转换对象为void *和回来？ [英] Convert object to void* and back?

问题描述

我想写围绕期望一个功能的 C函数包装指针和任意的用户数据（无效* ）。函数指针我已经想通了如何处理使用委托，但我无法弄清楚如何转换对象到无效* 。

I'm trying to write a wrapper around a C function that expects a function pointer and arbitrary user data (void*). The function pointer I've figured out how to deal with using delegates, but I can't figure out how to convert an object into a void*.

我可以把它 REF对象来代替，因为这就像一个指针，据我所知，但是当我尝试，我得到这样

I can make it a ref object instead, since that behaves like a pointer AFAIK, but when I try that I get an exception like

从非托管VARIANT到托管对象的转换过程中，检测到无效VARIANT。传递无效变种的CLR会导致意外的异常，损坏或数据丢失。

An invalid VARIANT was detected during a conversion from an unmanaged VARIANT to a managed object. Passing invalid VARIANTs to the CLR can cause unexpected exceptions, corruption or data loss.

该办法可能为我工作，但我想必须有传递任意数据的方法一个C DLL，以便它可以在以后传递回

This "solution" might work for me, but I figured there has to be a way to pass arbitrary data to a C DLL so that it can be passed back later?

推荐答案

就个人而言，我会建议使用结构在这里，这是你想什么更适用做（再加上你可以调整内部布局如果需要）。例如，使用结构美孚和的引用类型字段的富

Personally, I would advise using a struct here, which is much more applicable for what you are trying to do (plus you can tweak the internal layout if you need). For example, with a struct Foo, and a field on a reference-type foo:

unsafe void Bar()
{   
    fixed (Foo* ptr = &foo) // here foo is a field on a reference-type
    {
        void* v = ptr; // if you want void*
        IntPtr i = new IntPtr(ptr); // if you want IntPtr
        // use v or i here...
    }
}

请注意：如果富是局部变量的，那么它是在栈上，并没有必要一定固定：

Note: if foo is a local variable, then it is on the stack and doesn't even need to be fixed:

unsafe void Bar()
{
    Foo foo = new Foo();
    Foo* ptr = &foo; // here foo is a local variable

    void* v = ptr; // if you want void*
    IntPtr i = new IntPtr(ptr); // if you want IntPtr
    // use v or i here...
}

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