Unify the BigInteger serialization standard with NeoVM

src/neo/Helper.cs

@@ -197,6 +197,13 @@ internal static bool TestBit(this BigInteger i, int index)
             return (i & (BigInteger.One << index)) > BigInteger.Zero;
         }
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static byte[] ToByteArrayStandard(this BigInteger i)
+        {
+            if (i.IsZero) return Array.Empty<byte>();
+            return i.ToByteArray();
+        }
+
         public static string ToHexString(this byte[] value)
         {
             StringBuilder sb = new StringBuilder();

src/neo/SmartContract/Native/Tokens/GasToken.cs

@@ -47,7 +47,7 @@ protected override bool OnPersist(ApplicationEngine engine)
             StorageKey key = CreateStorageKey(Prefix_SystemFeeAmount, BitConverter.GetBytes(engine.Snapshot.PersistingBlock.Index));
             engine.Snapshot.Storages.Add(key, new StorageItem
             {
-                Value = sys_fee.ToByteArray(),
+                Value = sys_fee.ToByteArrayStandard(),
                 IsConstant = true
             });
             return true;

src/neo/SmartContract/Native/Tokens/NeoToken.cs

@@ -292,7 +292,7 @@ public static ValidatorState FromByteArray(byte[] data)
 
             public byte[] ToByteArray()
             {
-                return Votes.ToByteArray();
+                return Votes.ToByteArrayStandard();
             }
         }
 
@@ -322,7 +322,7 @@ public byte[] ToByteArray()
                 {
                     w.WriteVarInt(Votes.Length);
                     foreach (BigInteger vote in Votes)
-                        w.WriteVarBytes(vote.ToByteArray());
+                        w.WriteVarBytes(vote.ToByteArrayStandard());
                     w.Flush();
                     return ms.ToArray();
                 }

src/neo/SmartContract/Native/Tokens/Nep5Token.cs

@@ -80,11 +80,11 @@ internal protected virtual void Mint(ApplicationEngine engine, UInt160 account,
             storage.Value = state.ToByteArray();
             storage = engine.Snapshot.Storages.GetAndChange(CreateStorageKey(Prefix_TotalSupply), () => new StorageItem
             {
-                Value = BigInteger.Zero.ToByteArray()
+                Value = BigInteger.Zero.ToByteArrayStandard()
             });
             BigInteger totalSupply = new BigInteger(storage.Value);
             totalSupply += amount;
-            storage.Value = totalSupply.ToByteArray();
+            storage.Value = totalSupply.ToByteArrayStandard();
             engine.SendNotification(Hash, new StackItem[] { "Transfer", StackItem.Null, account.ToArray(), amount });
         }
 
@@ -110,7 +110,7 @@ internal protected virtual void Burn(ApplicationEngine engine, UInt160 account,
             storage = engine.Snapshot.Storages.GetAndChange(CreateStorageKey(Prefix_TotalSupply));
             BigInteger totalSupply = new BigInteger(storage.Value);
             totalSupply -= amount;
-            storage.Value = totalSupply.ToByteArray();
+            storage.Value = totalSupply.ToByteArrayStandard();
             engine.SendNotification(Hash, new StackItem[] { "Transfer", account.ToArray(), StackItem.Null, amount });
         }
 

tests/neo.UnitTests/SmartContract/Native/Tokens/UT_GasToken.cs

@@ -172,7 +172,7 @@ public void TestGetSysFeeAmount2()
             BigInteger sys_fee = new BigInteger(10);
             snapshot.Storages.Add(storageKey, new StorageItem
             {
-                Value = sys_fee.ToByteArray(),
+                Value = sys_fee.ToByteArrayStandard(),
                 IsConstant = true
             });
 

tests/neo.UnitTests/SmartContract/Native/Tokens/UT_Nep5Token.cs

@@ -51,10 +51,9 @@ public void TestTotalSupplyDecimal()
             BigInteger totalSupply = 100_000_000;
             totalSupply *= test.Factor;
 
-            byte[] value = totalSupply.ToByteArray();
             StorageItem item = new StorageItem
             {
-                Value = value
+                Value = totalSupply.ToByteArrayStandard()
             };
             var key = CreateStorageKey(Prefix_TotalSupply);