前段时间写了篇blog描述了时间轮算法(http://blog.sina.com.cn/s/blog_48d4cf2d0100pq9o.html),昨天终于动手用c++将其实现了,并通过了单元测试。我没有看Linux内核的实现代码,只是看了资料凭自己的理解来实现,在效率方面也没有尽量优化。所以下面的代码用来帮助理解算法可以,拿来实际用就不一定靠谱了。
另外我没有实现删除函数,因为懒得自己实现链表嘿嘿。参考:http://blog.youkuaiyun.com/lanmanck/archive/2009/09/07/4528759.aspx。删除的做法很简单,setTimer时直接返回链表结点,删除的时候干掉自己即可。
===========================timing_wheel.h================================
#pragma once
#include <list>
#include <boost/shared_ptr.hpp>
#include <boost/thread.hpp>
namespace global
{
typedef
unsigned int uint;
class
TimeoutHandler
{
public:
virtual
~TimeoutHandler(){}
virtual void
onTimeout() = 0;
};
class
TimingWheel
{
public:
TimingWheel();
~TimingWheel();
void
setTimer(uint inteval,
boost::shared_ptr<TimeoutHandler>
handler);
void
step();
private:
typedef
boost::shared_ptr<TimeoutHandler>
Handler;
struct
ListNode
{
uint
inteval;
Handler
handler;
ListNode(int
inteval_, Handler handler_)
:
inteval_r(inteval_)
,
handler(handler_)
{
}
};
enum
{BUCKET_CNT = 5};
uint
newest[BUCKET_CNT];
std::list<ListNode>*
buckets[BUCKET_CNT];
boost::recursive_mutex mtx;
};
}
===========================timing_wheel.cpp================================
#include "timing_wheel.h"
#include "xassert.h"
#include <stdexcept>
#include <vector>
namespace global
{
static const
uint ELEMENT_CNT_PER_BUCKET[] = {256, 64, 64, 64, 64};
static const
uint RIGHT_SHIFT_PER_BUCKET[] = {8, 6, 6, 6, 6};
static const
uint BASE_PER_BUCKET[] = {1, 256, 256*64, 256*64*64,
256*64*64*64};
TimingWheel::TimingWheel()
{
for (int
bucket_no = 0; bucket_no < BUCKET_CNT;
bucket_no++)
{
newest[bucket_no] = 0;
buckets[bucket_no] = new
std::list<ListNode>[ELEMENT_CNT_PER_BUCKET[bucket_no]];
}
}
TimingWheel::~TimingWheel()
{
for (int
bucket_no = 0; bucket_no < BUCKET_CNT;
bucket_no++)
{
delete[]
buckets[bucket_no];
}
}
void
TimingWheel::setTimer(uint inteval,
boost::shared_ptr<TimeoutHandler>
handler)
{
boost::recursive_mutex::scoped_lock lock(mtx);
XASSERT(inteval > 0);
uint
bucket_no = 0;
uint offset
= inteval;
uint left =
inteval;
while
(offset >= ELEMENT_CNT_PER_BUCKET[bucket_no])
{
offset
>>=
RIGHT_SHIFT_PER_BUCKET[bucket_no];
left -=
BASE_PER_BUCKET[bucket_no]*(ELEMENT_CNT_PER_BUCKET[bucket_no] -
newest[bucket_no] - (bucket_no == 0 ? 0 : 1));
++
bucket_no;
}
XASSERT(offset >= 1);
XASSERT(inteval >=
BASE_PER_BUCKET[bucket_no]*offset);
left -=
BASE_PER_BUCKET[bucket_no] * (offset - 1);
uint pos =
(newest[bucket_no] + offset) %
ELEMENT_CNT_PER_BUCKET[bucket_no];
buckets[bucket_no][pos].push_back(ListNode(left, handler));
}
void
TimingWheel::step()
{
std::vector<Handler> handlers;
{
boost::recursive_mutex::scoped_lock lock(mtx);
for (int
bucket_no = 0; bucket_no < BUCKET_CNT;
bucket_no++)
{
newest[bucket_no] = (newest[bucket_no] + 1) %
ELEMENT_CNT_PER_BUCKET[bucket_no];
std::list<ListNode>&
cur_list(buckets[bucket_no][newest[bucket_no]]);
while
(!cur_list.empty())
{
if
(bucket_no == 0 || cur_list.front().inteval == 0)
{
handlers.push_back(cur_list.front().handler);
}
else
{
setTimer(cur_list.front().inteval,
cur_list.front().handler);
}
cur_list.pop_front();
}
if
(newest[bucket_no] != 0)
{
break;
}
}
}
for
(std::size_t i = 0; i < handlers.size(); i++)
{
handlers[i]->onTimeout();
}
}
}