合约库模式实战分析
write by ravitn, 2022-09-06 21:59引言
库的两种方式：1.单独一个合约逻辑合约引用；2.在合约中包含库；库是一个特殊的合约； 在部署合约的时候，需要链到对应的库合约，有文章说使用库可以节省gas，真的这样吗，今天我们就来看一下：
目录
库使用模式
导入库模式合约
- 库合约
pragma solidity ^0.8.0;
library Adder{
function add(uint[] memory seeds) public pure returns(uint)
{
uint sum = 0;
for(uint i = 0; i<seeds.length; i++)
{
sum += seeds[i];
}
return sum;
}
}
- 逻辑合约
import "./Adder.sol";
pragma solidity ^0.8.0;
contract AdderImport{
uint256 private total;
//function to access the library
function sum(uint[] memory data)external pure returns(uint)
{
uint sum;
sum = Adder.add(data);
return sum;
}
function totalSum(uint[] memory data) external returns(uint)
{
total = Adder.add(data);
return total;
}
}
包含库模式合约
pragma solidity ^0.8.0;
library AdderX{
function add(uint[] memory seeds) public pure returns(uint)
{
uint sum = 0;
for(uint i = 0; i<seeds.length; i++)
{
sum += seeds[i];
}
return sum;
}
}
contract AdderInclude{
uint256 private total;
//function to access the library
function sum(uint[] memory data)external pure returns(uint)
{
uint sum;
sum = AdderX.add(data);
return sum;
}
function totalSum(uint[] memory data) external returns(uint)
{
total = AdderX.add(data);
return total;
}
}
实战
导入模式测试
describe("Library-test", function() {
it("AdderImport Test error", async function () {
const [owner, ravitn] = await ethers.getSigners();
console.log("owner:", owner.address);
const Adder = await ethers.getContractFactory("Adder");
const adder = await Adder.deploy();
await adder.deployed();
console.log("adder address:", adder.address);
const AdderImport = await ethers.getContractFactory("AdderImport", {
libraries: {
Adder: adder.address,
},
});
const adderImport = await AdderImport.deploy();
await adderImport.deployed();
console.log("adderImport address:", adderImport.address);
const txSum = await adderImport.sum([1,2]);
console.log("txSum:", txSum);
const total = await adderImport.totalSum([1,2]);
// console.log("total:", total);
expect(await adderImport.sum([1,2])).to.equal(3);
});
});
包含模式测试
describe("Library-test", function() {
it("AdderInclude Test error", async function () {
const [owner, ravitn] = await ethers.getSigners();
console.log("owner:", owner.address);
const AdderX = await ethers.getContractFactory("AdderX");
const adderX = await AdderX.deploy();
await adderX.deployed();
console.log("adderX address:", adderX.address);
const AdderInclude = await ethers.getContractFactory("AdderInclude", {
libraries: {
AdderX: adderX.address,
},
});
const adderInclude = await AdderInclude.deploy();
await adderInclude.deployed();
console.log("adderInclude address:", adderInclude.address);
const txSum = await adderInclude.sum([1,2]);
console.log("txSum:", txSum);
const total = await adderInclude.totalSum([1,2]);
// console.log("total:", total);
expect(await adderInclude.sum([1,2])).to.equal(3);
});
});
实战分析
使用hardhat，测试结果无论如何，库都要单独部署，链到对应的合约中。
我们来看一下AdderImport的MetaData JSON文件
{
"_format": "hh-sol-artifact-1",
"contractName": "AdderImport",
"sourceName": "contracts/library/AdderImport.sol",
"abi": [
{
"inputs": [
{
"internalType": "uint256[]",
"name": "data",
"type": "uint256[]"
}
],
"name": "sum",
"outputs": [
{
"internalType": "uint256",
"name": "",
"type": "uint256"
}
],
"stateMutability": "pure",
"type": "function"
}
],
"bytecode": "0x608060405234801561001057600080fd5b5061024e806100206000396000f3fe608060405234801561001057600080fd5b506004361061002b5760003560e01c80630194db8e14610030575b600080fd5b61004361003e3660046100e6565b610055565b60405190815260200160405180910390f35b60008073__$fd5d5809563fd152781d739c4c1c9489bf$__6310b0b5d5846040518263ffffffff1660e01b815260040161008f91906101be565b60206040518083038186803b1580156100a757600080fd5b505af41580156100bb573d6000803e3d6000fd5b505050506040513d601f19601f820116820180604052508101906100df91906101a6565b9392505050565b600060208083850312156100f8578182fd5b823567ffffffffffffffff8082111561010f578384fd5b818501915085601f830112610122578384fd5b81358181111561013457610134610202565b8060051b604051601f19603f8301168101818110858211171561015957610159610202565b604052828152858101935084860182860187018a1015610177578788fd5b8795505b8386101561019957803585526001959095019493860193860161017b565b5098975050505050505050565b6000602082840312156101b7578081fd5b5051919050565b6020808252825182820181905260009190848201906040850190845b818110156101f6578351835292840192918401916001016101da565b50909695505050505050565b634e487b7160e01b600052604160045260246000fdfea2646970667358221220b3bfe6bda8a933689f9df80b6ebdf2a9601df4c5c02913c70c11204f1554f96664736f6c63430008040033",
"deployedBytecode": "0x608060405234801561001057600080fd5b506004361061002b5760003560e01c80630194db8e14610030575b600080fd5b61004361003e3660046100e6565b610055565b60405190815260200160405180910390f35b60008073__$fd5d5809563fd152781d739c4c1c9489bf$__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",
"linkReferences": {
"contracts/library/Adder.sol": {
"Adder": [
{
"length": 20,
"start": 122
}
]
}
},
"deployedLinkReferences": {
"contracts/library/Adder.sol": {
"Adder": [
{
"length": 20,
"start": 90
}
]
}
}
}
在deployedBytecode和bytecode有一段占位符：
05180910390f35b60008073__$fd5d5809563fd152781d739c4c1c9489bf$__6310b0b
字节码中的值 $fd5d5809563fd152781d739c4c1c9489bf$ 只是库地址的占位符。在您的情况下，占位符将介于 $ 和 $ 之间。它有点隐蔽——所以搜索 __$（下划线下划线美元符号）。 来自Hardhat的元数据 JSON 告诉Hardhat用给定地址替换占位符。，库的地址是在部署时注入的——所以在这个阶段用实际地址替换占位符。
库合合约的本质是什么？
出于这个目的，我们对linkReferences元素和object元素感兴趣。
linkReferences：（第一个元素）描述了合约使用的库。bytecode是编译后的合约（字节码）。这就是部署并保存到区块链上的内容。在此示例中，字节码中的值 __$83229fb62534ab89035722de277194ff6d$__ 只是库地址的占位符。
，占位符将介于 __$ 和 $__ 之间。它有点隐蔽——所以搜索 __$（下划线下划线美元符号）。
部署字节码deployedBytecode包含同样的占位符；
下面是使用remix测试的文章gas节省说明
库的地址是在部署时注入的——所以在这个阶段用实际地址替换占位符。如果我们只是将该库用作普通合约并在编译时将其导入，
我们将使用合约代码部署其代码——因此不会节省 gas。
通过挖掘 metadata.json 文件并更新其设置，我们可以使用库来减小合约的大小并享受节省燃料的乐趣。
来自 Remix IDE 的元数据 JSON 告诉 Remix 用给定地址替换占位符。
经测试发现两种模式的gas消耗是一样的，具体如下
- 导入模式消耗的Gas
----------------------------|---------------------------|-------------|-----------------------------·
| Solc version: 0.8.4 · Optimizer enabled: true · Runs: 200 · Block limit: 30000000 gas │
·····························|···························|·············|······························
| Methods │
················|············|·············|·············|·············|···············|··············
| Contract · Method · Min · Max · Avg · # calls · chf (avg) │
················|············|·············|·············|·············|···············|··············
| AdderImport · totalSum · - · - · 49055 · 1 · - │
················|············|·············|·············|·············|···············|··············
| Deployments · · % of limit · │
·····························|·············|·············|·············|···············|··············
| Adder · - · - · 167482 · 0.6 % · - │
·····························|·············|·············|·············|···············|··············
| AdderImport · - · - · 219374 · 0.7 % · - │
·----------------------------|-------------|-------------|-------------|---------------|-------------·
- 包含方式消耗的gas
·-----------------------------|---------------------------|-------------|-----------------------------·
| Solc version: 0.8.4 · Optimizer enabled: true · Runs: 200 · Block limit: 30000000 gas │
······························|···························|·············|······························
| Methods │
·················|············|·············|·············|·············|···············|··············
| Contract · Method · Min · Max · Avg · # calls · chf (avg) │
·················|············|·············|·············|·············|···············|··············
| AdderInclude · totalSum · - · - · 49055 · 1 · - │
·················|············|·············|·············|·············|···············|··············
| Deployments · · % of limit · │
······························|·············|·············|·············|···············|··············
| AdderInclude · - · - · 219374 · 0.7 % · - │
······························|·············|·············|·············|···············|··············
| AdderX · - · - · 167482 · 0.6 % · - │
·-----------------------------|-------------|-------------|-------------|---------------|-------------·
从上面来看，两种方式没有太大的区别Gas消耗是一样的；
同时可以看出
逻辑合约调用库合约的方式:
- 针对修改逻辑合约存储的使用DELEGATECALL方式（Homestead之前是用CALLCODE），只能是这种方式，才能修改逻辑合约的存储。
我们使用remix部署包含库模式测试合约AdderInclude
creation of library tests/sad.sol:AdderX pending...
[vm]from: 0x5B3...eddC4to: AdderX.(constructor)value: 0 weidata: 0x610...50033logs: 0hash: 0xc1e...e5226
status true Transaction mined and execution succeed
transaction hash 0xc1eed194c1fbef1f5b3ac9b7c9e8d066c72fae4c1d445ac25dd72af7dc6e5226
from 0x5B38Da6a701c568545dCfcB03FcB875f56beddC4
to AdderX.(constructor)
gas 318992 gas
transaction cost 277384 gas
execution cost 277384 gas
input 0x610...50033
decoded input {}
decoded output -
logs []
val 0 wei
creation of AdderInclude pending...
[vm]from: 0x5B3...eddC4to: AdderInclude.(constructor)value: 0 weidata: 0x608...50033logs: 0hash: 0x064...5df47
status true Transaction mined and execution succeed
transaction hash 0x0649bd15a7bf20f600523e2ca018987facec5f84aa2533522e03a4cfb2d5df47
from 0x5B38Da6a701c568545dCfcB03FcB875f56beddC4
to AdderInclude.(constructor)
gas 393947 gas
transaction cost 342562 gas
execution cost 342562 gas
input 0x608...50033
decoded input {}
decoded output -
logs []
val 0 wei
发现部署合约发起了两笔交易，一个是部署库，一个是逻辑合约；
JAVA contract，同理；
使用导入模式是，remix测试同样发起两笔交易
测试发现；逻辑合约totalSum修改存储的方法，gas一致，没有什么区别；pure或view的sum计算方法，不收取gas费用。
总结
导入库合约和包含库合约之间不存，同样方法逻辑的调用gas费用一致，另外库调用形式，修改逻辑合约存储的使用DELEGATECALL方式（Homestead之前是用CALLCODE）。
附
面向开发人员的 Solidity：Solidity 中的库
Solidity For Developers: Libraries In Solidity
Deploying with Libraries on Remix-IDE
library-linking
SOLIDITY之LIBRARY 用法（一），以及USING A FOR B的特性（一个特殊的CONTRACT合约）
SOLIDITY之LIBRARY 用法（二）库的核心用法总结（一个特殊的CONTRACT合约）
[solidity系列教程<九>库(library)的使用](https://www.jianshu.com/p/ab7665691a60)
[库(Libraries)](https://www.tryblockchain.org/solidity-libraries-%E5%BA%93.html)