// Copyright 2015 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/>.
package backends
import (
"context"
"errors"
"fmt"
"math/big"
"sync"
"time"
"github.com/ethereum/go-ethereum"
"github.com/ethereum/go-ethereum/accounts/abi/bind"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/math"
"github.com/ethereum/go-ethereum/consensus/ethash"
"github.com/ethereum/go-ethereum/core"
"github.com/ethereum/go-ethereum/core/bloombits"
"github.com/ethereum/go-ethereum/core/rawdb"
"github.com/ethereum/go-ethereum/core/state"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/core/vm"
"github.com/ethereum/go-ethereum/eth/filters"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/event"
"github.com/ethereum/go-ethereum/params"
"github.com/ethereum/go-ethereum/rpc"
)
// This nil assignment ensures compile time that SimulatedBackend implements bind.ContractBackend.
var _ bind.ContractBackend = (*SimulatedBackend)(nil)
var errBlockNumberUnsupported = errors.New("SimulatedBackend cannot access blocks other than the latest block")
var errGasEstimationFailed = errors.New("gas required exceeds allowance or always failing transaction")
// SimulatedBackend implements bind.ContractBackend, simulating a blockchain in
// the background. Its main purpose is to allow easily testing contract bindings.
type SimulatedBackend struct {
database ethdb.Database // In memory database to store our testing data
blockchain *core.BlockChain // Ethereum blockchain to handle the consensus
mu sync.Mutex
pendingBlock *types.Block // Currently pending block that will be imported on request
pendingState *state.StateDB // Currently pending state that will be the active on on request
events *filters.EventSystem // Event system for filtering log events live
config *params.ChainConfig
}
// NewSimulatedBackend creates a new binding backend using a simulated blockchain
// for testing purposes.
func NewSimulatedBackend(alloc core.GenesisAlloc) *SimulatedBackend {
database := ethdb.NewMemDatabase()
genesis := core.Genesis{Config: params.AllEthashProtocolChanges, Alloc: alloc}
genesis.MustCommit(database)
blockchain, _ := core.NewBlockChain(database, nil, genesis.Config, ethash.NewFaker(), vm.Config{})
backend := &SimulatedBackend{
database: database,
blockchain: blockchain,
config: genesis.Config,
events: filters.NewEventSystem(new(event.TypeMux), &filterBackend{database, blockchain}, false),
}
backend.rollback()
return backend
}
// Commit imports all the pending transactions as a single block and starts a
// fresh new state.
func (b *SimulatedBackend) Commit() {
b.mu.Lock()
defer b.mu.Unlock()
if _, err := b.blockchain.InsertChain([]*types.Block{b.pendingBlock}); err != nil {
panic(err) // This cannot happen unless the simulator is wrong, fail in that case
}
b.rollback()
}
// Rollback aborts all pending transactions, reverting to the last committed state.
func (b *SimulatedBackend) Rollback() {
b.mu.Lock()
defer b.mu.Unlock()
b.rollback()
}
func (b *SimulatedBackend) rollback() {
blocks, _ := core.GenerateChain(b.config, b.blockchain.CurrentBlock(), ethash.NewFaker(), b.database, 1, func(int, *core.BlockGen) {})
statedb, _ := b.blockchain.State()
b.pendingBlock = blocks[0]
b.pendingState, _ = state.New(b.pendingBlock.Root(), statedb.Database())
}
// CodeAt returns the code associated with a certain account in the blockchain.
func (b *SimulatedBackend) CodeAt(ctx context.Context, contract common.Address, blockNumber *big.Int) ([]byte, error) {
b.mu.Lock()
defer b.mu.Unlock()
if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
return nil, errBlockNumberUnsupported
}
statedb, _ := b.blockchain.State()
return statedb.GetCode(contract), nil
}
// BalanceAt returns the wei balance of a certain account in the blockchain.
func (b *SimulatedBackend) BalanceAt(ctx context.Context, contract common.Address, blockNumber *big.Int) (*big.Int, error) {
b.mu.Lock()
defer b.mu.Unlock()
if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
return nil, errBlockNumberUnsupported
}
statedb, _ := b.blockchain.State()
return statedb.GetBalance(contract), nil
}
// NonceAt returns the nonce of a certain account in the blockchain.
func (b *SimulatedBackend) NonceAt(ctx context.Context, contract common.Address, blockNumber *big.Int) (uint64, error) {
b.mu.Lock()
defer b.mu.Unlock()
if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
return 0, errBlockNumberUnsupported
}
statedb, _ := b.blockchain.State()
return statedb.GetNonce(contract), nil
}
// StorageAt returns the value of key in the storage of an account in the blockchain.
func (b *SimulatedBackend) StorageAt(ctx context.Context, contract common.Address, key common.Hash, blockNumber *big.Int) ([]byte, error) {
b.mu.Lock()
defer b.mu.Unlock()
if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
return nil, errBlockNumberUnsupported
}
statedb, _ := b.blockchain.State()
val := statedb.GetState(contract, key)
return val[:], nil
}
// TransactionReceipt returns the receipt of a transaction.
func (b *SimulatedBackend) TransactionReceipt(ctx context.Context, txHash common.Hash) (*types.Receipt, error) {
receipt, _, _, _ := rawdb.ReadReceipt(b.database, txHash)
return receipt, nil
}
// PendingCodeAt returns the code associated with an account in the pending state.
func (b *SimulatedBackend) PendingCodeAt(ctx context.Context, contract common.Address) ([]byte, error) {
b.mu.Lock()
defer b.mu.Unlock()
return b.pendingState.GetCode(contract), nil
}
// CallContract executes a contract call.
func (b *SimulatedBackend) CallContract(ctx context.Context, call ethereum.CallMsg, blockNumber *big.Int) ([]byte, error) {
b.mu.Lock()
defer b.mu.Unlock()
if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
return nil, errBlockNumberUnsupported
}
state, err := b.blockchain.State()
if err != nil {
return nil, err
}
rval, _, _, err := b.callContract(ctx, call, b.blockchain.CurrentBlock(), state)
return rval, err
}
// PendingCallContract executes a contract call on the pending state.
func (b *SimulatedBackend) PendingCallContract(ctx context.Context, call ethereum.CallMsg) ([]byte, error) {
b.mu.Lock()
defer b.mu.Unlock()
defer b.pendingState.RevertToSnapshot(b.pendingState.Snapshot())
rval, _, _, err := b.callContract(ctx, call, b.pendingBlock, b.pendingState)
return rval, err
}
// PendingNonceAt implements PendingStateReader.PendingNonceAt, retrieving
// the nonce currently pending for the account.
func (b *SimulatedBackend) PendingNonceAt(ctx context.Context, account common.Address) (uint64, error) {
b.mu.Lock()
defer b.mu.Unlock()
return b.pendingState.GetOrNewStateObject(account).Nonce(), nil
}
// SuggestGasPrice implements ContractTransactor.SuggestGasPrice. Since the simulated
// chain doens't have miners, we just return a gas price of 1 for any call.
func (b *SimulatedBackend) SuggestGasPrice(ctx context.Context) (*big.Int, error) {
return big.NewInt(1), nil
}
// EstimateGas executes the requested code against the currently pending block/state and
// returns the used amount of gas.
func (b *SimulatedBackend) EstimateGas(ctx context.Context, call ethereum.CallMsg) (uint64, error) {
b.mu.Lock()
defer b.mu.Unlock()
// Determine the lowest and highest possible gas limits to binary search in between
var (
lo uint64 = params.TxGas - 1
hi uint64
cap uint64
)
if call.Gas >= params.TxGas {
hi = call.Gas
} else {
hi = b.pendingBlock.GasLimit()
}
cap = hi
// Create a helper to check if a gas allowance results in an executable transaction
executable := func(gas uint64) bool {
call.Gas = gas
snapshot := b.pendingState.Snapshot()
_, _, failed, err := b.callContract(ctx, call, b.pendingBlock, b.pendingState)
b.pendingState.RevertToSnapshot(snapshot)
if err != nil || failed {
return false
}
return true
}
// Execute the binary search and hone in on an executable gas limit
for lo+1 < hi {
mid := (hi + lo) / 2
if !executable(mid) {
lo = mid
} else {
hi = mid
}
}
// Reject the transaction as invalid if it still fails at the highest allowance
if hi == cap {
if !executable(hi) {
return 0, errGasEstimationFailed
}
}
return hi, nil
}
// callContract implements common code between normal and pending contract calls.
// state is modified during execution, make sure to copy it if necessary.
func (b *SimulatedBackend) callContract(ctx context.Context, call ethereum.CallMsg, block *types.Block, statedb *state.StateDB) ([]byte, uint64, bool, error) {
// Ensure message is initialized properly.
if call.GasPrice == nil {
call.GasPrice = big.NewInt(1)
}
if call.Gas == 0 {
call.Gas = 50000000
}
if call.Value == nil {
call.Value = new(big.Int)
}
// Set infinite balance to the fake caller account.
from := statedb.GetOrNewStateObject(call.From)
from.SetBalance(math.MaxBig256)
// Execute the call.
msg := callmsg{call}
evmContext := core.NewEVMContext(msg, block.Header(), b.blockchain, nil)
// Create a new environment which holds all relevant information
// about the transaction and calling mechanisms.
vmenv := vm.NewEVM(evmContext, statedb, b.config, vm.Config{})
gaspool := new(core.GasPool).AddGas(math.MaxUint64)
return core.NewStateTransition(vmenv, msg, gaspool).TransitionDb()
}
// SendTransaction updates the pending block to include the given transaction.
// It panics if the transaction is invalid.
func (b *SimulatedBackend) SendTransaction(ctx context.Context, tx *types.Transaction) error {
b.mu.Lock()
defer b.mu.Unlock()
sender, err := types.Sender(types.HomesteadSigner{}, tx)
if err != nil {
panic(fmt.Errorf("invalid transaction: %v", err))
}
nonce := b.pendingState.GetNonce(sender)
if tx.Nonce() != nonce {
panic(fmt.Errorf("invalid transaction nonce: got %d, want %d", tx.Nonce(), nonce))
}
blocks, _ := core.GenerateChain(b.config, b.blockchain.CurrentBlock(), ethash.NewFaker(), b.database, 1, func(number int, block *core.BlockGen) {
for _, tx := range b.pendingBlock.Transactions() {
block.AddTxWithChain(b.blockchain, tx)
}
block.AddTxWithChain(b.blockchain, tx)
})
statedb, _ := b.blockchain.State()
b.pendingBlock = blocks[0]
b.pendingState, _ = state.New(b.pendingBlock.Root(), statedb.Database())
return nil
}
// FilterLogs executes a log filter operation, blocking during execution and
// returning all the results in one batch.
//
// TODO(karalabe): Deprecate when the subscription one can return past data too.
func (b *SimulatedBackend) FilterLogs(ctx context.Context, query ethereum.FilterQuery) ([]types.Log, error) {
// Initialize unset filter boundaried to run from genesis to chain head
from := int64(0)
if query.FromBlock != nil {
from = query.FromBlock.Int64()
}
to := int64(-1)
if query.ToBlock != nil {
to = query.ToBlock.Int64()
}
// Construct and execute the filter
filter := filters.New(&filterBackend{b.database, b.blockchain}, from, to, query.Addresses, query.Topics)
logs, err := filter.Logs(ctx)
if err != nil {
return nil, err
}
res := make([]types.Log, len(logs))
for i, log := range logs {
res[i] = *log
}
return res, nil
}
// SubscribeFilterLogs creates a background log filtering operation, returning a
// subscription immediately, which can be used to stream the found events.
func (b *SimulatedBackend) SubscribeFilterLogs(ctx context.Context, query ethereum.FilterQuery, ch chan<- types.Log) (ethereum.Subscription, error) {
// Subscribe to contract events
sink := make(chan []*types.Log)
sub, err := b.events.SubscribeLogs(query, sink)
if err != nil {
return nil, err
}
// Since we're getting logs in batches, we need to flatten them into a plain stream
return event.NewSubscription(func(quit <-chan struct{}) error {
defer sub.Unsubscribe()
for {
select {
case logs := <-sink:
for _, log := range logs {
select {
case ch <- *log:
case err := <-sub.Err():
return err
case <-quit:
return nil
}
}
case err := <-sub.Err():
return err
case <-quit:
return nil
}
}
}), nil
}
// AdjustTime adds a time shift to the simulated clock.
func (b *SimulatedBackend) AdjustTime(adjustment time.Duration) error {
b.mu.Lock()
defer b.mu.Unlock()
blocks, _ := core.GenerateChain(b.config, b.blockchain.CurrentBlock(), ethash.NewFaker(), b.database, 1, func(number int, block *core.BlockGen) {
for _, tx := range b.pendingBlock.Transactions() {
block.AddTx(tx)
}
block.OffsetTime(int64(adjustment.Seconds()))
})
statedb, _ := b.blockchain.State()
b.pendingBlock = blocks[0]
b.pendingState, _ = state.New(b.pendingBlock.Root(), statedb.Database())
return nil
}
// callmsg implements core.Message to allow passing it as a transaction simulator.
type callmsg struct {
ethereum.CallMsg
}
func (m callmsg) From() common.Address { return m.CallMsg.From }
func (m callmsg) Nonce() uint64 { return 0 }
func (m callmsg) CheckNonce() bool { return false }
func (m callmsg) To() *common.Address { return m.CallMsg.To }
func (m callmsg) GasPrice() *big.Int { return m.CallMsg.GasPrice }
func (m callmsg) Gas() uint64 { return m.CallMsg.Gas }
func (m callmsg) Value() *big.Int { return m.CallMsg.Value }
func (m callmsg) Data() []byte { return m.CallMsg.Data }
// filterBackend implements filters.Backend to support filtering for logs without
// taking bloom-bits acceleration structures into account.
type filterBackend struct {
db ethdb.Database
bc *core.BlockChain
}
func (fb *filterBackend) ChainDb() ethdb.Database { return fb.db }
func (fb *filterBackend) EventMux() *event.TypeMux { panic("not supported") }
func (fb *filterBackend) HeaderByNumber(ctx context.Context, block rpc.BlockNumber) (*types.Header, error) {
if block == rpc.LatestBlockNumber {
return fb.bc.CurrentHeader(), nil
}
return fb.bc.GetHeaderByNumber(uint64(block.Int64())), nil
}
func (fb *filterBackend) GetReceipts(ctx context.Context, hash common.Hash) (types.Receipts, error) {
number := rawdb.ReadHeaderNumber(fb.db, hash)
if number == nil {
return nil, nil
}
return rawdb.ReadReceipts(fb.db, hash, *number), nil
}
func (fb *filterBackend) GetLogs(ctx context.Context, hash common.Hash) ([][]*types.Log, error) {
number := rawdb.ReadHeaderNumber(fb.db, hash)
if number == nil {
return nil, nil
}
receipts := rawdb.ReadReceipts(fb.db, hash, *number)
if receipts == nil {
return nil, nil
}
logs := make([][]*types.Log, len(receipts))
for i, receipt := range receipts {
logs[i] = receipt.Logs
}
return logs, nil
}
func (fb *filterBackend) SubscribeTxPreEvent(ch chan<- core.TxsPreEvent) event.Subscription {
return event.NewSubscription(func(quit <-chan struct{}) error {
<-quit
return nil
})
}
func (fb *filterBackend) SubscribeChainEvent(ch chan<- core.ChainEvent) event.Subscription {
return fb.bc.SubscribeChainEvent(ch)
}
func (fb *filterBackend) SubscribeRemovedLogsEvent(ch chan<- core.RemovedLogsEvent) event.Subscription {
return fb.bc.SubscribeRemovedLogsEvent(ch)
}
func (fb *filterBackend) SubscribeLogsEvent(ch chan<- []*types.Log) event.Subscription {
return fb.bc.SubscribeLogsEvent(ch)
}
func (fb *filterBackend) BloomStatus() (uint64, uint64) { return 4096, 0 }
func (fb *filterBackend) ServiceFilter(ctx context.Context, ms *bloombits.MatcherSession) {
panic("not supported")
}