我目前正在为PhysFS library编写一个包装器,并且偶然发现了一些关于托管对象编组的麻烦。以PHYSFS_enumerateFilesCallback方法为例,该方法将函数指针和用户定义的指针作为其参数。如何将托管对象传递给此方法?这就是我目前正在做的事情:
// This is the delegate signature
public delegate void EnumFilesCallback(IntPtr data, string origdir, string fname);
// This is the method signature
[DllImport(DLL_NAME, CallingConvention = CallingConvention.Cdecl)]
public static extern void PHYSFS_enumerateFilesCallback(string dir, EnumFilesCallback c, IntPtr d);
最后,这就是我将任意对象传递给该方法的方法:
// I use the unsafe keyword because the whole Interop class is declared so.
// This code was taken from https://msdn.microsoft.com/en-us/library/system.runtime.interopservices.gchandle(VS.71).aspx
public static void EnumerateFilesCallback(string dir, EnumFilesCallback c, object data)
{
unsafe
{
GCHandle objHandle = GCHandle.Alloc(data);
Interop.PHYSFS_enumerateFilesCallback(dir, c, (IntPtr)objHandle);
objHandle.Free();
}
}
当我运行此代码时:
static void Enum(IntPtr d, string origdir, string fname )
{
System.Runtime.InteropServices.GCHandle handle = (System.Runtime.InteropServices.GCHandle)d;
TestClass c = (TestClass)handle.Target;
Console.WriteLine("{0} {1}", origdir, fname);
}
static void Main(string[] args)
{
PhysFS.Init("");
PhysFS.Mount("D:\\", "/hello", true);
TestClass x = new TestClass() { a = 3, b = 4 }; // This can be any gibberish object
PhysFS.EnumerateFilesCallback("/hello/", Enum, x);
}
委托被合法数据调用 4 次,第五次包含垃圾数据,然后它抛出 AccessViolationException 我怀疑这是因为对象在调用委托之间被 GC。任何人都可以阐明这一点吗?
更新:更改挂载目录消除了垃圾数据,但仍然抛出异常,并且仍然在所有数据都可以使用之前