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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 find the derivation needed to actually trigger the
//! build, if necessary.
use nix_compat::{derivation::Derivation, nixhash::NixHash, store_path::StorePath};
use std::collections::HashMap;
/// Struct keeping track of all known Derivations in the current evaluation.
/// This keeps both the Derivation struct, as well as the "Hash derivation
/// modulo".
#[derive(Debug, Default)]
pub struct KnownPaths {
/// All known derivation or FOD hashes.
///
/// Keys are derivation paths, values are a tuple of the "hash derivation
/// modulo" and the Derivation struct itself.
derivations: HashMap<StorePath, (NixHash, Derivation)>,
/// A map from output path to (one) drv path.
/// Note that in the case of FODs, multiple drvs can produce the same output
/// path. We use one of them.
outputs_to_drvpath: HashMap<StorePath, StorePath>,
}
impl KnownPaths {
/// Fetch the opaque "hash derivation modulo" for a given derivation path.
pub fn get_hash_derivation_modulo(&self, drv_path: &StorePath) -> Option<&NixHash> {
self.derivations
.get(drv_path)
.map(|(hash_derivation_modulo, _derivation)| hash_derivation_modulo)
}
/// Return a reference to the Derivation for a given drv path.
pub fn get_drv_by_drvpath(&self, drv_path: &StorePath) -> Option<&Derivation> {
self.derivations
.get(drv_path)
.map(|(_hash_derivation_modulo, derivation)| derivation)
}
/// Return the drv path of the derivation producing the passed output path.
/// Note there can be multiple Derivations producing the same output path in
/// flight; this function will only return one of them.
pub fn get_drv_path_for_output_path(&self, output_path: &StorePath) -> Option<&StorePath> {
self.outputs_to_drvpath.get(output_path)
}
/// Insert a new Derivation into this struct.
/// The Derivation struct must pass validation, and its output paths need to
/// be fully calculated.
/// All input derivations this refers to must also be inserted to this
/// struct.
pub fn add(&mut self, drv_path: StorePath, drv: Derivation) {
// check input derivations to have been inserted.
#[cfg(debug_assertions)]
{
// TODO: b/264
// We assume derivations to be passed validated, so ignoring rest
// and expecting parsing is ok.
for input_drv_path_str in drv.input_derivations.keys() {
let (input_drv_path, _rest) =
StorePath::from_absolute_path_full(input_drv_path_str)
.expect("parse input drv path");
debug_assert!(self.derivations.contains_key(&input_drv_path));
}
}
// compute the hash derivation modulo
let hash_derivation_modulo = drv.derivation_or_fod_hash(|drv_path| {
self.get_hash_derivation_modulo(&drv_path.to_owned())
.unwrap_or_else(|| panic!("{} not found", drv_path))
.to_owned()
});
// For all output paths, update our lookup table.
// We only write into the lookup table once.
for output in drv.outputs.values() {
// We assume derivations to be passed validated, so ignoring rest
// and expecting parsing is ok.
// TODO: b/264
let (output_path, _rest) =
StorePath::from_absolute_path_full(&output.path).expect("parse output path");
self.outputs_to_drvpath
.entry(output_path)
.or_insert(drv_path.to_owned());
}
// insert the derivation itself
#[allow(unused_variables)] // assertions on this only compiled in debug builds
let old = self
.derivations
.insert(drv_path.to_owned(), (hash_derivation_modulo.clone(), drv));
#[cfg(debug_assertions)]
{
if let Some(old) = old {
debug_assert!(
old.0 == hash_derivation_modulo,
"hash derivation modulo for a given derivation should always be calculated the same"
);
}
}
}
}
|
