refactor(tvix/nix-compat): Inline `texthash` mod r/6067

It is moved into `store_path::utils` with the other path builders.

Change-Id: I3257170e442af5d83bcf79e63fa7387dd914597c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8410
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

1 files changed, 40 insertions, 1 deletions

diff --git a/tvix/nix-compat/src/store_path/utils.rs b/tvix/nix-compat/src/store_path/utils.rs
index 0d96414a212d..449117717260 100644
--- a/tvix/nix-compat/src/store_path/utils.rs
+++ b/tvix/nix-compat/src/store_path/utils.rs
@@ -1,6 +1,6 @@
 use crate::nixbase32;
+use crate::nixhash::NixHash;
 use crate::store_path::StorePath;
-use crate::texthash::text_hash_string;
 use sha2::{Digest, Sha256};
 
 use super::Error;
@@ -60,6 +60,45 @@ pub fn build_store_path_from_fingerprint(
     StorePath::from_string(format!("{}-{}", nixbase32::encode(&compressed), name).as_str())
 }
 
+/// This contains the Nix logic to create "text hash strings", which are used
+/// in `builtins.toFile`, as well as in Derivation Path calculation.
+///
+/// A text hash is calculated by concatenating the following fields, separated by a `:`:
+///
+///  - text
+///  - references, individually joined by `:`
+///  - the nix_hash_string representation of the sha256 digest of some contents
+///  - the value of `storeDir`
+///  - the name
+pub fn text_hash_string<S: AsRef<str>, I: IntoIterator<Item = S>, C: AsRef<[u8]>>(
+    name: &str,
+    content: C,
+    references: I,
+) -> String {
+    let mut s = String::from("text:");
+
+    for reference in references {
+        s.push_str(reference.as_ref());
+        s.push(':');
+    }
+
+    // the nix_hash_string representation of the sha256 digest of some contents
+    s.push_str(
+        &{
+            let content_digest = {
+                let hasher = Sha256::new_with_prefix(content);
+                hasher.finalize()
+            };
+            NixHash::new(crate::nixhash::HashAlgo::Sha256, content_digest.to_vec())
+        }
+        .to_nix_hash_string(),
+    );
+
+    s.push_str(&format!(":{}:{}", crate::store_path::STORE_DIR, name));
+
+    s
+}
+
 /// Nix placeholders (i.e. values returned by `builtins.placeholder`)
 /// are used to populate outputs with paths that must be
 /// string-replaced with the actual placeholders later, at runtime.