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|
//! This module implements logic required for persisting known paths
//! during an evaluation.
//!
//! Tvix needs to be able to keep track of each Nix store path that it
//! knows about during the scope of a single evaluation and its
//! related builds.
//!
//! This data is required to scan derivation inputs for the build
//! references (the "build closure") that they make use of.
//!
//! Please see //tvix/eval/docs/build-references.md for more
//! information.
use crate::refscan::{ReferenceScanner, STORE_PATH_LEN};
use std::{
collections::{hash_map, BTreeSet, HashMap},
ops::Index,
};
#[derive(Debug, PartialEq)]
pub enum PathKind {
/// A literal derivation (`.drv`-file), and the *names* of its outputs.
Derivation { output_names: BTreeSet<String> },
/// An output of a derivation, its name, and the path of its derivation.
Output { name: String, derivation: String },
/// A plain store path (e.g. source files copied to the store).
Plain,
}
#[derive(Debug, PartialEq)]
pub struct KnownPath {
pub path: String,
pub kind: PathKind,
}
impl KnownPath {
fn new(path: String, kind: PathKind) -> Self {
KnownPath { path, kind }
}
}
/// Internal struct to prevent accidental leaks of the truncated path
/// names.
#[repr(transparent)]
#[derive(Clone, Debug, Default, PartialEq, PartialOrd, Ord, Eq, Hash)]
pub struct PathName(String);
impl From<&str> for PathName {
fn from(s: &str) -> Self {
PathName(s[..STORE_PATH_LEN].to_string())
}
}
/// This instance is required to pass PathName instances as needles to
/// the reference scanner.
impl AsRef<[u8]> for PathName {
fn as_ref(&self) -> &[u8] {
self.0.as_ref()
}
}
#[derive(Debug, Default)]
pub struct KnownPaths {
/// All known paths, keyed by a truncated version of their store
/// path used for reference scanning.
paths: HashMap<PathName, KnownPath>,
/// All known replacement strings for derivations.
///
/// Keys are derivation paths, values are the opaque replacement
/// strings.
replacements: HashMap<String, String>,
}
impl Index<&PathName> for KnownPaths {
type Output = KnownPath;
fn index(&self, index: &PathName) -> &Self::Output {
&self.paths[index]
}
}
impl KnownPaths {
fn insert_path(&mut self, path: String, path_kind: PathKind) {
match self.paths.entry(path.as_str().into()) {
hash_map::Entry::Vacant(entry) => {
entry.insert(KnownPath::new(path, path_kind));
}
hash_map::Entry::Occupied(mut entry) => {
match (path_kind, &mut entry.get_mut().kind) {
// These variant combinations require no "merging action".
(PathKind::Plain, PathKind::Plain) => (),
(PathKind::Output { .. }, PathKind::Output { .. }) => (),
(
PathKind::Derivation { output_names: new },
PathKind::Derivation {
output_names: ref mut old,
},
) => {
old.extend(new);
}
_ => panic!(
"path '{}' inserted twice with different types",
entry.key().0
),
};
}
};
}
/// Mark a plain path as known.
pub fn plain<S: ToString>(&mut self, path: S) {
self.insert_path(path.to_string(), PathKind::Plain);
}
/// Mark a derivation as known.
pub fn drv<P: ToString, O: ToString>(&mut self, path: P, outputs: &[O]) {
self.insert_path(
path.to_string(),
PathKind::Derivation {
output_names: outputs.iter().map(ToString::to_string).collect(),
},
);
}
/// Mark a derivation output path as known.
pub fn output<P: ToString, N: ToString, D: ToString>(
&mut self,
output_path: P,
name: N,
drv_path: D,
) {
self.insert_path(
output_path.to_string(),
PathKind::Output {
name: name.to_string(),
derivation: drv_path.to_string(),
},
);
}
/// Checks whether there are any known paths. If not, a reference
/// scanner can not be created.
pub fn is_empty(&self) -> bool {
self.paths.is_empty()
}
/// Create a reference scanner from the current set of known paths.
pub fn reference_scanner(&self) -> ReferenceScanner<PathName> {
let candidates = self.paths.keys().map(Clone::clone).collect();
ReferenceScanner::new(candidates)
}
/// Fetch the opaque "replacement string" for a given derivation path.
pub fn get_replacement_string(&self, drv: &str) -> String {
// TODO: we rely on an invariant that things *should* have
// been calculated if we get this far.
self.replacements[drv].clone()
}
pub fn add_replacement_string<D: ToString>(&mut self, drv: D, replacement_str: &str) {
let old = self
.replacements
.insert(drv.to_string(), replacement_str.to_owned());
#[cfg(debug_assertions)]
{
if let Some(old) = old {
debug_assert!(
old == replacement_str,
"replacement string for a given derivation should always match"
);
}
}
}
}
|
