Lightweight blockstate

src/neo/Helper.cs

@@ -298,5 +298,16 @@ internal static IPEndPoint Unmap(this IPEndPoint endPoint)
                 return endPoint;
             return new IPEndPoint(endPoint.Address.Unmap(), endPoint.Port);
         }
+
+        internal static byte[] XOR(this byte[] value, byte[] other)
+        {
+            if (value.Length != other.Length) return null;
+
+            for (int i = 0; i < value.Length; i++)
+            {
+                value[i] ^= other[i];
+            }
+            return value;
+        }
     }
 }

src/neo/Ledger/Blockchain.cs

@@ -14,6 +14,7 @@
 using System.Collections.Immutable;
 using System.Diagnostics;
 using System.Linq;
+using System.Security.Cryptography;
 
 namespace Neo.Ledger
 {
@@ -390,14 +391,16 @@ private void Persist(Block block)
                     all_application_executed.Add(application_executed);
                 }
                 DataCache clonedSnapshot = snapshot.CreateSnapshot();
+                using var sha256 = SHA256.Create();
+                byte[] state = null;
                 // Warning: Do not write into variable snapshot directly. Write into variable clonedSnapshot and commit instead.
                 foreach (Transaction tx in block.Transactions)
                 {
                     using ApplicationEngine engine = ApplicationEngine.Create(TriggerType.Application, tx, clonedSnapshot, block, system.Settings, tx.SystemFee);
                     engine.LoadScript(tx.Script);
                     if (engine.Execute() == VMState.HALT)
                     {
-                        clonedSnapshot.Commit();
+                        state = sha256.ComputeHash(clonedSnapshot.Commit()).XOR(state);
                     }
                     else
                     {
@@ -417,6 +420,10 @@ private void Persist(Block block)
                 }
                 foreach (IPersistencePlugin plugin in Plugin.PersistencePlugins)
                     plugin.OnPersist(system, block, snapshot, all_application_executed);
+
+                // TODO: this should be moved to a native contract or somewhere to make is more reasonable
+                // The key should contain the block height
+                snapshot.Add(new StorageKey(), new StorageItem(state));
                 snapshot.Commit();
                 List<Exception> commitExceptions = null;
                 foreach (IPersistencePlugin plugin in Plugin.PersistencePlugins)

src/neo/Persistence/DataCache.cs

@@ -2,7 +2,10 @@
 using Neo.SmartContract;
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
+using System.Security.Cryptography;
+using Neo.Cryptography;
 
 namespace Neo.Persistence
 {
@@ -30,6 +33,16 @@ public class Trackable
             /// The state of the entry.
             /// </summary>
             public TrackState State;
+
+            public byte[] GetHash()
+            {
+                using MemoryStream ms = new();
+                using BinaryWriter writer = new(ms);
+                writer.Write(Key);
+                writer.Write(Item);
+                writer.Write((byte)State);
+                return ms.ToArray().Sha256();
+            }
         }
 
         private readonly Dictionary<StorageKey, Trackable> dictionary = new();
@@ -100,10 +113,14 @@ public void Add(StorageKey key, StorageItem value)
         /// <summary>
         /// Commits all changes in the cache to the underlying storage.
         /// </summary>
-        public virtual void Commit()
+        public virtual byte[] Commit()
         {
+            using var sha256 = SHA256.Create();
+            byte[] state = null;
             LinkedList<StorageKey> deletedItem = new();
             foreach (Trackable trackable in GetChangeSet())
+            {
+                state = sha256.ComputeHash(trackable.GetHash()).XOR(state);
                 switch (trackable.State)
                 {
                     case TrackState.Added:
@@ -119,11 +136,14 @@ public virtual void Commit()
                         deletedItem.AddFirst(trackable.Key);
                         break;
                 }
+            }
+
             foreach (StorageKey key in deletedItem)
             {
                 dictionary.Remove(key);
             }
             changeSet.Clear();
+            return state;
         }
 
         /// <summary>

src/neo/Persistence/SnapshotCache.cs

@@ -34,10 +34,11 @@ protected override void DeleteInternal(StorageKey key)
             snapshot?.Delete(key.ToArray());
         }
 
-        public override void Commit()
+        public override byte[] Commit()
         {
             base.Commit();
             snapshot.Commit();
+            return null;
         }
 
         protected override bool ContainsInternal(StorageKey key)