IO Structs

I/O types สำหรับ reading และ writing ใน Rust รวมถึง buffered I/O และ in-memory operations

1. BufReader

BufReader<R> wraps any Read type และ provides buffering เพื่อ reduce syscalls

Using BufReader

use std::io::{BufRead, BufReader, Cursor};

fn main() {
    // BufReader wraps any Read implementation
    let data = "line 1\nline 2\nline 3\n";
    let cursor = Cursor::new(data);
    let reader = BufReader::new(cursor);

    // Iterate lines
    println!("=== Lines ===");
    for line in reader.lines() {
        println!("  {:?}", line.unwrap());
    }

    // Custom buffer capacity
    let cursor = Cursor::new(data);
    let reader = BufReader::with_capacity(1024, cursor);
    println!("Buffer capacity: {}", reader.capacity());

    // read_line - reads including newline
    let cursor = Cursor::new("Hello\nWorld\n");
    let mut reader = BufReader::new(cursor);
    let mut line = String::new();

    reader.read_line(&mut line).unwrap();
    println!("\nFirst line (with newline): {:?}", line);

    // read_until - reads until delimiter
    let cursor = Cursor::new("a:b:c:d");
    let mut reader = BufReader::new(cursor);
    let mut buf = Vec::new();

    reader.read_until(b':', &mut buf).unwrap();
    println!("Until ':': {:?}", String::from_utf8_lossy(&buf));

    // Direct buffer access
    let cursor = Cursor::new("buffered data");
    let mut reader = BufReader::new(cursor);

    let buf = reader.fill_buf().unwrap();
    println!("Buffer contents: {:?}", String::from_utf8_lossy(buf));
    reader.consume(8);  // Mark bytes as consumed
}