AST.Sub.GetPointerSubtraction C# (CSharp) Метод

        public static ABT.Expr GetPointerSubtraction(ABT.Expr ptr, ABT.Expr offset) {
            if (ptr.Type.Kind != ABT.ExprTypeKind.POINTER) {
                throw new InvalidOperationException("Error: expect a pointer");
            }
            if (offset.Type.Kind != ABT.ExprTypeKind.LONG) {
                throw new InvalidOperationException("Error: expect an integer");
            }

            if (ptr.IsConstExpr && offset.IsConstExpr) {
                Int32 baseAddressValue = (Int32)((ABT.ConstPtr)ptr).Value;
                Int32 scaleFactorValue = ((ABT.PointerType)(ptr.Type)).RefType.SizeOf;
                Int32 offsetValue = ((ABT.ConstLong)offset).Value;
                return new ABT.ConstPtr((UInt32)(baseAddressValue - scaleFactorValue * offsetValue), ptr.Type, offset.Env);
            }

            return ABT.TypeCast.ToPointer(new ABT.Sub(
                    ABT.TypeCast.FromPointer(ptr, new ABT.LongType(ptr.Type.IsConst, ptr.Type.IsVolatile), ptr.Env),
                    new ABT.Multiply(
                        offset,
                        new ABT.ConstLong(((ABT.PointerType)(ptr.Type)).RefType.SizeOf, offset.Env)
                    )
                ), ptr.Type, offset.Env
            );
        }