Arithmetic Operations on Pointers (C# Programming Guide)
This topic discusses using the arithmetic operators + and - to manipulate pointers.
Note
You cannot perform any arithmetic operations on void pointers.
Adding and Subtracting Numeric Values to or From Pointers
You can add a value n of type int, uint, long, or ulong to a pointer, p,of any type except void*. The result p+n is the pointer resulting from adding n * sizeof(p) to the address of p. Similarly, p-n is the pointer resulting from subtracting n * sizeof(p) from the address of p.
Subtracting Pointers
You can also subtract pointers of the same type. The result is always of the type long. For example, if p1 and p2 are pointers of the type pointer-type*, then the expression p1-p2 results in:
((long)p1 - (long)p2)/sizeof(pointer_type)
No exceptions are generated when the arithmetic operation overflows the domain of the pointer, and the result depends on the implementation.
Example
// compile with: /unsafe
class PointerArithmetic
{
unsafe static void Main()
{
int* memory = stackalloc int[30];
long* difference;
int* p1 = &memory[4];
int* p2 = &memory[10];
difference = (long*)(p2 - p1);
System.Console.WriteLine("The difference is: {0}", (long)difference);
}
}
// Output: The difference is: 6
C# Language Specification
For more information, see the following sections in the C# Language Specification:
- 18.5.6 Pointer Arithmetic
See Also
Concepts
Reference
Unsafe Code and Pointers (C# Programming Guide)
Pointer Expressions (C# Programming Guide)
Manipulating Pointers (C# Programming Guide)
Pointer types (C# Programming Guide)
fixed Statement (C# Reference)