gets arch package sizes and sorts in increasing order

pacsize.rs

use std::error::Error;
use std::fs::{File, read_dir};
use std::io::{BufRead, BufReader};
use std::cmp::Ordering;
use std::fmt;

#[derive(Eq)]
struct Package {
  name: String,
  size: usize,
}

impl Ord for Package {
  fn cmp(&self, other: &Self) -> Ordering {
    self.size.cmp(&other.size)
  }
}

impl PartialOrd for Package {
  fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
    Some(self.cmp(other))
  }
}

impl PartialEq for Package {
  fn eq(&self, other: &Self) -> bool {
    self.size == other.size
  }
}

impl fmt::Display for Package {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    if self.size > 2_usize.pow(30) {
      write!(f, "{:>5.1} GiB", self.size as f32 / 2_usize.pow(30) as f32)?;
    } else if self.size > 2_usize.pow(20) {
      write!(f, "{:>5} MiB", self.size / 2_usize.pow(20))?;
    } else if self.size > 2_usize.pow(10) {
      write!(f, "{:>5} KiB", self.size / 2_usize.pow(10))?;
    } else {
      write!(f, "{:>5}   B", self.size)?;
    }
    write!(f, ": {}", self.name)
  }
}

fn main() -> Result<(), Box<dyn Error>> {
    let pkgs = read_dir("/var/lib/pacman/local/")?;
    let mut pkg_data: Vec<Package> = Vec::with_capacity(2048);

    for pkg in pkgs {
      let pkg = pkg?;
      if pkg.file_type()?.is_dir() {
        let mut desc_path = pkg.path();
        desc_path.push("desc");
        let desc = File::open(desc_path)?;
        let reader = BufReader::new(desc);
        let mut lines = reader.lines().skip_while(|line| line.as_ref().unwrap() != "%SIZE%");
        if let Some(size_str) = lines.nth(1) {
          let size_str = size_str?;
          let size = size_str.parse::<usize>()?;
          pkg_data.push(Package{name: pkg.file_name().into_string().unwrap(), size});
        }
      }
    }
    pkg_data.sort();
    for i in pkg_data {
      println!("{}", i);
    }
    Ok(())
}