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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 types
import (
"container/heap"
"encoding/binary"
"math/big"
"github.com/dexon-foundation/dexon-consensus-core/core/crypto"
)
// NodeSet is the node set structure as defined in DEXON consensus core.
type NodeSet struct {
Nodes map[NodeID]struct{}
}
// SubSetTarget is the sub set target for GetSubSet().
type SubSetTarget *big.Int
type subSetTargetType byte
const (
targetNotarySet subSetTargetType = iota
targetWitnessSet
targetDKGSet
)
type nodeRank struct {
ID NodeID
rank *big.Int
}
// rankHeap is a MaxHeap structure.
type rankHeap []*nodeRank
func (h rankHeap) Len() int { return len(h) }
func (h rankHeap) Less(i, j int) bool { return h[i].rank.Cmp(h[j].rank) > 0 }
func (h rankHeap) Swap(i, j int) { h[i], h[j] = h[j], h[i] }
func (h *rankHeap) Push(x interface{}) {
*h = append(*h, x.(*nodeRank))
}
func (h *rankHeap) Pop() interface{} {
old := *h
n := len(old)
x := old[n-1]
*h = old[0 : n-1]
return x
}
// NewNodeSet creates a new NodeSet instance.
func NewNodeSet() *NodeSet {
return &NodeSet{
Nodes: make(map[NodeID]struct{}),
}
}
// NewNotarySetTarget is the target for getting Notary Set.
func NewNotarySetTarget(crs []byte, shardID, chainID uint32) SubSetTarget {
binaryShardID := make([]byte, 4)
binary.LittleEndian.PutUint32(binaryShardID, shardID)
binaryChainID := make([]byte, 4)
binary.LittleEndian.PutUint32(binaryChainID, chainID)
return newTarget(targetNotarySet, crs, binaryShardID, binaryChainID)
}
// NewWitnessSetTarget is the target for getting DKG Set.
func NewWitnessSetTarget(crs []byte, round uint64) SubSetTarget {
binaryRound := make([]byte, 8)
binary.LittleEndian.PutUint64(binaryRound, round)
return newTarget(targetWitnessSet, crs, binaryRound)
}
// NewDKGSetTarget is the target for getting DKG Set.
func NewDKGSetTarget(crs []byte, round uint64) SubSetTarget {
binaryRound := make([]byte, 8)
binary.LittleEndian.PutUint64(binaryRound, round)
return newTarget(targetDKGSet, crs, binaryRound)
}
// GetSubSet returns the subset of given target.
func (ns *NodeSet) GetSubSet(size int, target SubSetTarget) NodeIDs {
h := rankHeap{}
idx := 0
for nID := range ns.Nodes {
if idx < size {
h = append(h, newNodeRank(nID, target))
} else if idx == size {
heap.Init(&h)
}
if idx >= size {
rank := newNodeRank(nID, target)
if rank.rank.Cmp(h[0].rank) < 0 {
h[0] = rank
heap.Fix(&h, 0)
}
}
idx++
}
nIDs := make(NodeIDs, 0, size)
for _, rank := range h {
nIDs = append(nIDs, rank.ID)
}
return nIDs
}
func newTarget(targetType subSetTargetType, data ...[]byte) SubSetTarget {
data = append(data, []byte{byte(targetType)})
h := crypto.Keccak256Hash(data...)
num := big.NewInt(0)
num.SetBytes(h[:])
return SubSetTarget(num)
}
func newNodeRank(ID NodeID, target SubSetTarget) *nodeRank {
num := big.NewInt(0)
num.SetBytes(ID.Hash[:])
num.Abs(num.Sub((*big.Int)(target), num))
return &nodeRank{
ID: ID,
rank: num,
}
}
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