/*
* Copyright Onix Solutions Limited [OnixS]. All rights reserved.
*
* This software owned by Onix Solutions Limited [OnixS] and is protected by copyright law
* and international copyright treaties.
*
* Access to and use of the software is governed by the terms of the applicable OnixS Software
* Services Agreement (the Agreement) and Customer end user license agreements granting
* a non-assignable, non-transferable and non-exclusive license to use the software
* for it's own data processing purposes under the terms defined in the Agreement.
*
* Except as otherwise granted within the terms of the Agreement, copying or reproduction of any part
* of this source code or associated reference material to any other location for further reproduction
* or redistribution, and any amendments to this copyright notice, are expressly prohibited.
*
* Any reproduction or redistribution for sale or hiring of the Software not in accordance with
* the terms of the Agreement is a violation of copyright law.
*/

#pragma once

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

namespace OnixS {
namespace Threading {

/// The thread-safe pool of objects by pointers.
/// The pool is safe for many writers and one reader.
/// The common scenario : a producer of data creates the objects using the pool
/// and sends them to a consumer threads to process, then these threads returns
/// objects back to producer's pool and so on.
class ONIXS_FIXENGINE_API ThreadSafePool
{
public:

    /// Initializes the instance.
    ///
    /// @param preferredSize The preferred size of the pool.
    /// @param allocator The allocator to provide a strategy to create/destroy pool items.
    ThreadSafePool(size_t preferredSize, PoolAllocatorBase & allocator);

    /// Removes pooled elements and cleans up internal resources.
    ~ThreadSafePool();

    /// Gets an item from the pool.
    /// Gives the ownership of the item to the smart pointer.
    /// If the pool is empty then creates an item by the allocator strategy.
    /// If the number of allocated elements becomes greater than the preferred pool size,
    /// after a high load, then destroys a one element, when possible, by the allocator strategy.
    ///
    /// @param poolItem The smart pointer to store the pool item.
    void get(ItemBaseUniquePtr & poolItem);

    /// Returns an item to the pool.
    /// Takes the ownership of the item from the smart pointer.
    ///
    /// @throw The DomainException if the smart pointer is null.
    ///
    /// @param poolItem The smart pointer to the pool item for returning to the pool.
    void put(ItemBaseUniquePtr & poolItem);

    /// Returns the preferred size of the pool.
    size_t preferredSize();

private:

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

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

}
}