ThreadLocalSingleton.h——base

#ifndef MUDUO_BASE_THREADLOCALSINGLETON_H

#define MUDUO_BASE_THREADLOCALSINGLETON_H

#include <boost/noncopyable.hpp>

#include <assert.h>

#include <pthread.h>

namespace muduo

{

template<typename T>

class ThreadLocalSingleton : boost::noncopyable

{

public:

static T& instance()

{

if (!t_value_)

{

t_value_ = new T();

deleter_.set(t_value_);

}

return *t_value_;

}

static T* pointer()

{

return t_value_;

}

private:

static void destructor(void* obj)

{

assert(obj == t_value_);

typedef char T_must_be_complete_type[sizeof(T) == 0 ? -1 : 1];

delete t_value_;

t_value_ = 0;

}

class Deleter

{

public:

Deleter()

{

pthread_key_create(&pkey_, &ThreadLocalSingleton::destructor);

}

~Deleter()

{

pthread_key_delete(pkey_);

}

void set(T* newObj)

{

assert(pthread_getspecific(pkey_) == NULL);

pthread_setspecific(pkey_, newObj);

}

pthread_key_t pkey_;

};

//这里可以不用static吗

//__thread T* t_value_; 可以吗

//不可以 同一线程里的 ThreadLocalSingleton<A> a，b；会有两个 t_value_ a.t_value,b.t_value;

//但是在不同线程里 __thread变量会告诉对象 t_value是线程局部变量。

static __thread T* t_value_;

static Deleter deleter_;

};

template<typename T>

__thread T* ThreadLocalSingleton<T>::t_value_ = 0;

template<typename T>

typename ThreadLocalSingleton<T>::Deleter ThreadLocalSingleton<T>::deleter_;

}

#endif