public void TrySetCoins(FetchCoinsResponse coins)
		{
			_Unspents = new Dictionary<uint256, UnspentOutputs>(coins.UnspentOutputs.Length);
			foreach (var coin in coins.UnspentOutputs)
			{
				if (coin != null)
					_Unspents.TryAdd(coin.TransactionId, coin);
			}
		}
        public override async Task <FetchCoinsResponse> FetchCoinsAsync(uint256[] txIds)
        {
            Guard.NotNull(txIds, nameof(txIds));

            FetchCoinsResponse result         = null;
            uint256            innerBlockHash = null;

            UnspentOutputs[] outputs     = new UnspentOutputs[txIds.Length];
            List <int>       miss        = new List <int>();
            List <uint256>   missedTxIds = new List <uint256>();

            using (_Lock.LockRead())
            {
                WaitOngoingTasks();
                for (int i = 0; i < txIds.Length; i++)
                {
                    CacheItem cache;
                    if (!_Unspents.TryGetValue(txIds[i], out cache))
                    {
                        miss.Add(i);
                        missedTxIds.Add(txIds[i]);
                    }
                    else
                    {
                        outputs[i] = cache.UnspentOutputs == null ? null :
                                     cache.UnspentOutputs.IsPrunable ? null :
                                     cache.UnspentOutputs.Clone();
                    }
                }
                PerformanceCounter.AddMissCount(miss.Count);
                PerformanceCounter.AddHitCount(txIds.Length - miss.Count);
            }
            var fetchedCoins = await Inner.FetchCoinsAsync(missedTxIds.ToArray()).ConfigureAwait(false);

            using (_Lock.LockWrite())
            {
                _Flushing.Wait();
                innerBlockHash = fetchedCoins.BlockHash;
                if (_BlockHash == null)
                {
                    Debug.Assert(_Unspents.Count == 0);
                    _InnerBlockHash = innerBlockHash;
                    _BlockHash      = innerBlockHash;
                }
                for (int i = 0; i < miss.Count; i++)
                {
                    var index   = miss[i];
                    var unspent = fetchedCoins.UnspentOutputs[i];
                    outputs[index] = unspent;
                    CacheItem cache = new CacheItem();
                    cache.ExistInInner    = unspent != null;
                    cache.IsDirty         = false;
                    cache.UnspentOutputs  = unspent;
                    cache.OriginalOutputs = unspent?._Outputs.ToArray();
                    _Unspents.TryAdd(txIds[index], cache);
                }
                result = new FetchCoinsResponse(outputs, _BlockHash);
            }

            if (CacheEntryCount > MaxItems)
            {
                Evict();
                if (CacheEntryCount > MaxItems)
                {
                    await FlushAsync().ConfigureAwait(false);

                    Evict();
                }
            }

            return(result);
        }