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snapshot.go
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snapshot.go
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// Copyright 2018 Wanchain Foundation Ltd
// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum 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 go-ethereum 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 go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
// The code is mostly inspired by POA of ethereum
package ethash
import (
"container/list"
"encoding/json"
"errors"
"github.com/wanchain/go-wanchain/common"
"github.com/wanchain/go-wanchain/core/types"
"github.com/wanchain/go-wanchain/ethdb"
"strings"
"fmt"
)
const (
windowRatio = 2 //
)
type Snapshot struct {
PermissionSigners map[common.Address]struct{}
Number uint64
Hash common.Hash
UsedSigners map[common.Address]struct{}
RecentSignersWindow *list.List
}
type plainSnapShot struct {
PermissionSigners map[common.Address]struct{} `json:"permissionSigners"`
Number uint64 `json:"number"`
Hash common.Hash `json:"hash"`
UsedSigners map[common.Address]struct{} `json:"usedSigners"`
RecentSignersWindow []common.Address `json:"recentSignersWindow"`
}
func newSnapshot(number uint64, hash common.Hash, signers []common.Address) *Snapshot {
snap := &Snapshot{
PermissionSigners: make(map[common.Address]struct{}),
Number: number,
Hash: hash,
UsedSigners: make(map[common.Address]struct{}),
RecentSignersWindow: list.New(),
}
for _, s := range signers {
snap.PermissionSigners[s] = struct{}{}
}
return snap
}
func loadSnapShot(db ethdb.Database, hash common.Hash) (*Snapshot, error) {
blob, err := db.Get(append([]byte("ppow-"), hash[:]...))
if err != nil {
return nil, err
}
plain := new(plainSnapShot)
if err := json.Unmarshal(blob, plain); err != nil {
return nil, err
}
snap := &Snapshot{
PermissionSigners: plain.PermissionSigners,
Number: plain.Number,
Hash: plain.Hash,
UsedSigners: plain.UsedSigners,
RecentSignersWindow: list.New(),
}
for _, v := range plain.RecentSignersWindow {
snap.RecentSignersWindow.PushBack(v)
}
return snap, nil
}
func (s *Snapshot) store(db ethdb.Database) error {
plain := &plainSnapShot{
PermissionSigners: s.PermissionSigners,
Number: s.Number,
Hash: s.Hash,
UsedSigners: s.UsedSigners,
RecentSignersWindow: make([]common.Address, 0),
}
for e := s.RecentSignersWindow.Front(); e != nil; e = e.Next() {
if _, ok := e.Value.(common.Address); ok {
plain.RecentSignersWindow = append(plain.RecentSignersWindow, e.Value.(common.Address))
}
}
blob, err := json.Marshal(plain)
if err != nil {
return err
}
return db.Put(append([]byte("ppow-"), plain.Hash[:]...), blob)
}
func (s *Snapshot) copy() *Snapshot {
cpy := &Snapshot{
PermissionSigners: s.PermissionSigners,
Number: s.Number,
Hash: s.Hash,
UsedSigners: make(map[common.Address]struct{}),
RecentSignersWindow: list.New(),
}
for signer := range s.UsedSigners {
cpy.UsedSigners[signer] = struct{}{}
}
cpy.RecentSignersWindow.PushBackList(s.RecentSignersWindow)
return cpy
}
func (s *Snapshot) updateSignerStatus(signer common.Address, isExist bool) {
if isExist {
//if signer already presence
if (s.RecentSignersWindow.Len()) > 0 {
s.RecentSignersWindow.PushFront(signer)
s.RecentSignersWindow.Remove(s.RecentSignersWindow.Back())
}
} else {
// This is the first time the signer appear
s.UsedSigners[signer] = struct{}{}
preWindowLen := s.RecentSignersWindow.Len()
newWindowLen := (len(s.UsedSigners) - 1) / windowRatio
if newWindowLen > preWindowLen {
s.RecentSignersWindow.PushFront(signer)
} else {
//windowLen unchanged
if newWindowLen > 0 {
s.RecentSignersWindow.PushFront(signer)
s.RecentSignersWindow.Remove(s.RecentSignersWindow.Back())
}
}
}
}
// apply creates a new authorization snapshot by applying the given headers to
// the original one.
// PermissionSigners is the full set of signers who can sign blocks
// UsedSigners is the set of signers who had sign blocks
// RecentSignersWindow is the set who can not sign next block
// len(RecentSignersWindow) = (len(UsedSigners)-1)/2
// so when n > 2, hacker should got (n / 2 + 1) key to reorg chain?
func (s *Snapshot) apply(headers []*types.Header) (*Snapshot, error) {
if len(headers) == 0 {
return s, nil
}
// Sanity check that the headers can be applied
for i := 0; i < len(headers)-1; i++ {
if headers[i+1].Number.Uint64() != headers[i].Number.Uint64()+1 {
return nil, errors.New("invalid applied headers")
}
}
if headers[0].Number.Uint64() != s.Number+1 {
return nil, errors.New("invalid applied header to snapshot")
}
snap := s.copy()
for _, header := range headers {
signer, err := ecrecover(header)
if err != nil || 0 != strings.Compare(signer.String(), header.Coinbase.String()) {
return nil, err
}
err = snap.isLegal4Sign(signer)
if err != nil {
return nil, err
}
_, ok := snap.UsedSigners[signer]
snap.updateSignerStatus(signer, ok)
}
snap.Hash = headers[len(headers)-1].Hash()
snap.Number = headers[len(headers)-1].Number.Uint64()
return snap, nil
}
func (s *Snapshot) isLegal4Sign(signer common.Address) error {
if _, ok := s.PermissionSigners[signer]; !ok {
fmt.Println(common.ToHex(signer[:]))
return errUnauthorized
}
for e := s.RecentSignersWindow.Front(); e != nil; e = e.Next() {
if _, ok := e.Value.(common.Address); ok {
wSigner := e.Value.(common.Address)
if signer == wSigner {
return errAuthorTooOften
}
}
}
return nil
}