按引用传递参数使用P / Invoke回来的垃圾 [英] Parameters passed by reference come back garbage using P/Invoke

问题描述

我在Linux上使用单声道/ C＃和具有下面的C＃代码：

I am using Mono/C# on Linux and have the following C# code:

[DllImport("libaiousb")]
extern static ResultCode QueryDeviceInfo(uint deviceIndex, 
    ref uint PID, ref uint nameSize, StringBuilder name, 
    ref uint DIOBytes, ref uint counters);

和我所说的Linux共享定义库调用如下：

And I call a Linux shared library call defined as follows:

unsigned long QueryDeviceInfo(
      unsigned long DeviceIndex
    , unsigned long *pPID
    , unsigned long *pNameSize
    , char *pName
    , unsigned long *pDIOBytes
    , unsigned long *pCounters
    )

我已经调用Linux函数之前设置的参数为已知值。我也把一个printf在Linux的功能的开始，预期所有参数打印值。所以参数似乎传递从C＃到Linux ok了。返回值也不错。

I have set the parameters to known values before calling the Linux function. I've also put a printf at the beginning of the Linux function and all the parameters are printing values as expected. So the parameters seem to be passed from C# to Linux ok. The return value is also good.

不过，所有被引用传递的其他参数回来的垃圾。

However, all the other parameters that are passed by reference come back garbage.

我修改Linux的功能，所以它只是改变了价值和回报。下面是代码：

I modified the Linux function so it simply modifies the values and returns. Here's that code:

unsigned long QueryDeviceInfo(
    unsigned long DeviceIndex
    , unsigned long *pPID
    , unsigned long *pNameSize
    , char *pName
    , unsigned long *pDIOBytes
    , unsigned long *pCounters
) {
printf ("PID = %d, DIOBYtes = %d, Counters = %d, Name= %s", *pPID, *pDIOBytes, *pCounters, pName);
*pPID = 9;
*pDIOBytes = 8;
*pCounters = 7;
*pNameSize = 6;
return AIOUSB_SUCCESS;

所有裁判参数还回来的垃圾。

All the ref parameters still come back as garbage.

任何想法？

推荐答案

libaiousb.c

unsigned long QueryDeviceInfo(
     unsigned long deviceIndex
   , unsigned long *pPID
   , unsigned long *pNameSize
   , char *pName
   , unsigned long *pDIOBytes
   , unsigned long *pCounters
   )
{
   *pPID = 9;
   *pDIOBytes = 8;
   *pCounters = 7;
   *pNameSize = 6;
   return 0;
}

libaiousb.so

gcc -shared -o libaiousb.so libaiousb.c

< STRONG> test.cs中

using System;
using System.Runtime.InteropServices;
using System.Text;

class Test
{
    [DllImport("libaiousb")]
    static extern uint QueryDeviceInfo(uint deviceIndex,
        ref uint pid, ref uint nameSize, StringBuilder name,
        ref uint dioBytes, ref uint counters);

    static void Main()
    {
        uint deviceIndex = 100;
        uint pid = 101;
        uint nameSize = 102;
        StringBuilder name = new StringBuilder("Hello World");
        uint dioBytes = 103;
        uint counters = 104;

        uint result = QueryDeviceInfo(deviceIndex,
            ref pid, ref nameSize, name,
            ref dioBytes, ref counters);

        Console.WriteLine(deviceIndex);
        Console.WriteLine(pid);
        Console.WriteLine(nameSize);
        Console.WriteLine(dioBytes);
        Console.WriteLine(counters);
        Console.WriteLine(result);
    }
}

将Test.exe

gmcs Test.cs

运行：

$ mono Test.exe
100
9
6
8
7
0

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