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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 (
"math/big"
"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/ethdb"
"github.com/ethereum/go-ethereum/event"
)
// 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, 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(b.blockchain.CurrentBlock(), b.database, 1, func(int, *core.BlockGen) {})
b.pendingBlock = blocks[0]
b.pendingState, _ = state.New(b.pendingBlock.Root(), b.database)
}
// ContractCall implements ContractCaller.ContractCall, executing the specified
// contract with the given input data.
func (b *SimulatedBackend) ContractCall(contract common.Address, data []byte, pending bool) ([]byte, error) {
// Create a copy of the current state db to screw around with
var (
block *types.Block
statedb *state.StateDB
)
if pending {
block, statedb = b.pendingBlock, b.pendingState
} else {
block = b.blockchain.CurrentBlock()
statedb, _ = b.blockchain.State()
}
statedb = statedb.Copy()
// Set infinite balance to the a fake caller account
from := statedb.GetOrNewStateObject(common.Address{})
from.SetBalance(common.MaxBig)
// Assemble the call invocation to measure the gas usage
msg := callmsg{
from: from,
to: &contract,
gasPrice: new(big.Int),
gasLimit: common.MaxBig,
value: new(big.Int),
data: data,
}
// Execute the call and return
vmenv := core.NewEnv(statedb, b.blockchain, msg, block.Header())
gaspool := new(core.GasPool).AddGas(common.MaxBig)
out, _, err := core.ApplyMessage(vmenv, msg, gaspool)
return out, err
}
// AccountNonce implements ContractTransactor.AccountNonce, retrieving the nonce
// currently pending for the account.
func (b *SimulatedBackend) AccountNonce(account common.Address) (uint64, error) {
return b.pendingState.GetOrNewStateObject(account).Nonce(), nil
}
// GasPrice implements ContractTransactor.GasPrice. Since the simulated chain
// doens't have miners, we just return a gas price of 1 for any call.
func (b *SimulatedBackend) GasPrice() (*big.Int, error) {
return big.NewInt(1), nil
}
// GasLimit implements ContractTransactor.GasLimit, executing the requested code
// against the currently pending block/state and returning the used gas.
func (b *SimulatedBackend) GasLimit(sender common.Address, contract *common.Address, value *big.Int, data []byte) (*big.Int, error) {
// Create a copy of the currently pending state db to screw around with
var (
block = b.pendingBlock
statedb = b.pendingState.Copy()
)
// Set infinite balance to the a fake caller account
from := statedb.GetOrNewStateObject(sender)
from.SetBalance(common.MaxBig)
// Assemble the call invocation to measure the gas usage
msg := callmsg{
from: from,
to: contract,
gasPrice: new(big.Int),
gasLimit: common.MaxBig,
value: value,
data: data,
}
// Execute the call and return
vmenv := core.NewEnv(statedb, b.blockchain, msg, block.Header())
gaspool := new(core.GasPool).AddGas(common.MaxBig)
_, gas, err := core.ApplyMessage(vmenv, msg, gaspool)
return gas, err
}
// Transact implements ContractTransactor.SendTransaction, delegating the raw
// transaction injection to the remote node.
func (b *SimulatedBackend) SendTransaction(tx *types.Transaction) error {
blocks, _ := core.GenerateChain(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 {
from *state.StateObject
to *common.Address
gasLimit *big.Int
gasPrice *big.Int
value *big.Int
data []byte
}
func (m callmsg) From() (common.Address, error) { return m.from.Address(), nil }
func (m callmsg) FromFrontier() (common.Address, error) { return m.from.Address(), nil }
func (m callmsg) Nonce() uint64 { return m.from.Nonce() }
func (m callmsg) To() *common.Address { return m.to }
func (m callmsg) GasPrice() *big.Int { return m.gasPrice }
func (m callmsg) Gas() *big.Int { return m.gasLimit }
func (m callmsg) Value() *big.Int { return m.value }
func (m callmsg) Data() []byte { return m.data }
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