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Diffstat (limited to 'tvix/nix-compat/src/derivation/mod.rs')
| -rw-r--r-- | tvix/nix-compat/src/derivation/mod.rs | 264 |
1 files changed, 264 insertions, 0 deletions
diff --git a/tvix/nix-compat/src/derivation/mod.rs b/tvix/nix-compat/src/derivation/mod.rs new file mode 100644 index 000000000000..0e98e24f43dd --- /dev/null +++ b/tvix/nix-compat/src/derivation/mod.rs @@ -0,0 +1,264 @@ +use crate::store_path::{ + self, build_output_path, build_regular_ca_path, build_text_path, StorePath, +}; +use bstr::BString; +use serde::{Deserialize, Serialize}; +use sha2::{Digest, Sha256}; +use std::collections::{BTreeMap, BTreeSet}; +use std::io; + +mod errors; +mod escape; +mod output; +mod validate; +mod write; + +#[cfg(test)] +mod tests; + +// Public API of the crate. +pub use crate::nixhash::{NixHash, NixHashWithMode}; +pub use errors::{DerivationError, OutputError}; +pub use output::Output; + +#[derive(Clone, Debug, Default, Eq, PartialEq, Serialize, Deserialize)] +pub struct Derivation { + #[serde(rename = "args")] + pub arguments: Vec<String>, + + pub builder: String, + + #[serde(rename = "env")] + pub environment: BTreeMap<String, BString>, + + #[serde(rename = "inputDrvs")] + pub input_derivations: BTreeMap<String, BTreeSet<String>>, + + #[serde(rename = "inputSrcs")] + pub input_sources: BTreeSet<String>, + + pub outputs: BTreeMap<String, Output>, + + pub system: String, +} + +impl Derivation { + /// write the Derivation to the given [std::io::Write], in ATerm format. + /// + /// The only errors returns are these when writing to the passed writer. + pub fn serialize(&self, writer: &mut impl std::io::Write) -> Result<(), io::Error> { + use write::*; + + writer.write_all(write::DERIVATION_PREFIX.as_bytes())?; + write_char(writer, write::PAREN_OPEN)?; + + write_outputs(writer, &self.outputs)?; + write_char(writer, COMMA)?; + + write_input_derivations(writer, &self.input_derivations)?; + write_char(writer, COMMA)?; + + write_input_sources(writer, &self.input_sources)?; + write_char(writer, COMMA)?; + + write_system(writer, &self.system)?; + write_char(writer, COMMA)?; + + write_builder(writer, &self.builder)?; + write_char(writer, COMMA)?; + + write_arguments(writer, &self.arguments)?; + write_char(writer, COMMA)?; + + write_enviroment(writer, &self.environment)?; + + write_char(writer, PAREN_CLOSE)?; + + Ok(()) + } + + /// return the ATerm serialization. + pub fn to_aterm_bytes(&self) -> Vec<u8> { + let mut buffer: Vec<u8> = Vec::new(); + + // invoke serialize and write to the buffer. + // Note we only propagate errors writing to the writer in serialize, + // which won't panic for the string we write to. + self.serialize(&mut buffer).unwrap(); + + buffer + } + + /// Returns the drv path of a [Derivation] struct. + /// + /// The drv path is calculated by invoking [build_text_path], using + /// the `name` with a `.drv` suffix as name, all [Derivation::input_sources] and + /// keys of [Derivation::input_derivations] as references, and the ATerm string of + /// the [Derivation] as content. + pub fn calculate_derivation_path(&self, name: &str) -> Result<StorePath, DerivationError> { + // append .drv to the name + let name = &format!("{}.drv", name); + + // collect the list of paths from input_sources and input_derivations + // into a (sorted, guaranteed by BTreeSet) list of references + let references: BTreeSet<String> = { + let mut inputs = self.input_sources.clone(); + let input_derivation_keys: Vec<String> = + self.input_derivations.keys().cloned().collect(); + inputs.extend(input_derivation_keys); + inputs + }; + + build_text_path(name, self.to_aterm_bytes(), references) + .map_err(|_e| DerivationError::InvalidOutputName(name.to_string())) + } + + /// 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. + /// + /// It returns a [NixHash], created by calculating the sha256 digest of + /// the derivation ATerm representation, except that: + /// - any input derivation paths have beed replaced "by the result of a + /// recursive call to this function" and that + /// - for fixed-output derivations the special + /// `fixed:out:${algo}:${digest}:${fodPath}` string is hashed instead of + /// the A-Term. + /// + /// If the derivation is not a fixed derivation, it's up to the caller of + /// this function to provide a lookup function to lookup these calculation + /// results of parent derivations at `fn_get_hash_derivation_modulo` (by + /// drv path). + pub fn derivation_or_fod_hash<F>(&self, fn_get_derivation_or_fod_hash: F) -> NixHash + where + F: Fn(&str) -> NixHash, + { + // 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. + 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>> = + BTreeMap::new(); + + // For each input_derivation, look up the + // derivation_or_fod_hash, and replace the derivation path with it's HEXLOWER + // digest. + // 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), + output_names.clone(), + ); + } + + // construct a new derivation struct with these replaced input derivation strings + let replaced_derivation = Derivation { + input_derivations: replaced_input_derivations, + ..self.clone() + }; + + // write the ATerm of that to the hash function + let mut hasher = Sha256::new(); + hasher.update(replaced_derivation.to_aterm_bytes()); + + hasher.finalize().to_vec() + }); + + // We populate the struct directly, as we know the sha256 digest has the + // right size. + NixHash { + algo: crate::nixhash::HashAlgo::Sha256, + digest: digest.to_vec(), + } + } + + /// This calculates all output paths of a Derivation and updates the struct. + /// It requires the struct to be initially without output paths. + /// This means, self.outputs[$outputName].path needs to be an empty string, + /// and self.environment[$outputName] needs to be an empty string. + /// + /// Output path calculation requires knowledge of the + /// derivation_or_fod_hash [NixHash], which (in case of non-fixed-output + /// derivations) also requires knowledge of other hash_derivation_modulo + /// [NixHash]es. + /// + /// We solve this by asking the caller of this function to provide the + /// hash_derivation_modulo of the current Derivation. + /// + /// On completion, self.environment[$outputName] and + /// self.outputs[$outputName].path are set to the calculated output path for all + /// outputs. + pub fn calculate_output_paths( + &mut self, + name: &str, + derivation_or_fod_hash: &NixHash, + ) -> Result<(), DerivationError> { + // The fingerprint and hash differs per output + for (output_name, output) in self.outputs.iter_mut() { + // Assert that outputs are not yet populated, to avoid using this function wrongly. + // We don't also go over self.environment, but it's a sufficient + // footgun prevention mechanism. + assert!(output.path.is_empty()); + + let path_name = output_path_name(name, output_name); + + // For fixed output derivation we use the per-output info, otherwise we use the + // derivation hash. + let abs_store_path = if let Some(ref hwm) = output.hash_with_mode { + build_regular_ca_path(&path_name, hwm, Vec::<String>::new(), false).map_err( + |e| DerivationError::InvalidOutputDerivationPath(output_name.to_string(), e), + )? + } else { + build_output_path(derivation_or_fod_hash, output_name, &path_name).map_err(|e| { + DerivationError::InvalidOutputDerivationPath( + output_name.to_string(), + store_path::BuildStorePathError::InvalidStorePath(e), + ) + })? + }; + + output.path = abs_store_path.to_absolute_path(); + self.environment.insert( + output_name.to_string(), + abs_store_path.to_absolute_path().into(), + ); + } + + Ok(()) + } +} + +/// Calculate the name part of the store path of a derivation [Output]. +/// +/// It's the name, and (if it's the non-out output), the output name +/// after a `-`. +fn output_path_name(derivation_name: &str, output_name: &str) -> String { + let mut output_path_name = derivation_name.to_string(); + if output_name != "out" { + output_path_name.push('-'); + output_path_name.push_str(output_name); + } + output_path_name +} |