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use crate::nix_hash;
use crate::output::Output;
use crate::write;
use serde::{Deserialize, Serialize};
use sha2::{Digest, Sha256};
use std::{collections::BTreeMap, fmt, fmt::Write, iter::FromIterator};
use tvix_store::nixbase32::NIXBASE32;
use tvix_store::nixpath::{NixPath, ParseNixPathError, STORE_DIR};
#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
pub struct Derivation {
#[serde(rename = "args")]
pub arguments: Vec<String>,
pub builder: String,
#[serde(rename = "env")]
pub environment: BTreeMap<String, String>,
#[serde(rename = "inputDrvs")]
pub input_derivations: BTreeMap<String, Vec<String>>,
#[serde(rename = "inputSrcs")]
pub input_sources: Vec<String>,
pub outputs: BTreeMap<String, Output>,
pub system: String,
}
/// This returns a store path, either of a derivation or a regular output.
/// The path_hash is compressed to 20 bytes, and nixbase32-encoded (32 characters)
fn build_store_path(
is_derivation: bool,
path_hash: &[u8],
name: &str,
) -> Result<NixPath, ParseNixPathError> {
let compressed = nix_hash::compress_hash(path_hash, 20);
if is_derivation {
NixPath::from_string(
format!(
"{}-{}{}",
NIXBASE32.encode(&compressed),
name,
write::DOT_FILE_EXT,
)
.as_str(),
)
} else {
NixPath::from_string(format!("{}-{}", NIXBASE32.encode(&compressed), name,).as_str())
}
}
impl Derivation {
pub fn serialize(&self, writer: &mut impl Write) -> Result<(), fmt::Error> {
writer.write_str(write::DERIVATION_PREFIX)?;
writer.write_char(write::PAREN_OPEN)?;
write::write_outputs(writer, &self.outputs)?;
write::write_input_derivations(writer, &self.input_derivations)?;
write::write_input_sources(writer, &self.input_sources)?;
write::write_system(writer, &self.system)?;
write::write_builder(writer, &self.builder)?;
write::write_arguments(writer, &self.arguments)?;
write::write_enviroment(writer, &self.environment)?;
writer.write_char(write::PAREN_CLOSE)?;
Ok(())
}
/// Returns the drv path of a Derivation struct.
///
/// The drv path is calculated like this:
/// - Write the fingerprint of the Derivation to the sha256 hash function.
/// This is: `text:`,
/// all d.InputDerivations and d.InputSources (sorted, separated by a `:`),
/// a `:`,
/// a `sha256:`, followed by the sha256 digest of the ATerm representation (hex-encoded)
/// a `:`,
/// the storeDir, followed by a `:`,
/// the name of a derivation,
/// a `.drv`.
/// - Write the .drv A-Term contents to a hash function
/// - Take the digest, run hash.CompressHash(digest, 20) on it.
/// - Encode it with nixbase32
/// - Use it (and the name) to construct a NixPath.
pub fn calculate_derivation_path(&self, name: &str) -> Result<NixPath, ParseNixPathError> {
let mut hasher = Sha256::new();
// collect the list of paths from input_sources and input_derivations
// into a sorted list, and join them by :
hasher.update(write::TEXT_COLON);
let concat_inputs: Vec<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.sort();
inputs
};
for input in concat_inputs {
hasher.update(input);
hasher.update(write::COLON);
}
// calculate the sha256 hash of the ATerm representation, and represent
// it as a hex-encoded string (prefixed with sha256:).
hasher.update(write::SHA256_COLON);
let digest = {
let mut derivation_hasher = Sha256::new();
derivation_hasher.update(self.to_string());
derivation_hasher.finalize()
};
hasher.update(format!("{:x}", digest));
hasher.update(write::COLON);
hasher.update(STORE_DIR);
hasher.update(write::COLON);
hasher.update(name);
hasher.update(write::DOT_FILE_EXT);
build_store_path(true, &hasher.finalize(), name)
}
}
impl fmt::Display for Derivation {
/// Formats the Derivation in ATerm representation.
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.serialize(f)
}
}
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