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//! Simple scanner for non-overlapping, known references of Nix store paths in a
//! given string.
//!
//! This is used for determining build references (see
//! //tvix/eval/docs/build-references.md for more details).
//!
//! The scanner itself is using the Wu-Manber string-matching algorithm, using
//! our fork of the `wu-mamber` crate.
use std::collections::BTreeSet;
use wu_manber::TwoByteWM;
pub const STORE_PATH_LEN: usize = "/nix/store/00000000000000000000000000000000".len();
/// Represents a "primed" reference scanner with an automaton that knows the set
/// of store paths to scan for.
pub struct ReferenceScanner<P: Ord + AsRef<[u8]>> {
candidates: Vec<P>,
searcher: Option<TwoByteWM>,
matches: Vec<usize>,
}
impl<P: Clone + Ord + AsRef<[u8]>> ReferenceScanner<P> {
/// Construct a new `ReferenceScanner` that knows how to scan for the given
/// candidate store paths.
pub fn new(candidates: Vec<P>) -> Self {
let searcher = if candidates.is_empty() {
None
} else {
Some(TwoByteWM::new(&candidates))
};
ReferenceScanner {
searcher,
candidates,
matches: Default::default(),
}
}
/// Scan the given str for all non-overlapping matches and collect them
/// in the scanner.
pub fn scan<S: AsRef<[u8]>>(&mut self, haystack: S) {
if haystack.as_ref().len() < STORE_PATH_LEN {
return;
}
if let Some(searcher) = &self.searcher {
for m in searcher.find(haystack) {
self.matches.push(m.pat_idx);
}
}
}
/// Finalise the reference scanner and return the resulting matches.
pub fn finalise(self) -> BTreeSet<P> {
self.matches
.into_iter()
.map(|idx| self.candidates[idx].clone())
.collect()
}
}
#[cfg(test)]
mod tests {
use super::*;
// The actual derivation of `nixpkgs.hello`.
const HELLO_DRV: &str = r#"Derive([("out","/nix/store/33l4p0pn0mybmqzaxfkpppyh7vx1c74p-hello-2.12.1","","")],[("/nix/store/6z1jfnqqgyqr221zgbpm30v91yfj3r45-bash-5.1-p16.drv",["out"]),("/nix/store/ap9g09fxbicj836zm88d56dn3ff4clxl-stdenv-linux.drv",["out"]),("/nix/store/pf80kikyxr63wrw56k00i1kw6ba76qik-hello-2.12.1.tar.gz.drv",["out"])],["/nix/store/9krlzvny65gdc8s7kpb6lkx8cd02c25b-default-builder.sh"],"x86_64-linux","/nix/store/4xw8n979xpivdc46a9ndcvyhwgif00hz-bash-5.1-p16/bin/bash",["-e","/nix/store/9krlzvny65gdc8s7kpb6lkx8cd02c25b-default-builder.sh"],[("buildInputs",""),("builder","/nix/store/4xw8n979xpivdc46a9ndcvyhwgif00hz-bash-5.1-p16/bin/bash"),("cmakeFlags",""),("configureFlags",""),("depsBuildBuild",""),("depsBuildBuildPropagated",""),("depsBuildTarget",""),("depsBuildTargetPropagated",""),("depsHostHost",""),("depsHostHostPropagated",""),("depsTargetTarget",""),("depsTargetTargetPropagated",""),("doCheck","1"),("doInstallCheck",""),("mesonFlags",""),("name","hello-2.12.1"),("nativeBuildInputs",""),("out","/nix/store/33l4p0pn0mybmqzaxfkpppyh7vx1c74p-hello-2.12.1"),("outputs","out"),("patches",""),("pname","hello"),("propagatedBuildInputs",""),("propagatedNativeBuildInputs",""),("src","/nix/store/pa10z4ngm0g83kx9mssrqzz30s84vq7k-hello-2.12.1.tar.gz"),("stdenv","/nix/store/cp65c8nk29qq5cl1wyy5qyw103cwmax7-stdenv-linux"),("strictDeps",""),("system","x86_64-linux"),("version","2.12.1")])"#;
#[test]
fn test_no_patterns() {
let mut scanner: ReferenceScanner<String> = ReferenceScanner::new(vec![]);
scanner.scan(HELLO_DRV);
let result = scanner.finalise();
assert_eq!(result.len(), 0);
}
#[test]
fn test_single_match() {
let mut scanner = ReferenceScanner::new(vec![
"/nix/store/4xw8n979xpivdc46a9ndcvyhwgif00hz-bash-5.1-p16".to_string(),
]);
scanner.scan(HELLO_DRV);
let result = scanner.finalise();
assert_eq!(result.len(), 1);
assert!(result.contains("/nix/store/4xw8n979xpivdc46a9ndcvyhwgif00hz-bash-5.1-p16"));
}
#[test]
fn test_multiple_matches() {
let candidates = vec![
// these exist in the drv:
"/nix/store/33l4p0pn0mybmqzaxfkpppyh7vx1c74p-hello-2.12.1".to_string(),
"/nix/store/pf80kikyxr63wrw56k00i1kw6ba76qik-hello-2.12.1.tar.gz.drv".to_string(),
"/nix/store/cp65c8nk29qq5cl1wyy5qyw103cwmax7-stdenv-linux".to_string(),
// this doesn't:
"/nix/store/fn7zvafq26f0c8b17brs7s95s10ibfzs-emacs-28.2.drv".to_string(),
];
let mut scanner = ReferenceScanner::new(candidates.clone());
scanner.scan(HELLO_DRV);
let result = scanner.finalise();
assert_eq!(result.len(), 3);
for c in candidates[..3].iter() {
assert!(result.contains(c));
}
}
}
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