You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: half_lock.rs
    path of file: ./repos/phaser/phaser/vendor/signal-hook-registry/src
    
    the code of the file until where you have to start completion: //! The half-lock structure
//!
//! We need a way to protect the structure with configured hooks â€’ a signal may happen in arbitrary
//! thread and needs to read them while another thread might be manipulating the structure.
//!
//! Under ordinary circumstances we would be happy to just use `Mutex<HashMap<c_int, _>>`. However,
//! as we use it in the signal handler, we are severely limited in what we can or can't use. So we
//! choose to implement kind of spin-look thing with atomics.
//!
//! In the reader it is alwa
    
    pub(crate) fn read(&self) -> ReadGuard<T> {
        // Relaxed should be enough; we only pick one or the other slot and the writer observes
        // that both were 0 at some time. So the actual value doesn't really matter for safety,
        // only the changing improves the performance.
        let gen = self.generation.load(Ordering::SeqCst);
        let lock = &self.lock[gen % 2];
        // Effectively locking something, acquire should be enough.
        let guard_cnt = lock.fetch_add(1, Ordering::SeqCst);

        // This is to prevent overflowing the counter in some degenerate cases, which could lead to
        // UB (freeing data while still in use). However, as this data structure is used only
        // internally and it's not possible to leak the guard and the guard itself takes some
        // memory, it should be really impossible to trigger this case. Still, we include it from
        // abundance of caution.
        //
        // This technically is not fully correct as enough threads being in between here and the
        // abort below could still overflow it and it could get freed for some *other* thread, but
        // that would mean having too many active threads to fit into RAM too and is even more
        // absurd corner case than the above.
        if guard_cnt > MAX_GUARDS {
            unsafe { libc::abort() };
        }

        // Acquire should be enough; we need to "download" the data, paired with the swap on the
        // same pointer.
        let data = self.data.load(Ordering::SeqCst);
        // Safe:
        // * It did point to valid data when put in.
        // * Protected by lock, so still valid.
        let data = unsafe { &*data };

        ReadGuard { data, lock }
    }