/*
 Sog 游戏基础库
 2016 by zouwei
 */

using System;
using System.Collections.Concurrent;
using System.Text;
using System.Threading;

namespace Sog.Memory
{
    public class ByteArrayCache
    {
        public int FixedSize { get; }

        private long MallocCount;
        private long FreeCount;
        
        private ConcurrentQueue<byte[]> m_queue = new ConcurrentQueue<byte[]>();

        public ByteArrayCache(int size)
        {
            this.FixedSize = size;
        }

        public byte[] Malloc()
        {
            Interlocked.Increment(ref MallocCount);

            //不要用Count > 0来判断，效率低
            if (m_queue.IsEmpty == false)
            {
                byte[] buffer;
                //只尝试一次，失败就算了
                if(m_queue.TryDequeue(out buffer))
                {
                    return buffer;
                }
            }

            //直接向系统申请内存，大小是固定的
            return new byte[FixedSize];
        }

        /// <summary>
        /// 释放内存的时候加入队列，下次使用
        /// </summary>
        /// <param name="buffer"></param>
        public void Free(byte[] buffer)
        {
            Interlocked.Increment(ref FreeCount);
            m_queue.Enqueue(buffer);
        }

        public int GetCacheCount()
        {
            return m_queue.Count;
        }

        public long GetMallocCount()
        {
            return MallocCount;
        }

        public long GetFreeCount()
        {
            return FreeCount;
        }
    }

    /// <summary>
    /// 这个byte[]如果只考虑消息的话，可以用一个大byte[]数组代替，返回数组的其中一段数据
    /// 问题是要考虑线程安全，以后可以试试，有没有效率高的办法
    /// </summary>
    public class ByteArrayCacheMgr : Singleton<ByteArrayCacheMgr>
    {
        //32,64,128,256,512,1K,2K,4K,8K,16K,32K,64K
        private ByteArrayCache[] m_cacheArray = new ByteArrayCache[12];

        public ByteArrayCacheMgr()
        {
            int size = 32;

            for(int i=0; i< m_cacheArray.Length ;i++ )
            {
                m_cacheArray[i] = new ByteArrayCache(size);
                size = size * 2;
            }
        }

        public byte[] Malloc(int size)
        {
            for(int i=0; i< m_cacheArray.Length; i++)
            {
                if(m_cacheArray[i].FixedSize >= size)
                {
                    return m_cacheArray[i].Malloc();
                }
            }

            //太大的就不管了，直接向系统申请，这个上层最好自己判断，不要调用这个
            return new byte[size];
        }

        public void Free(byte[] buffer)
        {
            for (int i = 0; i < m_cacheArray.Length; i++)
            {
                if (m_cacheArray[i].FixedSize == buffer.Length)
                {
                    m_cacheArray[i].Free(buffer);
                    break;
                }
            }
        }

        public string StatInfo()
        {
            StringBuilder sb = new StringBuilder(512);
            sb.Append("ByteArrayCacheMgr");
            int totalcount = 0;
            for (int i = 0; i < m_cacheArray.Length; i++)
            {
                var cache = m_cacheArray[i];
                totalcount += cache.GetCacheCount();
                sb.Append(" [");
                sb.Append(cache.FixedSize);
                sb.Append("]:");
                sb.Append(cache.GetCacheCount());
                sb.Append(" (");
                sb.Append(cache.GetMallocCount());
                sb.Append("-");
                sb.Append(cache.GetFreeCount());
                sb.Append(")");
            }

            sb.Append("total:");
            sb.Append(totalcount);
            return sb.ToString();
        }
    }
}