github.com/yinchengtsinghua/golang-Eos-dpos-Ethereum@v0.0.0-20190121132951-92cc4225ed8e/core/vm/gas_table.go

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//版权所有2017 Go Ethereum作者
//此文件是Go以太坊库的一部分。
//
//Go-Ethereum库是免费软件：您可以重新分发它和/或修改
//根据GNU发布的较低通用公共许可证的条款
//自由软件基金会，或者许可证的第3版，或者
//（由您选择）任何更高版本。
//
//Go以太坊图书馆的发行目的是希望它会有用，
//但没有任何保证；甚至没有
//适销性或特定用途的适用性。见
//GNU较低的通用公共许可证，了解更多详细信息。
//
//你应该收到一份GNU较低级别的公共许可证副本
//以及Go以太坊图书馆。如果没有，请参见<http://www.gnu.org/licenses/>。

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)
		val  = evm.StateDB.GetState(contract.Address(), common.BigToHash(x))
	)
//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）
	if val == (common.Hash{}) && y.Sign() != 0 {
//0＝＞0
		return params.SstoreSetGas, nil
	} else if val != (common.Hash{}) && y.Sign() == 0 {
//非0＝0
		evm.StateDB.AddRefund(params.SstoreRefundGas)
		return params.SstoreClearGas, nil
	} else {
//非0=>非0（或0=>0）
		return params.SstoreResetGas, 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
	}
	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
}