PInvoke的，指针和数组复制 [英] PInvoke, pointers and array copy

问题描述

我们正在建立一个应用程序在C＃.NET 4.0，对Win7的X64，X32定位

We're building an application on c#, .net 4.0, on Win7 x64, targeting x32.

我们在我们的应用程序中使用第三方库。据我们了解，该库是用C ++写的。然而，为了让C＃开发人员使用这个库，他们已经把它包使用P / Invoke，所以这就是我们如何调用API函数。

We are using a 3rd party library in our application. We understand that this library is written using C++. However, to let c# developers use this library, they've wrapped it using P/Invoke, so that's how we call the API functions.

其中一个API调用如下：

One of the API calls is as follows:

ReadFromDevice(int deviceAddress, int numBytes, Byte[] data);

此功能从外部设备读取数据的numBytes和数据[]放置它。正如你所看到的，希望看到一个C＃Byte数组作为第三个参数。现在，我们的问题是，我们想读取数据以predeclared阵列的任意位置。例如：

This function reads numBytes of data from an external device and places it in data[]. As you can see, it expects to see a C# Byte array as the 3rd argument. Now, our problem is, we would like to read data to an arbitrary location in a predeclared array. For example:

Byte[] myData = new Byte[1024*1024*16];
ReadFromDevice(0x100, 20000, &myData[350]) // Obviously not possible in C#

如果我们使用C / C ++，这将是微不足道的。鉴于底层API是用C ++，我觉得我们应该能够做到这一点在C＃中为好，不过，我无法弄清楚如何做到这一点在C＃。也许我们能以某种方式调用基础库不通过提供的P / Invoke接口，并编写自定义的界面？

If we were using C/C++, this would be trivial. Given that the underlying API is written in C++, I feel that we should be able to do this in c# as well, however, I can't figure out how to do this in c#. Maybe we can somehow call the underlying library not through the supplied P/Invoke interface and write a custom interface?

任何想法，将AP preciated。

Any ideas would be appreciated.

问候，

推荐答案

在这里其他的答案比较接近，没有一个是比较齐全的。

While the other answers here are close, none are quite complete.

首先，你只需要简单地声明自己的P / Invoke声明。这是关于P中的甜蜜的事/调用;从未有只有一个办法做到这一点。

First you simply need to declare your own p/invoke declaration. This is the sweet thing about p/invoke; There's never just one way to do it.

[DllImport("whatever.dll")]
unsafe extern static void ReadFromDevice(int deviceAddress, int numBytes, byte* data);

现在你可以把它叫做

unsafe static void ReadFromDevice(int deviceAddress, byte[] data, int offset, int numBytes)
{
    fixed (byte* p = data)
    {
        ReadFromDevice(deviceAddress, numBytes, p + offset);
    }
}

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