Month: March 2025

    let s = "sato".to_string().into_bytes();
    println!("{:?}", s);
    let l = LittleEndian::read_u32(&s);
    println!("{}", l);
    let b = BigEndian::read_u32(&s);
    println!("{}", b);

    let mut wtr = vec![];
    wtr.write_u32::<LittleEndian>(l).unwrap();
    println!("{:?}", wtr);

[115, 97, 116, 111]
1869898099
1935766639
[115, 97, 116, 111]

構造体をバイト列にする

#[derive(Serialize, Deserialize, Debug)]
struct Name {
    family: Vec<u8>,
    first: Vec<u8>,
}

    let name1 = Name {family: "sato".to_string().into_bytes(), first: "taro".to_string().into_bytes()};
    println!("{:?}", name1);
    let family = String::from_utf8(name1.family).unwrap();
    println!("{}", family);

Name { family: [115, 97, 116, 111], first: [116, 97, 114, 111] }
sato

なるほどー　前処理、後処理が多くなるが、安全性は高まりそう。

“{:?}”, resp だとstatusだが、resp.text().await.unwrap()とすると、bodyを表示できる。

    let mut post_url = format!("http://192.168.33.10:3000/health");
    let client = reqwest::Client::new();
    let resp = client.post(post_url)
        .header(reqwest::header::CONTENT_TYPE, "application/json")
        .json(&str)
        .send()
        .await
        .unwrap();
    println!("{:?}", resp);
    println!("{}", resp.text().await.unwrap());

Finished `dev` profile [unoptimized + debuginfo] target(s) in 7.43s
Running `target/debug/axum`
Response { url: Url { scheme: “http”, cannot_be_a_base: false, username: “”, password: None, host: Some(Ipv4(192.168.33.10)), port: Some(3000), path: “/health”, query: None, fragment: None }, status: 200, headers: {“content-type”: “text/plain; charset=utf-8”, “content-length”: “8”, “date”: “Thu, 13 Mar 2025 13:44:24 GMT”} }
All good

下のように書くと、DNSエラーとなる。

#[tokio::main]
async fn main()  {
    let res = tokio::spawn(async move {
        let v = get_myip().await.unwrap();
        println!("{}", v);
    });    
}   

pub async fn get_myip() -> Result<String, Box<dyn std::error::Error>> {

    let ip: Ip = serde_json::from_str(&reqwest::get("https://httpbin.org/ip")
        .await?
        .text()
        .await?)?;
    Ok(ip.origin)
}

しかし、実行されるまで待って、res.await.unwrap();とすれば、エラーは解消される。

    let res = tokio::spawn(async move {
        let v = get_myip().await.unwrap();
        println!("{}", v);
    });
    res.await.unwrap();

レスポンスがないままtokio::spawnが終了してしまうからっぽい。
うーん、奥が深い… httpbin.org　に問題があるかと思ったけど、全然違った…

echoサーバにリクエストを送り、このレスポンスが、”foo”なので、received_msgがfooだと思っていたが、

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut ws = WebSocket::connect("wss://echo.websocket.org/").await?;
    ws.send_text("foo".to_string()).await?;
    ws.receive().await?;
    if let Frame::Text { payload: received_msg, .. } =  ws.receive().await? {
        println!("{}", received_msg);
    }
    ws.close(None).await?;
    Ok(())
}  

Finished `dev` profile [unoptimized + debuginfo] target(s) in 1.60s
Running `target/debug/app`
foo

以下のように書くと、”Request served by *****”がレスポンスで帰ってくる。websocketのreceiveは以下のように書くのが正解

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let mut ws = WebSocket::connect("wss://echo.websocket.org/").await?;
    ws.send_text("foo".to_string()).await?;
    if let Frame::Text { payload: received_msg, .. } =  ws.receive().await? {
        println!("{}", received_msg);
    }
    ws.close(None).await?;
    Ok(())
}   

Finished `dev` profile [unoptimized + debuginfo] target(s) in 2.07s
Running `target/debug/app`
Request served by 7811941c69e658

File::createとwrite_allで元のデータは上書かれる。
例えば、元データが4行で、上書きデータが2行だった場合でも、上書き後は2行になる。

{"family":"john","first":"fox"}
{"family":"adam","first":"can"}
{"family":"john","first":"fox"}
{"family":"adam","first":"can"}

use serde::{Serialize, Deserialize};
use std::path::Path;
use std::fs::{File};
use std::io::{Write};

#[derive(Serialize, Deserialize, Clone, Debug)]
struct Name {
    family: String,
    first: String,
}

#[tokio::main]
async fn main() {

    let name1 = Name {family:"yamada".to_string(), first: "taro".to_string()};
    let name2 = Name {family:"sato".to_string(), first: "kazuki".to_string()};

    let mut vect: Vec<Name> = Vec::new();
    vect.push(name1);
    vect.push(name2);

    let file_path = format!("./data/names.txt");
    let mut file = File::create(file_path.clone()).unwrap();
    for name in vect {
        let serialized: Vec<u8> = serde_json::to_vec(&name).unwrap();
        file.write_all(&serialized).expect("write failed");
        file.write_all(b"\n").expect("write failed");
    }
    println!("done");

}  

{"family":"yamada","first":"taro"}
{"family":"sato","first":"kazuki"}

なるほどね！