coreutils/src/hru.rs

/*
 * Copyright (c) 2023–2024 Emma Tebibyte <emma@tebibyte.media>
 * SPDX-License-Identifier: AGPL-3.0-or-later
 *
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU Affero General Public License as published by the Free
 * Software Foundation, either version 3 of the License, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see https://www.gnu.org/licenses/.
 */

use std::{
	cmp::Ordering,
	env::args,
	io::stdin,
	process::exit,
};

extern crate sysexits;

use sysexits::EX_SOFTWARE;

fn auto_c(input: u64) -> (u64, u32) {
	let mut number = input;
	let mut remainder = 0;
	let mut exp: u32 = 0;

	if number % 10 > 0 { }
	else {
		while remainder == 0 {
			number /= 10;
			remainder = number % 10;
			exp += 1;
		}
	}

	let list: Vec<u32> = vec![3, 6, 9, 12, 15, 18, 21, 24, 27, 30];
	let mut exps = list.iter().peekable();

	while let Some(i) = exps.next() {
		match exp.cmp(i) {
			Ordering::Less => {
				number = input;
				break;
			},
			Ordering::Equal => break,
			Ordering::Greater => {
				if let Some(p) = exps.peek() {
					match exp.cmp(p) {
						Ordering::Less => {
							let exp_e = 10_u64.checked_pow(exp)
								.unwrap_or_else(|| { exit(EX_SOFTWARE); });

							let index_e = 10_u64.checked_pow(i.to_owned())
								.unwrap_or_else(|| { exit(EX_SOFTWARE); });

							number *= exp_e / index_e;
							exp = *i;
							break;
						},
						Ordering::Greater => continue,
						_ => break,
					};
				}
			},
		};
	}

	(number, exp)
}


fn main() {
	let argv = args().collect::<Vec<String>>();
	let mut buf = String::new();
	let _ = stdin().read_line(&mut buf);

	let n: u64 = match buf.trim().parse() {
		Ok(f) => f,
		Err(err) => {
			eprintln!("{}: {}", argv[0], err);
			exit(1);
		},
	};

	let (number, prefix) = auto_c(n);

	let si_prefix = format!("{}B", match prefix {
		3 => "K",
		6 => "M",
		9 => "G",
		12 => "T",
		15 => "P",
		18 => "E",
		21 => "Z",
		24 => "Y",
		27 => "R",
		30 => "Q",
		_ => "",
	});

	println!("{} {}", number.to_string(), si_prefix);
}