Add zerocopy instance to raw bindings struct

This will come in handy later, when we integrate harmonia. It is a very
stable thing to do.

Cargo.lock

@@ -316,6 +316,7 @@ dependencies = [
  "bindgen",
  "nix-bindings-util-sys",
  "pkg-config",
+ "zerocopy",
 ]
 
 [[package]]
@@ -611,3 +612,23 @@ name = "wit-bindgen"
 version = "0.46.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f17a85883d4e6d00e8a97c586de764dabcc06133f7f1d55dce5cdc070ad7fe59"
+
+[[package]]
+name = "zerocopy"
+version = "0.8.30"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4ea879c944afe8a2b25fef16bb4ba234f47c694565e97383b36f3a878219065c"
+dependencies = [
+ "zerocopy-derive",
+]
+
+[[package]]
+name = "zerocopy-derive"
+version = "0.8.30"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cf955aa904d6040f70dc8e9384444cb1030aed272ba3cb09bbc4ab9e7c1f34f5"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]

nix-bindings-store-sys/Cargo.toml

@@ -13,6 +13,7 @@ path = "src/lib.rs"
 
 [dependencies]
 nix-bindings-util-sys = { path = "../nix-bindings-util-sys", version = "0.2.1" }
+zerocopy = { version = "0.8", features = ["derive"] }
 
 [build-dependencies]
 bindgen = "0.69"

nix-bindings-store-sys/build.rs

@@ -9,6 +9,22 @@ impl bindgen::callbacks::ParseCallbacks for StripNixPrefix {
     }
 }
 
+#[derive(Debug)]
+struct AddZerocopyDerives {}
+impl bindgen::callbacks::ParseCallbacks for AddZerocopyDerives {
+    fn add_derives(&self, info: &bindgen::callbacks::DeriveInfo<'_>) -> Vec<String> {
+        if info.name == "store_path_hash_part" {
+            vec![
+                "zerocopy::FromBytes".to_string(),
+                "zerocopy::IntoBytes".to_string(),
+                "zerocopy::Immutable".to_string(),
+            ]
+        } else {
+            vec![]
+        }
+    }
+}
+
 fn main() {
     println!("cargo:rerun-if-changed=include/nix-c-store.h");
     println!("cargo:rustc-link-lib=nixstorec");
@@ -29,6 +45,7 @@ fn main() {
         .clang_args(args)
         .parse_callbacks(Box::new(bindgen::CargoCallbacks::new()))
         .parse_callbacks(Box::new(StripNixPrefix))
+        .parse_callbacks(Box::new(AddZerocopyDerives {}))
         // Blocklist symbols from nix-bindings-util-sys
         .blocklist_file(".*nix_api_util\\.h")
         .generate()