number_prefix/
parse.rs

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1use std::{error::Error, fmt, str};
2
3use super::{NumberPrefix, Prefix};
4
5
6impl<T: str::FromStr> str::FromStr for NumberPrefix<T> {
7    type Err = NumberPrefixParseError;
8
9    fn from_str(s: &str) -> Result<Self, Self::Err> {
10        let splitted = s.find(|p| {
11            p == 'k' || p == 'K' || p == 'M' || p == 'G' || p == 'T' ||
12            p == 'P' || p == 'E' || p == 'Z' || p == 'Y'
13        });
14
15        let num_prefix = s.split_at(splitted.unwrap_or(s.len()));
16        let num = match num_prefix.0.trim().parse::<T>() {
17            Ok(n)  => n,
18            Err(_) => return Err(NumberPrefixParseError(())),
19        };
20
21        let prefix_unit = num_prefix.1.trim_matches(|p|
22                p == 'b' || p == 'B' || p == 'm'
23            );
24
25        let prefix = match prefix_unit {
26            "k"  |
27            "K"  => Prefix::Kilo,
28            "M"  => Prefix::Mega,
29            "G"  => Prefix::Giga,
30            "T"  => Prefix::Tera,
31            "P"  => Prefix::Peta,
32            "E"  => Prefix::Exa,
33            "Z"  => Prefix::Zetta,
34            "Y"  => Prefix::Yotta,
35            "Ki" => Prefix::Kibi,
36            "Mi" => Prefix::Mebi,
37            "Gi" => Prefix::Gibi,
38            "Ti" => Prefix::Tebi,
39            "Pi" => Prefix::Pebi,
40            "Ei" => Prefix::Exbi,
41            "Zi" => Prefix::Zebi,
42            "Yi" => Prefix::Yobi,
43            ""   => return Ok(NumberPrefix::Standalone(num)),
44            _    => return Err(NumberPrefixParseError(())),
45        };
46
47        Ok(NumberPrefix::Prefixed(prefix, num))
48    }
49}
50
51
52/// The error returned when a `NumberPrefix` is failed to be parsed.
53#[derive(Debug, Copy, Clone, PartialEq, Eq)]
54pub struct NumberPrefixParseError(());
55
56impl fmt::Display for NumberPrefixParseError {
57    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
58        fmt.write_str("invalid prefix syntax")
59    }
60}
61
62impl Error for NumberPrefixParseError {
63}
64
65
66#[cfg(test)]
67mod test {
68    use super::*;
69
70    #[test]
71    fn parse_examples() {
72        let parse_example_a = "7.05E".parse::<NumberPrefix<f64>>();
73        let parse_example_b = "7.05".parse::<NumberPrefix<f64>>();
74        let parse_example_c = "7.05 GiB".parse::<NumberPrefix<f64>>();
75
76        assert_eq!(parse_example_a, Ok(NumberPrefix::Prefixed(Prefix::Exa, 7.05_f64)));
77        assert_eq!(parse_example_b, Ok(NumberPrefix::Standalone(7.05_f64)));
78        assert_eq!(parse_example_c, Ok(NumberPrefix::Prefixed(Prefix::Gibi, 7.05_f64)));
79    }
80
81    #[test]
82    fn bad_parse() {
83        let parsed = "bogo meters per second".parse::<NumberPrefix<f64>>();
84
85        assert_ne!(parsed, Ok(NumberPrefix::Prefixed(Prefix::Kilo, 7.05_f64)));
86    }
87}
number_prefix/parse.rs

number_prefix/
parse.rs
