C++到C#:指针和数组

Question

下面是一个Win32控制台应用程序过程,演示了各种指针对数组的依赖性.通过例如取消注释标记为"// uncomment ..."的行来更改原始数组(模型)中的值会导致输出发生更改.我的问题是如何在C#托管代码环境中获取或模仿这种行为(即不使用不安全和指针)？

#include "stdafx.h"
#include <iostream>
using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
    float model[100];
    for(int i = 0; i < 100; i++) { model[i] = i; }

    // uncomment these to alter the results
    //model[5] = 5000;
    //model[20] = 20000;
    //model[38] = 38000;

    static const int componentCount = 5;

    float* coefs = model;                   // coefs points to model[0]
    float* mean = coefs + componentCount;   // mean points to model[0 + componentCount] == model[5]
    float* cov = mean + 3*componentCount;   // cov points to model[0 + componentCount + 3*componentCount] == model[20] 

    int ci = 2;
    float* c = cov + 9*ci;  // c points to model[0 + componentCount + 3*componentCount + 9*ci] == model[38] 

    int i = 0;
    cout <<"model : "<< model[i] << endl;   // 0
    cout <<"coefs : "<< coefs[i] << endl;   // 0
    cout <<"mean  : "<< mean[i] << endl;    // 5 (or 5000)
    cout <<"cov   : "<< cov[i] << endl;     // 20 (or 20000)
    cout <<"ci    : "<< ci << endl;         // 2
    cout <<"c     : "<< c[i] << endl;       // 38 (or 38000)

cin.get(); }

Answer 1

你可以在没有不安全代码的情况下在C#中做同样的事情:

struct ArrayPointer<T>
{
    private T[] array;
    private int offset;
    public ArrayPointer(T[] array) : this(array, 0)
    {
    }
    private ArrayPointer(T[] array, int offset)
    {
        Debug.Assert(array != null);
        Debug.Assert(offset >= 0);
        Debug.Assert(offset < array.Length);
        this.array = array;
        this.offset = offset;
    }
    public static ArrayPointer<T> operator+(ArrayPointer<T> p1, int p2)
    {
        return new ArrayPointer<T>(p1.array, p1.offset + p2);
    }

等等.定义加法,减法,递增,递减,比较,索引,数组转换等运算符​​.然后你可以说:

int[] arr = whatever;
ArrayPointer<int> pointer = arr;
pointer+=2;
pointer--;
int x = pointer[3];

等等.

这种方法有很多不错的特性.例如,如果您在p1和p2是指向不同数组内部的指针时比较p1> p2,则可以执行调试断言.这几乎总是C中的一个错误,但很难抓住.