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
