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uucore: create parse_size::Parser struct

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Add a `uucore::parse_size::Parser` struct which will allow future
commits to add fields that change the behavior of `parse_size()`.
This commit is contained in:
Jeffrey Finkelstein 2022-11-18 20:20:30 -05:00
parent 2f311c7a2d
commit 847378f8d2
1 changed files with 88 additions and 49 deletions
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137
src/uucore/src/lib/parser/parse_size.rs
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@ -10,6 +10,93 @@ use std::fmt;
use crate::display::Quotable;
/// Parser for sizes in SI or IEC units (multiples of 1000 or 1024 bytes).
///
/// The [`Parser::parse`] function performs the parse.
#[derive(Default)]
pub struct Parser {
}
impl Parser {
/// Parse a size string into a number of bytes.
///
/// A size string comprises an integer and an optional unit. The unit
/// may be K, M, G, T, P, E, Z or Y (powers of 1024), or KB, MB,
/// etc. (powers of 1000), or b which is 512.
/// Binary prefixes can be used, too: KiB=K, MiB=M, and so on.
///
/// # Errors
///
/// Will return `ParseSizeError` if it's not possible to parse this
/// string into a number, e.g. if the string does not begin with a
/// numeral, or if the unit is not one of the supported units described
/// in the preceding section.
///
/// # Examples
///
/// ```rust
/// use uucore::parse_size::parse_size;
/// assert_eq!(Ok(123), parse_size("123"));
/// assert_eq!(Ok(9 * 1000), parse_size("9kB")); // kB is 1000
/// assert_eq!(Ok(2 * 1024), parse_size("2K")); // K is 1024
/// ```
pub fn parse(&self, size: &str) -> Result<u64, ParseSizeError> {
if size.is_empty() {
return Err(ParseSizeError::parse_failure(size));
}
// Get the numeric part of the size argument. For example, if the
// argument is "123K", then the numeric part is "123".
let numeric_string: String = size.chars().take_while(|c| c.is_ascii_digit()).collect();
let number: u64 = if !numeric_string.is_empty() {
match numeric_string.parse() {
Ok(n) => n,
Err(_) => return Err(ParseSizeError::parse_failure(size)),
}
} else {
1
};
// Get the alphabetic units part of the size argument and compute
// the factor it represents. For example, if the argument is "123K",
// then the unit part is "K" and the factor is 1024. This may be the
// empty string, in which case, the factor is 1.
//
// The lowercase "b" (used by `od`, `head`, `tail`, etc.) means
// "block" and the Posix block size is 512. The uppercase "B"
// means "byte".
let unit = &size[numeric_string.len()..];
let (base, exponent): (u128, u32) = match unit {
"" => (1, 0),
"b" => (512, 1),
"KiB" | "kiB" | "K" | "k" => (1024, 1),
"MiB" | "miB" | "M" | "m" => (1024, 2),
"GiB" | "giB" | "G" | "g" => (1024, 3),
"TiB" | "tiB" | "T" | "t" => (1024, 4),
"PiB" | "piB" | "P" | "p" => (1024, 5),
"EiB" | "eiB" | "E" | "e" => (1024, 6),
"ZiB" | "ziB" | "Z" | "z" => (1024, 7),
"YiB" | "yiB" | "Y" | "y" => (1024, 8),
"KB" | "kB" => (1000, 1),
"MB" | "mB" => (1000, 2),
"GB" | "gB" => (1000, 3),
"TB" | "tB" => (1000, 4),
"PB" | "pB" => (1000, 5),
"EB" | "eB" => (1000, 6),
"ZB" | "zB" => (1000, 7),
"YB" | "yB" => (1000, 8),
_ if numeric_string.is_empty() => return Err(ParseSizeError::parse_failure(size)),
_ => return Err(ParseSizeError::invalid_suffix(size)),
};
let factor = match u64::try_from(base.pow(exponent)) {
Ok(n) => n,
Err(_) => return Err(ParseSizeError::size_too_big(size)),
};
number
.checked_mul(factor)
.ok_or_else(|| ParseSizeError::size_too_big(size))
}
}
/// Parse a size string into a number of bytes.
///
/// A size string comprises an integer and an optional unit. The unit
@ -33,55 +120,7 @@ use crate::display::Quotable;
/// assert_eq!(Ok(2 * 1024), parse_size("2K")); // K is 1024
/// ```
pub fn parse_size(size: &str) -> Result<u64, ParseSizeError> {
if size.is_empty() {
return Err(ParseSizeError::parse_failure(size));
}
// Get the numeric part of the size argument. For example, if the
// argument is "123K", then the numeric part is "123".
let numeric_string: String = size.chars().take_while(|c| c.is_ascii_digit()).collect();
let number: u64 = if !numeric_string.is_empty() {
match numeric_string.parse() {
Ok(n) => n,
Err(_) => return Err(ParseSizeError::parse_failure(size)),
}
} else {
1
};
// Get the alphabetic units part of the size argument and compute
// the factor it represents. For example, if the argument is "123K",
// then the unit part is "K" and the factor is 1024. This may be the
// empty string, in which case, the factor is 1.
let unit = &size[numeric_string.len()..];
let (base, exponent): (u128, u32) = match unit {
"" => (1, 0),
"b" => (512, 1), // (`od`, `head` and `tail` use "b")
"KiB" | "kiB" | "K" | "k" => (1024, 1),
"MiB" | "miB" | "M" | "m" => (1024, 2),
"GiB" | "giB" | "G" | "g" => (1024, 3),
"TiB" | "tiB" | "T" | "t" => (1024, 4),
"PiB" | "piB" | "P" | "p" => (1024, 5),
"EiB" | "eiB" | "E" | "e" => (1024, 6),
"ZiB" | "ziB" | "Z" | "z" => (1024, 7),
"YiB" | "yiB" | "Y" | "y" => (1024, 8),
"KB" | "kB" => (1000, 1),
"MB" | "mB" => (1000, 2),
"GB" | "gB" => (1000, 3),
"TB" | "tB" => (1000, 4),
"PB" | "pB" => (1000, 5),
"EB" | "eB" => (1000, 6),
"ZB" | "zB" => (1000, 7),
"YB" | "yB" => (1000, 8),
_ if numeric_string.is_empty() => return Err(ParseSizeError::parse_failure(size)),
_ => return Err(ParseSizeError::invalid_suffix(size)),
};
let factor = match u64::try_from(base.pow(exponent)) {
Ok(n) => n,
Err(_) => return Err(ParseSizeError::size_too_big(size)),
};
number
.checked_mul(factor)
.ok_or_else(|| ParseSizeError::size_too_big(size))
Parser::default().parse(size)
}
#[derive(Debug, PartialEq, Eq)]