188 lines
6.9 KiB
Go
188 lines
6.9 KiB
Go
// Copyright 2016 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package backends
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import (
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"math/big"
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"github.com/ethereum/go-ethereum/accounts/abi/bind"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/core"
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"github.com/ethereum/go-ethereum/core/state"
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"github.com/ethereum/go-ethereum/core/types"
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"github.com/ethereum/go-ethereum/ethdb"
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"github.com/ethereum/go-ethereum/event"
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)
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// This nil assignment ensures compile time that SimulatedBackend implements bind.ContractBackend.
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var _ bind.ContractBackend = (*SimulatedBackend)(nil)
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// SimulatedBackend implements bind.ContractBackend, simulating a blockchain in
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// the background. Its main purpose is to allow easily testing contract bindings.
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type SimulatedBackend struct {
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database ethdb.Database // In memory database to store our testing data
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blockchain *core.BlockChain // Ethereum blockchain to handle the consensus
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pendingBlock *types.Block // Currently pending block that will be imported on request
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pendingState *state.StateDB // Currently pending state that will be the active on on request
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}
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// NewSimulatedBackend creates a new binding backend using a simulated blockchain
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// for testing purposes.
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func NewSimulatedBackend(accounts ...core.GenesisAccount) *SimulatedBackend {
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database, _ := ethdb.NewMemDatabase()
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core.WriteGenesisBlockForTesting(database, accounts...)
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blockchain, _ := core.NewBlockChain(database, new(core.FakePow), new(event.TypeMux))
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backend := &SimulatedBackend{
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database: database,
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blockchain: blockchain,
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}
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backend.Rollback()
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return backend
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}
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// Commit imports all the pending transactions as a single block and starts a
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// fresh new state.
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func (b *SimulatedBackend) Commit() {
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if _, err := b.blockchain.InsertChain([]*types.Block{b.pendingBlock}); err != nil {
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panic(err) // This cannot happen unless the simulator is wrong, fail in that case
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}
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b.Rollback()
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}
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// Rollback aborts all pending transactions, reverting to the last committed state.
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func (b *SimulatedBackend) Rollback() {
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blocks, _ := core.GenerateChain(b.blockchain.CurrentBlock(), b.database, 1, func(int, *core.BlockGen) {})
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b.pendingBlock = blocks[0]
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b.pendingState, _ = state.New(b.pendingBlock.Root(), b.database)
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}
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// ContractCall implements ContractCaller.ContractCall, executing the specified
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// contract with the given input data.
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func (b *SimulatedBackend) ContractCall(contract common.Address, data []byte, pending bool) ([]byte, error) {
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// Create a copy of the current state db to screw around with
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var (
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block *types.Block
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statedb *state.StateDB
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)
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if pending {
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block, statedb = b.pendingBlock, b.pendingState.Copy()
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} else {
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block = b.blockchain.CurrentBlock()
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statedb, _ = b.blockchain.State()
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}
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// Set infinite balance to the a fake caller account
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from := statedb.GetOrNewStateObject(common.Address{})
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from.SetBalance(common.MaxBig)
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// Assemble the call invocation to measure the gas usage
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msg := callmsg{
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from: from,
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to: &contract,
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gasPrice: new(big.Int),
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gasLimit: common.MaxBig,
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value: new(big.Int),
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data: data,
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}
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// Execute the call and return
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vmenv := core.NewEnv(statedb, b.blockchain, msg, block.Header(), nil)
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gaspool := new(core.GasPool).AddGas(common.MaxBig)
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out, _, err := core.ApplyMessage(vmenv, msg, gaspool)
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return out, err
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}
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// PendingAccountNonce implements ContractTransactor.PendingAccountNonce, retrieving
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// the nonce currently pending for the account.
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func (b *SimulatedBackend) PendingAccountNonce(account common.Address) (uint64, error) {
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return b.pendingState.GetOrNewStateObject(account).Nonce(), nil
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}
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// SuggestGasPrice implements ContractTransactor.SuggestGasPrice. Since the simulated
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// chain doens't have miners, we just return a gas price of 1 for any call.
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func (b *SimulatedBackend) SuggestGasPrice() (*big.Int, error) {
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return big.NewInt(1), nil
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}
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// EstimateGasLimit implements ContractTransactor.EstimateGasLimit, executing the
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// requested code against the currently pending block/state and returning the used
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// gas.
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func (b *SimulatedBackend) EstimateGasLimit(sender common.Address, contract *common.Address, value *big.Int, data []byte) (*big.Int, error) {
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// Create a copy of the currently pending state db to screw around with
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var (
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block = b.pendingBlock
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statedb = b.pendingState.Copy()
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)
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// Set infinite balance to the a fake caller account
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from := statedb.GetOrNewStateObject(sender)
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from.SetBalance(common.MaxBig)
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// Assemble the call invocation to measure the gas usage
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msg := callmsg{
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from: from,
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to: contract,
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gasPrice: new(big.Int),
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gasLimit: common.MaxBig,
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value: value,
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data: data,
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}
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// Execute the call and return
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vmenv := core.NewEnv(statedb, b.blockchain, msg, block.Header(), nil)
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gaspool := new(core.GasPool).AddGas(common.MaxBig)
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_, gas, err := core.ApplyMessage(vmenv, msg, gaspool)
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return gas, err
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}
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// SendTransaction implements ContractTransactor.SendTransaction, delegating the raw
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// transaction injection to the remote node.
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func (b *SimulatedBackend) SendTransaction(tx *types.Transaction) error {
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blocks, _ := core.GenerateChain(b.blockchain.CurrentBlock(), b.database, 1, func(number int, block *core.BlockGen) {
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for _, tx := range b.pendingBlock.Transactions() {
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block.AddTx(tx)
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}
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block.AddTx(tx)
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})
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b.pendingBlock = blocks[0]
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b.pendingState, _ = state.New(b.pendingBlock.Root(), b.database)
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return nil
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}
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// callmsg implements core.Message to allow passing it as a transaction simulator.
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type callmsg struct {
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from *state.StateObject
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to *common.Address
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gasLimit *big.Int
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gasPrice *big.Int
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value *big.Int
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data []byte
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}
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func (m callmsg) From() (common.Address, error) { return m.from.Address(), nil }
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func (m callmsg) FromFrontier() (common.Address, error) { return m.from.Address(), nil }
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func (m callmsg) Nonce() uint64 { return m.from.Nonce() }
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func (m callmsg) To() *common.Address { return m.to }
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func (m callmsg) GasPrice() *big.Int { return m.gasPrice }
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func (m callmsg) Gas() *big.Int { return m.gasLimit }
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func (m callmsg) Value() *big.Int { return m.value }
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func (m callmsg) Data() []byte { return m.data }
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