build(cargo): Add cbindgen support via build.rs

rekordcrate-ffi/Cargo.toml

@@ -14,5 +14,8 @@ exclude = [".*"]
 [dependencies]
 rekordcrate = { version = "0.1.1", path = "../rekordcrate" }
 
+[build-dependencies]
+cbindgen = "0.24.3"
+
 [lib]
 crate_type = ["cdylib"]

rekordcrate-ffi/build.rs

@@ -0,0 +1,36 @@
+// Copyright (c) 2022 Jan Holthuis <[email protected]>
+//
+// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy
+// of the MPL was not distributed with this file, You can obtain one at
+// http://mozilla.org/MPL/2.0/.
+//
+// SPDX-License-Identifier: MPL-2.0
+
+use std::env;
+use std::path::PathBuf;
+
+fn main() {
+    let crate_dir = env::var("CARGO_MANIFEST_DIR").unwrap();
+    let output_file = target_dir()
+        .join("include")
+        .join("rekordcrate.h")
+        .display()
+        .to_string();
+
+    cbindgen::Builder::new()
+        .with_crate(crate_dir)
+        .generate()
+        .expect("Unable to generate bindings")
+        .write_to_file(&output_file);
+}
+
+/// Find the location of the `target/` directory. Note that this may be
+/// overridden by `cmake`, so we also need to check the `CARGO_TARGET_DIR`
+/// variable.
+fn target_dir() -> PathBuf {
+    if let Ok(target) = env::var("CARGO_TARGET_DIR") {
+        PathBuf::from(target)
+    } else {
+        PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap()).join("target")
+    }
+}