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|
use std::error;
use std::fmt;
use std::io;
use std::num::ParseIntError;
use regex::Regex;
/// An error that occurs when parsing a human readable size description.
///
/// This error provides an end user friendly message describing why the
/// description couldn't be parsed and what the expected format is.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct ParseSizeError {
original: String,
kind: ParseSizeErrorKind,
}
#[derive(Clone, Debug, Eq, PartialEq)]
enum ParseSizeErrorKind {
InvalidFormat,
InvalidInt(ParseIntError),
Overflow,
}
impl ParseSizeError {
fn format(original: &str) -> ParseSizeError {
ParseSizeError {
original: original.to_string(),
kind: ParseSizeErrorKind::InvalidFormat,
}
}
fn int(original: &str, err: ParseIntError) -> ParseSizeError {
ParseSizeError {
original: original.to_string(),
kind: ParseSizeErrorKind::InvalidInt(err),
}
}
fn overflow(original: &str) -> ParseSizeError {
ParseSizeError {
original: original.to_string(),
kind: ParseSizeErrorKind::Overflow,
}
}
}
impl error::Error for ParseSizeError {
fn description(&self) -> &str {
"invalid size"
}
}
impl fmt::Display for ParseSizeError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
use self::ParseSizeErrorKind::*;
match self.kind {
InvalidFormat => write!(
f,
"invalid format for size '{}', which should be a sequence \
of digits followed by an optional 'K', 'M' or 'G' \
suffix",
self.original
),
InvalidInt(ref err) => write!(
f,
"invalid integer found in size '{}': {}",
self.original, err
),
Overflow => write!(f, "size too big in '{}'", self.original),
}
}
}
impl From<ParseSizeError> for io::Error {
fn from(size_err: ParseSizeError) -> io::Error {
io::Error::new(io::ErrorKind::Other, size_err)
}
}
/// Parse a human readable size like `2M` into a corresponding number of bytes.
///
/// Supported size suffixes are `K` (for kilobyte), `M` (for megabyte) and `G`
/// (for gigabyte). If a size suffix is missing, then the size is interpreted
/// as bytes. If the size is too big to fit into a `u64`, then this returns an
/// error.
///
/// Additional suffixes may be added over time.
pub fn parse_human_readable_size(size: &str) -> Result<u64, ParseSizeError> {
lazy_static::lazy_static! {
// Normally I'd just parse something this simple by hand to avoid the
// regex dep, but we bring regex in any way for glob matching, so might
// as well use it.
static ref RE: Regex = Regex::new(r"^([0-9]+)([KMG])?$").unwrap();
}
let caps = match RE.captures(size) {
Some(caps) => caps,
None => return Err(ParseSizeError::format(size)),
};
let value: u64 =
caps[1].parse().map_err(|err| ParseSizeError::int(size, err))?;
let suffix = match caps.get(2) {
None => return Ok(value),
Some(cap) => cap.as_str(),
};
let bytes = match suffix {
"K" => value.checked_mul(1 << 10),
"M" => value.checked_mul(1 << 20),
"G" => value.checked_mul(1 << 30),
// Because if the regex matches this group, it must be [KMG].
_ => unreachable!(),
};
bytes.ok_or_else(|| ParseSizeError::overflow(size))
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn suffix_none() {
let x = parse_human_readable_size("123").unwrap();
assert_eq!(123, x);
}
#[test]
fn suffix_k() {
let x = parse_human_readable_size("123K").unwrap();
assert_eq!(123 * (1 << 10), x);
}
#[test]
fn suffix_m() {
let x = parse_human_readable_size("123M").unwrap();
assert_eq!(123 * (1 << 20), x);
}
#[test]
fn suffix_g() {
let x = parse_human_readable_size("123G").unwrap();
assert_eq!(123 * (1 << 30), x);
}
#[test]
fn invalid_empty() {
assert!(parse_human_readable_size("").is_err());
}
#[test]
fn invalid_non_digit() {
assert!(parse_human_readable_size("a").is_err());
}
#[test]
fn invalid_overflow() {
assert!(parse_human_readable_size("9999999999999999G").is_err());
}
#[test]
fn invalid_suffix() {
assert!(parse_human_readable_size("123T").is_err());
}
}
|
