Assembly
- 6 mins内联汇编小汇总
compound
CErc20.sol保证转账成功函数
function doTransferIn(address from, uint amount)virtual override internal returns(uint){
//省略...
token.transferFrom(from, address(this), amount);
bool success;
assembly{
switch returndatasize() // Pushes the size of the return data buffer onto the stack将返回值缓冲区的大小压入堆栈
case 0 {
success := not(0)//非运算
}
case 32 {
returndatacopy(0, 0, 32)//Copies data from the return data buffer to memory将数据从返回值缓冲区复制到内存
success := mload(0)// 从内存读取
}
default {
revert(0, 0)
}
}
require(success, "TOKEN_TRANSFER_IN_FAILED");
//省略...
}
returndatacopy函数源码
func opReturnDataCopy(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]byte, error) {
var (
memOffset = scope.Stack.pop() // 出栈, 内存下标
dataOffset = scope.Stack.pop() // 出栈, 数据
length = scope.Stack.pop() // 出栈, 数据长度
)
offset64, overflow := dataOffset.Uint64WithOverflow()
if overflow { // 检查数据是否溢出2^64
return nil, ErrReturnDataOutOfBounds
}
// we can reuse dataOffset now (aliasing it for clarity)
var end = dataOffset // 复制一份
end.Add(&dataOffset, &length) // 计算end位置
end64, overflow := end.Uint64WithOverflow()
if overflow || uint64(len(interpreter.returnData)) < end64 {
// 检查溢出
return nil, ErrReturnDataOutOfBounds
}
// 从interpreter的bytes数组中取切片
// 把切片放入内存中
scope.Memory.Set(memOffset.Uint64(), length.Uint64(), interpreter.returnData[offset64:end64])
return nil, nil
}
uniswapv2
UniswapV2Factory.sol
function createPair(address tokenA, address tokenB) external returns(address pair){
//省略...
bytes memory bytecode = type(UniswapV2Pair).creationCode;
bytes32 salt = keccak256(abi.encodePacked(token0, token1))
assembly{
// add就是相加
// mload, 从内存读取
// create2 根据salt生成固定地址
pair := create2(0, // 创建合约时往合约中打的 ETH 数量
add(bytecode, 32), //memory_start（代码在内存中的起始位置，一般固定为 add(bytecode, 0x20) ）
mload(bytecode), //memory_length（代码长度，一般固定为 mload(bytecode) ）
salt)
}
//省略...
}
evm opcode example
byte(vm.PUSH1), 0x00, // salt + 32
byte(vm.PUSH1), byte(len(initCode)), // size
byte(vm.PUSH1), byte(32 - len(initCode)), // offset
byte(vm.PUSH1), 0x00, // endowment
byte(vm.CREATE2),
create2源码
func opCreate2(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]byte, error) {
if interpreter.readOnly {
return nil, ErrWriteProtection
}
var (
endowment = scope.Stack.pop()//endowment（创建合约时往合约中打的 ETH 数量）
offset, size = scope.Stack.pop(), scope.Stack.pop()
salt = scope.Stack.pop()
// 根据下标和长度, 从内存中取出input,也就是代码
input = scope.Memory.GetCopy(int64(offset.Uint64()), int64(size.Uint64()))
gas = scope.Contract.Gas
)
// Apply EIP150
gas -= gas / 64
scope.Contract.UseGas(gas)
// reuse size int for stackvalue
stackvalue := size
//TODO: use uint256.Int instead of converting with toBig()
bigEndowment := big0
if !endowment.IsZero() {
bigEndowment = endowment.ToBig()
}
res, addr, returnGas, suberr := interpreter.evm.Create2(scope.Contract, input, gas,
bigEndowment, &salt)
// Push item on the stack based on the returned error.
if suberr != nil {
stackvalue.Clear()
} else {
stackvalue.SetBytes(addr.Bytes())
}
scope.Stack.push(&stackvalue)
scope.Contract.Gas += returnGas
if suberr == ErrExecutionReverted {
interpreter.returnData = res // set REVERT data to return data buffer
return res, nil
}
interpreter.returnData = nil // clear dirty return data buffer
return nil, nil
}
func (evm *EVM) Create2(caller ContractRef, code []byte, gas uint64, endowment *big.Int, salt *uint256.Int) (ret []byte, contractAddr common.Address, leftOverGas uint64, err error) {
codeAndHash := &codeAndHash{code: code}
contractAddr = crypto.CreateAddress2(caller.Address(), salt.Bytes32(), codeAndHash.Hash().Bytes())
return evm.create(caller, codeAndHash, gas, endowment, contractAddr, CREATE2)
}
func CreateAddress2(b common.Address, salt [32]byte, inithash []byte) common.Address {
// 计算地址
return common.BytesToAddress(Keccak256([]byte{0xff}, b.Bytes(), salt[:], inithash)[12:])
}