以太坊源码分析之七智能合约
这个以太坊之所以较之于比特币看上去更高大上一些，主要原因是提供了智能合约，以太坊的智能合约确实提供了一个更方便、更开放区块链的接口。
首先说明一下，要想看懂以太坊的智能合约部分，首先要对智能合约有所了解，回头会专门写一个智能合约编写的系列。扯回来。
先看智能合约的入口，不管智能合约还是交易，创建的时候儿都是有Transaction来实现的。不同的是创建的目标是一样的，在前面的交易中提到过，没有目标地址的创建即为智能合约的地址。
一、合约的创建
//如果TO为空，则为智能合约交易，前面提到过
if tx.To() == nil {
//前面这调用SendTx->addTx
signer := types.MakeSigner(b.ChainConfig(), b.CurrentBlock().Number())
from, err := types.Sender(signer, tx)
if err != nil {
return common.Hash{}, err
}
addr := crypto.CreateAddress(from, tx.Nonce())
log.Info("Submitted contract creation", "fullhash", tx.Hash().Hex(), "contract", addr.Hex())
}
其它节点通过网络传播过来的Tx（handler.go:handle()->handleMsg:case msg.Code == TxMsg->AddRemotes）：
func (pool *TxPool) AddRemotes(txs []*types.Transaction) []error {
return pool.addTxs(txs, false)
}
// addTx enqueues a single transaction into the pool if it is valid.
func (pool *TxPool) addTx(tx *types.Transaction, local bool) error {
pool.mu.Lock()
defer pool.mu.Unlock()
// Try to inject the transaction and update any state
replace, err := pool.add(tx, local)
if err != nil {
return err
}
// If we added a new transaction, run promotion checks and return
if !replace {
from, _ := types.Sender(pool.signer, tx) // already validated
pool.promoteExecutables([]common.Address{from})
}
return nil
}
从前面的分析可以看出其实最终他们都调用了promoteExecutables这个函数来进行预执行，判断是否合格的交易。在addr := crypto.CreateAddress(from, tx.Nonce())可以看到，一个预先被预测出来（看下面分析）的合约地址被创建出来写入日志。
为什么说是预测，因为只有真正上链，这个地址才会真正创建出来，如下：
/core/blockchain.go
// SetReceiptsData computes all the non-consensus fields of the receipts
func SetReceiptsData(config *params.ChainConfig, block *types.Block, receipts types.Receipts) {
……
for j := 0; j < len(receipts); j++ {
// The transaction hash can be retrieved from the transaction itself
receipts[j].TxHash = transactions[j].Hash()
// The contract address can be derived from the transaction itself
if transactions[j].To() == nil {
// Deriving the signer is expensive, only do if it's actually needed
from, _ := types.Sender(signer, transactions[j])
receipts[j].ContractAddress = crypto.CreateAddress(from, transactions[j].Nonce())
}
}…….
}
看看是一样的代码吧，如果用交易信息来查看，则提交上去时，地址是空的，等真正打包上链，这个地址才会有。明白了原因吧。所以不管是交易还是合约都是交易需要走下面流程：
Addtx->判断是否合约->promoteExecutables
下面来看具体的创建过程：
// TransitionDb will transition the state by applying the current message and
// returning the result including the the used gas. It returns an error if it
// failed. An error indicates a consensus issue.
func (st *StateTransition) TransitionDb() (ret []byte, usedGas uint64, failed bool, err error) {
if err = st.preCheck(); err != nil {
return
}
msg := st.msg
sender := st.from() // err checked in preCheck
homestead := st.evm.ChainConfig().IsHomestead(st.evm.BlockNumber)
contractCreation := msg.To() == nil
// Pay intrinsic gas
gas, err := IntrinsicGas(st.data, contractCreation, homestead)
if err != nil {
return nil, 0, false, err
}
if err = st.useGas(gas); err != nil {
return nil, 0, false, err
}
var (
evm = st.evm
// vm errors do not effect consensus and are therefor
// not assigned to err, except for insufficient balance
// error.
vmerr error
)
if contractCreation {
//创建合约
ret, _, st.gas, vmerr = evm.Create(sender, st.data, st.gas, st.value)
} else {
// Increment the nonce for the next transaction
st.state.SetNonce(sender.Address(), st.state.GetNonce(sender.Address())+1)
ret, st.gas, vmerr = evm.Call(sender, st.to().Address(), st.data, st.gas, st.value)
}
if vmerr != nil {
log.Debug("VM returned with error", "err", vmerr)
// The only possible consensus-error would be if there wasn't
// sufficient balance to make the transfer happen. The first
// balance transfer may never fail.
if vmerr == vm.ErrInsufficientBalance {
return nil, 0, false, vmerr
}
}
st.refundGas()
st.state.AddBalance(st.evm.Coinbase, new(big.Int).Mul(new(big.Int).SetUint64(st.gasUsed()), st.gasPrice))
return ret, st.gasUsed(), vmerr != nil, err
}
从AddTx---ApplyTransaction—ApplyMessage到上面的函数终于是一个合约创建好了。需要注意的，这个AddTx和前面的交易的不是一个，别弄混。这个是从DeployContract（base.go）这个函数过来的。它调用transact再SendTransaction（simulated.go）-AddTx。
而在TransitionDb中调用：
//core/vm/evm.go
// Create creates a new contract using code as deployment code.
func (evm *EVM) Create(caller ContractRef, code []byte, gas uint64, value *big.Int) (ret []byte, contractAddr common.Address, leftOverGas uint64, err error) {
// Depth check execution. Fail if we're trying to execute above the
// limit.
if evm.depth > int(params.CallCreateDepth) {
return nil, common.Address{}, gas, ErrDepth
}
//见下面的检测费用够不够
if !evm.CanTransfer(evm.StateDB, caller.Address(), value) {
return nil, common.Address{}, gas, ErrInsufficientBalance
}
// Ensure there's no existing contract already at the designated address
//设置随机值
nonce := evm.StateDB.GetNonce(caller.Address())
evm.StateDB.SetNonce(caller.Address(), nonce+1)
//创建合约地址，和上面是不是一样，不同的情况分别创建这里是部署时
contractAddr = crypto.CreateAddress(caller.Address(), nonce)
contractHash := evm.StateDB.GetCodeHash(contractAddr)
if evm.StateDB.GetNonce(contractAddr) != 0 || (contractHash != (common.Hash{}) && contractHash != emptyCodeHash) {
return nil, common.Address{}, 0, ErrContractAddressCollision
}
// Create a new account on the state
snapshot := evm.StateDB.Snapshot()
evm.StateDB.CreateAccount(contractAddr)
if evm.ChainConfig().IsEIP158(evm.BlockNumber) {
evm.StateDB.SetNonce(contractAddr, 1)
}
//见下面的传输数据
evm.Transfer(evm.StateDB, caller.Address(), contractAddr, value)
// initialise a new contract and set the code that is to be used by the
// E The contract is a scoped evmironment for this execution context
// only.
//创建合约
contract := NewContract(caller, AccountRef(contractAddr), value, gas)
contract.SetCallCode(&contractAddr, crypto.Keccak256Hash(code), code)
if evm.vmConfig.NoRecursion && evm.depth > 0 {
return nil, contractAddr, gas, nil
}
if evm.vmConfig.Debug && evm.depth == 0 {
evm.vmConfig.Tracer.CaptureStart(caller.Address(), contractAddr, true, code, gas, value)
}
start := time.Now()
//预先执行合约，见下面
ret, err = run(evm, contract, nil)
// check whether the max code size has been exceeded
maxCodeSizeExceeded := evm.ChainConfig().IsEIP158(evm.BlockNumber) && len(ret) > params.MaxCodeSize
// if the contract creation ran successfully and no errors were returned
// calculate the gas required to store the code. If the code could not
// be stored due to not enough gas set an error and let it be handled
// by the error checking condition below.
if err == nil && !maxCodeSizeExceeded {
createDataGas := uint64(len(ret)) * params.CreateDataGas
if contract.UseGas(createDataGas) {
//更新接口代码
evm.StateDB.SetCode(contractAddr, ret)
} else {
err = ErrCodeStoreOutOfGas
}
}
// When an error was returned by the EVM or when setting the creation code
// above we revert to the snapshot and consume any gas remaining. Additionally
// when we're in homestead this also counts for code storage gas errors.
if maxCodeSizeExceeded || (err != nil && (evm.ChainConfig().IsHomestead(evm.BlockNumber) || err != ErrCodeStoreOutOfGas)) {
evm.StateDB.RevertToSnapshot(snapshot)
if err != errExecutionReverted {
contract.UseGas(contract.Gas)
}
}
// Assign err if contract code size exceeds the max while the err is still empty.
if maxCodeSizeExceeded && err == nil {
err = errMaxCodeSizeExceeded
}
if evm.vmConfig.Debug && evm.depth == 0 {
evm.vmConfig.Tracer.CaptureEnd(ret, gas-contract.Gas, time.Since(start), err)
}
return ret, contractAddr, contract.Gas, err
}
它会调用core/evm.go
// NewEVMContext creates a new context for use in the EVM.
func NewEVMContext(msg Message, header *types.Header, chain ChainContext, author *common.Address) vm.Context {
// If we don't have an explicit author (i.e. not mining), extract from the header
var beneficiary common.Address
if author == nil {
beneficiary, _ = chain.Engine().Author(header) // Ignore error, we're past header validation
} else {
beneficiary = *author
}
return vm.Context{
CanTransfer: CanTransfer,
Transfer: Transfer,
GetHash: GetHashFn(header, chain),
Origin: msg.From(),
Coinbase: beneficiary,
BlockNumber: new(big.Int).Set(header.Number),
Time: new(big.Int).Set(header.Time),
Difficulty: new(big.Int).Set(header.Difficulty),
GasLimit: header.GasLimit,
GasPrice: new(big.Int).Set(msg.GasPrice()),
}
}
// GetHashFn returns a GetHashFunc which retrieves header hashes by number
func GetHashFn(ref *types.Header, chain ChainContext) func(n uint64) common.Hash {
return func(n uint64) common.Hash {
for header := chain.GetHeader(ref.ParentHash, ref.Number.Uint64()-1); header != nil; header = chain.GetHeader(header.ParentHash, header.Number.Uint64()-1) {
if header.Number.Uint64() == n {
return header.Hash()
}
}
return common.Hash{}
}
}
// CanTransfer checks wether there are enough funds in the address' account to make a transfer.
// This does not take the necessary gas in to account to make the transfer valid.
func CanTransfer(db vm.StateDB, addr common.Address, amount *big.Int) bool {
return db.GetBalance(addr).Cmp(amount) >= 0
}
// Transfer subtracts amount from sender and adds amount to recipient using the given Db
func Transfer(db vm.StateDB, sender, recipient common.Address, amount *big.Int) {
db.SubBalance(sender, amount)
db.AddBalance(recipient, amount)
}
再往下调用就是执行部分了，后面再分析，这里先埋个坑。
最后更新接口代码：
func (self *StateDB) SetCode(addr common.Address, code []byte) {
stateObject := self.GetOrNewStateObject(addr)
if stateObject != nil {
stateObject.SetCode(crypto.Keccak256Hash(code), code)
}
}
func (self *stateObject) SetCode(codeHash common.Hash, code []byte) {
prevcode := self.Code(self.db.db)
self.db.journal = append(self.db.journal, codeChange{
account: &self.address,
prevhash: self.CodeHash(),
prevcode: prevcode,
})
self.setCode(codeHash, code)
}
func (self *stateObject) setCode(codeHash common.Hash, code []byte) {
self.code = code
self.data.CodeHash = codeHash[:]
self.dirtyCode = true
if self.onDirty != nil {
self.onDirty(self.Address())
self.onDirty = nil
}
}
到现在一个智能合约就创建成功了。
二、合约的调用：
EVM的调用接口在 vm/inferface.go
// CallContext provides a basic interface for the EVM calling conventions. The EVM EVM
// depends on this context being implemented for doing subcalls and initialising new EVM contracts.
type CallContext interface {
// Call another contract
Call(env *EVM, me ContractRef, addr common.Address, data []byte, gas, value *big.Int) ([]byte, error)
// Take another's contract code and execute within our own context
CallCode(env *EVM, me ContractRef, addr common.Address, data []byte, gas, value *big.Int) ([]byte, error)
// Same as CallCode except sender and value is propagated from parent to child scope
DelegateCall(env *EVM, me ContractRef, addr common.Address, data []byte, gas *big.Int) ([]byte, error)
// Create a new contract
Create(env *EVM, me ContractRef, data []byte, gas, value *big.Int) ([]byte, common.Address, error)
}
在vm/evm.go中实现
这里只分析一个：
func (evm *EVM) Call(caller ContractRef, addr common.Address, input []byte, gas uint64, value *big.Int) (ret []byte, leftOverGas uint64, err error) {
if evm.vmConfig.NoRecursion && evm.depth > 0 {
return nil, gas, nil
}
// Fail if we're trying to execute above the call depth limit
if evm.depth > int(params.CallCreateDepth) {
return nil, gas, ErrDepth
}
// Fail if we're trying to transfer more than the available balance
if !evm.Context.CanTransfer(evm.StateDB, caller.Address(), value) {
return nil, gas, ErrInsufficientBalance
}
var (
to = AccountRef(addr)
snapshot = evm.StateDB.Snapshot()
)
if !evm.StateDB.Exist(addr) {
precompiles := PrecompiledContractsHomestead
if evm.ChainConfig().IsByzantium(evm.BlockNumber) {
precompiles = PrecompiledContractsByzantium
}
if precompiles[addr] == nil && evm.ChainConfig().IsEIP158(evm.BlockNumber) && value.Sign() == 0 {
return nil, gas, nil
}
evm.StateDB.CreateAccount(addr)
}
evm.Transfer(evm.StateDB, caller.Address(), to.Address(), value)
// Initialise a new contract and set the code that is to be used by the EVM.
// The contract is a scoped environment for this execution context only.
contract := NewContract(caller, to, value, gas)
contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))
start := time.Now()
// Capture the tracer start/end events in debug mode
if evm.vmConfig.Debug && evm.depth == 0 {
evm.vmConfig.Tracer.CaptureStart(caller.Address(), addr, false, input, gas, value)
defer func() { // Lazy evaluation of the parameters
evm.vmConfig.Tracer.CaptureEnd(ret, gas-contract.Gas, time.Since(start), err)
}()
}
ret, err = run(evm, contract, input)
// When an error was returned by the EVM or when setting the creation code
// above we revert to the snapshot and consume any gas remaining. Additionally
// when we're in homestead this also counts for code storage gas errors.
if err != nil {
evm.StateDB.RevertToSnapshot(snapshot)
if err != errExecutionReverted {
contract.UseGas(contract.Gas)
}
}
return ret, contract.Gas, err
}
Call，CallCode, DelegateCall, StaticCall四者有什么区别呢？先说简单的，静态调用表示不能修改状态，类似于const函数，委托调用是委托别人调用。麻烦在前两个Call和CallCode，它们的区别在于存储不同，啥意思呢？举一个例子：
A调用Call() B，使用B的存储，如果A调用CallCode() B,则使用A的存储。详细的见下面的相关解释。
https://ethereum.stackexchange.com/questions/3667/difference-between-call-callcode-and-delegatecall
// Execute executes the code using the input as call data during the execution.
// It returns the EVM's return value, the new state and an error if it failed.
//
// Executes sets up a in memory, temporarily, environment for the execution of
// the given code. It enabled the JIT by default and make sure that it's restored
// to it's original state afterwards.
func Execute(code, input []byte, cfg *Config) ([]byte, *state.StateDB, error) {
if cfg == nil {
cfg = new(Config)
}
setDefaults(cfg)
if cfg.State == nil {
db, _ := ethdb.NewMemDatabase()
cfg.State, _ = state.New(common.Hash{}, state.NewDatabase(db))
}
var (
address = common.StringToAddress("contract")
vmenv = NewEnv(cfg)
sender = vm.AccountRef(cfg.Origin)
)
cfg.State.CreateAccount(address)
// set the receiver's (the executing contract) code for execution.
cfg.State.SetCode(address, code)
// Call the code with the given configuration.
ret, _, err := vmenv.Call(
sender,
common.StringToAddress("contract"),
input,
cfg.GasLimit,
cfg.Value,
)
return ret, cfg.State, err
}
// Create executes the code using the EVM create method
func Create(input []byte, cfg *Config) ([]byte, common.Address, uint64, error) {
if cfg == nil {
cfg = new(Config)
}
setDefaults(cfg)
if cfg.State == nil {
db, _ := ethdb.NewMemDatabase()
cfg.State, _ = state.New(common.Hash{}, state.NewDatabase(db))
}
var (
vmenv = NewEnv(cfg)
sender = vm.AccountRef(cfg.Origin)
)
// Call the code with the given configuration.
code, address, leftOverGas, err := vmenv.Create(
sender,
input,
cfg.GasLimit,
cfg.Value,
)
return code, address, leftOverGas, err
}
// Call executes the code given by the contract's address. It will return the
// EVM's return value or an error if it failed.
//
// Call, unlike Execute, requires a config and also requires the State field to
// be set.
func Call(address common.Address, input []byte, cfg *Config) ([]byte, uint64, error) {
setDefaults(cfg)
vmenv := NewEnv(cfg)
sender := cfg.State.GetOrNewStateObject(cfg.Origin)
// Call the code with the given configuration.
ret, leftOverGas, err := vmenv.Call(
sender,
address,
input,
cfg.GasLimit,
cfg.Value,
)
return ret, leftOverGas, err
}
三、合约的执行
合约的执行是需要一个执行机，也就是Stack，它来操作内存并控制Code的动作流程
// stack is an object for basic stack operations. Items popped to the stack are
// expected to be changed and modified. stack does not take care of adding newly
// initialised objects.
type Stack struct {
data []*big.Int
}
func newstack() *Stack {
return &Stack{data: make([]*big.Int, 0, 1024)}
}
func (st *Stack) Data() []*big.Int {
return st.data
}
func (st *Stack) push(d *big.Int) {
// NOTE push limit (1024) is checked in baseCheck
//stackItem := new(big.Int).Set(d)
//st.data = append(st.data, stackItem)
st.data = append(st.data, d)
}
func (st *Stack) pushN(ds ...*big.Int) {
st.data = append(st.data, ds...)
}
func (st *Stack) pop() (ret *big.Int) {
ret = st.data[len(st.data)-1]
st.data = st.data[:len(st.data)-1]
return
}
func (st *Stack) len() int {
return len(st.data)
}
func (st *Stack) swap(n int) {
st.data[st.len()-n], st.data[st.len()-1] = st.data[st.len()-1], st.data[st.len()-n]
}
func (st *Stack) dup(pool *intPool, n int) {
st.push(pool.get().Set(st.data[st.len()-n]))
}
func (st *Stack) peek() *big.Int {
return st.data[st.len()-1]
}
// Back returns the n'th item in stack
func (st *Stack) Back(n int) *big.Int {
return st.data[st.len()-n-1]
}
func (st *Stack) require(n int) error {
if st.len() < n {
return fmt.Errorf("stack underflow (%d <=> %d)", len(st.data), n)
}
return nil
}
func (st *Stack) Print() {
fmt.Println("### stack ###")
if len(st.data) > 0 {
for i, val := range st.data {
fmt.Printf("%-3d %v\n", i, val)
}
} else {
fmt.Println("-- empty --")
}
fmt.Println("#############")
}
它调用的内存控制：
// Memory implements a simple memory model for the ethereum virtual machine.
type Memory struct {
store []byte
lastGasCost uint64
}
func NewMemory() *Memory {
return &Memory{}
}
// Set sets offset + size to value
func (m *Memory) Set(offset, size uint64, value []byte) {
// length of store may never be less than offset + size.
// The store should be resized PRIOR to setting the memory
if size > uint64(len(m.store)) {
panic("INVALID memory: store empty")
}
// It's possible the offset is greater than 0 and size equals 0. This is because
// the calcMemSize (common.go) could potentially return 0 when size is zero (NO-OP)
if size > 0 {
copy(m.store[offset:offset+size], value)
}
}
// Resize resizes the memory to size
func (m *Memory) Resize(size uint64) {
if uint64(m.Len()) < size {
m.store = append(m.store, make([]byte, size-uint64(m.Len()))...)
}
}
// Get returns offset + size as a new slice
func (self *Memory) Get(offset, size int64) (cpy []byte) {
if size == 0 {
return nil
}
if len(self.store) > int(offset) {
cpy = make([]byte, size)
copy(cpy, self.store[offset:offset+size])
return
}
return
}
// GetPtr returns the offset + size
func (self *Memory) GetPtr(offset, size int64) []byte {
if size == 0 {
return nil
}
if len(self.store) > int(offset) {
return self.store[offset : offset+size]
}
return nil
}
// Len returns the length of the backing slice
func (m *Memory) Len() int {
return len(m.store)
}
// Data returns the backing slice
func (m *Memory) Data() []byte {
return m.store
}
func (m *Memory) Print() {
fmt.Printf("### mem %d bytes ###\n", len(m.store))
if len(m.store) > 0 {
addr := 0
for i := 0; i+32 <= len(m.store); i += 32 {
fmt.Printf("%03d: % x\n", addr, m.store[i:i+32])
addr++
}
} else {
fmt.Println("-- empty --")
}
fmt.Println("####################")
}
内存的操作（在指令instructions.go中）
func opMload(pc *uint64, evm *EVM, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) {
offset := stack.pop()
val := new(big.Int).SetBytes(memory.Get(offset.Int64(), 32))
stack.push(val)
evm.interpreter.intPool.put(offset)
return nil, nil
}
func opMstore(pc *uint64, evm *EVM, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) {
// pop value of the stack
mStart, val := stack.pop(), stack.pop()
memory.Set(mStart.Uint64(), 32, math.PaddedBigBytes(val, 32))
evm.interpreter.intPool.put(mStart, val)
return nil, nil
}
func opMstore8(pc *uint64, evm *EVM, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) {
off, val := stack.pop().Int64(), stack.pop().Int64()
memory.store[off] = byte(val & 0xff)
return nil, nil
}
操作码部分太多，不列出来了。然后就是执行了，要填坑了：
再看看run:vm/evm.go
// run runs the given contract and takes care of running precompiles with a fallback to the byte code interpreter.
func run(evm *EVM, contract *Contract, input []byte) ([]byte, error) {
if contract.CodeAddr != nil {
//调用原生合约（预编译好，不用解释器解释）
precompiles := PrecompiledContractsHomestead
if evm.ChainConfig().IsByzantium(evm.BlockNumber) {
precompiles = PrecompiledContractsByzantium
}
if p := precompiles[*contract.CodeAddr]; p != nil {
return RunPrecompiledContract(p, input, contract)
}
}
//否则调用解释器进行解释执行
return evm.interpreter.Run(contract, input)
}
它会调用：
// RunPrecompiledContract runs and evaluates the output of a precompiled contract.
func RunPrecompiledContract(p PrecompiledContract, input []byte, contract *Contract) (ret []byte, err error) {
gas := p.RequiredGas(input)
if contract.UseGas(gas) {
return p.Run(input)
}
return nil, ErrOutOfGas
}
//下面为原生合约的Map中四个Run中的一个
func (c *ecrecover) Run(input []byte) ([]byte, error) {
const ecRecoverInputLength = 128
input = common.RightPadBytes(input, ecRecoverInputLength)
// "input" is (hash, v, r, s), each 32 bytes
// but for ecrecover we want (r, s, v)
r := new(big.Int).SetBytes(input[64:96])
s := new(big.Int).SetBytes(input[96:128])
v := input[63] - 27
// tighter sig s values input homestead only apply to tx sigs
if !allZero(input[32:63]) || !crypto.ValidateSignatureValues(v, r, s, false) {
return nil, nil
}
// v needs to be at the end for libsecp256k1
pubKey, err := crypto.Ecrecover(input[:32], append(input[64:128], v))
// make sure the public key is a valid one
if err != nil {
return nil, nil
}
// the first byte of pubkey is bitcoin heritage
return common.LeftPadBytes(crypto.Keccak256(pubKey[1:])[12:], 32), nil
}
如果不是预编译好的合约（可以认为类似于标准库），调用解释器（vm/interpreter.go）：
func (in *Interpreter) Run(contract *Contract, input []byte) (ret []byte, err error) {
// Increment the call depth which is restricted to 1024
in.evm.depth++
defer func() { in.evm.depth-- }()
// Reset the previous call's return data. It's unimportant to preserve the old buffer
// as every returning call will return new data anyway.
in.returnData = nil
// Don't bother with the execution if there's no code.
if len(contract.Code) == 0 {
return nil, nil
}
var (
op OpCode // current opcode
mem = NewMemory() // bound memory
stack = newstack() // local stack
// For optimisation reason we're using uint64 as the program counter.
// It's theoretically possible to go above 2^64. The YP defines the PC
// to be uint256. Practically much less so feasible.
pc = uint64(0) // program counter
cost uint64
// copies used by tracer
pcCopy uint64 // needed for the deferred Tracer
gasCopy uint64 // for Tracer to log gas remaining before execution
logged bool // deferred Tracer should ignore already logged steps
)
contract.Input = input
if in.cfg.Debug {
defer func() {
if err != nil {
if !logged {
in.cfg.Tracer.CaptureState(in.evm, pcCopy, op, gasCopy, cost, mem, stack, contract, in.evm.depth, err)
} else {
in.cfg.Tracer.CaptureFault(in.evm, pcCopy, op, gasCopy, cost, mem, stack, contract, in.evm.depth, err)
}
}
}()
}
// The Interpreter main run loop (contextual). This loop runs until either an
// explicit STOP, RETURN or SELFDESTRUCT is executed, an error occurred during
// the execution of one of the operations or until the done flag is set by the
// parent context.
for atomic.LoadInt32(&in.evm.abort) == 0 {
if in.cfg.Debug {
// Capture pre-execution values for tracing.
logged, pcCopy, gasCopy = false, pc, contract.Gas
}
// Get the operation from the jump table and validate the stack to ensure there are
// enough stack items available to perform the operation.
op = contract.GetOp(pc)
operation := in.cfg.JumpTable[op]
if !operation.valid {
return nil, fmt.Errorf("invalid opcode 0x%x", int(op))
}
if err := operation.validateStack(stack); err != nil {
return nil, err
}
// If the operation is valid, enforce and write restrictions
if err := in.enforceRestrictions(op, operation, stack); err != nil {
return nil, err
}
var memorySize uint64
// calculate the new memory size and expand the memory to fit
// the operation
if operation.memorySize != nil {
memSize, overflow := bigUint64(operation.memorySize(stack))
if overflow {
return nil, errGasUintOverflow
}
// memory is expanded in words of 32 bytes. Gas
// is also calculated in words.
if memorySize, overflow = math.SafeMul(toWordSize(memSize), 32); overflow {
return nil, errGasUintOverflow
}
}
if !in.cfg.DisableGasMetering {
// consume the gas and return an error if not enough gas is available.
// cost is explicitly set so that the capture state defer method cas get the proper cost
cost, err = operation.gasCost(in.gasTable, in.evm, contract, stack, mem, memorySize)
if err != nil || !contract.UseGas(cost) {
return nil, ErrOutOfGas
}
}
if memorySize > 0 {
mem.Resize(memorySize)
}
if in.cfg.Debug {
in.cfg.Tracer.CaptureState(in.evm, pc, op, gasCopy, cost, mem, stack, contract, in.evm.depth, err)
logged = true
}
// execute the operation
res, err := operation.execute(&pc, in.evm, contract, mem, stack)
// verifyPool is a build flag. Pool verification makes sure the integrity
// of the integer pool by comparing values to a default value.
if verifyPool {
verifyIntegerPool(in.intPool)
}
// if the operation clears the return data (e.g. it has returning data)
// set the last return to the result of the operation.
if operation.returns {
in.returnData = res
}
switch {
case err != nil:
return nil, err
case operation.reverts:
return res, errExecutionReverted
case operation.halts:
return res, nil
case !operation.jumps:
pc++
}
}
return nil, nil
}
这样智能合约从创建到调用，最后执行，从字节码部署，到Code的组装，内存分配，然后栈执行，解释器动作，一套流程就把智能合约基本理清楚了。
在下一篇的虚拟机里，举一个例子看一下整个调用走的流程，这样会更清晰一些。
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