JNA内存源码解析Memory，释放内存

源码版本5.15.0

Memory new出来了之后，不用手动去释放内存，Cleaner.getCleaner().register注册了之后会一直轮询直到对象被GC的时候，自动释放Native内存。

public Memory(long size) {
      this.size = size;
      if (size <= 0) {
          throw new IllegalArgumentException("Allocation size must be greater than zero");
      }
      peer = malloc(size);
      if (peer == 0)
          throw new OutOfMemoryError("Cannot allocate " + size + " bytes");

      allocatedMemory.put(peer, new WeakReference<>(this));
      // GC时触发MemoryDisposer任务，释放内存
      cleanable = Cleaner.getCleaner().register(this, new MemoryDisposer(peer));
}

private static final class MemoryDisposer implements Runnable {

	private long peer;

	public MemoryDisposer(long peer) {
		this.peer = peer;
	}

	@Override
	public synchronized void run() {
		try {
			free(peer);
		} finally {
			allocatedMemory.remove(peer);
			peer = 0;
		}
	}

}

// Cleaner Starting CleanerThread 任务执行代码
@Override
public void run() {
	while (true) {
		try {
			Reference<? extends Object> ref = referenceQueue.remove(CLEANER_LINGER_TIME);
			if (ref instanceof CleanerRef) {
                // CleanerRef为虚引用，当对象被GC的时候队列会有虚引用对象被塞进来，然后触发自定义的clean方法
				((CleanerRef) ref).clean();
			} else if (ref == null) {
				synchronized (referenceQueue) {
					Logger logger = Logger.getLogger(Cleaner.class.getName());
					if (firstCleanable == null) {
						cleanerThread = null;
						logger.log(Level.FINE, "Shutting down CleanerThread");
						break;
					} else if (logger.isLoggable(Level.FINER)) {
						StringBuilder registeredCleaners = new StringBuilder();
						for(CleanerRef cleanerRef = firstCleanable; cleanerRef != null; cleanerRef = cleanerRef.next) {
							if(registeredCleaners.length() != 0) {
								registeredCleaners.append(", ");
							}
							registeredCleaners.append(cleanerRef.cleanupTask.toString());
						}
						logger.log(Level.FINER, "Registered Cleaners: {0}", registeredCleaners.toString());
					}
				}
			}
		} catch (InterruptedException ex) {
			// Can be raised on shutdown. If anyone else messes with
			// our reference queue, well, there is no way to separate
			// the two cases.
			// https://groups.google.com/g/jna-users/c/j0fw96PlOpM/m/vbwNIb2pBQAJ
			break;
		} catch (Exception ex) {
			Logger.getLogger(Cleaner.class.getName()).log(Level.SEVERE, null, ex);
		}
	}
}