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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 types
import (
"container/heap"
"encoding/binary"
"math/big"
"github.com/byzantine-lab/dexon-consensus/common"
"github.com/byzantine-lab/dexon-consensus/core/crypto"
)
// NodeSet is the node set structure as defined in DEXON consensus core.
type NodeSet struct {
IDs map[NodeID]struct{}
}
// SubSetTarget is the sub set target for GetSubSet().
type SubSetTarget struct {
data [][]byte
}
type subSetTargetType byte
const (
targetNotarySet subSetTargetType = iota
targetNodeLeader
)
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{
IDs: make(map[NodeID]struct{}),
}
}
// NewNodeSetFromMap creates a new NodeSet from NodeID map.
func NewNodeSetFromMap(nodes map[NodeID]struct{}) *NodeSet {
nIDs := make(map[NodeID]struct{}, len(nodes))
for nID := range nodes {
nIDs[nID] = struct{}{}
}
return &NodeSet{
IDs: nIDs,
}
}
// NewNotarySetTarget is the target for getting Notary Set.
func NewNotarySetTarget(crs common.Hash) *SubSetTarget {
return newTarget(targetNotarySet, crs[:])
}
// NewNodeLeaderTarget is the target for getting leader of fast BA.
func NewNodeLeaderTarget(crs common.Hash, height uint64) *SubSetTarget {
binaryHeight := make([]byte, 8)
binary.LittleEndian.PutUint64(binaryHeight, height)
return newTarget(targetNodeLeader, crs[:], binaryHeight)
}
// Add a NodeID to the set.
func (ns *NodeSet) Add(ID NodeID) {
ns.IDs[ID] = struct{}{}
}
// Clone the NodeSet.
func (ns *NodeSet) Clone() *NodeSet {
nsCopy := NewNodeSet()
for ID := range ns.IDs {
nsCopy.Add(ID)
}
return nsCopy
}
// GetSubSet returns the subset of given target.
func (ns *NodeSet) GetSubSet(
size int, target *SubSetTarget) map[NodeID]struct{} {
if size == 0 {
return make(map[NodeID]struct{})
}
h := rankHeap{}
idx := 0
for nID := range ns.IDs {
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(map[NodeID]struct{}, size)
for _, rank := range h {
nIDs[rank.ID] = struct{}{}
}
return nIDs
}
func newTarget(targetType subSetTargetType, data ...[]byte) *SubSetTarget {
data = append(data, []byte{byte(targetType)})
return &SubSetTarget{
data: data,
}
}
func newNodeRank(ID NodeID, target *SubSetTarget) *nodeRank {
data := make([][]byte, 1, len(target.data)+1)
data[0] = make([]byte, len(ID.Hash))
copy(data[0], ID.Hash[:])
data = append(data, target.data...)
h := crypto.Keccak256Hash(data...)
num := new(big.Int).SetBytes(h[:])
return &nodeRank{
ID: ID,
rank: num,
}
}
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