msg_queue.h

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#pragma once

#include <atomic>

// A simple queue. No locks, but only works with a single thread as producer and a single thread as
// a consumer. Mutex up as needed.

template <typename ElementType, size_t QueueSize>
class MsgQueue {
 ElementType queue_[QueueSize];
 std::atomic_uint nextAdd_{0};
 std::atomic_uint nextSend_{0};
 std::atomic_uint pendingSends_{0};

public:
 MsgQueue() {}

 ElementType* GetNextAddMessage()
 {
 // if we are falling behind, bail
 if (pendingSends_.load() >= QueueSize) {
 return nullptr;
 }
 auto index = (nextAdd_++) % QueueSize;
 return &queue_[index];
 }
 void CommitAdd() { ++pendingSends_; }

 bool HavePendingSends() const { return pendingSends_.load() != 0; }
 ElementType* GetNextSendMessage()
 {
 auto index = (nextSend_++) % QueueSize;
 return &queue_[index];
 }
 void CommitSend() { --pendingSends_; }
};