boost :: asio使用带有字符串的boost :: array构建缓冲区

如何解决boost :: asio使用带有字符串的boost :: array构建缓冲区

我正在通过遵循文档中的示例并对其进行扩展来学习如何使用boost :: asio。 示例Daytime.4和Daytime.5显示了如何实现同步udp服务器-客户端通信。该示例通过构造一个char类型的boost数组，然后在该数组之外构造一个boost缓冲区来发送数据：

//structure
-frontend
 -node_modules
 -src
   -component
   -setupTests.ts
   -App.tsx
   -etc
 -babel.config.js
 -jest.config.js
 -package.json
 -tsconfig.json

//package.json
"scripts": {
"start": "react-scripts start","build": "react-scripts build","test": "react-scripts test","test:coverage": "react-scripts test --coverage --runInBand --watchAll=false",}
"devDependencies": {
"@babel/core": "^7.12.1","@babel/preset-env": "^7.12.1","@babel/preset-react": "^7.12.1","@testing-library/jest-dom": "^5.11.4","@types/jest": "^26.0.14","jest": "^26.5.3","ts-jest": "^26.4.1","@types/enzyme": "^3.10.7","@types/enzyme-adapter-react-16": "^1.0.6","@types/jsdom": "^16.2.4","enzyme": "^3.11.0","enzyme-adapter-react-16": "^1.15.5","eslint": "^7.9.0","@typescript-eslint/eslint-plugin": "^4.1.1","@typescript-eslint/parser": "^4.1.1","eslint-config-prettier": "^6.11.0","eslint-plugin-prettier": "^3.1.4","eslint-plugin-react": "^7.20.6","prettier": "^2.1.2"
}


//jest.config.js
module.exports = {
preset: 'ts-jest',snapshotSerializers: ['enzyme-to-json/serializer'],testEnvironment: 'node',transform: {
'^.+\\.tsx?$': 'ts-jest'
},"testRegex": "(/__tests__/.*|(\\.|/)(test|spec))\\.(js|ts|tsx)?$",modulefileExtensions: ['ts','tsx','js','jsx','json','node'],setupFilesAfterEnv: ['<rootDir>/src/setupTests.ts'],collectCoverage: true,transformIgnorePatterns: ["[/\\\\]node_modules[/\\\\].+\\.(js|jsx|mjs)$"]
};

//setupTests.ts
import enzyme from "enzyme";
import Adapter from "enzyme-adapter-react-16";
import "@testing-library/jest-dom";
enzyme.configure({ adapter: new Adapter() });

//ts.config.json
{
"compilerOptions": {
"target": "es5","lib": ["dom","dom.iterable","esnext"],"allowJs": true,"skipLibCheck": true,"esModuleInterop": true,"allowSyntheticDefaultImports": true,"forceConsistentCasingInFileNames": true,"module": "esnext","moduleResolution": "node","resolveJsonModule": true,"isolatedModules": true,"jsx": "react","strict": true,"noEmit": true,// we don't need to generate files as react works directly
"types": [
  "jest","node","react"
] },"include": ["src"],"exclude": ["./node_modules","*.js"]
}

//babel.config.js
module.exports = {
presets: [
['@babel/preset-env',{targets: {node: 'current'}}],+ '@babel/preset-typescript',],};

//Burger.tsx


import React from "react";
import "./burger.css";

//clickEvent
type Props = {
// eslint-disable-next-line @typescript-eslint/ban-types
clickEvent: Function;
isItClicked: boolean;
};
const Burger: React.FC<Props> = (props) => {
// eslint-disable-next-line react/prop-types
const { clickEvent,isItClicked } = props;

return (
<div
 data-testid="no-classes"
  id="burger"
  onClick={() => clickEvent()}
  className={isItClicked ? "cross" : ""}
 >
  <span></span>
  <span></span>
  <span></span>
</div>
);
};

export default Burger;

//burger.css
#burger {
position: absolute;
}

//burger.test.js
import * as React from 'react';
import Burger from "../Burger.tsx"
import { mount } from 'enzyme';

describe("We test the innerHTML of the burger",() => {
let wrapper;
beforeEach(() => {
wrapper = mount(<Burger />);
});
test("Snapshot burger ",() => {
//It works
expect(wrapper).toMatchSnapshot();
});
test("burger style css",() => {
//it doesn't work
expect(wrapper.find("#burger")).toHaveStyle('position: absolute')
});  
});

还有一个示例，他们采用std :: string并将其直接传递给缓冲区构造函数：

boost::array<char,1> send_buf  = {{ 0 }};
socket.send_to(boost::asio::buffer(send_buf),receiver_endpoint);

到目前为止一切顺利。我现在尝试填充字符串数组并将该数组发送到udp服务器。这总是导致服务器在实际消息之前接收到垃圾字符。 当我这样构造发送缓冲区时：

std::string message = make_daytime_string();
boost::system::error_code ignored_error;
socket.send_to(boost::asio::buffer(message),remote_endpoint,ignored_error);

我得到这样的输出：std::string message = "I am still here"; boost::array<std::string,1> send_buf2 = {{ message}}; socket.send_to(boost::asio::buffer(send_buf2),receiver_endpoint); 当我的数组是这样构造的：

 |��I am still here

我在输出中仅得到内存垃圾字符。两种情况下的接收长度均为32（字符）。

服务器读取如下消息：

boost::array<std::string,1> send_buf2  = {{ "I am still here" }};

这是构造发送缓冲区的一种不好的方法吗？还是有解决此问题的方法？

解决方法

您调用buffer函数的以下重载：

template<
    typename PodType,std::size_t N>
mutable_buffer buffer(
    boost::array< PodType,N > & data);

仅适用于POD。 string不是POD类型。

boost asio中的缓冲区可以视为一对：指向数据的指针和数据的长度。在您的情况下，您将创建一个缓冲区，该缓冲区指向字符串的二进制表示形式，而不是由字符串管理的数据-std :: string内部指针所指向的字符序列（使用小字符串优化时，此输出|��I am still here是可能的）。这就解释了为什么要获得32个字节，对于实现库来说，它仅为sizeof(std::string)。

如果要发送由boost :: array字符串管理的数据，则可以使用复合缓冲区：

const boost::array<std::string,2> a{{"I am still here","xxx"}};
std::vector<boost::asio::const_buffers_1> v;
v.push_back(boost::asio::buffer(a[0]));
v.push_back(boost::asio::buffer(a[1]));

创建缓冲区向量，并将基于std::string创建的缓冲区一一添加到该向量。