请问c语言dowhel循环咋么打,HashedWheelTimer源码学习

基本概念

tickDuration: 每 tick 一次的时间间隔

ticksPerWheel : 轮中的 slot 数

remainingRounds： 第几轮 = (calculated - tick) / wheel.length

deadline： 得到过期时间。 long deadline = System.nanoTime() + unit.toNanos(delay) - startTime;

demo例子

HashedWheelTimer hashedWheelTimer = new HashedWheelTimer(Executors.defaultThreadFactory(),1,TimeUnit.SECONDS,64);

hashedWheelTimer.newTimeout(timeout -> {

log.info(String.valueOf(System.currentTimeMillis()));

System.out.println("64定时器执行了");

}, 120, TimeUnit.SECONDS);

hashedWheelTimer.newTimeout(timeout -> {

log.info(String.valueOf(System.currentTimeMillis()));

System.out.println("64定时器执行了");

}, 56, TimeUnit.SECONDS);

HashedWheelTimer 初始化

private static HashedWheelBucket[] createWheel(int ticksPerWheel) {

HashedWheelBucket[] wheel = new HashedWheelBucket[ticksPerWheel];

for (int i = 0; i < wheel.length; i ++) {

wheel[i] = new HashedWheelBucket();

}

return wheel;

}

根据ticksPerWheel的值 ，生成对应的HashedWheelBucket，如例子中给出的是64个槽，则生成64个，如果不是2的平方则自动给出一个最近的值；

HashedWheelBucket数据结构

class HashedWheelBucket {

// Used for the linked-list datastructure

private HashedWheelTimeout head;

private HashedWheelTimeout tail;

/**

* Add {@link HashedWheelTimeout} to this bucket.

*/

public void addTimeout(HashedWheelTimeout timeout) {

assert timeout.bucket == null;

timeout.bucket = this;

if (head == null) {

head = tail = timeout;

} else {

tail.next = timeout;

timeout.prev = tail;

tail = timeout;

}

}

HashedWheelTimeout 数据结构

class HashedWheelTimeout implements Timeout {

private final long deadline;

long remainingRounds; // 轮数

HashedWheelTimeout next;

HashedWheelTimeout prev;

}

程序开始; tick++; 查看是否有新过期任务加入进来；最后检查是否有过期的

do {

final long deadline = waitForNextTick();

if (deadline > 0) {

// 获取当前所对应的槽

int idx = (int) (tick & mask);

processCancelledTasks();

HashedWheelBucket bucket =

wheel[idx];

transferTimeoutsToBuckets();

bucket.expireTimeouts(deadline);

tick++;

}

} while (1);

循环链表找到过期的task；每次进来，轮数小于等于0才过期；否则会把有轮数量的减一。

public void expireTimeouts(long deadline) {

HashedWheelTimeout timeout = head;

// process all timeouts

while (timeout != null) {

HashedWheelTimeout next = timeout.next;

if (timeout.remainingRounds <= 0) {

next = remove(timeout);

if (timeout.deadline <= deadline) {

// 回到用户函数

timeout.expire();

} else {

// The timeout was placed into a wrong slot. This should never happen.

throw new IllegalStateException(String.format(

"timeout.deadline (%d) > deadline (%d)", timeout.deadline, deadline));

}

} else if (timeout.isCancelled()) {

next = remove(timeout);

} else {

timeout.remainingRounds --;

}

timeout = next;

}

}