P / Invoke问题 [英] Problem with P/Invoke

问题描述

嗨
我用C＃编写了一个代码来加载非托管dll中的函数。

这是代码。

Hi I have written a code in C# to load functions in an unmanaged dll.
This is the code.

class Program
 {
     static unsafe void Main(string[] args)
     {
         int deviceNr;
         char* Info;
         int intMyReturnVal;
         deviceNr = 0;
         Info = null;
         intMyReturnVal = sample_getinfo(deviceNr, Info);
     }

     [DllImport("opcard2lib.dll")]
     private unsafe static extern int sample_getinfo(int deviceNr, char* Info);
 }

这是dll supllier的API函数说明。



1. Sample_GetInfo



原型：

DLLReturnType

Sample_GetInfo（int deviceNr，

char * Info）;



参数：

deviceNr是系统中找到的卡的数量

Info是信息的字符串处理程序关于系统中的当前卡



返回：

成功时返回0（零）。否则返回错误代码。



说明：

此功能提供有关系统中已安装卡的信息。返回的信息
信息字符串中的
如下所示：

SN YY.SN rev。 RRR，其中：

YY - 生产年份

SN - 序列号

RRR - 固件版本



问题是，当我运行此代码时，我得到以下错误异常：

尝试读取或写入受保护的内存。这通常表示其他内存已损坏。



我已经在VB.net中写了这个并得到了相同的结果。

我将非常感谢你的帮助。

and this is the API function description by dll supllier.

1. Sample_GetInfo

Prototype:
DLLReturnType
Sample_GetInfo (int deviceNr,
char* Info);

Parameters:
deviceNr is a number of found card in system
Info is handler for string with information about current card in system

Returns:
Returns 0 (zero) when success. Otherwise return an error code.

Description:
This function provide information about installed card in system. Information returned
in Info string looks like below:
„SN YY.SN rev. RRR", where:
YY – year of production
SN – serial number
RRR – firmware revision

The problem is that when I run this code I get the bellow error exception:
Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

I have written this in VB.net to and get the same result.
I would appreciate your help.

推荐答案

首先， char * info ，通过本机函数签名，应该是输入参数。或者它可以通过指针返回一个字符。默认情况下，输入 char * 参数被编组为 System.String 参数。并且你正在传递null。你不能返回任何东西。

-SA

First of all, char* info, by your native function signature, is supposed to be input parameter. Or it can return a character via a pointer. By default, input char* parameter is marshaled as System.String parameter. And you are passing null. You cannot return anything.

—SA

由SA详细阐述将null传递给导致错误的sample_getinfo。分配内存的快速解决方案到这个指针。



更改此行

As elaborated by SA you are passing null to sample_getinfo that caused the error. A quick solution to allocate memory to this pointer.

change this line

char* Info;

到这个

to this

char* Info = new char[255];

再试一次。

and try again.

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