rust-core_io/build.rs

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Rust
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extern crate rustc_version;
use std::env;
use std::fs::File;
use std::io::Write;
use std::path::PathBuf;
use std::ops::{Neg,Sub};
/*
* Let me explain this hack. For the sync shell script it's easiest if every
* line in mapping.rs looks exactly the same. This means that specifying an
* array literal is not possible. include!() can only expand to expressions, so
* just specifying the contents of an array is also not possible.
*
* This leaves us with trying to find an expression in which every line looks
* the same. This can be done using the `-` operator. This can be a unary
* operator (first thing on the first line), or a binary operator (later
* lines). That is exactly what's going on here, and Neg and Sub simply build a
* vector of the operangs.
*/
struct Mapping(&'static str,&'static str);
impl Neg for Mapping {
type Output = Vec<Mapping>;
fn neg(self) -> Vec<Mapping> {
vec![self.into()]
}
}
impl Sub<Mapping> for Vec<Mapping> {
type Output=Vec<Mapping>;
fn sub(mut self, rhs: Mapping) -> Vec<Mapping> {
self.push(rhs.into());
self
}
}
fn main() {
let mappings=include!("mapping.rs");
let compiler=rustc_version::version_meta().commit_hash.expect("Couldn't determine compiler version");
let io_commit=mappings.iter().find(|&&Mapping(elem,_)|elem==compiler).expect("Unknown compiler version, upgrade core_io?").1;
let mut dest_path=PathBuf::from(env::var_os("OUT_DIR").unwrap());
dest_path.push("io.rs");
let mut f=File::create(&dest_path).unwrap();
let mut target_path=PathBuf::from(env::var_os("CARGO_MANIFEST_DIR").unwrap());
target_path.push("src");
target_path.push(io_commit);
target_path.push("mod.rs");
f.write_all(br#"#[path=""#).unwrap();
f.write_all(target_path.into_os_string().into_string().unwrap().as_bytes()).unwrap();
f.write_all(br#""] mod io;"#).unwrap();
}