兄弟连区块链入门教程eth源码分析core-vm源码分析二

兄弟连区块链入门教程eth源码分析core-vm源码分析（二），合约创建 Create 会创建一个新的合约。

// 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

}

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

// 确保特定的地址没有合约存在

nonce := evm.StateDB.GetNonce(caller.Address())

evm.StateDB.SetNonce(caller.Address(), nonce+1)

contractAddr = crypto.CreateAddress(caller.Address(), nonce)

contractHash := evm.StateDB.GetCodeHash(contractAddr)

if evm.StateDB.GetNonce(contractAddr) != 0 || (contractHash != (common.Hash{}) && contractHash != emptyCodeHash) { //如果已经存在

return nil, common.Address{}, 0, ErrContractAddressCollision

}

// Create a new account on the state

snapshot := evm.StateDB.Snapshot() //创建一个StateDB的快照，以便回滚

evm.StateDB.CreateAccount(contractAddr) //创建账户

if evm.ChainConfig().IsEIP158(evm.BlockNumber) {

evm.StateDB.SetNonce(contractAddr, 1) //设置nonce

}

evm.Transfer(evm.StateDB, caller.Address(), contractAddr, value) //转账

// 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.

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

}

ret, err = run(evm, snapshot, contract, nil) //执行合约的初始化代码

// check whether the max code size has been exceeded

// 检查初始化生成的代码的长度不超过限制

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.

//如果合同创建成功并且没有错误返回，则计算存储代码所需的GAS。 如果由于没有足够的GAS而导致代码不能被存储设置错误，并通过下面的错误检查条件来处理。

if err == nil && !maxCodeSizeExceeded {

createDataGas := uint64(len(ret)) * params.CreateDataGas

if contract.UseGas(createDataGas) {

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.

// 当错误返回我们回滚修改，

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

}

return ret, contractAddr, contract.Gas, err

}

Call方法, 无论我们转账或者是执行合约代码都会调用到这里， 同时合约里面的call指令也会执行到这里。

// Call executes the contract associated with the addr with the given input as

// parameters. It also handles any necessary value transfer required and takes

// the necessary steps to create accounts and reverses the state in case of an

// execution error or failed value transfer.

// Call 执行与给定的input作为参数与addr相关联的合约。

// 它还处理所需的任何必要的转账操作，并采取必要的步骤来创建帐户

// 并在任意错误的情况下回滚所做的操作。

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

// 调用深度最多1024

if evm.depth > int(params.CallCreateDepth) {

return nil, gas, ErrDepth

}

// Fail if we're trying to transfer more than the available balance

// 查看我们的账户是否有足够的金钱。

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) { // 查看指定地址是否存在

// 如果地址不存在，查看是否是 native go的合约， native go的合约在

// contracts.go 文件里面

precompiles := PrecompiledContractsHomestead

if evm.ChainConfig().IsByzantium(evm.BlockNumber) {

precompiles = PrecompiledContractsByzantium

}

if precompiles[addr] == nil && evm.ChainConfig().IsEIP158(evm.BlockNumber) && value.Sign() == 0 {

// 如果不是指定的合约地址， 并且value的值为0那么返回正常，而且这次调用没有消耗Gas

return nil, gas, nil

}

// 负责在本地状态创建addr

evm.StateDB.CreateAccount(addr)

}

// 执行转账

evm.Transfer(evm.StateDB, caller.Address(), to.Address(), value)

// initialise a new contract and set the code that is to be used by the

// E 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))

ret, err = run(evm, snapshot, 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 {

// 如果是由revert指令触发的错误，因为ICO一般设置了人数限制或者资金限制

// 在大家抢购的时候很可能会触发这些限制条件，导致被抽走不少钱。这个时候

// 又不能设置比较低的GasPrice和GasLimit。因为要速度快。

// 那么不会使用剩下的全部Gas，而是只会使用代码执行的Gas

// 不然会被抽走 GasLimit *GasPrice的钱，那可不少。

contract.UseGas(contract.Gas)

}

}

return ret, contract.Gas, err

}

剩下的三个函数 CallCode, DelegateCall, 和 StaticCall，这三个函数不能由外部调用，只能由Opcode触发。

CallCode

// CallCode differs from Call in the sense that it executes the given address'

// code with the caller as context.

// CallCode与Call不同的地方在于它使用caller的context来执行给定地址的代码。

func (evm *EVM) CallCode(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.CanTransfer(evm.StateDB, caller.Address(), value) {

return nil, gas, ErrInsufficientBalance

}

var (

snapshot = evm.StateDB.Snapshot()

to = AccountRef(caller.Address()) //这里是最不同的地方 to的地址被修改为caller的地址了 而且没有转账的行为

)

// 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.

contract := NewContract(caller, to, value, gas)

contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))

ret, err = run(evm, snapshot, contract, input)

if err != nil {

evm.StateDB.RevertToSnapshot(snapshot)

if err != errExecutionReverted {

contract.UseGas(contract.Gas)

}

}

return ret, contract.Gas, err

}

DelegateCall

// DelegateCall differs from CallCode in the sense that it executes the given address'

// code with the caller as context and the caller is set to the caller of the caller.

// DelegateCall 和 CallCode不同的地方在于 caller被设置为 caller的caller

func (evm *EVM) DelegateCall(caller ContractRef, addr common.Address, input []byte, gas uint64) (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

}

var (

snapshot = evm.StateDB.Snapshot()

to = AccountRef(caller.Address())

)

// Initialise a new contract and make initialise the delegate values

// 标识为AsDelete()

contract := NewContract(caller, to, nil, gas).AsDelegate()

contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))

ret, err = run(evm, snapshot, contract, input)

if err != nil {

evm.StateDB.RevertToSnapshot(snapshot)

if err != errExecutionReverted {

contract.UseGas(contract.Gas)

}

}

return ret, contract.Gas, err

}

// StaticCall executes the contract associated with the addr with the given input

// as parameters while disallowing any modifications to the state during the call.

// Opcodes that attempt to perform such modifications will result in exceptions

// instead of performing the modifications.

// StaticCall不允许执行任何修改状态的操作，

func (evm *EVM) StaticCall(caller ContractRef, addr common.Address, input []byte, gas uint64) (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

}

// Make sure the readonly is only set if we aren't in readonly yet

// this makes also sure that the readonly flag isn't removed for

// child calls.

if !evm.interpreter.readOnly {

evm.interpreter.readOnly = true

defer func() { evm.interpreter.readOnly = false }()

}

var (

to = AccountRef(addr)

snapshot = evm.StateDB.Snapshot()

)

// 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, new(big.Int), gas)

contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))

// 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.

ret, err = run(evm, snapshot, contract, input)

if err != nil {

evm.StateDB.RevertToSnapshot(snapshot)

if err != errExecutionReverted {

contract.UseGas(contract.Gas)

}

}

return ret, contract.Gas, err

}