com.github.edgar615.util.concurrent.StripedLock Maven / Gradle / Ivy
package com.github.edgar615.util.concurrent;
import java.util.concurrent.locks.ReentrantLock;
/**
* 条纹锁，与Guava的Striped类似，内部维护了一组{@link ReentrantLock}用来做并发控制
*
* 锁的数量可以是{2, 4, 8, 16, 32, 64}中的任何一个
*/
public class StripedLock {
private static final int MIN = 1;
private static final int MAX = 6;
/**
* 委托的锁的数组
*/
private final ReentrantLock[] locks;
/**
* 创建条纹锁，锁的数量可以是{2, 4, 8, 16, 32, 64}中的任何一个。
*
* @param storagePower 锁的数量= Math.pow(2, storagePower)，因此该值必须在1-6之间
*/
private StripedLock(int storagePower) {
if (!(storagePower >= MIN && storagePower <= MAX)) {
throw new IllegalArgumentException("storage power must be in [1..6]");
}
int lockSize = (int) Math.pow(2, storagePower);
locks = new ReentrantLock[lockSize];
for (int i = 0; i < locks.length; i++) {
locks[i] = new ReentrantLock();
}
}
/**
* 默认的条纹锁，内部有16个 ReentrantLock
*
* @return StripedLock
*/
public static StripedLock create() {
return new StripedLock(4);
}
/**
* 创建条纹锁，锁的数量可以是{2, 4, 8, 16, 32, 64}中的任何一个。
*
* @param storagePower 锁的数量= Math.pow(2, storagePower)，因此该值必须在1-6之间
* @return StripedLock
*/
public static StripedLock create(int storagePower) {
return new StripedLock(storagePower);
}
/**
* 根据id获取一个锁
*
* @param id value, from which lock is derived
*/
public void lock(int id) {
getLock(id).lock();
}
/**
* 根据id释放一个锁.
*
* @param id value, from which lock is derived
*/
public void unlock(int id) {
getLock(id).unlock();
}
/**
* Map function between integer and lock from locks array.
*
* @param id argument
* @return lock which is result of function
*/
private ReentrantLock getLock(int id) {
return locks[id & (locks.length - 1)];
}
}