将本机指针转换为 C++\CLI 托管对象引用？

Question

我有一个通过委托调用的回调。在其中，我需要处理从记录过程到达的缓冲区数据。通常，在非托管上下文中，我可以对 dwParam1 执行reinterpret_cast 来获取对象引用。但在托管上下文中，如何将 DWORD_PTR 转换为托管对象引用？

    static void WaveInProc(HWAVEIN hwi, UINT uMsg, DWORD_PTR dwInstance, DWORD_PTR dwParam1, DWORD_PTR dwParam2) 
    {
        ControlLib::SoundDevice^ soudDevice = ?cast_native2managed?(dwParam1);

Answer 1

在这里，或多或少 gcroot （根据我上面的评论）所做的：

using namespace System;
using namespace System::Runtime::InteropServices;

// track an object by a normal (not pinned) handle, encoded in a DWORD_PTR
DWORD_PTR ParamFromObject(Object^ obj)
{
    return reinterpret_cast<DWORD_PTR>(GCHandle::ToIntPtr(GCHandle::Alloc(obj)).ToPointer());
}

static void WaveInProc(PVOID hwi, UINT uMsg, DWORD_PTR dwInstance, DWORD_PTR dwParam1, DWORD_PTR dwParam2) 
{
    // unwrap the encoded handle...
    GCHandle h = GCHandle::FromIntPtr(IntPtr(reinterpret_cast<void*>(dwParam1)));
    try
    {
        // and cast your object back out
        SoundDevice^ x = safe_cast<SoundDevice^>(h.Target);
    }
    finally
    {
        // remember to free the handle when you're done, otherwise your object will never be collected
        GCHandle::Free(h);
    }
}