chapter 7 code

ch7/queue_spsc.cpp

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+#include <iostream>
+#include <cstdio>
+#include <atomic>
+#include <memory>
+#include <thread>
+
+template <typename T>
+class queue
+{
+  private:
+    struct node
+    {
+        std::shared_ptr<T> data;
+        node* next;
+
+        node()
+        : next(nullptr)
+        {}
+    };
+
+    std::atomic<node*> head;
+    std::atomic<node*> tail;
+    
+    node* pop_head()
+    {
+        node* const old_head = head.load();
+        if (old_head == tail.load()) {
+            return nullptr;
+        }
+        head.store(old_head->next);
+        return old_head;
+    }
+  public:
+    queue()
+    : head(new node)
+    , tail(head.load())
+    {}
+
+    queue(const queue& other)=delete;
+    queue& operator=(const queue& other)=delete;
+
+    ~queue()
+    {
+        while (node* const old_head = head.load()) {
+            head.store(old_head->next);
+            delete old_head;
+        }
+    }
+
+    std::shared_ptr<T> pop()
+    {
+        node* old_head = pop_head();
+        if (!old_head) {
+            return std::shared_ptr<T>();
+        }
+
+        std::shared_ptr<T> const res(old_head->data);
+        delete old_head;
+        return res;
+    }
+
+    void push(T new_value)
+    {
+        std::shared_ptr<T> new_data(std::make_shared<T>(new_value));
+        node* p = new node;
+        node* const old_tail = tail.load();
+        old_tail->data.swap(new_data);
+        old_tail->next = p;
+        tail.store(p);
+    }
+};
+
+void push(queue<int>* q)
+{
+    for (int i = 0; i < 10; ++i) {
+        printf("pushing %d\n", i);
+        q->push(i);
+    }
+}
+
+void pop(queue<int>* q)
+{
+    int i = 0;
+    while (i < 10) {
+        std::shared_ptr<int> p = q->pop();
+        if (p) {
+            printf("poping %d\n", *p);
+            ++i;
+        }
+    }
+}
+
+int main()
+{
+    queue<int> q;
+    std::thread t1(push, &q);
+    std::thread t2(pop, &q);
+    t1.join();
+    t2.join();
+    return 0;
+}
+