Merge pull request #15516 from jkotas/revert

Revert "Add optional integer offset to OwnedMemory Pin (#15410)"

Author: jkotas

src/mscorlib/shared/System/Buffers/MemoryHandle.cs

@@ -21,6 +21,18 @@ public unsafe struct MemoryHandle : IDisposable
             _handle = handle;
         }
 
+        internal void AddOffset(int offset)
+        {
+            if (_pointer == null)
+            {
+                ThrowHelper.ThrowArgumentNullException(ExceptionArgument.pointer);
+            }
+            else
+            {
+                _pointer = (void*)((byte*)_pointer + offset);
+            }
+        }
+
         [CLSCompliant(false)]
         public void* Pointer => _pointer;
 

src/mscorlib/shared/System/Buffers/OwnedMemory.cs

@@ -25,7 +25,7 @@ public Memory<T> Memory
             }
         }
 
-        public abstract MemoryHandle Pin(int offset = 0);
+        public abstract MemoryHandle Pin();
 
         protected internal abstract bool TryGetArray(out ArraySegment<T> arraySegment);
 

src/mscorlib/shared/System/Memory.cs

@@ -234,7 +234,8 @@ public unsafe MemoryHandle Retain(bool pin = false)
             {
                 if (_index < 0)
                 {
-                    memoryHandle = ((OwnedMemory<T>)_object).Pin((_index & RemoveOwnedFlagBitMask) * Unsafe.SizeOf<T>());
+                    memoryHandle = ((OwnedMemory<T>)_object).Pin();
+                    memoryHandle.AddOffset((_index & RemoveOwnedFlagBitMask) * Unsafe.SizeOf<T>());
                 }
                 else if (typeof(T) == typeof(char) && _object is string s)
                 {

src/mscorlib/shared/System/ReadOnlyMemory.cs

@@ -216,7 +216,8 @@ public unsafe MemoryHandle Retain(bool pin = false)
             {
                 if (_index < 0)
                 {
-                    memoryHandle = ((OwnedMemory<T>)_object).Pin((_index & RemoveOwnedFlagBitMask) * Unsafe.SizeOf<T>());
+                    memoryHandle = ((OwnedMemory<T>)_object).Pin();
+                    memoryHandle.AddOffset((_index & RemoveOwnedFlagBitMask) * Unsafe.SizeOf<T>());
                 }
                 else if (typeof(T) == typeof(char) && _object is string s)
                 {