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refactor(tvix/nix-compat): remove get_fixed_output() func

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The behaviour of this function is a bit unintuitive, and cl/8310 already
inlined the other consumer of it.

Rewrite the last consumer of the function, so we can drop it.

Change-Id: I59c8486037ce3f777667d1d9e4f4a9316d5a0cb9
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8311
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
This commit is contained in:
Florian Klink 2023-03-15 12:42:09 +01:00 committed by flokli
parent 09b30f895a
commit def2d32319
1 changed files with 52 additions and 66 deletions
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72
tvix/nix-compat/src/derivation/mod.rs
View file

@ -76,24 +76,6 @@ impl Derivation {
buffer
}
/// Returns the fixed output path and its [NixHashWithMode]
/// (if the Derivation is fixed output), or None if there is no fixed output.
/// This takes some shortcuts in case more than one output exists, as this
/// can't be a valid fixed-output Derivation.
pub fn get_fixed_output(&self) -> Option<(&String, &NixHashWithMode)> {
if self.outputs.len() != 1 {
return None;
}
if let Some(out_output) = self.outputs.get("out") {
if let Some(out_output_hash) = &out_output.hash_with_mode {
return Some((&out_output.path, out_output_hash));
}
// There has to be a hash, otherwise it would not be FOD
}
None
}
/// Returns the drv path of a Derivation struct.
///
/// The drv path is calculated like this:
@ -130,17 +112,13 @@ impl Derivation {
// calculate the sha256 hash of the ATerm representation, and represent
// it as a hex-encoded string (prefixed with sha256:).
let aterm_digest = {
let mut derivation_hasher = Sha256::new();
derivation_hasher.update(self.to_aterm_string());
derivation_hasher.finalize()
};
let h = NixHash::new(crate::nixhash::HashAlgo::Sha256, aterm_digest.to_vec());
let aterm_digest = Sha256::new_with_prefix(self.to_aterm_string())
.finalize()
.to_vec();
s.push_str(&format!(
"{}:{}:{}.drv",
h.to_nix_hash_string(),
NixHash::new(HashAlgo::Sha256, aterm_digest).to_nix_hash_string(),
store_path::STORE_DIR,
name,
));
@ -148,6 +126,25 @@ impl Derivation {
utils::build_store_path(true, &s, name)
}
/// Returns the FOD digest, if the derivation is fixed-output, or None if
/// it's not.
fn fod_digest(&self) -> Option<Vec<u8>> {
if self.outputs.len() != 1 {
return None;
}
let out_output = self.outputs.get("out")?;
Some(
Sha256::new_with_prefix(format!(
"fixed:out:{}:{}",
out_output.hash_with_mode.clone()?.to_nix_hash_string(),
out_output.path
))
.finalize()
.to_vec(),
)
}
/// Calculates the hash of a derivation modulo fixed-output subderivations.
///
/// This is called `hashDerivationModulo` in nixcpp.
@ -168,21 +165,11 @@ impl Derivation {
where
F: Fn(&str) -> NixHash,
{
let mut hasher = Sha256::new();
let digest = match self.get_fixed_output() {
// Fixed-output derivations return a fixed hash
Some((fixed_output_path, fixed_output_hash)) => {
hasher.update(format!(
"fixed:out:{}:{}",
fixed_output_hash.to_nix_hash_string(),
fixed_output_path
));
hasher.finalize()
}
// Fixed-output derivations return a fixed hash.
// Non-Fixed-output derivations return a hash of the ATerm notation, but with all
// input_derivation paths replaced by a recursive call to this function.
// We use fn_get_derivation_or_fod_hash here, so callers can precompute this.
None => {
let digest = self.fod_digest().unwrap_or({
// This is a new map from derivation_or_fod_hash.digest (as lowerhex)
// to list of output names
let mut replaced_input_derivations: BTreeMap<String, BTreeSet<String>> =
@ -194,8 +181,7 @@ impl Derivation {
// This is not the [NixHash::to_nix_hash_string], but without the sha256: prefix).
for (drv_path, output_names) in &self.input_derivations {
replaced_input_derivations.insert(
data_encoding::HEXLOWER
.encode(&fn_get_derivation_or_fod_hash(drv_path).digest),
data_encoding::HEXLOWER.encode(&fn_get_derivation_or_fod_hash(drv_path).digest),
output_names.clone(),
);
}
@ -207,11 +193,11 @@ impl Derivation {
};
// write the ATerm of that to the hash function
let mut hasher = Sha256::new();
hasher.update(replaced_derivation.to_aterm_string());
hasher.finalize()
}
};
hasher.finalize().to_vec()
});
NixHash::new(crate::nixhash::HashAlgo::Sha256, digest.to_vec())
}