涉及指针时如何 P/Invoke
在尝试学习在 C# 中使用 PInvoke 时，我有点不确定如何处理涉及简单值类型的指针的各种情况。
我从非托管 DLL 导入以下两个函数：
public int USB4_Initialize(short* device);
public int USB4_GetCount(short device, short encoder, unsigned long* value);
第一个函数使用指针作为输入，第二个函数使用指针作为输出。它们在 C++ 中的用法相当简单：
// Pointer as an input
short device = 0; // Always using device 0.
USB4_Initialize(&device);
// Pointer as an output
unsigned long count;
USB4_GetCount(0,0,&count); // count is output
我在 C# 中的第一次尝试产生了以下 P/Invokes：
[DllImport("USB4.dll")]
public static extern int USB4_Initialize(IntPtr deviceCount); //short*
[DllImport("USB4.dll")]
public static extern int USB4_GetCount(short deviceNumber, short encoder, IntPtr value); //ulong*
如何以与上面的 C++ 代码相同的方式在 C# 中使用这些函数？ 是否有更好的方法声明这些类型的方法，也许使用MarshalAs？
In an attempt to learn to use PInvoke in C#, I'm a little unsure how to handle various cases with pointers involving simple value types.
I'm importing the following two functions from an unmanaged DLL:
public int USB4_Initialize(short* device);
public int USB4_GetCount(short device, short encoder, unsigned long* value);
The first function uses the pointer as an input, the second as an output. Their usage is fairly simple in C++:
// Pointer as an input
short device = 0; // Always using device 0.
USB4_Initialize(&device);
// Pointer as an output
unsigned long count;
USB4_GetCount(0,0,&count); // count is output
My first attempt in C# results in the following P/Invokes:
[DllImport("USB4.dll")]
public static extern int USB4_Initialize(IntPtr deviceCount); //short*
[DllImport("USB4.dll")]
public static extern int USB4_GetCount(short deviceNumber, short encoder, IntPtr value); //ulong*
How do I use these functions in C# in the same way as the C++ code above? Is there a better way to declare these types, perhaps using MarshalAs?
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如果指针指向单个基本类型而不是数组，请使用 ref / out 来描述参数。
在这些示例中，out 可能更合适，但两者都可以。
If the pointer is to a single primitive type and not an array, use ref / out to describe the parameter
In these examples out is probably more appropriate but either will work.
.NET 运行时可以为您执行大量转换（称为“封送处理”）。虽然显式 IntPtr 始终会完全按照您的指示执行操作，但您可以用
ref关键字替换这样的指针。然后你可以这样称呼它们：
The .NET runtime can do a lot of that conversion (referred to as "marshaling") for you. While an explicit IntPtr will always do EXACTLY what you tell it to, you can likely substitute the
refkeyword for a pointer like that.You can then call them like this: