fast way to read line count of csv

line_count.rs

fn calculate_buffer_size(file_size: u64) -> usize {
    let buffer_size = if file_size < (1 << 20) {
        8192
    } else if file_size < (1 << 30) {
        1 << 20
    } else {
        1 << 30
    };
    buffer_size as usize
}

let file = File::open(path).unwrap();
let file_size = file.metadata().unwrap().len();
let buffer_size = calculate_buffer_size(file_size);
let mut file = File::open(path).unwrap();
let mut buffer = vec![0; buffer_size];
let mut line_count = 0;
let mut bytes_read;

loop {
    bytes_read = file.read(&mut buffer).unwrap();
    if bytes_read == 0 {
        break;
    }
    println!("Line count: {}", line_count);
    line_count += std::str::from_utf8(&buffer[..bytes_read])
        .unwrap()
        .matches('\n')
        .count();
}
println!("Line count: {}", line_count);