TryPop shouldn't change the state of the stack when returns false (#304)

neo-project · Mar 22, 2020 · f292fed · f292fed
1 parent f6234fd
commit f292fed
Show file tree

Hide file tree

Showing 2 changed files with 41 additions and 5 deletions.
diff --git a/src/neo-vm/EvaluationStack.cs b/src/neo-vm/EvaluationStack.cs
@@ -89,6 +89,17 @@ internal bool Reverse(int n)
             return true;
         }
 
+        public bool TryPeek<T>(out T item) where T : StackItem
+        {
+            if (innerList.Count == 0)
+            {
+                item = default;
+                return false;
+            }
+            item = innerList[^1] as T;
+            return item != null;
+        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public bool TryPop<T>(out T item) where T : StackItem
         {

diff --git a/src/neo-vm/ExecutionEngine.cs b/src/neo-vm/ExecutionEngine.cs
@@ -1274,17 +1274,19 @@ public bool TryPop(out bool b)
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public bool TryPop(out ReadOnlySpan<byte> b)
         {
-            if (!TryPop(out StackItem item))
+            if (!CurrentContext.EvaluationStack.TryPeek(out StackItem item))
             {
                 b = default;
                 return false;
             }
             switch (item)
             {
                 case PrimitiveType primitive:
+                    CurrentContext.EvaluationStack.Pop();
                     b = primitive.Span;
                     return true;
                 case Buffer buffer:
+                    CurrentContext.EvaluationStack.Pop();
                     b = buffer.InnerBuffer;
                     return true;
                 default:
@@ -1311,16 +1313,39 @@ public bool TryPop(out BigInteger i)
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public bool TryPop(out int i)
         {
-            if (!TryPop(out BigInteger item) || item < int.MinValue || item > int.MaxValue)
+            if (!CurrentContext.EvaluationStack.TryPeek(out PrimitiveType item))
             {
                 i = default;
                 return false;
             }
-            else
+            BigInteger bi = item.ToBigInteger();
+            if (bi < int.MinValue || bi > int.MaxValue)
             {
-                i = (int)item;
-                return true;
+                i = default;
+                return false;
+            }
+            CurrentContext.EvaluationStack.Pop();
+            i = (int)bi;
+            return true;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public bool TryPop(out uint i)
+        {
+            if (!CurrentContext.EvaluationStack.TryPeek(out PrimitiveType item))
+            {
+                i = default;
+                return false;
             }
+            BigInteger bi = item.ToBigInteger();
+            if (bi < uint.MinValue || bi > uint.MaxValue)
+            {
+                i = default;
+                return false;
+            }
+            CurrentContext.EvaluationStack.Pop();
+            i = (uint)bi;
+            return true;
         }
     }
 }