68 releases

0.12.1 Jun 19, 2025
0.11.3 Jan 6, 2025
0.11.2 Jun 24, 2023
0.11.1 Aug 8, 2022
0.1.0 Nov 27, 2014

#5 in Data structures

Download history 2716861/week @ 2025-03-22 2114529/week @ 2025-03-29 2183265/week @ 2025-04-05 1950826/week @ 2025-04-12 1930609/week @ 2025-04-19 1821663/week @ 2025-04-26 1840972/week @ 2025-05-03 1927169/week @ 2025-05-10 2004273/week @ 2025-05-17 1777717/week @ 2025-05-24 1972428/week @ 2025-05-31 2034925/week @ 2025-06-07 2032495/week @ 2025-06-14 2158491/week @ 2025-06-21 1944494/week @ 2025-06-28 1801411/week @ 2025-07-05

8,288,449 downloads per month
Used in 7,037 crates (741 directly)

MIT license

50KB
1K SLoC

Rust-PHF

CI Latest Version

Documentation

Rust-PHF is a library to generate efficient lookup tables at compile time using perfect hash functions.

It currently uses the CHD algorithm and can generate a 100,000 entry map in roughly .4 seconds.

MSRV (minimum supported rust version) is Rust 1.61.

Usage

PHF data structures can be constructed via either the procedural macros in the phf_macros crate or code generation supported by the phf_codegen crate.

To compile the phf crate with a dependency on libcore instead of libstd, enabling use in environments where libstd will not work, set default-features = false for the dependency:

[dependencies]
# to use `phf` in `no_std` environments
phf = { version = "0.12", default-features = false }

phf_macros

use phf::phf_map;

#[derive(Clone)]
pub enum Keyword {
    Loop,
    Continue,
    Break,
    Fn,
    Extern,
}

static KEYWORDS: phf::Map<&'static str, Keyword> = phf_map! {
    "loop" => Keyword::Loop,
    "continue" => Keyword::Continue,
    "break" => Keyword::Break,
    "fn" => Keyword::Fn,
    "extern" => Keyword::Extern,
};

pub fn parse_keyword(keyword: &str) -> Option<Keyword> {
    KEYWORDS.get(keyword).cloned()
}
[dependencies]
phf = { version = "0.12", features = ["macros"] }

Note

Currently, the macro syntax has some limitations and may not work as you want. See #183 or #196 for example.

phf_codegen

To use phf_codegen on build.rs, you have to add dependencies under [build-dependencies]:

[build-dependencies]
phf = { version = "0.12", default-features = false }
phf_codegen = "0.12"

Then put code on build.rs:

use std::env;
use std::fs::File;
use std::io::{BufWriter, Write};
use std::path::Path;

fn main() {
    let path = Path::new(&env::var("OUT_DIR").unwrap()).join("codegen.rs");
    let mut file = BufWriter::new(File::create(&path).unwrap());

    write!(
        &mut file,
        "static KEYWORDS: phf::Map<&'static str, Keyword> = {}",
        phf_codegen::Map::new()
            .entry("loop", "Keyword::Loop")
            .entry("continue", "Keyword::Continue")
            .entry("break", "Keyword::Break")
            .entry("fn", "Keyword::Fn")
            .entry("extern", "Keyword::Extern")
            .build()
    )
    .unwrap();
    write!(&mut file, ";\n").unwrap();
}

and lib.rs:

#[derive(Clone)]
enum Keyword {
    Loop,
    Continue,
    Break,
    Fn,
    Extern,
}

include!(concat!(env!("OUT_DIR"), "/codegen.rs"));

pub fn parse_keyword(keyword: &str) -> Option<Keyword> {
    KEYWORDS.get(keyword).cloned()
}

Dependencies

~230KB