1#pragma once
 2
 3#include <atomic>
 4
 5// A simple queue. No locks, but only works with a single thread as producer and a single thread as
 6// a consumer. Mutex up as needed.
 7
 8template <typename ElementType, size_t QueueSize>
 9class MsgQueue {
10    ElementType queue_[QueueSize];
11    std::atomic_uint nextAdd_{0};
12    std::atomic_uint nextSend_{0};
13    std::atomic_uint pendingSends_{0};
14
15public:
16    MsgQueue() {}
17
18    ElementType* GetNextAddMessage()
19    {
20        // if we are falling behind, bail
21        if (pendingSends_.load() >= QueueSize) {
22            return nullptr;
23        }
24        auto index = (nextAdd_++) % QueueSize;
25        return &queue_[index];
26    }
27    void CommitAdd() { ++pendingSends_; }
28
29    bool HavePendingSends() const { return pendingSends_.load() != 0; }
30    ElementType* GetNextSendMessage()
31    {
32        auto index = (nextSend_++) % QueueSize;
33        return &queue_[index];
34    }
35    void CommitSend() { --pendingSends_; }
36};