phf_codegen 0.8.0

Codegen library for PHF types

A set of builders to generate Rust source for PHF data structures at compile time.

The provided builders are intended to be used in a Cargo build script to generate a Rust source file that will be included in a library at build time.

Examples

build.rs

extern crate phf_codegen;

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());

writeln!(
&mut file,
"static KEYWORDS: phf::Map<&'static str, Keyword> = \n{};\n",
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();
}

lib.rs

extern crate phf;

#[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()
}
Byte-String Keys

Byte strings by default produce references to fixed-size arrays; the compiler needs a hint to coerce them to slices:

build.rs

extern crate phf_codegen;

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());

writeln!(
&mut file,
"static KEYWORDS: phf::Map<&'static [u8], Keyword> = \n{};\n",
phf_codegen::Map::<&[u8]>::new()
.entry(b"loop", "Keyword::Loop")
.entry(b"continue", "Keyword::Continue")
.entry(b"break", "Keyword::Break")
.entry(b"fn", "Keyword::Fn")
.entry(b"extern", "Keyword::Extern")
.build()
).unwrap();
}

lib.rs

extern crate phf;

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

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

pub fn parse_keyword(keyword: &[u8]) -> Option<Keyword> {
KEYWORDS.get(keyword).cloned()
}

Note

The compiler's stack will overflow when processing extremely long method chains (500+ calls). When generating large PHF data structures, consider looping over the entries or making each call a separate statement:

let entries = [("hello", "1"), ("world", "2")];

let mut builder = phf_codegen::Map::new();
for &(key, value) in &entries {
builder.entry(key, value);
}
// ...
let mut builder = phf_codegen::Map::new();
builder.entry("hello", "1");
builder.entry("world", "2");
// ...