units/src/conv/bytes.rs

use super::*;
use smallmap::Map;

#[derive(Debug)]
pub struct Bytes;

const KB: u64 = 1024;

lazy_static! {
    static ref SUFFIX: Map<char, u64> = smallmap::smallmap! {
	{'k' => KB},
	{'m' => KB * KB},
	{'g' => KB * KB * KB},
	{'p' => KB * KB * KB * KB},
    };
}

impl Conversion for Bytes
{
    const UNIT: &'static str = "bytes";

    type Output = u64;

    fn convert(&self, input: &str) -> Result<(Self::Output, Option<Self::Unit>), Self::Error>
    {
	#[macro_export] macro_rules! parse {
	    ($non:expr) => (($non).parse::<u64>().map_err(|e| ConversionError(format!("Failed to parse u64: {}", e)))?)
	}

	let (o, u) = match input.char_indices().last().map(|(idx, chr)| (chr.to_lowercase().next().unwrap(), &input[..idx])) {
	    Some((chr, _)) if chr.is_numeric() => (parse!(input), 1),
	    
	    Some((ref chr, non)) if SUFFIX.contains_key(chr) => (parse!(non), *SUFFIX.get(chr).unwrap()),
	    
	    Some((chr, _)) => return Err(ConversionError(format!("Unknown suffix {}", chr))),
	    None => (0, 1),
	};

	Ok((o * u, Some(u)))
    }
}