realPath

fn realPath(
    ev: *Evented,
    sync: *CancelRegion.Sync,
    fd: fd_t,
    out_buffer: []u8,
) File.RealPathError!usize {
    _ = ev;
    var procfs_buf: [std.fmt.count("/proc/self/fd/{d}\x00", .{std.math.minInt(fd_t)})]u8 = undefined;
    const proc_path = std.mem.printSentinel(&procfs_buf, "/proc/self/fd/{d}", .{fd}, 0) catch
        unreachable;
    while (true) {
        try sync.cancel_region.await(.nothing);
        const rc = linux.readlink(proc_path, out_buffer.ptr, out_buffer.len);
        switch (linux.errno(rc)) {
            .SUCCESS => return rc,
            .INTR => {},
            .ACCES => return error.AccessDenied,
            .FAULT => |err| return errnoBug(err),
            .IO => return error.FileSystem,
            .LOOP => return error.SymLinkLoop,
            .NAMETOOLONG => return error.NameTooLong,
            .NOENT => return error.FileNotFound,
            .NOMEM => return error.SystemResources,
            .NOTDIR => return error.NotDir,
            .ILSEQ => |err| return errnoBug(err),
            else => |err| return unexpectedErrno(err),
        }
    }
}