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// Copyright 2016 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 (
"fmt"
"math/big"
"github.com/ethereum/go-ethereum"
"github.com/ethereum/go-ethereum/accounts/abi/bind"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core"
"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/ethdb"
"github.com/ethereum/go-ethereum/event"
"golang.org/x/net/context"
)
// Default chain configuration which sets homestead phase at block 0 (i.e. no frontier)
var chainConfig = &core.ChainConfig{HomesteadBlock: big.NewInt(0)}
// This nil assignment ensures compile time that SimulatedBackend implements bind.ContractBackend.
var _ bind.ContractBackend = (*SimulatedBackend)(nil)
// 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
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
}
// NewSimulatedBackend creates a new binding backend using a simulated blockchain
// for testing purposes.
func NewSimulatedBackend(accounts ...core.GenesisAccount) *SimulatedBackend {
database, _ := ethdb.NewMemDatabase()
core.WriteGenesisBlockForTesting(database, accounts...)
blockchain, _ := core.NewBlockChain(database, chainConfig, new(core.FakePow), new(event.TypeMux))
backend := &SimulatedBackend{
database: database,
blockchain: blockchain,
}
backend.Rollback()
return backend
}
// Commit imports all the pending transactions as a single block and starts a
// fresh new state.
func (b *SimulatedBackend) Commit() {
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() {
blocks, _ := core.GenerateChain(nil, b.blockchain.CurrentBlock(), b.database, 1, func(int, *core.BlockGen) {})
b.pendingBlock = blocks[0]
b.pendingState, _ = state.New(b.pendingBlock.Root(), b.database)
}
// CodeAt implements ChainStateReader.CodeAt, returning the code associated with
// a certain account at a given block number in the blockchain.
func (b *SimulatedBackend) CodeAt(ctx context.Context, contract common.Address, blockNumber *big.Int) ([]byte, error) {
if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
return nil, fmt.Errorf("SimulatedBackend cannot access blocks other than the latest block")
}
statedb, _ := b.blockchain.State()
return statedb.GetCode(contract), nil
}
// PendingCodeAt implements PendingStateReader.PendingCodeAt, returning the
// code associated with a certain account in the pending state of the blockchain.
func (b *SimulatedBackend) PendingCodeAt(ctx context.Context, contract common.Address) ([]byte, error) {
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) {
if blockNumber != nil && blockNumber.Cmp(b.blockchain.CurrentBlock().Number()) != 0 {
return nil, fmt.Errorf("SimulatedBackend cannot access blocks other than the latest block")
}
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) {
rval, _, err := b.callContract(ctx, call, b.pendingBlock, b.pendingState.Copy())
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) {
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) (*big.Int, error) {
_, gas, err := b.callContract(ctx, call, b.pendingBlock, b.pendingState.Copy())
return gas, err
}
// callContract implemens 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, *big.Int, error) {
// Ensure message is initialized properly.
if call.GasPrice == nil {
call.GasPrice = big.NewInt(1)
}
if call.Gas == nil || call.Gas.BitLen() == 0 {
call.Gas = big.NewInt(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(common.MaxBig)
// Execute the call.
msg := callmsg{call}
vmenv := core.NewEnv(statedb, chainConfig, b.blockchain, msg, block.Header(), vm.Config{})
gaspool := new(core.GasPool).AddGas(common.MaxBig)
ret, gasUsed, _, err := core.NewStateTransition(vmenv, msg, gaspool).TransitionDb()
return ret, gasUsed, err
}
// 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 {
sender, err := tx.From()
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(nil, b.blockchain.CurrentBlock(), b.database, 1, func(number int, block *core.BlockGen) {
for _, tx := range b.pendingBlock.Transactions() {
block.AddTx(tx)
}
block.AddTx(tx)
})
b.pendingBlock = blocks[0]
b.pendingState, _ = state.New(b.pendingBlock.Root(), b.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, error) { return m.CallMsg.From, nil }
func (m callmsg) FromFrontier() (common.Address, error) { return m.CallMsg.From, nil }
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() *big.Int { return m.CallMsg.Gas }
func (m callmsg) Value() *big.Int { return m.CallMsg.Value }
func (m callmsg) Data() []byte { return m.CallMsg.Data }
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