Added validation for Pin methods

Author: Sergio0694

Microsoft.Toolkit.HighPerformance/Buffers/Internals/ArrayMemoryManager{TFrom,TTo}.cs

@@ -68,6 +68,11 @@ public override Span<TTo> GetSpan()
         /// <inheritdoc/>
         public override unsafe MemoryHandle Pin(int elementIndex = 0)
         {
+            if ((uint)elementIndex >= (uint)(this.length * Unsafe.SizeOf<TFrom>() / Unsafe.SizeOf<TTo>()))
+            {
+                ThrowArgumentExceptionForInvalidIndex();
+            }
+
             int
                 bytePrefix = this.offset + Unsafe.SizeOf<TFrom>(),
                 byteSuffix = elementIndex * Unsafe.SizeOf<TTo>(),
@@ -99,5 +104,13 @@ public MemoryManager<T> Cast<T>(int offset, int length)
         {
             return new ArrayMemoryManager<TFrom, T>(this.array, this.offset + offset, length);
         }
+
+        /// <summary>
+        /// Throws an <see cref="ArgumentOutOfRangeException"/> when the target index for <see cref="Pin"/> is invalid.
+        /// </summary>
+        private static void ThrowArgumentExceptionForInvalidIndex()
+        {
+            throw new ArgumentOutOfRangeException("elementIndex", "The input index is not in the valid range");
+        }
     }
 }

Microsoft.Toolkit.HighPerformance/Buffers/Internals/ProxyMemoryManager{TFrom,TTo}.cs

@@ -58,6 +58,11 @@ public override Span<TTo> GetSpan()
         /// <inheritdoc/>
         public override MemoryHandle Pin(int elementIndex = 0)
         {
+            if ((uint)elementIndex >= (uint)(this.length * Unsafe.SizeOf<TFrom>() / Unsafe.SizeOf<TTo>()))
+            {
+                ThrowArgumentExceptionForInvalidIndex();
+            }
+
             int byteOffset = elementIndex * Unsafe.SizeOf<TTo>();
 
 #if NETSTANDARD1_4
@@ -95,6 +100,14 @@ public MemoryManager<T> Cast<T>(int offset, int length)
             return new ProxyMemoryManager<TFrom, T>(this.memoryManager, this.offset + offset, length);
         }
 
+        /// <summary>
+        /// Throws an <see cref="ArgumentOutOfRangeException"/> when the target index for <see cref="Pin"/> is invalid.
+        /// </summary>
+        private static void ThrowArgumentExceptionForInvalidIndex()
+        {
+            throw new ArgumentOutOfRangeException("elementIndex", "The input index is not in the valid range");
+        }
+
         /// <summary>
         /// Throws an <see cref="ArgumentOutOfRangeException"/> when <see cref="Pin"/> receives an invalid target index.
         /// </summary>