rust: split "util" crate

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Link: https://lore.kernel.org/r/20250827104147.717203-7-marcandre.lureau@redhat.com
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 49 insertions, 0 deletions

diff --git a/rust/util/build.rs b/rust/util/build.rs
new file mode 100644
index 0000000000..5654d1d562
--- /dev/null
+++ b/rust/util/build.rs
@@ -0,0 +1,49 @@
+// Copyright 2024, Linaro Limited
+// Author(s): Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#[cfg(unix)]
+use std::os::unix::fs::symlink as symlink_file;
+#[cfg(windows)]
+use std::os::windows::fs::symlink_file;
+use std::{env, fs::remove_file, io::Result, path::Path};
+
+fn main() -> Result<()> {
+    let manifest_dir = env!("CARGO_MANIFEST_DIR");
+    let file = if let Ok(root) = env::var("MESON_BUILD_ROOT") {
+        let sub = get_rust_subdir(manifest_dir).unwrap();
+        format!("{root}/{sub}/bindings.inc.rs")
+    } else {
+        // Placing bindings.inc.rs in the source directory is supported
+        // but not documented or encouraged.
+        format!("{manifest_dir}/src/bindings.inc.rs")
+    };
+
+    let file = Path::new(&file);
+    if !Path::new(&file).exists() {
+        panic!(concat!(
+            "\n",
+            "    No generated C bindings found! Maybe you wanted one of\n",
+            "    `make clippy`, `make rustfmt`, `make rustdoc`?\n",
+            "\n",
+            "    For other uses of `cargo`, start a subshell with\n",
+            "    `pyvenv/bin/meson devenv`, or point MESON_BUILD_ROOT to\n",
+            "    the top of the build tree."
+        ));
+    }
+
+    let out_dir = env::var("OUT_DIR").unwrap();
+    let dest_path = format!("{out_dir}/bindings.inc.rs");
+    let dest_path = Path::new(&dest_path);
+    if dest_path.symlink_metadata().is_ok() {
+        remove_file(dest_path)?;
+    }
+    symlink_file(file, dest_path)?;
+
+    println!("cargo:rerun-if-changed=build.rs");
+    Ok(())
+}
+
+fn get_rust_subdir(path: &str) -> Option<&str> {
+    path.find("/rust").map(|index| &path[index + 1..])
+}