build.rs

fn main() {
    println!("cargo:rerun-if-changed=vendor");

    #[cfg(all(feature = "fuse-overlayfs-vendored", target_os = "linux"))]
    {
        let d = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("vendor/fuse-overlayfs/");
        if !d.exists() {
            panic!("fuse-overlayfs submodule is not present fuse-overlayfs-vendored cannot be used")
        }
        const EXEC: &str = "fuse-overlayfs";
        let basedir = std::path::Path::new("./target/vendored");
        let outdir = basedir.join(EXEC);
        if !outdir.exists() {
            std::fs::create_dir_all(&outdir).unwrap()
        }
        let exec_path = outdir.join("bin").join(EXEC);
        let build = || {
            let srcdir = outdir.join("src");
            if !srcdir.exists() {
                std::fs::create_dir(&srcdir).unwrap();
            }
            fs_extra::dir::copy(
                &d,
                &srcdir,
                &fs_extra::dir::CopyOptions::new()
                    .overwrite(true)
                    .content_only(true),
            )
            .unwrap();
            autotools::Config::new(srcdir)
                .out_dir(std::fs::canonicalize(&outdir).expect("cannot canonicalize"))
                .reconf("-fis")
                .build()
        };
        #[cfg(feature = "build-cache")]
        if vendored::need_rebuild(&d, &outdir, vec![]) {
            build();
        }
        #[cfg(not(feature = "build-cache"))]
        build();
        println!(
            "cargo::rustc-env=FUSE-OVERLAYFS-BIN={}",
            &exec_path.to_string_lossy()
        );
    }

    #[cfg(all(feature = "unionfs-fuse-vendored", target_os = "linux"))]
    {
        let d = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("vendor/unionfs-fuse/");
        if !d.exists() {
            panic!("unionfs-fuse submodule is not present unionfs-fuse-vendored cannot be used")
        }

        const EXEC: &str = "unionfs";
        let outdir = std::path::Path::new("./target/vendored").join(EXEC);
        if !outdir.exists() {
            std::fs::create_dir_all(&outdir).unwrap()
        }
        let exec_path = outdir.join("build/src").join(EXEC);
        let build = || {
            cmake::Config::new(&d)
                .out_dir(std::fs::canonicalize(&outdir).expect("cannot canonicalize"))
                .very_verbose(false)
                .build();
        };
        #[cfg(feature = "build-cache")]
        if vendored::need_rebuild(&d, &outdir, vec![]) {
            build();
        }
        #[cfg(not(feature = "build-cache"))]
        build();
        println!(
            "cargo::rustc-env=UNIONFS-FUSE-BIN={}",
            &exec_path.to_string_lossy()
        );
    }
}

#[cfg(any(feature = "fuse-overlayfs-vendored", feature = "unionfs-fuse-vendored"))]
mod vendored {
    #[inline]
    #[allow(dead_code)]
    #[cfg(feature = "build-cache")]
    pub fn need_rebuild<P: AsRef<std::path::Path>, Q: AsRef<std::path::Path>>(
        src: P,
        out: Q,
        exception: Vec<String>,
    ) -> bool {
        use serde::{Deserialize, Serialize};

        #[derive(Serialize, Deserialize)]
        struct Cache {
            new_or_edited: Vec<(String, [u8; 16])>,
        }

        let cache_file = out.as_ref().join("cache.tag");
        let cache: Option<Cache> = std::fs::File::open(&cache_file)
            .ok()
            .map(std::io::BufReader::new)
            .and_then(|x| serde_json::from_reader(x).ok());

        let mut hashed = vec![];

        fn check_dir(
            hashed: &mut Vec<(String, [u8; 16])>,
            src: &std::path::Path,
            exception: &[String],
        ) {
            for entry in std::fs::read_dir(src).unwrap() {
                let entry = entry.unwrap();
                let path = entry.path();
                if entry.file_type().unwrap().is_dir() {
                    check_dir(hashed, &path, exception);
                    continue;
                }
                let path_str = path.to_string_lossy().to_string();
                if !exception.contains(&path_str) {
                    let buf = std::fs::read(src.join(&path_str)).unwrap();
                    let hash = md5::compute(&buf).0;
                    hashed.push((path_str, hash));
                }
            }
        }

        check_dir(&mut hashed, src.as_ref(), &exception);

        if !cache.is_some_and(|x| x.new_or_edited == hashed) {
            println!("Detected changes in vendored dependency. Updating cache.");

            let new_cache = Cache {
                new_or_edited: hashed,
            };
            std::fs::write(cache_file, serde_json::to_string(&new_cache).unwrap())
                .expect("Unable to write cache file");
            true
        } else {
            println!("No changes detected in vendored dependency.");
            false
        }
    }
}