Table of Contents

• Table of Contents
  • Overview
  • Installation
  • Examples
  • Time Units
  • Customization
  • Benchmarks
  • Comparison
  • Platform support
  • Todo
  • License

Overview

fundu provides a flexible and fast parser to convert rust strings into a std::time::Duration and for negative durations into a time::Duration. Some examples for valid input strings with the standard feature:

• "1.41"
• "42"
• "2e-8", "2e+8" (or likewise "2.0e8")
• ".5" or likewise "0.5"
• "3." or likewise "3.0"
• "inf", "+inf", "infinity", "+infinity"
• "1w" (1 week) or likewise "7d", "168h", "10080m", "604800s", ...

For examples of the custom feature see Customization section. A quick summary of features provided by this crate:

• Precision: There are no floating point calculations and the input is precisely parsed as it is. So, what you put in you is what you get out within the range of a Duration. (See also Comparison)
• Performance: The parser is blazingly fast (Benchmarks)
• Customization: TimeUnits, the number format and other aspects are easily configurable (Customization)
• Sound limits: The duration evaluates to Duration::MAX if the input number was larger than that maximum or if the input string was positive infinity.
• Negative_Durations: Negative numbers can be parsed to negative time::Durations when the negative feature is activated.
• Error handling: The error messages try to be informative on their own but can also be easily adjusted (See also Examples)

fundu aims for good performance and being a lightweight crate. It is purely built on top of the rust stdlib, and there are no additional dependencies required in the standard configuration. The accepted number format is per default the scientific floating point format and compatible with f64::from_str. However, the number format and other aspects can be customized up to formats like systemd time spans. See also the examples Examples section and the examples folder. For a direct comparison of fundu vs the rust native methods Duration::(try_)from_secs_f64 see Comparison.

For further details see the Documentation!

Installation

Add this to Cargo.toml for fundu with the standard feature.

[dependencies]
fundu = "0.5.1"

fundu is split into two main features, standard (providing DurationParser and parse_duration) and custom (providing the CustomDurationParser). The first is described here in in detail, the latter adds fully customizable identifiers for time units. Most of the time only one of the parsers is needed. To include only the CustomDurationParser add the following to Cargo.toml:

[dependencies]
fundu = { version = "0.5.1", default-features = false, features = ["custom"] }

Activating the negative feature allows parsing negative numbers to negative time::Durations.

Examples

If only the default parser is required once, then the parse_duration method can be used.

use fundu::parse_duration;
use std::time::Duration;

let input = "1.0e2s";
assert_eq!(parse_duration(input).unwrap(), Duration::new(100, 0));

When a customization of the accepted TimeUnits is required, then DurationParser::with_time_units can be used.

use fundu::DurationParser;
use fundu::TimeUnit::*;
use std::time::Duration;

let input = "3m";
assert_eq!(
    DurationParser::with_time_units(&[Minute]).parse(input).unwrap(),
    Duration::new(180, 0)
);

When no time units are configured, seconds is assumed.

use fundu::DurationParser;
use std::time::Duration;

let input = "1.0e2";
assert_eq!(
    DurationParser::without_time_units().parse(input).unwrap(),
    Duration::new(100, 0)
);

However, setting the default time unit to something different than seconds can be achieved with

use fundu::{DurationParser, TimeUnit::*};
use std::time::Duration;

assert_eq!(
    DurationParser::without_time_units()
        .default_unit(MilliSecond)
        .parse("1000")
        .unwrap(),
    Duration::new(1, 0)
);

Note the following will return an error because y (Years) is not in the default set of TimeUnits.

use fundu::DurationParser;

assert_eq!(
    DurationParser::new().parse("3y").unwrap_err().to_string(),
    "Time unit error: Invalid time unit: 'y' at column 1"
);

The parser is reusable and the set of time units is fully customizable

use fundu::{DurationParser, TimeUnit::*};
use std::time::Duration;

let parser = DurationParser::with_time_units(&[NanoSecond, Minute, Hour]);
for (input, expected) in &[
    ("9e3ns", Duration::new(0, 9000)),
    ("10m", Duration::new(600, 0)),
    ("1.1h", Duration::new(3960, 0)),
    ("7", Duration::new(7, 0)),
] {
    assert_eq!(parser.parse(input).unwrap(), *expected);
}

The identifiers for time units can be fully customized with any number of valid utf-8 sequences if the custom feature is activated:

use fundu::{CustomDurationParser, TimeUnit::*};
use std::time::Duration;

let parser = CustomDurationParser::with_time_units(
    &[
        (MilliSecond, &["χιλιοστό του δευτερολέπτου"]),
        (Second, &["s", "secs"]),
        (Hour, &["⏳"])
    ]
);
for (input, expected) in &[
    (".3χιλιοστό του δευτερολέπτου", Duration::new(0, 300_000)),
    ("1e3secs", Duration::new(1000, 0)),
    ("1.1⏳", Duration::new(3960, 0)),
] {
    assert_eq!(parser.parse(input).unwrap(), *expected);
}

It's also possible to parse multiple durations at once with parse_multiple. The different durations can be separated by an optional delimiter (a closure matching a u8) defined with parse_multiple. If the delimiter is not encountered, a number also indicates a new duration.

use std::time::Duration;

use fundu::DurationParser;

let mut parser = DurationParser::new();
parser.parse_multiple(Some(|byte| matches!(byte, b' ' | b'\t')));

assert_eq!(parser.parse("1.5h 2e+2ns"), Ok(Duration::new(5400, 200)));
assert_eq!(parser.parse("55s500ms"), Ok(Duration::new(55, 500_000_000)));
assert_eq!(parser.parse("1\t1"), Ok(Duration::new(2, 0)));
assert_eq!(parser.parse("1.   .1"), Ok(Duration::new(1, 100_000_000)));
assert_eq!(parser.parse("2h"), Ok(Duration::new(2 * 60 * 60, 0)));
assert_eq!(
    parser.parse("300ms20s 5d"),
    Ok(Duration::new(5 * 60 * 60 * 24 + 20, 300_000_000))
);

See also the examples folder for common recipes and integration with other crates. Run an example with

cargo run --example $FILE_NAME_WITHOUT_FILETYPE_SUFFIX

like the systemd time span parser example

# For some of the examples a help is available. To pass arguments to the example itself separate the arguments for cargo and the example with `--`
$ cargo run --example systemd --features custom --no-default-features -- --help
...

# To actually run the example execute
$ cargo run --example systemd --features custom --no-default-features '300ms20s 5day'
Original: 300ms20s 5day
      μs: 432020300000
   Human: 5d 20s 300ms

Time units

Second is the default time unit (if not specified otherwise for example with DurationParser::default_unit) which is applied when no time unit was encountered in the input string. The table below gives an overview of the constructor methods and which time units are available. If a custom set of time units is required, DurationParser::with_time_units can be used.

Note that Months and Years are not included in the default set of time units. The current implementation uses an approximate calculation of Months and Years in seconds and if they are included in the final configuration, the Julian year based calculation is used. (See table above)

With the CustomDurationParser from the custom feature, the identifiers for time units can be fully customized.

Customization

Unlike other crates, fundu does not try to establish a standard for time units and their identifiers or a specific number format. So, a lot of these aspects can be adjusted with ease when initializing or building the parser. Here's an incomplete example for possible customizations of the number format:

use std::time::Duration;

use fundu::TimeUnit::*;
use fundu::{DurationParser, ParseError};

let parser = DurationParser::builder()
    // Use a custom set of time units. For demonstration purposes just NanoSecond = `ns`
    .custom_time_units(&[NanoSecond])
    // Allow some whitespace characters as delimiter between the number and the time unit
    .allow_delimiter(|byte| matches!(byte, b'\t' | b'\n' | b'\r' | b' '))
    // Makes the number optional. If no number was encountered `1` is assumed
    .number_is_optional()
    // Disable parsing the fractional part of the number => 1.0 will return an error
    .disable_fraction()
    // Disable parsing the exponent => 1e0 will return an error
    .disable_exponent()
    // Finally, build a reusable DurationParser
    .build();

// Some valid input
for (input, expected) in &[
    ("ns", Duration::new(0, 1)),
    ("1000\t\n\r ns", Duration::new(0, 1000)),
] {
    assert_eq!(parser.parse(input).unwrap(), *expected);
}

// Some invalid input
for (input, expected) in &[
    (
        "1.0ns",
        ParseError::Syntax(1, "No fraction allowed".to_string()),
    ),
    (
        "1e9ns",
        ParseError::Syntax(1, "No exponent allowed".to_string()),
    ),
] {
    assert_eq!(parser.parse(input).unwrap_err(), *expected);
}

Here's an example for fully-customizable time units which uses the CustomDurationParser from the custom feature:

use std::time::Duration;

use fundu::TimeUnit::*;
use fundu::{CustomDurationParser, Multiplier};

let mut parser = CustomDurationParser::with_time_units(&[
    (Second, &["s", "secs", "seconds"]),
    (Minute, &["min"]),
    (Hour, &["ώρα"]),
]);

// Let's define a custom time unit `fortnight == 2 weeks` which isn't part of the basic
// [`TimeUnit`]s:
parser.custom_time_unit(Week, Multiplier(2, 0), &["f", "fortnight", "fortnights"]);

assert_eq!(parser.parse("42e-1ώρα").unwrap(), Duration::new(15120, 0));
assert_eq!(
    parser.parse("1fortnight").unwrap(),
    Duration::new(60 * 60 * 24 * 7 * 2, 0)
);

Benchmarks

To run the benchmarks on your machine, clone the repository

git clone https://github.com/Joining7943/fundu.git
cd fundu

and then run all benchmarks with

cargo bench --all-features

The iai-callgrind (feature = with-iai) and flamegraph (feature = with-flamegraph) benchmarks can only be run on unix. Use the --features option of cargo to run the benchmarks for specific features:

cargo bench --features standard,custom,negative

The above won't run the flamegraph and iai-callgrind benchmarks.

Benchmarks can be further filtered for example with

cargo bench --bench benchmarks_standard
cargo bench --bench benchmarks_standard -- 'parsing speed'
cargo bench --features custom --no-default-features --bench benchmarks_custom

For more infos, see the help with

cargo bench --help # The cargo help for bench
cargo bench --bench benchmarks_standard -- --help # The criterion help

To get a rough idea about the parsing times, here the average parsing speed of some inputs on a comparatively slow machine (Quad core 3000Mhz, 8GB DDR3, Linux)

For comparison, fundu's precision and additional features only add a very low performance overhead for small and some mixed input and performs better than the reference function from the stdlib as the input gets larger (the reference function is Duration::from_secs_f64(input.parse().unwrap())):

The initialization for fixed size time unit sets with DurationParser::new, DurationParser::with_all_time_units takes around 1-2 ns and is negligibly small. The initialization time for custom sets with DurationParser::with_time_units has a maximum of around 10 ns.

Comparison fundu vs Duration::from_secs_f64

Here's a short incomplete overview of differences and advantages of fundu over using Duration::from_secs_f64(input.parse().unwrap()) (and Duration::try_from_secs_f64(input.parse().unwrap()))

fundu has a small impact on performance when the input is small but performs better for large input (See performance). Depending on the input data and if you need to parse a massive amount of inputs and don't need the full precision or any of fundu's features, you may prefer using the native methods from the rust stdlib.

Platform support

Since fundu is purely built on top of the rust stdlib without platform specific code, this library should be compatible with all platforms. Please open an issue if you find any unsupported platforms which rust itself supports.

See also the CI

TODO

• Provide other year calculations:
  • mean Gregorian year
  • Sidereal year
  • Tropical year

See also Changelog

License

MIT license (LICENSE or http://opensource.org/licenses/MIT)