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
```rust,no_run
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());
write!(&mut file, "static KEYWORDS: phf::Map<&'static str, Keyword> =
").unwrap();
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(&mut file)
.unwrap();
write!(&mut file, ";\n").unwrap();
}
```
lib.rs
```ignore
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 {
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:
```rust
let entries = [("hello", "1"), ("world", "2")];
let mut builder = phf_codegen::Map::new();
for &(key, value) in &entries {
builder.entry(key, value);
}
// ...
```
```rust
let mut builder = phf_codegen::Map::new();
builder.entry("hello", "1");
builder.entry("world", "2");
// ...
```