ソフトウェアエンジニアの技術ブログ：Software engineer tech blog

use std::os::raw::c_int;

#[link(name="mylib", kind="static")]
extern "C" {
	fn twice(n: c_int) -> c_int;
}

fn main() {
	let n = 12;
	unsafe {
		println!("{}の2倍は{}", n, twice(n));
	}
}

use std::time::Instant;

fun main() {
	i16func();
	i64func();
}

fn i16func(){
	let mut v:16 = 0;
	let start = Instant::now();
	for _ in 0..1000 {
		for _ in 0..10000 {
			v = v + 1;
		}
		v = v - 10000;
	}
	let elepse = start.elapsed();
	println!("i16={:?}", v);
}

fn i64func() {
	let mut v:i64 = 0;
	let start = Instant::now();
	for _ in 0..1000 {
		for _ in 0..10000 {
			v = v + 1;
		}
		v = v- 10000;
	}
	let elepse = start.elapsed();
	println!("i64={:?}", v);
	println!("{}ミリ秒", elepse.as_millis());
}

use std::time::Instant;

fn main() {
	f32func();
	f64func();
}

fn f32func() {
	const NDATA:usize = 10000;
	let mut a:[f32; NDATA] = [0.0; NDATA];
	for i in 0..NDATA {
		a[i] = (NDATA - i) as f32;
	}
	println!("並び替えスタート");
	let start = Instant::now();
	for i in 0..NDATA{
		for j in 0..NDATA {
			if a[i] < a[j] {
				let tmp = a[i];
				a[i] = a[j];
				a[j] = tmp;
			}
		}
	}
	let elepse = start.elapsed();
	println!("並べ替え終了");
	println!("{}ミリ秒", elepse.as_millis());
}

fn f64func() {
	const NDATA:usize = 10000;
	let mut a:[f64; NDATA] = [0.0; NDATA];
	for i in 0..NDATA {
		a[i] = (NDATA - i) as f64;
	}
	let start = Instant::now();
	for i in 0..NDATA {
		for j in 0..NDATA {
			if a[i] < a[j] {
				let tmp = a[i];
				a[i] = a[j];
				a[j] = tmp;
			}
		}
	}
	let elepse = start.elapsed();
	println!("並び替え終了");
	println!("{}ミリ秒", elepse.as_millis());
}

プログラムの実行が継続できないような重大な問題をパニックという
パニックは他の言語の例外処理に似ている
Cargo.tomlファイルのpanic=’abort’で異常終了する

let f = File::open("sample.txt");
let f = match f {
	Ok(file) => file,
	Err(error) => {
		panic!("ファイル開けません: {:?}", error)
	}
}

アサートはプログラムの途中で値が妥当であるか調べる
assert_eq!(left, right);

let f = 3.7_f64;

assert_eq!(f.floor(), 3.0);
println!("f={}", f);

### メモリ管理
メモリはランタイムが管理するので考える必要はない

Box: std::boxed::Boxを使うことでヒープにメモリを確保することができる

struct Point {
	x: i32,
	y: i32,
}

impl Clone for Poin {
	fn clone(&self) -> Self {
		Point {
			x: self.x.clone(),
			y: self.y.clone(),
		}
	}
}

fn main() {
	let p1 = Point {x: 12, y:25};
	let p2: Box<Point> = Box::new(Point {x: 23, y: 45});
	println!("{:?}", type_of(p1.clone()));
	println!("{:?}", type_of(p2.clone()));
	println!("{}, {}", p1.x, p1.y);
	println!("{}, {}", p2.x, p2.y);
}

fn type_of<T>(_: T) -> &'static str {
	std::any::type_name::<T>()
}

use std::mem;

struct Point {
	x: i32,
	y: i32,
}

fn main() {
	let p = Point {x: 12, y: 25};
	let a = [1,2,3,4,5,6,7,8,9];

	println!("pのサイズ={}", mem::size_of_val(&p));
	println!("aのサイズ={}", mem::size_of_val(&a));
}

TCPというプロトコルを使って情報を受け渡すサーバとクライアント

サーバ側

use std::net::{TcpListener,TcpStream};
use std::thread;
use std::io::{Read,Write,Error};

fn handle_data(mut stream: TcpStream) -> Result<(), Error> {
	println!("Connection from: {}", stream.peer_addr()?);
	let mut buf = [0; 512];
	loop {
		let byte_read = stream.read(&mut buf)?;
		for i in 0..byte_read {
			if buf[i] > 0x60 {
				buf[i] = buf[i] - 0x20;
			}
		}
		if byte_read == 0 {return Ok(());}
		stream.write(&buf[..byte_read])?;
	}
}

fn main() {
	let coninfo = "localhost:8000";
	let listener = TcpListener::bind(coninfo).expect("バインドできません。");
	for steam in listener.incoming(){
		match stream {
			Err(e) => {eprintln!("failed: {}", e)}
			Ok(stream) => {
				thread::spawn(move || {
					handle_data(stream).
						unwrap_or_else(|error| eprintln!("{:?}", error));
				});
			} 
		}
	}
}

クライアント側

use std::net::{TcpStream};
use std::str;
use std::io::{self,BufRead,BufReader,Write};

fn main() {
	let coinfo = "localhost:8000";

	let mut stream = TcpStream::connect(coinfo).expect("サーバに接続できません。");

	loop {
		let mut input = String::new();
		io::stdin().read_line(&mut input).expect("標準入力からの入力エラー");
		stream.write(input.as_bytes()).expect("サーバに送れません。");

		let mut reader = BufReader::new(&stream);
		reader.read_until(b'¥n', &mut buffer).expect("サーバから受け取れません");

		print!("{}", str::from_utf8(&buffer).expect("テキストを表示できません"));
	}
}

じゃんけんサーバ

use std::net::{TcpListener, TcpStream};
use std::thread;
use std::io::{Read,Write,Error};
use rand::{thread_rng, Rng};

fn handle_data(mut stream: TcpStream) -> Result<(), Error> {
	println!("Connection from: {}", stream.peer_addr()?);
	let mut buf = [0; 512];
	loop {
		let mut userte = false;
		let mut cpmsg = String::new();
		let mut msg = String::from("");
		let byte_read = stream.read(&mut buf)?;
		if byte_read == 0 {return Ok(());}

		let mut rng = thread_rng();
		let x: u16 = rng.gen_range(0, 3);

		match x {
			0 => cpmsg.insert_str(0, "私はグー"),
			1 => cpmsg.insert_str(0, "私はチョキ"),
			2 => cpmsg.insert_str(0, "私はパー"),
			_ => cpmsg.insert_str(0, ""),
		}
		let client_msg = String::from_utf8(buf.to_vec()).unwrap();
		msg.insert_str(0, &cpmsg);
		if client_msg.starts_with("グー") {
			userte=true;
			match x {
				0 => msg.push_str(":あいこ¥n");
				1 => msg.push_str(":あなたの勝ち¥n");
				2 => msg.push_str(":あなたの負け¥n");
				_ => ();
			}
		} else if client_msg.starts_with("チョキ"){
			userte=true;
			match x {
				0 => msg.push_str(":あなたの負け¥n");
				1 => msg.push_str(":あいこ¥n");
				2 => msg.push_str(":あなたの勝ち¥n");
				_ => ();
			}
		} else if client_msg.starts_with("パー"){
			userte=true;
			match x {
				0 => msg.push_str(":あなたの勝ち¥n");
				1 => msg.push_str(":あなたの負け¥n");
				2 => msg.push_str(":あいこ¥n");
				_ => ();
			}
		} if userte {
			let bytes = msg.as_bytes();
			let len = bytes.len();
			stream.write(&bytes[..len])?;
		} else {
			stream.write(&buf[..byte_read])?;
		}
		stream.flush()?;
	}
}

fn main() {
	let coninfo = "localhost:8000";
	let listener = TcpListener::bind(coninfo).expect("バインドできません。");
	for stream in listenr.incoming() {
		match stream {
			Err (e) => {eprintln!("failed: {}", e)}
			Ok(stream) => {
				thread::spawn(move || {
					handle_data(stream).
						unwrap_or_else(|error| eprintln!("{:?}", error));
				});
			}
		}
	}
}

単純なファイル入出力はstd::fsやstd::ioにある関数を使う
std::fs::read(), std::fs::read_dir(), std::fs::read_to_string(), std::fs_write()

use std::fs;

fn main() {
	let result = fs::read_to_string("sample.txt");
	println!("{:?}", result);
}

use std::fs;

fn main() {
	match fs::read_to_string("sample.txt"){
		Ok(result) => println!("{}", result),
		Err(msg) => println!("エラー:{}", msg),
	}
}

use std::io::BufReader;
use std::io::prelude::*;
use std::fs::File;

fn main() -> std::io::Result<()> {
	let f = File::open("sample.txt")?;
	let reader = BufReader::new(f);

	for line in reader.lines() {
		println!("{}", line?);
	}
	Ok(())

}

use std::io;
use std::io::prelude::*;
use std::fs::File;

fn main() -> std::io::Result<()> {
	let mut f = File::open("sample.txt")?;
	let mut buffer = [0; 1000];

	let n = f.read(&mut buffer)?;

	println!("{:?}", &buffer[..n]);
	Ok(())
}

use std::fs::File;
use std::io::Write;

fn main() -> std::io::Result<()> {
	let txt = "こんにちは¥nHappy Rust¥n";
	let mut file = File::create("test.txt")?;
	write!(file, "{}", txt)?;
	file.flush()?;
	Ok(())

}

use std::fs::File;
use std::io::{Write, BufWriter};

fn main() -> std::io::Result<()> {
	let file = File::create("sample2.txt")?;
	let mut writer = BufWrite::new(file);
	let data:&str = "Hello¥nHappy Dogs";
	writer.write_all(data.as_bytes())?;
	writer.flush()?;
	Ok(())
}

use qrcode::QrCode;
use image::Luma;

fn main() {
	let code = QrCode::new(b"A0023213").unwrap();
	let image = code.render::<Luma<u8>>().build();

	image.save("sample.png").unwrap();
}

Rustのファイルシステムにアクセスするときは、std::fsモジュールにある関数を使うことができる
canonicalize(), copy(), create_dir(), create_dir_all(), hard_link(), metadata(), read_link(), remove_dir(), remove_dir_all(), remove_file(), rename(), set_permissions(), soft_link(), symlink_metadata()

pub fn copy>, Q: AsRef>(from: P, to: Q) -> Result

use std::env;
use std::fs;

fn main() -> std::io::Result<()> {
	let argv: Vec<String> = env::args().collect();
	let argc = argv.len();
	if argc < 3 {
		println!("引数を2個指定ください。");
		std::process::exit(1);
	}

	let src = &argv[1];
	let dest = &argv[2];
	fs::copy(src, dest)?;
	Ok(())
}

use std::fs;

fn main() -> std::io::Result<()> {
	fs::create_dir("./misc/subdir")?;
	Ok(())
}

use std::fs;
use std::path::PathBuf;

fn main() {
	let srcdir = PathBuf::from("./src");
	println!("{:?}", fs::canonicalize(&srcdir));
}

関数を非同期実行することができる
async/awaitは、時間のかかる処理をするときに、処理が終わるまでのスレッドを別のタスクの処理に使うことができる機能を提供する

use futures::executor::block_on;

fn wait() -> f64 {
	let mut x:f64 = 0.0;
	for _ in 1..10000 {
		for _ in 1..10000 {
			x = x * 1.001;
		}
	}
	x
}

async fn print_dot(){
	println!(".");
}

async fn print_plus(){
	plusfunc().await;
}

async fn print_minus() {
	wait();
	println!("-");
}

async fn plusfunc(){
	wait();
	println!("+");
}

async fn async_main() {
	let f1 = print_plus();
	let f2 = print_minus();
	let f3 = print_dot();
	println!("Hello");
	futures::join!(f1, f2, f3);
}

fn main(){
	block_on(async_main());
}