指向 C++/CLI 中托管数组的指针

发布于 2024-09-15 07:23:27 字数 547 浏览 2 评论 0原文

好吧，我知道你通常会如何声明一个指针：

void SomeFunction(array<float> ^managedArray)
{
  pin_ptr<float> managedArrayPtr = &managedArray[0];
}

这工作得很好，除非 ManagedArray 不包含任何元素。在这种情况下，它会抛出 IndexOutOfRangeException。

在 C# 中，您可以这样做：

void SomeFunction(float[] managedArray)
{
  fixed (float* managedArrayPtr = managedArray)
  {
  }
}

它不进行内存访问，即使 ManagedArray 为空也能工作。我是否真的必须在所有使用托管数组指针的地方检查元素的数量，或者 C++/CLI 是否有办法像 C# 那样执行此操作？它应该使用 ASM 中的“lea”指令，该指令不进行内存访问。

非常感谢任何帮助！

原文

Alright, I know how you normally would declare a pointer:

void SomeFunction(array<float> ^managedArray)
{
  pin_ptr<float> managedArrayPtr = &managedArray[0];
}

This works fine except when managedArray contains no elements. In that case, it throws an IndexOutOfRangeException.

In C# you can do this:

void SomeFunction(float[] managedArray)
{
  fixed (float* managedArrayPtr = managedArray)
  {
  }
}

Which does no memory access and works even if managedArray is empty.
Do I really have to check for the number of elements everywhere I use pointers to managed arrays or does C++/CLI have a way to do it like C#?
It should be using the 'lea' instruction in ASM which does no memory access.

Any help is greatly appreciated!

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甜｀诱少女 2024-09-22 07:23:27

当数组为空时尝试读取它没有多大意义。只需检查一下：

void SomeFunction(array<float> ^managedArray)
{
    if (managedArray->Length > 0) {
        pin_ptr<float> managedArrayPtr = managedArray;
        //etc...
    }
}

There isn't much point in trying to read from the array when it is empty. Just check for that:

void SomeFunction(array<float> ^managedArray)
{
    if (managedArray->Length > 0) {
        pin_ptr<float> managedArrayPtr = managedArray;
        //etc...
    }
}

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握住你手 2024-09-22 07:23:27

好问题。不幸的是我对 C++/CLI 不太熟悉。我确实知道您可以使用 GCHandle 结构手动进行固定，并且可以处理空数组。但它并不像使用pin_ptr那么优雅。

void SomeFunction(array<float> ^managedArray) 
{ 
 GCHandle handle = GCHandle::Alloc(managedArray, GCHandleType::Pinned);
 try 
 {
  float* ptr = (float*)(void*)handle.AddrOfPinnedObject();
 }
 finally
 {
  handle.Free();
 }
}

Good question. Unfortunately I am not that familiar with C++/CLI. I do know that you can do the pinning manually using the GCHandle struct and will work on empty arrays. It is not as elegant as using pin_ptr though.

void SomeFunction(array<float> ^managedArray) 
{ 
 GCHandle handle = GCHandle::Alloc(managedArray, GCHandleType::Pinned);
 try 
 {
  float* ptr = (float*)(void*)handle.AddrOfPinnedObject();
 }
 finally
 {
  handle.Free();
 }
}

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