diff options
Diffstat (limited to 'tvix/derivation/src/derivation.rs')
| -rw-r--r-- | tvix/derivation/src/derivation.rs | 171 |
1 files changed, 169 insertions, 2 deletions
diff --git a/tvix/derivation/src/derivation.rs b/tvix/derivation/src/derivation.rs index a9e769543e..2afe672e2e 100644 --- a/tvix/derivation/src/derivation.rs +++ b/tvix/derivation/src/derivation.rs @@ -1,9 +1,9 @@ use crate::nix_hash; -use crate::output::Output; +use crate::output::{Hash, Output}; use crate::write; use serde::{Deserialize, Serialize}; use sha2::{Digest, Sha256}; -use std::{collections::BTreeMap, fmt, fmt::Write, iter::FromIterator}; +use std::{collections::BTreeMap, fmt, fmt::Write}; use tvix_store::nixbase32::NIXBASE32; use tvix_store::nixpath::{NixPath, ParseNixPathError, STORE_DIR}; @@ -147,6 +147,173 @@ impl Derivation { build_store_path(true, &hasher.finalize(), name) } + + /// Calculate the drv replacement string for a given derivation. + /// + /// This is either called on a struct without output paths populated, + /// to provide the `drv_replacement_str` value for the `calculate_output_paths` + /// function call, or called on a struct with output paths populated, to + /// calculate / cache lookups for calls to fn_get_drv_replacement. + /// + /// `fn_get_drv_replacement` is used to look up the drv replacement strings + /// for input_derivations the Derivation refers to. + pub fn calculate_drv_replacement_str<F>(&self, fn_get_drv_replacement: F) -> String + where + F: Fn(&str) -> String, + { + let mut hasher = Sha256::new(); + let digest = match self.get_fixed_output() { + Some((fixed_output_path, fixed_output_hash)) => { + hasher.update("fixed:out:"); + hasher.update(&fixed_output_hash.algo); + hasher.update(":"); + hasher.update(&fixed_output_hash.digest); + hasher.update(":"); + hasher.update(fixed_output_path); + hasher.finalize() + } + None => { + let mut replaced_input_derivations: BTreeMap<String, Vec<String>> = BTreeMap::new(); + + // For each input_derivation, look up the replacement. + for (drv_path, input_derivation) in &self.input_derivations { + replaced_input_derivations.insert( + fn_get_drv_replacement(drv_path).to_string(), + input_derivation.to_vec(), + ); + } + + // 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 + hasher.update(replaced_derivation.to_string()); + + hasher.finalize() + } + }; + + format!("{:x}", digest) + } + + /// 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 "drv replacement + /// strings", and in case of non-fixed-output derivations, also knowledge + /// of "drv replacement" strings (recursively) of all input derivations. + /// + /// We solve this by asking the caller of this function to provide + /// the drv replacement string of the current derivation itself, + /// which is ran on the struct without output paths. + /// + /// This sound terribly ugly, but won't be too much of a concern later on, as + /// naming fixed-output paths once uploaded will be a tvix-store concern, + /// so there's no need to calculate them here anymore. + /// + /// 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, + drv_replacement_str: &str, + ) -> Result<(), ParseNixPathError> { + let mut hasher = Sha256::new(); + + // Check if the Derivation is fixed output, because they cause + // different fingerprints to be hashed. + match self.get_fixed_output() { + None => { + // 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()); + + hasher.update("output:"); + hasher.update(output_name); + hasher.update(":sha256:"); + hasher.update(drv_replacement_str); + hasher.update(":"); + hasher.update(tvix_store::nixpath::STORE_DIR); + hasher.update(":"); + + // calculate the output_name_path, which is the part of the NixPath after the digest. + let mut output_path_name = name.to_string(); + if output_name != "out" { + output_path_name.push('-'); + output_path_name.push_str(output_name); + } + + hasher.update(output_path_name.as_str()); + + let digest = hasher.finalize_reset(); + + let abs_store_path = format!( + "{}/{}", + tvix_store::nixpath::STORE_DIR, + build_store_path(false, &digest, &output_path_name)? + ); + + output.path = abs_store_path.clone(); + self.environment + .insert(output_name.to_string(), abs_store_path); + } + } + Some((fixed_output_path, fixed_output_hash)) => { + // 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!(fixed_output_path.is_empty()); + + let digest = { + // Fixed-output derivation. + // There's two different hashing strategies in place, depending on the value of hash.algo. + // This code is _weird_ but it is what Nix is doing. See: + // https://github.com/NixOS/nix/blob/1385b2007804c8a0370f2a6555045a00e34b07c7/src/libstore/store-api.cc#L178-L196 + if fixed_output_hash.algo == "r:sha256" { + hasher.update("source:"); + hasher.update("sha256"); + hasher.update(":"); + hasher.update(fixed_output_hash.digest.clone()); // nixbase32 + } else { + hasher.update("output:out:sha256:"); + // This is drv_replacement for FOD, with an empty fixed_output_path. + hasher.update(drv_replacement_str); + } + hasher.update(":"); + hasher.update(tvix_store::nixpath::STORE_DIR); + hasher.update(":"); + hasher.update(name); + hasher.finalize() + }; + + let abs_store_path = format!( + "{}/{}", + tvix_store::nixpath::STORE_DIR, + build_store_path(false, &digest, name)? + ); + + self.outputs.insert( + "out".to_string(), + Output { + path: abs_store_path.clone(), + hash: Some(fixed_output_hash.clone()), + }, + ); + self.environment.insert("out".to_string(), abs_store_path); + } + }; + + Ok(()) + } } impl fmt::Display for Derivation { |