OXYGENHUB
# e38bb032e38b oxygenflow / crates / flow / src / cpio.rs
1.7 KiB · Rust · last changed OxygenFlow M0: pipeline parser and canonical job graph, receipts, the runner API types, flow-init, the Firecracker tier, flow check, run, rootfs import and runner 1 month ago source blame history raw
e0918b88 Andy McCall 1 
//! A minimal `newc` cpio writer for the per-job initramfs: regular files
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//! at the archive root, owned by root.
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pub struct Entry<'a> {
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    pub name: &'a str,
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    pub mode: u32,
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    pub data: &'a [u8],
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}
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fn header(out: &mut Vec<u8>, ino: u32, mode: u32, size: usize, name: &str) {
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    let fields = [ino, mode, 0, 0, 1, 0, size as u32, 0, 0, 0, 0, (name.len() + 1) as u32, 0];
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    out.extend_from_slice(b"070701");
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    for f in fields {
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        out.extend_from_slice(format!("{f:08X}").as_bytes());
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    }
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    out.extend_from_slice(name.as_bytes());
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    out.push(0);
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    pad(out);
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}
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fn pad(out: &mut Vec<u8>) {
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    while !out.len().is_multiple_of(4) {
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        out.push(0);
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    }
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}
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pub fn newc(entries: &[Entry]) -> Vec<u8> {
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    let mut out = Vec::new();
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    for (i, e) in entries.iter().enumerate() {
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        header(&mut out, i as u32 + 1, 0o100000 | e.mode, e.data.len(), e.name);
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        out.extend_from_slice(e.data);
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        pad(&mut out);
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    }
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    header(&mut out, 0, 0, 0, "TRAILER!!!");
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    out
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}
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#[cfg(test)]
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mod tests {
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    use super::*;
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    #[test]
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    fn system_cpio_reads_it() {
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        let dir = tempfile::tempdir().unwrap();
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        let archive = newc(&[Entry { name: "init", mode: 0o755, data: b"#!x\n" }, Entry { name: "job.json", mode: 0o644, data: b"{}" }]);
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        std::fs::write(dir.path().join("a.cpio"), &archive).unwrap();
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        let listed = std::process::Command::new("cpio").args(["-it", "--quiet", "-F"]).arg(dir.path().join("a.cpio")).output();
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        if let Ok(o) = listed {
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            if o.status.success() {
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                assert_eq!(String::from_utf8_lossy(&o.stdout), "init\njob.json\n");
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            }
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        }
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        assert!(archive.len().is_multiple_of(4));
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        assert!(archive.windows(10).any(|w| w == b"TRAILER!!!"));
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    }
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}