兄弟连区块链入门教程eth源码分析core-vm源码分析（二）

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

}