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IntPtr.Subtraction(IntPtr, Int32) Operator

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Definition

Namespace:
System
Assembly:
System.Runtime.dll
Assembly:
mscorlib.dll
Assembly:
netstandard.dll
Source:
IntPtr.cs
Source:
IntPtr.cs
Source:
IntPtr.cs

Subtracts an offset from a signed integer.

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

nativeint

The signed integer to subtract the offset from.

offset
Int32

The offset to subtract.

Returns

IntPtr

nativeint

A new signed integer 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

#nowarn "9"
open System.Runtime.InteropServices
open FSharp.NativeInterop

[<EntryPoint>]
let main _ =
    let arr =
        [| 2; 4; 6; 8; 10; 12; 14; 16; 18; 20 |]

    use parr = fixed &arr[arr.GetUpperBound 0]
    
    let ptr = NativePtr.toNativeInt parr

    for i = 0 to arr.GetUpperBound 0 do
        let newPtr = ptr - nativeint i * nativeint sizeof<int>
        printf $"{Marshal.ReadInt32 newPtr}   "
    0

    // 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 signed integer in the executing process. Instead, it is performed in an unchecked context.

In C# starting from version 11 and when targeting the .NET 7 or later runtime, this API is only accessible via reflection. The subtraction operator is directly recognized by the language and will follow the normal language behavior for subtraction operations, including overflowing in a checked context if the result is too small to represent.

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

Applies to

See also