fix minor issue

Discreet/DB/AlreadyPresentException.cs

@@ -0,0 +1,18 @@
+using Discreet.Common.Exceptions;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Discreet.DB
+{
+    public class AlreadyPresentException : VerifyException
+    {
+        public AlreadyPresentException(string msg) : base("Discreet.Coin.Verify: " + msg) { }
+
+        public AlreadyPresentException(string type, string msg) : base("Discreet.Coin." + type + ".Verify: " + msg) { }
+
+        public AlreadyPresentException(string type, string vertype, string msg) : base("Discreet.Coin." + type + "Verify" + vertype + ": " + msg) { }
+    }
+}

Discreet/DB/ValidationCache.cs

@@ -136,7 +136,7 @@ private Exception validate(bool many = false)
             if (!block.Hash().Equals(block.Header.BlockHash)) return new VerifyException("Block", $"Block hash in header does not match calculated block hash");
             if (blockBuffer.BlockExists(block.Header.BlockHash))
             {
-                return new VerifyException("Block", $"Block already present");
+                return new AlreadyPresentException("Block", $"Block already present");
             }
             if (block.Transactions == null || block.Transactions.Length == 0) return new VerifyException("Block", "Block contains no transactions");
             if (block.Header.NumTXs != block.Transactions.Length) return new VerifyException("Block", $"Block tx mismatch: expected {block.Header.NumTXs}; got {block.Transactions.Length}");

Discreet/Daemon/Daemon.cs

@@ -437,7 +437,11 @@ public async Task<bool> Start()
                         {
                             var vcache = new DB.ValidationCache(messageCache.GetAllCachedBlocks(_beginHeight, _newHeight));
                             (exc, _beginHeight, var goodBlocks, var reget) = vcache.ValidateReturnFailures();
-
+                            if (exc is AlreadyPresentException apex)
+                            {
+                                // ignore this
+                                exc = null;
+                            }
                             if (exc != null && reget != null)
                             {
                                 // first, flush valid blocks

Discreet/Network/Handler.cs

@@ -892,7 +892,7 @@ public async Task HandleGetBlocks(GetBlocksPacket p, IPEndPoint senderEndpoint)
 
         public async Task HandleGetTxs(GetTransactionsPacket p, IPEndPoint senderEndpoint)
         {
-            DB.DataView dataView = DB.DataView.GetView();
+            IView dataView = BlockBuffer.Instance;
 
             List<FullTransaction> txs = new();
             List<InventoryVector> notFound = new();
@@ -1386,7 +1386,7 @@ public async Task HandleBlocks(BlocksPacket p, Peerbloom.Connection conn)
 
         public async Task HandleGetHeaders(GetHeadersPacket p, Peerbloom.Connection conn)
         {
-            DB.DataView dataView = DB.DataView.GetView();
+            IView dataView = BlockBuffer.Instance;
 
             List<BlockHeader> headers = new();
             List<InventoryVector> notFound = new();