IntPtr.Subtraction(IntPtr, Int32) IntPtr.Subtraction(IntPtr, Int32) IntPtr.Subtraction(IntPtr, Int32) IntPtr.Subtraction(IntPtr, Int32) Operator

Definition

Subtracts an offset from the value of a pointer.

public:
 static IntPtr operator -(IntPtr pointer, int offset);
public static IntPtr operator - (IntPtr pointer, int offset);
static member ( - ) : nativeint * int -> nativeint
Public Shared Operator - (pointer As IntPtr, offset As Integer) As IntPtr

Parameters

pointer
IntPtr IntPtr IntPtr IntPtr

The pointer to subtract the offset from.

offset
Int32 Int32 Int32 Int32

The offset to subtract.

Returns

A new pointer that reflects the subtraction of offset from pointer.

Remarks

The Subtraction method defines the subtraction operation for IntPtr objects. It enables code such as the following.

int[] arr = { 2, 4, 6, 8, 10, 12, 14, 16, 18, 20};
unsafe {            
   fixed(int* parr = &arr[arr.GetUpperBound(0)])
   {
      IntPtr ptr = new IntPtr(parr);
      for (int ctr = 0; ctr <= arr.GetUpperBound(0); ctr++)
      {
         IntPtr newPtr = ptr - ctr * sizeof(Int32);
         Console.Write("{0}   ", Marshal.ReadInt32(newPtr));
      }
   }
}   
// The example displays the following output:
//       20   18   16   14   12   10   8   6   4   2      
Dim arr() As Integer = {2, 4, 6, 8, 10, 12, 14, 16, 18, 20 }
Dim ptr As IntPtr = Marshal.UnsafeAddrOfPinnedArrayElement(arr, arr.GetUpperBound(0))
For ctr As Integer= 0 To arr.GetUpperBound(0)
   Dim newPtr As IntPtr = ptr - ctr * Len(arr(0))
   Console.Write("{0}   ", Marshal.ReadInt32(newPtr))
Next

Languages that do not support custom operators can call the Subtract method instead.

The subtraction operation does not throw an exception if the result is too small to represent as a pointer on the specified platform. Instead, it is performed in an unchecked context.

The equivalent method for this operator is IntPtr.Subtract(IntPtr, Int32)

Applies to

See also