寫在前面

在前面以太坊go-ethereum源碼研讀（一）中所討論的Process函數(shù)調(diào)用了該applyTransaction函數(shù)來執(zhí)行交易相關(guān)指令，于是進(jìn)一步對該函數(shù)進(jìn)行分析，以明晰以太坊交易的全過程。
分析過程中一些結(jié)構(gòu)體或函數(shù)在以太坊go-ethereum源碼研讀（一）中已經(jīng)討論到，對這些結(jié)構(gòu)體和函數(shù)則不在此文中過多贅述。
同時(shí)對于創(chuàng)建合約的create函數(shù)和進(jìn)一步執(zhí)行交易的call函數(shù)在下一篇研讀中繼續(xù)分析。

相關(guān)變量

相關(guān)結(jié)構(gòu)體

TxContext

位于core\vm\evm.go

// TxContext provides the EVM with information about a transaction.
// All fields can change between transactions.
type TxContext struct {
	// Message information
	Origin   common.Address // Provides information for ORIGIN
	GasPrice *big.Int       // Provides information for GASPRICE
}

事務(wù)信息相關(guān)結(jié)構(gòu)體。
與BlockContext進(jìn)行對比，進(jìn)一步理解區(qū)塊信息和事務(wù)信息的不同所在。

StateTransition

位于core\state_transition.go

type StateTransition struct {
	gp         *GasPool
	msg        Message
	gas        uint64
	gasPrice   *big.Int
	gasFeeCap  *big.Int
	gasTipCap  *big.Int
	initialGas uint64
	value      *big.Int
	data       []byte
	state      vm.StateDB
	evm        *vm.EVM
}

事務(wù)狀態(tài)信息

相關(guān)函數(shù)

applyTransaction

func applyTransaction(msg types.Message, config *params.ChainConfig, author *common.Address, gp *GasPool, statedb *state.StateDB, blockNumber *big.Int, blockHash common.Hash, tx *types.Transaction, usedGas *uint64, evm *vm.EVM) (*types.Receipt, error) {
	// Create a new context to be used in the EVM environment.
	txContext := NewEVMTxContext(msg)
	evm.Reset(txContext, statedb)

	// Apply the transaction to the current state (included in the env).
	result, err := ApplyMessage(evm, msg, gp)
	if err != nil {
		return nil, err
	}

	// Update the state with pending changes.
	var root []byte
	if config.IsByzantium(blockNumber) {
		statedb.Finalise(true)
	} else {
		root = statedb.IntermediateRoot(config.IsEIP158(blockNumber)).Bytes()
	}
	*usedGas += result.UsedGas

	// Create a new receipt for the transaction, storing the intermediate root and gas used
	// by the tx.
	receipt := &types.Receipt{Type: tx.Type(), PostState: root, CumulativeGasUsed: *usedGas}
	if result.Failed() {
		receipt.Status = types.ReceiptStatusFailed
	} else {
		receipt.Status = types.ReceiptStatusSuccessful
	}
	receipt.TxHash = tx.Hash()
	receipt.GasUsed = result.UsedGas

	// If the transaction created a contract, store the creation address in the receipt.
	if msg.To() == nil {
		receipt.ContractAddress = crypto.CreateAddress(evm.TxContext.Origin, tx.Nonce())
	}

	// Set the receipt logs and create the bloom filter.
	receipt.Logs = statedb.GetLogs(tx.Hash(), blockHash)
	receipt.Bloom = types.CreateBloom(types.Receipts{receipt})
	receipt.BlockHash = blockHash
	receipt.BlockNumber = blockNumber
	receipt.TransactionIndex = uint(statedb.TxIndex())
	return receipt, err
}

位于core\state_processor.go
首先調(diào)用NewEVMTxContext函數(shù)根據(jù)已轉(zhuǎn)換為Message格式的事務(wù)信息建立虛擬機(jī)事務(wù)上下文信息，因前述Process函數(shù)中已根據(jù)區(qū)塊上下文信息建立了虛擬機(jī)整體的上下文信息，故需再調(diào)用Reset函數(shù)重設(shè)事務(wù)上下文信息。
然后調(diào)用ApplyMessage函數(shù)在當(dāng)前上下文下執(zhí)行事務(wù)。

NewEVMTxContext

位于core\evm.go

func NewEVMTxContext(msg Message) vm.TxContext {
	return vm.TxContext{
		Origin:   msg.From(),
		GasPrice: new(big.Int).Set(msg.GasPrice()),
	}
}

根據(jù)事務(wù)信息建立虛擬機(jī)上下文信息。

Reset

位于core\vm\evm.go

// Reset resets the EVM with a new transaction context.Reset
// This is not threadsafe and should only be done very cautiously.
func (evm *EVM) Reset(txCtx TxContext, statedb StateDB) {
	evm.TxContext = txCtx
	evm.StateDB = statedb
}

重設(shè)虛擬機(jī)事務(wù)上下文，要注意該函數(shù)并不是線程安全的。

ApplyMessage

// ApplyMessage computes the new state by applying the given message
// against the old state within the environment.
//
// ApplyMessage returns the bytes returned by any EVM execution (if it took place),
// the gas used (which includes gas refunds) and an error if it failed. An error always
// indicates a core error meaning that the message would always fail for that particular
// state and would never be accepted within a block.
func ApplyMessage(evm *vm.EVM, msg Message, gp *GasPool) (*ExecutionResult, error) {
	return NewStateTransition(evm, msg, gp).TransitionDb()
}

位于core\state_transition.go
該函數(shù)通過應(yīng)用給定消息來計(jì)算新的狀態(tài)，返回EVM執(zhí)行后的返回字節(jié)和使用的gas，執(zhí)行失敗的話還會返回error。
首先調(diào)用NewStateTransition初始化一個(gè)事務(wù)狀態(tài)對象，然后調(diào)用對象中的TransitionDb來應(yīng)用當(dāng)前消息并轉(zhuǎn)移狀態(tài)，最后返回evm的執(zhí)行結(jié)果。

NewStateTransition

// NewStateTransition initialises and returns a new state transition object.
func NewStateTransition(evm *vm.EVM, msg Message, gp *GasPool) *StateTransition {
	return &StateTransition{
		gp:        gp,
		evm:       evm,
		msg:       msg,
		gasPrice:  msg.GasPrice(),
		gasFeeCap: msg.GasFeeCap(),
		gasTipCap: msg.GasTipCap(),
		value:     msg.Value(),
		data:      msg.Data(),
		state:     evm.StateDB,
	}
}

位于core\state_transition.go
初始化并返回一個(gè)事務(wù)狀態(tài)對象。

TransitionDb

// TransitionDb will transition the state by applying the current message and
// returning the evm execution result with following fields.
//
// - used gas:
//      total gas used (including gas being refunded)
// - returndata:
//      the returned data from evm
// - concrete execution error:
//      various **EVM** error which aborts the execution,
//      e.g. ErrOutOfGas, ErrExecutionReverted
//
// However if any consensus issue encountered, return the error directly with
// nil evm execution result.
func (st *StateTransition) TransitionDb() (*ExecutionResult, error) {
	// First check this message satisfies all consensus rules before
	// applying the message. The rules include these clauses
	//
	// 1. the nonce of the message caller is correct
	// 2. caller has enough balance to cover transaction fee(gaslimit * gasprice)
	// 3. the amount of gas required is available in the block
	// 4. the purchased gas is enough to cover intrinsic usage
	// 5. there is no overflow when calculating intrinsic gas
	// 6. caller has enough balance to cover asset transfer for **topmost** call

	// Check clauses 1-3, buy gas if everything is correct
	if err := st.preCheck(); err != nil {
		return nil, err
	}
	msg := st.msg
	sender := vm.AccountRef(msg.From())
	homestead := st.evm.ChainConfig().IsHomestead(st.evm.Context.BlockNumber)
	istanbul := st.evm.ChainConfig().IsIstanbul(st.evm.Context.BlockNumber)
	london := st.evm.ChainConfig().IsLondon(st.evm.Context.BlockNumber)
	contractCreation := msg.To() == nil

	// Check clauses 4-5, subtract intrinsic gas if everything is correct
	gas, err := IntrinsicGas(st.data, st.msg.AccessList(), contractCreation, homestead, istanbul)
	if err != nil {
		return nil, err
	}
	if st.gas < gas {
		return nil, fmt.Errorf("%w: have %d, want %d", ErrIntrinsicGas, st.gas, gas)
	}
	st.gas -= gas

	// Check clause 6
	if msg.Value().Sign() > 0 && !st.evm.Context.CanTransfer(st.state, msg.From(), msg.Value()) {
		return nil, fmt.Errorf("%w: address %v", ErrInsufficientFundsForTransfer, msg.From().Hex())
	}

	// Set up the initial access list.
	if rules := st.evm.ChainConfig().Rules(st.evm.Context.BlockNumber); rules.IsBerlin {
		st.state.PrepareAccessList(msg.From(), msg.To(), vm.ActivePrecompiles(rules), msg.AccessList())
	}
	var (
		ret   []byte
		vmerr error // vm errors do not effect consensus and are therefore not assigned to err
	)
	if contractCreation {
		ret, _, st.gas, vmerr = st.evm.Create(sender, st.data, st.gas, st.value)
	} else {
		// Increment the nonce for the next transaction
		st.state.SetNonce(msg.From(), st.state.GetNonce(sender.Address())+1)
		ret, st.gas, vmerr = st.evm.Call(sender, st.to(), st.data, st.gas, st.value)
	}

	if !london {
		// Before EIP-3529: refunds were capped to gasUsed / 2
		st.refundGas(params.RefundQuotient)
	} else {
		// After EIP-3529: refunds are capped to gasUsed / 5
		st.refundGas(params.RefundQuotientEIP3529)
	}
	effectiveTip := st.gasPrice
	if london {
		effectiveTip = cmath.BigMin(st.gasTipCap, new(big.Int).Sub(st.gasFeeCap, st.evm.Context.BaseFee))
	}
	st.state.AddBalance(st.evm.Context.Coinbase, new(big.Int).Mul(new(big.Int).SetUint64(st.gasUsed()), effectiveTip))

	return &ExecutionResult{
		UsedGas:    st.gasUsed(),
		Err:        vmerr,
		ReturnData: ret,
	}, nil
}

位于core\state_transition.go
該函數(shù)用于應(yīng)用消息，轉(zhuǎn)移狀態(tài)，返回的執(zhí)行結(jié)果中包括使用的gas，返回的evm數(shù)據(jù)，和報(bào)錯(cuò)。
該函數(shù)首先檢查消息是否滿足共識機(jī)制的規(guī)則。檢查項(xiàng)包括

該函數(shù)首先調(diào)用preCheck函數(shù)來檢查前3條條款是否滿足。
然后根據(jù)msg.To是否為空判斷該交易是否為創(chuàng)建合約。

隨后調(diào)用IntrinsicGas檢查購買的gas量是否足夠覆蓋內(nèi)部數(shù)據(jù)。對其返回的gas值進(jìn)行比較，不足則報(bào)錯(cuò)，否則則減去其對應(yīng)的量。

隨后首先判斷是否有交易金額，若有則調(diào)用CanTransfer來檢查調(diào)用者是否有足夠余額支付交易金額。

接下來查詢需要滿足的規(guī)則，若為Berlin版本，則需要考慮預(yù)編譯的accessList來減輕了 EIP-2929 引入的一些 gas 成本增加。（可深究）
（參考鏈接: Ethereum Berlin Upgrade Announcement）

因?yàn)橐蛱摂M機(jī)產(chǎn)生的錯(cuò)誤并不屬于共識層面，故這里引入一個(gè)變量vmerr用于表示虛擬機(jī)層面的錯(cuò)誤。

若該交易為創(chuàng)建合約，則調(diào)用Create函數(shù)，不然則設(shè)置交易nonce加1，調(diào)用Call函數(shù)來執(zhí)行。

隨后根據(jù)不同版本，以及剩余gas量調(diào)用refundGas進(jìn)行退款。

接下來計(jì)算小費(fèi)的值，取min(gasTipCap,最大可支付單價(jià)和強(qiáng)制執(zhí)行的最小單價(jià)的差值)為小費(fèi)單價(jià)值。最后乘上gasUsed并得到小費(fèi)總值并加在結(jié)算給礦工金額的Coinbase中。

最后返回執(zhí)行結(jié)果，即花費(fèi)的gas量，虛擬機(jī)的報(bào)錯(cuò)，和虛擬機(jī)返回?cái)?shù)據(jù)。

preCheck

func (st *StateTransition) preCheck() error {
	// Only check transactions that are not fake
	if !st.msg.IsFake() {
		// Make sure this transaction's nonce is correct.
		stNonce := st.state.GetNonce(st.msg.From())
		if msgNonce := st.msg.Nonce(); stNonce < msgNonce {
			return fmt.Errorf("%w: address %v, tx: %d state: %d", ErrNonceTooHigh,
				st.msg.From().Hex(), msgNonce, stNonce)
		} else if stNonce > msgNonce {
			return fmt.Errorf("%w: address %v, tx: %d state: %d", ErrNonceTooLow,
				st.msg.From().Hex(), msgNonce, stNonce)
		} else if stNonce+1 < stNonce {
			return fmt.Errorf("%w: address %v, nonce: %d", ErrNonceMax,
				st.msg.From().Hex(), stNonce)
		}
		// Make sure the sender is an EOA
		if codeHash := st.state.GetCodeHash(st.msg.From()); codeHash != emptyCodeHash && codeHash != (common.Hash{}) {
			return fmt.Errorf("%w: address %v, codehash: %s", ErrSenderNoEOA,
				st.msg.From().Hex(), codeHash)
		}
	}
	// Make sure that transaction gasFeeCap is greater than the baseFee (post london)
	if st.evm.ChainConfig().IsLondon(st.evm.Context.BlockNumber) {
		// Skip the checks if gas fields are zero and baseFee was explicitly disabled (eth_call)
		if !st.evm.Config.NoBaseFee || st.gasFeeCap.BitLen() > 0 || st.gasTipCap.BitLen() > 0 {
			if l := st.gasFeeCap.BitLen(); l > 256 {
				return fmt.Errorf("%w: address %v, maxFeePerGas bit length: %d", ErrFeeCapVeryHigh,
					st.msg.From().Hex(), l)
			}
			if l := st.gasTipCap.BitLen(); l > 256 {
				return fmt.Errorf("%w: address %v, maxPriorityFeePerGas bit length: %d", ErrTipVeryHigh,
					st.msg.From().Hex(), l)
			}
			if st.gasFeeCap.Cmp(st.gasTipCap) < 0 {
				return fmt.Errorf("%w: address %v, maxPriorityFeePerGas: %s, maxFeePerGas: %s", ErrTipAboveFeeCap,
					st.msg.From().Hex(), st.gasTipCap, st.gasFeeCap)
			}
			// This will panic if baseFee is nil, but basefee presence is verified
			// as part of header validation.
			if st.gasFeeCap.Cmp(st.evm.Context.BaseFee) < 0 {
				return fmt.Errorf("%w: address %v, maxFeePerGas: %s baseFee: %s", ErrFeeCapTooLow,
					st.msg.From().Hex(), st.gasFeeCap, st.evm.Context.BaseFee)
			}
		}
	}
	return st.buyGas()
}

位于core\state_transition.go
該函數(shù)首先檢查交易是否為假，而在上一篇文章提到的AsMessage函數(shù)中已將IsFake設(shè)置為false。同時(shí)還會檢查交易的nonce值是否正確，倘若出錯(cuò)，則根據(jù)錯(cuò)誤中的nonce大小報(bào)不同的錯(cuò)誤類型。通過判斷它的codeHash值是否為空，來檢查發(fā)起方是否為一個(gè)外部賬戶（EOA）。
同時(shí)若為倫敦分叉，則要求最大可支付給單價(jià)必須大于其要求強(qiáng)制執(zhí)行的最低費(fèi)用，同時(shí)判斷單價(jià)和小費(fèi)是否有溢出，以及小費(fèi)是否比單價(jià)還要大，根據(jù)這些錯(cuò)誤報(bào)告不同的錯(cuò)誤類型。
最后調(diào)用buyGas函數(shù)檢查gas值的一些要求，同時(shí)購買gas。

buyGas

func (st *StateTransition) buyGas() error {
	mgval := new(big.Int).SetUint64(st.msg.Gas())
	mgval = mgval.Mul(mgval, st.gasPrice)
	balanceCheck := mgval
	if st.gasFeeCap != nil {
		balanceCheck = new(big.Int).SetUint64(st.msg.Gas())
		balanceCheck = balanceCheck.Mul(balanceCheck, st.gasFeeCap)
		balanceCheck.Add(balanceCheck, st.value)
	}
	if have, want := st.state.GetBalance(st.msg.From()), balanceCheck; have.Cmp(want) < 0 {
		return fmt.Errorf("%w: address %v have %v want %v", ErrInsufficientFunds, st.msg.From().Hex(), have, want)
	}
	if err := st.gp.SubGas(st.msg.Gas()); err != nil {
		return err
	}
	st.gas += st.msg.Gas()

	st.initialGas = st.msg.Gas()
	st.state.SubBalance(st.msg.From(), mgval)
	return nil
}

位于core\state_transition.go
該函數(shù)檢查了發(fā)起者賬戶余額是否足夠支付最大單價(jià)下的油費(fèi)即（gasFeeCap*gas量），同時(shí)檢查區(qū)塊的gaspool是否有足夠gas支持本次交易。都滿足后則將交易狀態(tài)中的初始gas值設(shè)為當(dāng)前消息中的gas值，同時(shí)從發(fā)起者賬戶中扣除油費(fèi)（gasPrice * gas量）。
最后無錯(cuò)誤即返回nil值。

IntrinsicGas

// IntrinsicGas computes the 'intrinsic gas' for a message with the given data.
func IntrinsicGas(data []byte, accessList types.AccessList, isContractCreation bool, isHomestead, isEIP2028 bool) (uint64, error) {
	// Set the starting gas for the raw transaction
	var gas uint64
	if isContractCreation && isHomestead {
		gas = params.TxGasContractCreation
	} else {
		gas = params.TxGas
	}
	// Bump the required gas by the amount of transactional data
	if len(data) > 0 {
		// Zero and non-zero bytes are priced differently
		var nz uint64
		for _, byt := range data {
			if byt != 0 {
				nz++
			}
		}
		// Make sure we don't exceed uint64 for all data combinations
		nonZeroGas := params.TxDataNonZeroGasFrontier
		if isEIP2028 {
			nonZeroGas = params.TxDataNonZeroGasEIP2028
		}
		if (math.MaxUint64-gas)/nonZeroGas < nz {
			return 0, ErrGasUintOverflow
		}
		gas += nz * nonZeroGas

		z := uint64(len(data)) - nz
		if (math.MaxUint64-gas)/params.TxDataZeroGas < z {
			return 0, ErrGasUintOverflow
		}
		gas += z * params.TxDataZeroGas
	}
	if accessList != nil {
		gas += uint64(len(accessList)) * params.TxAccessListAddressGas
		gas += uint64(accessList.StorageKeys()) * params.TxAccessListStorageKeyGas
	}
	return gas, nil
}

位于core\state_transition.go
首先它先判斷交易是否為創(chuàng)建合約以及是否為“家園”硬分叉來計(jì)算該交易的基礎(chǔ)價(jià)格。
（鏈接: 家園硬分叉的介紹）
同時(shí)枚舉數(shù)據(jù)中的為零字節(jié)量和非零字節(jié)量并記錄，根據(jù)對應(yīng)版本，計(jì)算各自所需gas量。并在計(jì)算過程中考慮了gas累加可能導(dǎo)致的上溢問題。同時(shí)計(jì)算EVM 執(zhí)行過程中會觸及的賬戶和合約存儲位置的gas花費(fèi)。
最后返回所需gas值。（奇怪的是，對于accessList產(chǎn)生的gas量累加不需要檢查溢出嗎？）

CanTransfer

// CanTransfer checks whether 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
}

位于core\evm.go
檢查用戶的余額是否足夠支付交易金額。

Rules

位于params\config.go

// Rules ensures c's ChainID is not nil.
func (c *ChainConfig) Rules(num *big.Int) Rules {
	chainID := c.ChainID
	if chainID == nil {
		chainID = new(big.Int)
	}
	return Rules{
		ChainID:          new(big.Int).Set(chainID),
		IsHomestead:      c.IsHomestead(num),
		IsEIP150:         c.IsEIP150(num),
		IsEIP155:         c.IsEIP155(num),
		IsEIP158:         c.IsEIP158(num),
		IsByzantium:      c.IsByzantium(num),
		IsConstantinople: c.IsConstantinople(num),
		IsPetersburg:     c.IsPetersburg(num),
		IsIstanbul:       c.IsIstanbul(num),
		IsBerlin:         c.IsBerlin(num),
		IsLondon:         c.IsLondon(num),
	}
}

根據(jù)區(qū)塊號查詢并返回當(dāng)前需滿足的規(guī)則。

refundGas

func (st *StateTransition) refundGas(refundQuotient uint64) {
	// Apply refund counter, capped to a refund quotient
	refund := st.gasUsed() / refundQuotient
	if refund > st.state.GetRefund() {
		refund = st.state.GetRefund()
	}
	st.gas += refund

	// Return ETH for remaining gas, exchanged at the original rate.
	remaining := new(big.Int).Mul(new(big.Int).SetUint64(st.gas), st.gasPrice)
	st.state.AddBalance(st.msg.From(), remaining)

	// Also return remaining gas to the block gas counter so it is
	// available for the next transaction.
	st.gp.AddGas(st.gas)
}

位于core\state_transition.go
根據(jù)不同版本，計(jì)算最大可退款gas數(shù)，和當(dāng)前剩余量進(jìn)行比較，取最小值。
將當(dāng)前狀態(tài)的gas量加上該值，并根據(jù)當(dāng)前狀態(tài)的gas量計(jì)算需要退給調(diào)用者的eth，同時(shí)將區(qū)塊的gaspool里加上當(dāng)前狀態(tài)剩余gas量。文章來源地址http://www.zghlxwxcb.cn/news/detail-424859.html

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