocks)-len(nonMainChain)]
leftMainChainIdx := 0
rightMainChainIdx := 0
idxMainChain := 0
for idx, block := range blocksWithTimestamp {
if idxMainChain >= len(mainChain) {
err = ErrInvalidMainChain
return
} else if block.Hash == mainChain[idxMainChain].Hash {
rightMainChainIdx = idx
blocksWithTimestamp[idx].ConsensusInfo.Timestamp, err =
getMedianTime(block)
if err != nil {
return
}
// Process Non-MainChain blocks.
if rightMainChainIdx > leftMainChainIdx {
for idx, timestamp := range interpoTime(
blocksWithTimestamp[leftMainChainIdx].ConsensusInfo.Timestamp,
blocksWithTimestamp[rightMainChainIdx].ConsensusInfo.Timestamp,
rightMainChainIdx-leftMainChainIdx-1) {
blocksWithTimestamp[leftMainChainIdx+idx+1].ConsensusInfo.Timestamp =
timestamp
}
}
leftMainChainIdx = idx
idxMainChain++
}
}
if !outputFirstBlock {
blocksWithTimestamp = blocksWithTimestamp[1:]
}
return
}
func (ct *consensusTimestamp) selectMainChain(blocks []*types.Block) (
mainChain []*types.Block, nonMainChain []*types.Block) {
for _, block := range blocks {
if len(mainChain) != 0 {
if _, exists := block.Acks[mainChain[len(mainChain)-1].Hash]; !exists {
nonMainChain = append(nonMainChain, block)
continue
}
}
nonMainChain = []*types.Block{}
mainChain = append(mainChain, block)
}
return
}
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