diff options
Diffstat (limited to 'tvix/derivation/src/derivation.rs')
| -rw-r--r-- | tvix/derivation/src/derivation.rs | 24 |
1 files changed, 22 insertions, 2 deletions
diff --git a/tvix/derivation/src/derivation.rs b/tvix/derivation/src/derivation.rs index d937bd91a7fa..74e68ce1d7c5 100644 --- a/tvix/derivation/src/derivation.rs +++ b/tvix/derivation/src/derivation.rs @@ -1,6 +1,6 @@ use crate::output::{Hash, Output}; use crate::write; -use crate::{nix_hash, DerivationError}; +use crate::DerivationError; use serde::{Deserialize, Serialize}; use sha2::{Digest, Sha256}; use std::collections::BTreeSet; @@ -29,6 +29,26 @@ pub struct Derivation { pub system: String, } +/// compress_hash takes an arbitrarily long sequence of bytes (usually +/// a hash digest), and returns a sequence of bytes of length +/// output_size. +/// +/// It's calculated by rotating through the bytes in the output buffer +/// (zero- initialized), and XOR'ing with each byte of the passed +/// input. It consumes 1 byte at a time, and XOR's it with the current +/// value in the output buffer. +/// +/// This mimics equivalent functionality in C++ Nix. +fn compress_hash(input: &[u8], output_size: usize) -> Vec<u8> { + let mut output: Vec<u8> = vec![0; output_size]; + + for (ii, ch) in input.iter().enumerate() { + output[ii % output_size] ^= ch; + } + + output +} + /// 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( @@ -36,7 +56,7 @@ fn build_store_path( path_hash: &[u8], name: &str, ) -> Result<StorePath, DerivationError> { - let compressed = nix_hash::compress_hash(path_hash, 20); + let compressed = compress_hash(path_hash, 20); if is_derivation { StorePath::from_string( format!( |