sviolet.thistle.model.concurrent.lock.AbstractHashLocks Maven / Gradle / Ivy
/*
* Copyright (C) 2015-2018 S.Violet
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Project GitHub: https://github.com/shepherdviolet/thistle
* Email: [email protected]
*/
package sviolet.thistle.model.concurrent.lock;
import sviolet.thistle.util.math.MathUtils;
/**
* 产生指定数量的同步锁, 根据字符串的哈希获取锁对象, 这样可以把同步代码块分散, 提高并发性能
*
* @author S.Violet
*/
abstract class AbstractHashLocks {
private T[] locks;
private int barrier;
AbstractHashLocks() {
this(32);
}
/**
* @param hashLockNum 锁数量, 16 32 64 128 256 512 1024, 数量越多发生碰撞的可能性更低, 但是消耗更多的内存
*/
AbstractHashLocks(int hashLockNum) {
//limit
if (hashLockNum < 16 || hashLockNum > 1024 || !MathUtils.isPowerOfTwo(hashLockNum)) {
throw new IllegalArgumentException("hashLockNum must be 16 32 64 128 256 512 1024");
}
//create lock
locks = newArray(hashLockNum);
for (int i = 0 ; i < hashLockNum ; i++) {
locks[i] = newLock();
}
//build barrier
barrier = hashLockNum - 1;
}
abstract T[] newArray(int hashLockNum);
abstract T newLock();
/**
* 根据字符串的哈希获取锁对象
* @param str 字符串, 尽量不要送null
* @return ReentrantLock
*/
public T getLock(String str){
int slot = hash(str) & barrier;
return locks[slot];
}
/**
* hash
*/
private int hash(Object key) {
int h;
return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
}
}