ThreadSafeQueue.h

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* Copyright Onix Solutions Limited [OnixS]. All rights reserved.
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#pragma once

#include <OnixS/FIXEngine/ABI.h>
#include <OnixS/FIXEngine/Threading/Definitions.h>

namespace OnixS {
namespace Threading {

struct ThreadSafeQueueResult
{
    enum Enum
    {
        /// No data during the timeout.
        Timeout,

        /// We get data immediately or after waiting during the timeout.
        Data,

        // We don't get data but was signaled to stop wait.
        Signaled
    };
};

/// The thread-safe queue to send data from some thread(s) to another single thread.
/// The thread-safe queue owns enqueued elements and deallocates element's memory on the destruction.
class ONIXS_FIXENGINE_API ThreadSafeQueue
{
public:

    /// Initializes the instance.
    ThreadSafeQueue();

    /// Cleans up enqueued elements and internal resources.
    ~ThreadSafeQueue();

    /// Adds an item to the queue.
    /// Takes the ownership of the item from the smart pointer.
    ///
    /// @throw The DomainException if the smart pointer is null.
    ///
    /// @param enqueueItem The smart pointer to the allocated item to enqueue.
    void enqueue(ItemBaseUniquePtr & enqueueItem);

    /// Tries to get an item from the queue during the timeout.
    /// Gives the ownership of the item to the smart pointer.
    /// Returns the `ThreadSafeQueueResult` value which reflects the result status ('Timeout', 'Data', 'Signaled').
    ///
    /// @param dequeueItem The smart pointer to store the dequeued item.
    /// @param waitInMs The waiting timeout.
    ThreadSafeQueueResult::Enum dequeue(ItemBaseUniquePtr & dequeueItem, const int waitInMs = InfiniteTimeout);

    /// Removes all elements from the queue.
    void clear();

    /// Returns 'true' if the queue is empty, otherwise 'false'.
    bool empty() const;

    /// Wakes up the queue if it was in the waiting mode.
    /// The `dequeue` method will return the 'Signaled' status if it was in the waiting mode.
    void signal();

private:

    /// Implementation details.
    struct Impl;
    Impl * impl_;

    /// The copying and assignment are prohibited.
    ThreadSafeQueue(const ThreadSafeQueue &);
    ThreadSafeQueue & operator = (const ThreadSafeQueue &);
};

}
}