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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::STORE_PATH_LEN;
use nix_compat::nixhash::NixHash;
use std::collections::{BTreeSet, HashMap};
#[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,
}
/// 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())
}
}
impl From<String> for PathName {
fn from(s: String) -> Self {
s.as_str().into()
}
}
/// 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 derivation or FOD hashes.
///
/// Keys are derivation paths, values is the NixHash.
derivation_or_fod_hashes: HashMap<String, NixHash>,
}
impl KnownPaths {
/// Fetch the opaque "hash derivation modulo" for a given derivation path.
pub fn get_hash_derivation_modulo(&self, drv_path: &str) -> NixHash {
// TODO: we rely on an invariant that things *should* have
// been calculated if we get this far.
self.derivation_or_fod_hashes[drv_path].clone()
}
pub fn add_hash_derivation_modulo<D: ToString>(
&mut self,
drv: D,
hash_derivation_modulo: &NixHash,
) {
#[allow(unused_variables)] // assertions on this only compiled in debug builds
let old = self
.derivation_or_fod_hashes
.insert(drv.to_string(), hash_derivation_modulo.to_owned());
#[cfg(debug_assertions)]
{
if let Some(old) = old {
debug_assert!(
old == *hash_derivation_modulo,
"hash derivation modulo for a given derivation should always be calculated the same"
);
}
}
}
}
|
