gas_table.go

//<developer>
//    <name>linapex 曹一峰</name>
//    <email>linapex@163.com</email>
//    <wx>superexc</wx>
//    <qqgroup>128148617</qqgroup>
//    <url>https://jsq.ink</url>
//    <role>pku engineer</role>
//    <date>2019-03-16 19:16:36</date>
//</624450082275594240>


package vm

import (
	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/math"
	"github.com/ethereum/go-ethereum/params"
)

//memorygascosts计算用于内存扩展的二次气体。它这样做
//仅用于扩展的内存区域，而不是总内存。
func memoryGasCost(mem *Memory, newMemSize uint64) (uint64, error) {

	if newMemSize == 0 {
		return 0, nil
	}
//uint64中的最大值是max_word_count-1
//上面的任何东西都会导致溢出。
//此外，一个新的Memsize会导致
//大于0x7ffffffff的newmemsizewords将导致平方运算
//溢出。
//常量0xffffffge0是可以在没有
//溢出气体计算
	if newMemSize > 0xffffffffe0 {
		return 0, errGasUintOverflow
	}

	newMemSizeWords := toWordSize(newMemSize)
	newMemSize = newMemSizeWords * 32

	if newMemSize > uint64(mem.Len()) {
		square := newMemSizeWords * newMemSizeWords
		linCoef := newMemSizeWords * params.MemoryGas
		quadCoef := square / params.QuadCoeffDiv
		newTotalFee := linCoef + quadCoef

		fee := newTotalFee - mem.lastGasCost
		mem.lastGasCost = newTotalFee

		return fee, nil
	}
	return 0, nil
}

func constGasFunc(gas uint64) gasFunc {
	return func(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
		return gas, nil
	}
}

func gasCallDataCopy(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}

	var overflow bool
	if gas, overflow = math.SafeAdd(gas, GasFastestStep); overflow {
		return 0, errGasUintOverflow
	}

	words, overflow := bigUint64(stack.Back(2))
	if overflow {
		return 0, errGasUintOverflow
	}

	if words, overflow = math.SafeMul(toWordSize(words), params.CopyGas); overflow {
		return 0, errGasUintOverflow
	}

	if gas, overflow = math.SafeAdd(gas, words); overflow {
		return 0, errGasUintOverflow
	}
	return gas, nil
}

func gasReturnDataCopy(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}

	var overflow bool
	if gas, overflow = math.SafeAdd(gas, GasFastestStep); overflow {
		return 0, errGasUintOverflow
	}

	words, overflow := bigUint64(stack.Back(2))
	if overflow {
		return 0, errGasUintOverflow
	}

	if words, overflow = math.SafeMul(toWordSize(words), params.CopyGas); overflow {
		return 0, errGasUintOverflow
	}

	if gas, overflow = math.SafeAdd(gas, words); overflow {
		return 0, errGasUintOverflow
	}
	return gas, nil
}

func gasSStore(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	var (
		y, x    = stack.Back(1), stack.Back(0)
		current = evm.StateDB.GetState(contract.Address(), common.BigToHash(x))
	)
//遗留气体计量只考虑当前状态
	if !evm.chainRules.IsConstantinople {
//这将检查3个场景并相应地计算气体：
//
//1。从零值地址到非零值（新值）
//2。从非零值地址到零值地址（删除）
//三。从非零变为非零（变化）
		switch {
case current == (common.Hash{}) && y.Sign() != 0: //0＝＞0
			return params.SstoreSetGas, nil
case current != (common.Hash{}) && y.Sign() == 0: //非0＝0
			evm.StateDB.AddRefund(params.SstoreRefundGas)
			return params.SstoreClearGas, nil
default: //非0=>非0（或0=>0）
			return params.SstoreResetGas, nil
		}
	}
//新的天然气计量基于净天然气成本（EIP-1283）：
//
//1。如果当前值等于新值（这是一个无操作），则扣除200气体。
//2。如果当前值不等于新值
//2.1。如果原始值等于当前值（当前执行上下文未更改此存储槽）
//2.1.1如果原值为0，则扣除20000气体。
//2.1.2否则扣除5000气。如果新值为0，则向退款柜台添加15000汽油。
//2.2。如果原始值不等于当前值（此存储槽脏），则扣除200气体。适用以下两个条款。
//2.2.1如果原始值不是0
//2.2.1.1如果当前值为0（也意味着新值不是0），请从退款柜台取出15000气体。我们可以证明退款柜台永远不会低于0。
//2.2.1.2如果新值为0（也就是说当前值不是0），则向退款柜台添加15000气体。
//2.2.2.如果原始值等于新值（此存储槽被重置）
//2.2.2.1如果原值为0，在退款柜台加19800汽油。
//2.2.2.2否则，在退款柜台加4800汽油。
	value := common.BigToHash(y)
if current == value { //NOOP（1）
		return params.NetSstoreNoopGas, nil
	}
	original := evm.StateDB.GetCommittedState(contract.Address(), common.BigToHash(x))
	if original == current {
if original == (common.Hash{}) { //创建插槽（2.1.1）
			return params.NetSstoreInitGas, nil
		}
if value == (common.Hash{}) { //删除插槽（2.1.2b）
			evm.StateDB.AddRefund(params.NetSstoreClearRefund)
		}
return params.NetSstoreCleanGas, nil //写入现有插槽（2.1.2）
	}
	if original != (common.Hash{}) {
if current == (common.Hash{}) { //重新创建插槽（2.2.1.1）
			evm.StateDB.SubRefund(params.NetSstoreClearRefund)
} else if value == (common.Hash{}) { //删除插槽（2.2.1.2）
			evm.StateDB.AddRefund(params.NetSstoreClearRefund)
		}
	}
	if original == value {
if original == (common.Hash{}) { //重置为原始不存在的插槽（2.2.2.1）
			evm.StateDB.AddRefund(params.NetSstoreResetClearRefund)
} else { //重置为原有插槽（2.2.2.2）
			evm.StateDB.AddRefund(params.NetSstoreResetRefund)
		}
	}
	return params.NetSstoreDirtyGas, nil
}

func makeGasLog(n uint64) gasFunc {
	return func(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
		requestedSize, overflow := bigUint64(stack.Back(1))
		if overflow {
			return 0, errGasUintOverflow
		}

		gas, err := memoryGasCost(mem, memorySize)
		if err != nil {
			return 0, err
		}

		if gas, overflow = math.SafeAdd(gas, params.LogGas); overflow {
			return 0, errGasUintOverflow
		}
		if gas, overflow = math.SafeAdd(gas, n*params.LogTopicGas); overflow {
			return 0, errGasUintOverflow
		}

		var memorySizeGas uint64
		if memorySizeGas, overflow = math.SafeMul(requestedSize, params.LogDataGas); overflow {
			return 0, errGasUintOverflow
		}
		if gas, overflow = math.SafeAdd(gas, memorySizeGas); overflow {
			return 0, errGasUintOverflow
		}
		return gas, nil
	}
}

func gasSha3(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	var overflow bool
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}

	if gas, overflow = math.SafeAdd(gas, params.Sha3Gas); overflow {
		return 0, errGasUintOverflow
	}

	wordGas, overflow := bigUint64(stack.Back(1))
	if overflow {
		return 0, errGasUintOverflow
	}
	if wordGas, overflow = math.SafeMul(toWordSize(wordGas), params.Sha3WordGas); overflow {
		return 0, errGasUintOverflow
	}
	if gas, overflow = math.SafeAdd(gas, wordGas); overflow {
		return 0, errGasUintOverflow
	}
	return gas, nil
}

func gasCodeCopy(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}

	var overflow bool
	if gas, overflow = math.SafeAdd(gas, GasFastestStep); overflow {
		return 0, errGasUintOverflow
	}

	wordGas, overflow := bigUint64(stack.Back(2))
	if overflow {
		return 0, errGasUintOverflow
	}
	if wordGas, overflow = math.SafeMul(toWordSize(wordGas), params.CopyGas); overflow {
		return 0, errGasUintOverflow
	}
	if gas, overflow = math.SafeAdd(gas, wordGas); overflow {
		return 0, errGasUintOverflow
	}
	return gas, nil
}

func gasExtCodeCopy(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}

	var overflow bool
	if gas, overflow = math.SafeAdd(gas, gt.ExtcodeCopy); overflow {
		return 0, errGasUintOverflow
	}

	wordGas, overflow := bigUint64(stack.Back(3))
	if overflow {
		return 0, errGasUintOverflow
	}

	if wordGas, overflow = math.SafeMul(toWordSize(wordGas), params.CopyGas); overflow {
		return 0, errGasUintOverflow
	}

	if gas, overflow = math.SafeAdd(gas, wordGas); overflow {
		return 0, errGasUintOverflow
	}
	return gas, nil
}

func gasExtCodeHash(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	return gt.ExtcodeHash, nil
}

func gasMLoad(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	var overflow bool
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, errGasUintOverflow
	}
	if gas, overflow = math.SafeAdd(gas, GasFastestStep); overflow {
		return 0, errGasUintOverflow
	}
	return gas, nil
}

func gasMStore8(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	var overflow bool
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, errGasUintOverflow
	}
	if gas, overflow = math.SafeAdd(gas, GasFastestStep); overflow {
		return 0, errGasUintOverflow
	}
	return gas, nil
}

func gasMStore(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	var overflow bool
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, errGasUintOverflow
	}
	if gas, overflow = math.SafeAdd(gas, GasFastestStep); overflow {
		return 0, errGasUintOverflow
	}
	return gas, nil
}

func gasCreate(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	var overflow bool
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}
	if gas, overflow = math.SafeAdd(gas, params.CreateGas); overflow {
		return 0, errGasUintOverflow
	}
	return gas, nil
}

func gasCreate2(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	var overflow bool
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}
	if gas, overflow = math.SafeAdd(gas, params.Create2Gas); overflow {
		return 0, errGasUintOverflow
	}
	wordGas, overflow := bigUint64(stack.Back(2))
	if overflow {
		return 0, errGasUintOverflow
	}
	if wordGas, overflow = math.SafeMul(toWordSize(wordGas), params.Sha3WordGas); overflow {
		return 0, errGasUintOverflow
	}
	if gas, overflow = math.SafeAdd(gas, wordGas); overflow {
		return 0, errGasUintOverflow
	}

	return gas, nil
}

func gasBalance(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	return gt.Balance, nil
}

func gasExtCodeSize(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	return gt.ExtcodeSize, nil
}

func gasSLoad(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	return gt.SLoad, nil
}

func gasExp(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	expByteLen := uint64((stack.data[stack.len()-2].BitLen() + 7) / 8)

	var (
gas      = expByteLen * gt.ExpByte //不需要进行溢出检查。最大为256*expbyte气体
		overflow bool
	)
	if gas, overflow = math.SafeAdd(gas, GasSlowStep); overflow {
		return 0, errGasUintOverflow
	}
	return gas, nil
}

func gasCall(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	var (
		gas            = gt.Calls
		transfersValue = stack.Back(2).Sign() != 0
		address        = common.BigToAddress(stack.Back(1))
		eip158         = evm.ChainConfig().IsEIP158(evm.BlockNumber)
	)
	if eip158 {
		if transfersValue && evm.StateDB.Empty(address) {
			gas += params.CallNewAccountGas
		}
	} else if !evm.StateDB.Exist(address) {
		gas += params.CallNewAccountGas
	}
	if transfersValue {
		gas += params.CallValueTransferGas
	}
	memoryGas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}
	var overflow bool
	if gas, overflow = math.SafeAdd(gas, memoryGas); overflow {
		return 0, errGasUintOverflow
	}

	evm.callGasTemp, err = callGas(gt, contract.Gas, gas, stack.Back(0))
	if err != nil {
		return 0, err
	}
	if gas, overflow = math.SafeAdd(gas, evm.callGasTemp); overflow {
		return 0, errGasUintOverflow
	}
	return gas, nil
}

func gasCallCode(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	gas := gt.Calls
	if stack.Back(2).Sign() != 0 {
		gas += params.CallValueTransferGas
	}
	memoryGas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}
	var overflow bool
	if gas, overflow = math.SafeAdd(gas, memoryGas); overflow {
		return 0, errGasUintOverflow
	}

	evm.callGasTemp, err = callGas(gt, contract.Gas, gas, stack.Back(0))
	if err != nil {
		return 0, err
	}
	if gas, overflow = math.SafeAdd(gas, evm.callGasTemp); overflow {
		return 0, errGasUintOverflow
	}
	return gas, nil
}

func gasReturn(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	return memoryGasCost(mem, memorySize)
}

func gasRevert(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	return memoryGasCost(mem, memorySize)
}

func gasSuicide(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	var gas uint64
//EIP150家用天然气再定价叉：
	if evm.ChainConfig().IsEIP150(evm.BlockNumber) {
		gas = gt.Suicide
		var (
			address = common.BigToAddress(stack.Back(0))
			eip158  = evm.ChainConfig().IsEIP158(evm.BlockNumber)
		)

		if eip158 {
//如果为空并转移值
			if evm.StateDB.Empty(address) && evm.StateDB.GetBalance(contract.Address()).Sign() != 0 {
				gas += gt.CreateBySuicide
			}
		} else if !evm.StateDB.Exist(address) {
			gas += gt.CreateBySuicide
		}
	}

	if !evm.StateDB.HasSuicided(contract.Address()) {
		evm.StateDB.AddRefund(params.SuicideRefundGas)
	}
	return gas, nil
}

func gasDelegateCall(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}
	var overflow bool
	if gas, overflow = math.SafeAdd(gas, gt.Calls); overflow {
		return 0, errGasUintOverflow
	}

	evm.callGasTemp, err = callGas(gt, contract.Gas, gas, stack.Back(0))
	if err != nil {
		return 0, err
	}
	if gas, overflow = math.SafeAdd(gas, evm.callGasTemp); overflow {
		return 0, errGasUintOverflow
	}
	return gas, nil
}

func gasStaticCall(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	gas, err := memoryGasCost(mem, memorySize)
	if err != nil {
		return 0, err
	}
	var overflow bool
	if gas, overflow = math.SafeAdd(gas, gt.Calls); overflow {
		return 0, errGasUintOverflow
	}

	evm.callGasTemp, err = callGas(gt, contract.Gas, gas, stack.Back(0))
	if err != nil {
		return 0, err
	}
	if gas, overflow = math.SafeAdd(gas, evm.callGasTemp); overflow {
		return 0, errGasUintOverflow
	}
	return gas, nil
}

func gasPush(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	return GasFastestStep, nil
}

func gasSwap(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	return GasFastestStep, nil
}

func gasDup(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
	return GasFastestStep, nil
}