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authorJürgen Hahn <mail.jhahn@gmail.com>2023-01-02T15·09+0100
committerjrhahn <mail.jhahn@gmail.com>2023-01-04T12·24+0000
commit6f993b8bde8201213fe2953ea663ac387de916e3 (patch)
treef82cd8094172c18a5eb0601f278fa4205e48344c /tvix/derivation/src/nix_hash.rs
parent79c05f38109d2eac07b9ba893b9b6f67fd34c29c (diff)
feat(tvix/derivation): add nix drv path generation to Derivation r/5580
This adds a function to generate the derivation path. The computation
is based on the Go implementation.

Change-Id: Iae89db4976f5fd9208f0453f73688689a245cd66
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7729
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Diffstat (limited to 'tvix/derivation/src/nix_hash.rs')
-rw-r--r--tvix/derivation/src/nix_hash.rs15
1 files changed, 15 insertions, 0 deletions
diff --git a/tvix/derivation/src/nix_hash.rs b/tvix/derivation/src/nix_hash.rs
new file mode 100644
index 000000000000..a49d444faa53
--- /dev/null
+++ b/tvix/derivation/src/nix_hash.rs
@@ -0,0 +1,15 @@
+/// CompressHash takes an arbitrary 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.
+pub 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
+}