如何将System :: array转换为std :: vector？ [英] How to convert System::array to std::vector?

问题描述

有没有简单的方法可以将CLI / .NET System :: array 转换为C ++ std :: vector ，除了按元素进行操作外？

Is there any easy way to convert a CLI/.NET System::array to a C++ std::vector, besides doing it element-wise?

我正在编写包装方法（ SetLowerBoundsWrapper，在下面）在CLI / C ++中，它接受 System :: array 作为参数，并将等效的 std :: vector 传递给原生C ++方法（ set_lower_bounds ）。目前，我的操作如下：

I'm writing a wrapper method (SetLowerBoundsWrapper, below) in CLI/C++ that accepts a System::array as an argument, and passes the equivalent std::vector to a native C++ method (set_lower_bounds). Currently I do this as follows:

using namespace System;

void SetLowerBoundsWrapper(array<double>^ lb)
{
    int n = lb->Length;
    std::vector<double> lower(n); //create a std::vector
    for(int i = 0; i<n ; i++)
    {
        lower[i] = lb[i];         //copy element-wise
    } 
    _opt->set_lower_bounds(lower);
}

推荐答案

另一种方法是让。 NET BCL代替C ++标准库来工作：

Another approach, letting the .NET BCL do the work instead of the C++ standard library:

#include <vector>

void SetLowerBoundsWrapper(array<double>^ lb)
{
    using System::IntPtr;
    using System::Runtime::InteropServices::Marshal;

    std::vector<double> lower(lb->Length);
    Marshal::Copy(lb, 0, IntPtr(&lower[0]), lb->Length);
    _opt->set_lower_bounds(lower);
}

---

以下两者均针对我使用VC ++ 2010 SP1，并且完全等效：

---

The following both compile for me with VC++ 2010 SP1, and are exactly equivalent:

#include <algorithm>
#include <vector>

void SetLowerBoundsWrapper(array<double>^ lb)
{
    std::vector<double> lower(lb->Length);
    {
        pin_ptr<double> pin(&lb[0]);
        double *first(pin), *last(pin + lb->Length);
        std::copy(first, last, lower.begin());
    }
    _opt->set_lower_bounds(lower);
}

void SetLowerBoundsWrapper2(array<double>^ lb)
{
    std::vector<double> lower(lb->Length);
    {
        pin_ptr<double> pin(&lb[0]);
        std::copy(
            static_cast<double*>(pin),
            static_cast<double*>(pin + lb->Length),
            lower.begin()
        );
    }
    _opt->set_lower_bounds(lower);
}

人为的范围是允许 pin_ptr 尽早取消固定内存，以免妨碍GC。

The artificial scope is to allow the pin_ptr to unpin the memory as early as possible, so as not to hinder the GC.

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