47 lines
886 B
C++
47 lines
886 B
C++
//
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// Created by light on 20-2-7.
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//
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#include <iostream>
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using namespace std;
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#include <mutex>
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#define barrier() __asm__ volatile ("lwsync")
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// method 1 operator new + placement new
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//singleton *instance() {
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// if (p == nullptr) {
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// lock_guard<mutex> guard(lock_);
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// if (p == nullptr) {
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// singleton *tmp = static_cast<singleton *>(operator new(sizeof(singleton)));
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// new(p)singleton();
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// p = tmp;
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// }
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// }
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// return p;
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//}
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class singleton {
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private:
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singleton() {}
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static singleton *p;
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static mutex lock_;
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public:
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static singleton *instance();
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};
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singleton *singleton::p = nullptr;
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singleton *singleton::instance() {
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if (p == nullptr) {
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lock_guard<mutex> guard(lock_);
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barrier();
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if (p == nullptr) {
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p = new singleton();
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}
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}
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return p;
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}
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