path: root/vendor/github.com/byzantine-lab/dexon-consensus/core/types/nodeset.go

// 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,
    }
}