stuffr_cli/compat/

mod.rs

//! Compatibility links: when the binary is invoked under another tool's name
//! (through a symlink), it behaves as that tool, with that tool's flags,
//! messages and exit codes, not stuffr's.

use std::collections::BTreeMap;
use std::ffi::{OsStr, OsString};
use std::io::{self, IsTerminal};
use std::path::{Path, PathBuf};
use std::process::ExitCode;

pub mod bzip2;
pub mod bzip2recover;
pub mod compress;
pub mod gzip;
mod host;
pub mod links;
pub mod lz4;
pub mod unzip;
pub mod xz;
pub mod zstd;

#[cfg(test)]
pub(crate) use host::ARM_TEST_LOCK;
#[doc(hidden)]
pub use host::InputReads;
/// The whole-run signal hook `stuffr bench` registers (kill its memory
/// child, clear its bar) before the shared cleanup handler re-raises.
#[cfg(unix)]
pub(crate) use host::hook_run_signals;
/// The armed-temporary entry point `stuffr bench` shares with the families.
pub(crate) use host::{CleanupGuard, create_armed, with_run_signals_held};
#[cfg(all(test, unix))]
pub(crate) use host::{armed_path, disarm_inherited};

/// What [`run_in_counted`] returns: the exit code, standard output,
/// standard error, and the inputs opened with what was read from each.
#[doc(hidden)]
pub type CountedRun = (i32, Vec<u8>, Vec<u8>, BTreeMap<PathBuf, InputReads>);

/// A family of tools the binary can impersonate.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[non_exhaustive]
pub enum Family {
    /// `bzip2`, `bunzip2`, `bzcat`.
    Bzip2,
    /// `gzip`, `gunzip`, `zcat`, `gzcat`, in the flavour
    /// [`gzip::default_flavour`] or `STUFFR_GZIP_FLAVOR` picks.
    Gzip,
    /// `xz`, `unxz`, `xzcat`, `lzma`, `unlzma`, `lzcat`.
    Xz,
    /// `zstd`, `unzstd`, `zstdcat`, `zstdmt`.
    Zstd,
    /// `lz4`, `unlz4`, `lz4cat`, `lz4c`.
    Lz4,
    /// `unzip`, `zipinfo`, `funzip`, in the flavour
    /// [`unzip::default_flavour`] or `STUFFR_UNZIP_FLAVOR` picks.
    Unzip,
    /// `compress`, `uncompress`, in the flavour
    /// [`compress::default_flavour`] or `STUFFR_COMPRESS_FLAVOR` picks.
    Compress,
}

/// Invoked name to family. The name is matched exactly, after the directory
/// is stripped.
const NAMES: &[(&str, Family)] = &[
    ("bzip2", Family::Bzip2),
    ("bunzip2", Family::Bzip2),
    ("bzcat", Family::Bzip2),
    ("bzip2recover", Family::Bzip2),
    ("gzip", Family::Gzip),
    ("gunzip", Family::Gzip),
    ("zcat", Family::Gzip),
    ("gzcat", Family::Gzip),
    ("xz", Family::Xz),
    ("unxz", Family::Xz),
    ("xzcat", Family::Xz),
    ("lzma", Family::Xz),
    ("unlzma", Family::Xz),
    ("lzcat", Family::Xz),
    ("zstd", Family::Zstd),
    ("unzstd", Family::Zstd),
    ("zstdcat", Family::Zstd),
    ("zstdmt", Family::Zstd),
    ("lz4", Family::Lz4),
    ("unlz4", Family::Lz4),
    ("lz4cat", Family::Lz4),
    ("lz4c", Family::Lz4),
    ("unzip", Family::Unzip),
    ("zipinfo", Family::Unzip),
    ("funzip", Family::Unzip),
    ("compress", Family::Compress),
    ("uncompress", Family::Compress),
];

/// Every compatibility name, from the one table `family_for` also reads.
pub fn names() -> &'static [&'static str] {
    static LIST: std::sync::OnceLock<Vec<&'static str>> = std::sync::OnceLock::new();
    LIST.get_or_init(|| NAMES.iter().map(|&(n, _)| n).collect())
}

/// The family and canonical name for an `argv[0]`, or `None` when it is not a
/// compatibility name. Only the final path component counts, and on Windows a
/// trailing `.exe` is ignored.
pub fn family_for(argv0: &OsStr) -> Option<(Family, &'static str)> {
    let file = Path::new(argv0).file_name()?;
    let file = file.to_str()?;
    #[cfg(windows)]
    let file = file.strip_suffix(".exe").unwrap_or(file);
    NAMES
        .iter()
        .find(|(n, _)| *n == file)
        .map(|&(n, fam)| (fam, n))
}

/// Run the compatibility tool `args[0]` names, or return `None` when it names
/// none (the caller then behaves as `stuffr`). The tool gets the arguments
/// after `args[0]`; `bzip2recover`, which prints its `argv[0]` verbatim,
/// gets `args[0]` as well.
pub fn dispatch(args: Vec<OsString>) -> Option<ExitCode> {
    // The interrupt integration test's helper (`host::signal_test`), in
    // debug builds only.
    #[cfg(all(unix, debug_assertions))]
    if Path::new(args.first()?).file_name() == Some(OsStr::new("__compat-signal-test")) {
        return Some(host::signal_test(&args[1..]));
    }
    let (family, name) = family_for(args.first()?)?;
    let mut args = args.into_iter();
    let argv0 = args.next().unwrap_or_default();
    let rest = args.collect();
    Some(match family {
        // bzip2recover prints its argv[0] in full, so it gets it.
        Family::Bzip2 if name == "bzip2recover" => bzip2recover::run(argv0, rest),
        Family::Bzip2 => bzip2::run(name, rest),
        Family::Gzip => gzip::run(name, rest),
        Family::Xz => xz::run(name, &argv0, rest),
        Family::Zstd => zstd::run(name, &argv0, rest),
        Family::Lz4 => lz4::run(name, &argv0, rest),
        Family::Unzip => unzip::run(name, &argv0, rest),
        Family::Compress => compress::run(name, rest),
    })
}

/// Run the compatibility tool `name` names in-process, without touching the
/// process: operands resolve against `dir`, `stdin` stands in for standard
/// input, and the exit code, standard output and standard error come back.
/// Neither stream is a terminal, the environment is not read and `SIGPIPE`
/// keeps its disposition. `None` when `name` is not a compatibility name.
/// The gzip family runs as `gzip_flavour` (the environment's
/// `STUFFR_GZIP_FLAVOR` is not read); the other families ignore it. The
/// unzip and compress families run as [`unzip::default_flavour`] and
/// [`compress::default_flavour`] here; pick theirs with [`run_in_counted`].
/// Same code as [`dispatch`] below the process boundary; for the fuzz
/// target, not a stable interface.
#[doc(hidden)]
pub fn run_in(
    dir: &Path,
    name: &str,
    args: Vec<OsString>,
    stdin: &[u8],
    gzip_flavour: gzip::Flavour,
) -> Option<(i32, Vec<u8>, Vec<u8>)> {
    run_in_counted(
        dir,
        name,
        args,
        stdin,
        gzip_flavour,
        unzip::default_flavour(),
        compress::default_flavour(),
    )
    .map(|(code, out, err, _)| (code, out, err))
}

/// [`run_in`], also returning the inputs the run opened and what it read
/// from each, by path. Only the gzip family counts its inputs; the map is
/// empty for the others. The xz family runs with a fixed machine and a
/// capped decoder memory limit ([`xz::run_in_counted`]), the zstd family
/// with a fixed machine and R9's bounds ([`zstd::run_in_counted`]), and
/// the lz4 family with a fixed machine ([`lz4::run_in_counted`]). The unzip
/// family runs as `unzip_flavour` (R7; `STUFFR_UNZIP_FLAVOR` is not read),
/// as [`unzip::run_in_counted`] describes, and the compress family as
/// `compress_flavour` (`STUFFR_COMPRESS_FLAVOR` is not read), counting its
/// inputs ([`compress::run_in_counted`]).
#[doc(hidden)]
pub fn run_in_counted(
    dir: &Path,
    name: &str,
    args: Vec<OsString>,
    stdin: &[u8],
    gzip_flavour: gzip::Flavour,
    unzip_flavour: unzip::Flavour,
    compress_flavour: compress::Flavour,
) -> Option<CountedRun> {
    let (family, canonical) = family_for(OsStr::new(name))?;
    Some(match family {
        Family::Bzip2 if canonical == "bzip2recover" => {
            let (code, err) = bzip2recover::run_in(dir, name.as_bytes(), &args);
            (code, Vec::new(), err, BTreeMap::new())
        }
        Family::Bzip2 => {
            let (code, out, err) = bzip2::run_in(dir, canonical, &args, stdin);
            (code, out, err, BTreeMap::new())
        }
        Family::Gzip => gzip::run_in_counted(gzip_flavour, dir, canonical, &args, stdin, &|_| None),
        Family::Xz => xz::run_in_counted(dir, canonical, &args, stdin, &|_| None),
        Family::Zstd => zstd::run_in_counted(dir, canonical, &args, stdin, &|_| None),
        Family::Lz4 => lz4::run_in_counted(dir, canonical, &args, stdin, &|_| None),
        Family::Unzip => {
            unzip::run_in_counted(unzip_flavour, dir, canonical, &args, stdin, &|_| None)
        }
        Family::Compress => {
            compress::run_in_counted(compress_flavour, dir, canonical, &args, stdin, &|_| None)
        }
    })
}

/// Whether stdin is a terminal.
pub(crate) fn stdin_is_tty() -> bool {
    io::stdin().is_terminal()
}

/// Whether stdout is a terminal.
pub(crate) fn stdout_is_tty() -> bool {
    io::stdout().is_terminal()
}

/// Copy the access and modification times, permission bits and (where
/// permitted) owner in `meta` onto `to`. A refused `chown` (`EPERM`) is
/// ignored, as the reference tools do; every other failure is returned.
///
/// Takes metadata rather than a path because bzip2 saves its input's
/// metadata before reading it, so the access time it copies is the one from
/// before the read. `to` is opened for writing to set the times, so call
/// this before restricting `to`'s permissions any further.
pub(crate) fn copy_metadata_from(meta: &std::fs::Metadata, to: &Path) -> io::Result<()> {
    copy_metadata_with_mtime(meta, to, None)
}

/// [`copy_metadata_from`], with `mtime` as the modification time instead of
/// `meta`'s when given (a gzip header's stored time, under `gunzip -N`).
pub(crate) fn copy_metadata_with_mtime(
    meta: &std::fs::Metadata,
    to: &Path,
    mtime: Option<std::time::SystemTime>,
) -> io::Result<()> {
    let mut times = std::fs::FileTimes::new();
    if let Ok(t) = meta.accessed() {
        times = times.set_accessed(t);
    }
    if let Some(t) = mtime.or_else(|| meta.modified().ok()) {
        times = times.set_modified(t);
    }
    std::fs::File::options()
        .write(true)
        .open(to)?
        .set_times(times)?;
    #[cfg(unix)]
    {
        use std::os::unix::fs::MetadataExt;
        match std::os::unix::fs::chown(to, Some(meta.uid()), Some(meta.gid())) {
            Err(e) if e.kind() != io::ErrorKind::PermissionDenied => return Err(e),
            _ => {}
        }
    }
    // After `chown`, which may clear set-id bits.
    std::fs::set_permissions(to, meta.permissions())
}

#[cfg(test)]
mod tests {
    use super::*;

    /// The gzip flavour `run_in` gets; the bzip2 family ignores it.
    const G: gzip::Flavour = gzip::Flavour::Gnu;

    /// The unzip flavour `run_in_counted` gets; the other families ignore
    /// it.
    const U: unzip::Flavour = unzip::Flavour::Apple;

    /// The compress flavour `run_in_counted` gets; the other families
    /// ignore it.
    const C: compress::Flavour = compress::Flavour::Apple;

    /// `STUFFR_UNZIP_FLAVOR` selects `apple` or `ubuntu`, unset or empty is
    /// the default, and anything else (another case, a blank) is refused.
    #[test]
    fn flavour_var_rejects_other_values() {
        let d = unzip::default_flavour();
        assert_eq!(unzip::flavour_from(None), Ok(d));
        assert_eq!(unzip::flavour_from(Some("".into())), Ok(d));
        assert_eq!(
            unzip::flavour_from(Some("apple".into())),
            Ok(unzip::Flavour::Apple)
        );
        assert_eq!(
            unzip::flavour_from(Some("ubuntu".into())),
            Ok(unzip::Flavour::Ubuntu)
        );
        for bad in ["Apple", "UBUNTU", " apple", "debian", "bsd"] {
            assert_eq!(unzip::flavour_from(Some(bad.into())), Err(bad.into()));
        }
    }

    /// `run_in_counted` reaches the unzip family in the flavour it is
    /// given, and `zipinfo` and `funzip` by name.
    #[test]
    fn run_in_counted_reaches_the_unzip_family() {
        let dir = std::env::temp_dir();
        let run = |name: &str, f: unzip::Flavour| {
            let (code, out, err, reads) =
                run_in_counted(&dir, name, vec!["-h".into()], b"", G, f, C).unwrap();
            assert!(reads.is_empty(), "{reads:?}");
            (code, String::from_utf8(out).unwrap(), err)
        };
        let (code, out, _) = run("unzip", unzip::Flavour::Apple);
        assert_eq!(code, 0);
        assert!(out.contains("Please report bugs to Apple."), "{out}");
        let (_, out, _) = run("unzip", unzip::Flavour::Ubuntu);
        assert!(!out.contains("Apple"), "{out}");
        let (code, out, _) = run("zipinfo", U);
        assert_eq!(code, 0);
        assert!(
            out.starts_with("ZipInfo 3.00 of 20 April 2009, by stuffr "),
            "{out}"
        );
        // `-h` is funzip's password; with no terminal it never shows usage,
        // and what it answers then is Task 12's.
        let (code, out, _) = run("funzip", U);
        assert!(unzip::EXIT_CODES_APPLE.contains(&code), "exit {code}");
        assert!(!out.contains("fUnZip"), "{out}");
    }

    /// `run_in_counted` reaches the compress family by both names, in the
    /// flavour it is given, and counts the inputs it opens.
    #[test]
    fn run_in_counted_reaches_the_compress_family() {
        /// Removes the directory when dropped, a panic's unwind included.
        struct Guard(std::path::PathBuf);
        impl Drop for Guard {
            fn drop(&mut self) {
                let _ = std::fs::remove_dir_all(&self.0);
            }
        }
        let dir = std::env::temp_dir().join(format!("stuffr-run-in-z-{}", std::process::id()));
        let _ = std::fs::remove_dir_all(&dir);
        std::fs::create_dir_all(&dir).unwrap();
        let _guard = Guard(dir.clone());
        std::fs::write(dir.join("a"), b"hello hello hello hello\n").unwrap();
        for (c, usage) in [
            (
                compress::Flavour::Apple,
                "uncompress: illegal option -- x\nusage: uncompress [-cfv] [-b bits] [file ...]\n",
            ),
            (
                compress::Flavour::Ncompress,
                "Unknown flag: 'x'; Usage: uncompress [-dfhvcVr] [-b maxbits] [--] [path ...]\n",
            ),
        ] {
            let (code, _, err, _) =
                run_in_counted(&dir, "uncompress", vec!["-x".into()], b"", G, U, c).unwrap();
            assert_eq!(code, 1, "{c:?}");
            assert!(
                String::from_utf8_lossy(&err).starts_with(usage),
                "{c:?}: {}",
                String::from_utf8_lossy(&err)
            );
            let (code, out, err, reads) = run_in_counted(
                &dir,
                "compress",
                vec!["-c".into(), "a".into()],
                b"",
                G,
                U,
                c,
            )
            .unwrap();
            assert_eq!(code, 0, "{c:?}: {}", String::from_utf8_lossy(&err));
            assert!(out.starts_with(&[0x1f, 0x9d, 0x90]), "{c:?}");
            assert_eq!(reads[&dir.join("a")].opens, 1, "{c:?}");
        }
    }

    /// The `compat` fuzz target picks its tool from `COMPAT_NAMES`; a name
    /// added here and not there would go unfuzzed.
    #[test]
    fn fuzz_names_match_the_dispatch_table() {
        assert_eq!(stuffr::testing::COMPAT_NAMES, names());
    }

    #[test]
    fn compat_names_are_recognised_by_file_name_only() {
        use std::ffi::OsStr;
        assert_eq!(family_for(OsStr::new("bzip2")).map(|f| f.1), Some("bzip2"));
        assert_eq!(
            family_for(OsStr::new("/usr/local/bin/bunzip2")).map(|f| f.1),
            Some("bunzip2")
        );
        assert_eq!(family_for(OsStr::new("bzcat")).map(|f| f.1), Some("bzcat"));
        assert_eq!(
            family_for(OsStr::new("bzip2recover")).map(|f| f.1),
            Some("bzip2recover")
        );
        assert!(family_for(OsStr::new("stuffr")).is_none());
        assert!(family_for(OsStr::new("/x/bzip2/stuffr")).is_none());
        assert!(family_for(OsStr::new("bzip2x")).is_none());
        #[cfg(windows)]
        assert_eq!(
            family_for(OsStr::new("bzip2.exe")).map(|f| f.1),
            Some("bzip2")
        );
    }

    #[test]
    fn stuffr_itself_does_not_dispatch() {
        assert!(dispatch(vec!["stuffr".into(), "list".into()]).is_none());
    }

    #[test]
    fn dispatch_ignores_an_empty_argv() {
        assert!(dispatch(Vec::new()).is_none());
    }

    #[cfg(unix)]
    #[test]
    fn dispatch_ignores_a_non_utf8_argv0() {
        use std::os::unix::ffi::OsStrExt;
        let bad = OsStr::from_bytes(b"bzip2\xff").to_os_string();
        assert!(dispatch(vec![bad]).is_none());
        let bad = OsStr::from_bytes(b"/x/\xffbzip2").to_os_string();
        assert!(dispatch(vec![bad]).is_none());
    }

    /// `run_in` reaches both families, resolves operands against its
    /// directory and captures standard output.
    #[test]
    fn run_in_works_inside_its_directory() {
        let dir = std::env::temp_dir().join(format!("stuffr-run-in-{}", std::process::id()));
        let _ = std::fs::remove_dir_all(&dir);
        std::fs::create_dir_all(&dir).unwrap();
        std::fs::write(dir.join("a"), b"hello hello hello\n").unwrap();
        let (code, out, err) =
            run_in(&dir, "bzip2", vec!["-k".into(), "a".into()], b"", G).unwrap();
        assert_eq!(
            (code, out.len()),
            (0, 0),
            "{}",
            String::from_utf8_lossy(&err)
        );
        let packed = std::fs::read(dir.join("a.bz2")).unwrap();
        assert!(packed.starts_with(b"BZh9"));
        let (code, out, _) = run_in(&dir, "bzcat", vec![], &packed, G).unwrap();
        assert_eq!((code, out.as_slice()), (0, &b"hello hello hello\n"[..]));
        let (code, out, err) = run_in(&dir, "bzip2recover", vec!["a.bz2".into()], b"", G).unwrap();
        assert_eq!(
            (code, out.len()),
            (0, 0),
            "{}",
            String::from_utf8_lossy(&err)
        );
        assert!(dir.join("rec00001a.bz2").exists());
        // A damaged stream from stdin: exit 2, stdin is never a terminal.
        let (code, _, err) = run_in(&dir, "bunzip2", vec![], b"BZh9garbage", G).unwrap();
        assert_eq!(code, 2, "{}", String::from_utf8_lossy(&err));
        assert!(run_in(&dir, "stuffr", vec![], b"", G).is_none());
        let _ = std::fs::remove_dir_all(&dir);
    }

    /// `run_in_counted` reports, for the gzip family in either flavour, each
    /// input opened, how often, its length and the bytes read from it; a
    /// file only listed (`-l`) is still an open; the bzip2 family counts
    /// nothing.
    #[test]
    fn run_in_counted_counts_the_gzip_familys_inputs() {
        let dir = std::env::temp_dir().join(format!("stuffr-run-in-count-{}", std::process::id()));
        for flavour in [gzip::Flavour::Gnu, gzip::Flavour::Bsd] {
            let _ = std::fs::remove_dir_all(&dir);
            std::fs::create_dir_all(&dir).unwrap();
            std::fs::write(dir.join("a"), b"hello hello hello\n").unwrap();
            let args = |a: &[&str]| a.iter().map(OsString::from).collect::<Vec<_>>();
            let (code, _, err, reads) =
                run_in_counted(&dir, "gzip", args(&["-k", "a"]), b"", flavour, U, C).unwrap();
            assert_eq!(code, 0, "{}", String::from_utf8_lossy(&err));
            let a = reads[&dir.join("a")];
            assert_eq!((a.opens, a.bytes, a.len), (1, 18, 18), "{flavour:?}");
            assert_eq!(reads.len(), 1, "{reads:?}");

            let len = std::fs::metadata(dir.join("a.gz")).unwrap().len();
            for mode in [&["-t", "a.gz", "a.gz"][..], &["-l", "a.gz"]] {
                let (code, _, err, reads) =
                    run_in_counted(&dir, "gzip", args(mode), b"", flavour, U, C).unwrap();
                assert_eq!(code, 0, "{}", String::from_utf8_lossy(&err));
                let gz = reads[&dir.join("a.gz")];
                assert_eq!(gz.opens, mode.len() as u64 - 1, "{flavour:?} {mode:?}");
                assert_eq!(gz.len, len);
                assert!(gz.bytes > 0 && gz.bytes <= 2 * len * gz.opens, "{gz:?}");
            }
            let (_, _, _, reads) =
                run_in_counted(&dir, "bzip2", args(&["-k", "a"]), b"", flavour, U, C).unwrap();
            assert!(reads.is_empty(), "{reads:?}");
        }
        let _ = std::fs::remove_dir_all(&dir);
    }

    /// The zstd family counts every file it reads: an input, a `-D`
    /// dictionary and a `--filelist` list (the fuzz target's read bound
    /// is blind to an open that bypasses `Host::track`).
    #[test]
    fn run_in_counted_counts_the_zstd_familys_inputs() {
        let dir = std::env::temp_dir().join(format!("stuffr-run-in-zstd-{}", std::process::id()));
        let _ = std::fs::remove_dir_all(&dir);
        std::fs::create_dir_all(&dir).unwrap();
        let args = |a: &[&str]| a.iter().map(OsString::from).collect::<Vec<_>>();
        let run = |a: &[&str]| {
            let (code, _, err, reads) =
                run_in_counted(&dir, "zstd", args(a), b"", gzip::Flavour::Gnu, U, C).unwrap();
            assert_eq!(code, 0, "{a:?}: {}", String::from_utf8_lossy(&err));
            reads
        };
        std::fs::write(dir.join("a"), b"hello hello hello\n").unwrap();
        std::fs::write(dir.join("d.dict"), b"a raw dictionary\n").unwrap();
        std::fs::write(dir.join("l"), b"a\n").unwrap();

        let reads = run(&["-q", "-k", "a"]);
        assert_eq!(
            reads[&dir.join("a")],
            InputReads {
                opens: 1,
                bytes: 18,
                len: 18
            }
        );
        let zst = std::fs::metadata(dir.join("a.zst")).unwrap().len();

        let reads = run(&["-d", "-c", "-D", "d.dict", "a.zst"]);
        let dict = reads[&dir.join("d.dict")];
        assert_eq!(
            dict,
            InputReads {
                opens: 1,
                bytes: 17,
                len: 17
            }
        );
        assert_eq!(reads[&dir.join("a.zst")].len, zst);

        let reads = run(&["-c", "--filelist=l"]);
        assert_eq!(
            reads[&dir.join("l")],
            InputReads {
                opens: 1,
                bytes: 2,
                len: 2
            }
        );
        assert_eq!(reads[&dir.join("a")].opens, 1);
        let _ = std::fs::remove_dir_all(&dir);
    }

    /// Output past the sandbox's cap fails as a full disk does: exit 1.
    #[test]
    fn run_in_caps_what_a_run_writes() {
        let dir = std::env::temp_dir().join(format!("stuffr-run-in-cap-{}", std::process::id()));
        let _ = std::fs::remove_dir_all(&dir);
        std::fs::create_dir_all(&dir).unwrap();
        let big = vec![0u8; 9 * 1024 * 1024];
        let (code, packed, _) = run_in(&dir, "bzip2", vec![], &big, G).unwrap();
        assert_eq!(code, 0);
        let (code, out, err) = run_in(&dir, "bzcat", vec![], &packed, G).unwrap();
        let err = String::from_utf8_lossy(&err);
        assert_eq!(code, 1, "{err}");
        // A write the budget cannot hold fails whole, so the output stops
        // within one buffered write (64 KiB) of the cap, never past it.
        let cap = 8 * 1024 * 1024;
        assert!(
            out.len() <= cap && out.len() > cap - 64 * 1024,
            "{}",
            out.len()
        );
        assert!(err.contains("I/O or other error"), "{err}");
        // `-t` writes nothing, but its decoding is charged to the same cap.
        let (code, out, err) = run_in(&dir, "bzip2", vec!["-t".into()], &packed, G).unwrap();
        let err = String::from_utf8_lossy(&err);
        assert_eq!((code, out.len()), (1, 0), "{err}");
        assert!(err.contains("I/O or other error"), "{err}");
        let _ = std::fs::remove_dir_all(&dir);
    }

    #[test]
    fn names_lists_the_table() {
        assert_eq!(
            names(),
            [
                "bzip2",
                "bunzip2",
                "bzcat",
                "bzip2recover",
                "gzip",
                "gunzip",
                "zcat",
                "gzcat",
                "xz",
                "unxz",
                "xzcat",
                "lzma",
                "unlzma",
                "lzcat",
                "zstd",
                "unzstd",
                "zstdcat",
                "zstdmt",
                "lz4",
                "unlz4",
                "lz4cat",
                "lz4c",
                "unzip",
                "zipinfo",
                "funzip",
                "compress",
                "uncompress"
            ]
        );
    }

    #[test]
    fn copy_metadata_carries_mtime_and_permissions() {
        let dir = std::env::temp_dir().join(format!("stuffr-meta-{}", std::process::id()));
        std::fs::create_dir_all(&dir).unwrap();
        let (a, b) = (dir.join("a"), dir.join("b"));
        std::fs::write(&a, b"x").unwrap();
        std::fs::write(&b, b"y").unwrap();
        let old = std::time::SystemTime::UNIX_EPOCH + std::time::Duration::from_secs(1_000_000_000);
        std::fs::File::options()
            .write(true)
            .open(&a)
            .unwrap()
            .set_modified(old)
            .unwrap();
        #[cfg(unix)]
        {
            use std::os::unix::fs::PermissionsExt;
            std::fs::set_permissions(&a, std::fs::Permissions::from_mode(0o640)).unwrap();
        }
        copy_metadata_from(&std::fs::metadata(&a).unwrap(), &b).unwrap();
        let (ma, mb) = (
            std::fs::metadata(&a).unwrap(),
            std::fs::metadata(&b).unwrap(),
        );
        assert_eq!(ma.modified().unwrap(), mb.modified().unwrap());
        assert_eq!(ma.permissions(), mb.permissions());
        let _ = std::fs::remove_dir_all(&dir);
    }
}