#perfect-hash #compiler-plugin #lookup-tables #hash-table #hashing #hash-map

nightly phf_mac

Compiler plugin for perfect hash function data structures

14 releases (5 breaking)

Uses old Rust 2015

0.5.0 Jan 17, 2015
0.4.9 Jan 9, 2015
0.4.2 Dec 23, 2014
0.3.0 Dec 15, 2014
0.0.1 Nov 22, 2014

#1907 in Data structures

Download history 48/week @ 2024-02-22 52/week @ 2024-02-29 23/week @ 2024-03-07 15/week @ 2024-03-14 71/week @ 2024-03-28 24/week @ 2024-04-04

95 downloads per month

MIT license

17KB
413 lines

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 = "0.11", 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 = "0.11", 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 = "0.11.1", default-features = false }
phf_codegen = "0.11.1"

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

~0–460KB