From 82151d407d8021fa8865cf8dd51c4d5cf0a4b702 Mon Sep 17 00:00:00 2001
From: B3n30 <bene_thomas@web.de>
Date: Sat, 25 Nov 2017 14:56:57 +0100
Subject: CoreTiming: Reworked CoreTiming (cherry-picked from Citra #3119)

* CoreTiming: New CoreTiming; Add Test for CoreTiming
---
 src/common/threadsafe_queue.h | 122 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 122 insertions(+)
 create mode 100644 src/common/threadsafe_queue.h

(limited to 'src/common/threadsafe_queue.h')

diff --git a/src/common/threadsafe_queue.h b/src/common/threadsafe_queue.h
new file mode 100644
index 000000000..a0c731e8c
--- /dev/null
+++ b/src/common/threadsafe_queue.h
@@ -0,0 +1,122 @@
+// Copyright 2010 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+// a simple lockless thread-safe,
+// single reader, single writer queue
+
+#include <algorithm>
+#include <atomic>
+#include <cstddef>
+#include <mutex>
+#include "common/common_types.h"
+
+namespace Common {
+template <typename T, bool NeedSize = true>
+class SPSCQueue {
+public:
+    SPSCQueue() : size(0) {
+        write_ptr = read_ptr = new ElementPtr();
+    }
+    ~SPSCQueue() {
+        // this will empty out the whole queue
+        delete read_ptr;
+    }
+
+    u32 Size() const {
+        static_assert(NeedSize, "using Size() on FifoQueue without NeedSize");
+        return size.load();
+    }
+
+    bool Empty() const {
+        return !read_ptr->next.load();
+    }
+    T& Front() const {
+        return read_ptr->current;
+    }
+    template <typename Arg>
+    void Push(Arg&& t) {
+        // create the element, add it to the queue
+        write_ptr->current = std::forward<Arg>(t);
+        // set the next pointer to a new element ptr
+        // then advance the write pointer
+        ElementPtr* new_ptr = new ElementPtr();
+        write_ptr->next.store(new_ptr, std::memory_order_release);
+        write_ptr = new_ptr;
+        if (NeedSize)
+            size++;
+    }
+
+    void Pop() {
+        if (NeedSize)
+            size--;
+        ElementPtr* tmpptr = read_ptr;
+        // advance the read pointer
+        read_ptr = tmpptr->next.load();
+        // set the next element to nullptr to stop the recursive deletion
+        tmpptr->next.store(nullptr);
+        delete tmpptr; // this also deletes the element
+    }
+
+    bool Pop(T& t) {
+        if (Empty())
+            return false;
+
+        if (NeedSize)
+            size--;
+
+        ElementPtr* tmpptr = read_ptr;
+        read_ptr = tmpptr->next.load(std::memory_order_acquire);
+        t = std::move(tmpptr->current);
+        tmpptr->next.store(nullptr);
+        delete tmpptr;
+        return true;
+    }
+
+    // not thread-safe
+    void Clear() {
+        size.store(0);
+        delete read_ptr;
+        write_ptr = read_ptr = new ElementPtr();
+    }
+
+private:
+    // stores a pointer to element
+    // and a pointer to the next ElementPtr
+    class ElementPtr {
+    public:
+        ElementPtr() : next(nullptr) {}
+        ~ElementPtr() {
+            ElementPtr* next_ptr = next.load();
+
+            if (next_ptr)
+                delete next_ptr;
+        }
+
+        T current;
+        std::atomic<ElementPtr*> next;
+    };
+
+    ElementPtr* write_ptr;
+    ElementPtr* read_ptr;
+    std::atomic<u32> size;
+};
+
+// a simple thread-safe,
+// single reader, multiple writer queue
+
+template <typename T, bool NeedSize = true>
+class MPSCQueue : public SPSCQueue<T, NeedSize> {
+public:
+    template <typename Arg>
+    void Push(Arg&& t) {
+        std::lock_guard<std::mutex> lock(write_lock);
+        SPSCQueue<T, NeedSize>::Push(t);
+    }
+
+private:
+    std::mutex write_lock;
+};
+} // namespace Common
-- 
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