C# .NET using C dll : Attempted to read or write protected memory.

[adypoly]

Hi guys...

I am having a typical problem in using one of the native dll in C#

I'll explain what am trying to do, I've a dll written in C language which i am trying to include in my C# project, the solutions builds fine but once i try to run the program it gives an exception as "Attempted to read or write protected memory. This is often an indication that other memory is corrupt" I am passing two integer pointer variables as the parameters, one as input and the other stores the output, the function jus changes the format of the data from input. I tried using break points and tried to read the data in the immediate window and for my surprise i can get the values in the immediate window, but when am trying to write that into the console window it gives an error, not only the value if i try to write anything in the console or try to execute any statement after the function call it gives an error, I tried lots of solutions those were available in the net, like changing the compiler option and all.. but nothing works.. it wud b gud if anyone cud give me a solution for this... thanx in advance...

here goes the source code

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace testing
{
    class Program 
    {
        // Thsi is the dll which i am importing
        [DllImport ("encoder.dll", EntryPoint = "encoder")]
        //this method takes 2 pointers as parameters and the result is stored in out_bits
        public static extern unsafe void encoder (Int16* msg_bits, Int16* out_bits);

        static void Main(string[] args)
        {
            Byte i;
            Int16[] msg_bit = new Int16[44];
            Int16[] out_bit = new Int16[2 * 44];
            //just filling the array with 1s
            for (i = 0; i < 44; i++)
            {
                msg_bit[i] = 1;
                Console.Write (msg_bit[i]);
            }
            //byte[] msg_bits = (byte) msg_bit; 
            Console.WriteLine ("Testing begins");
            unsafe
            {
                //calling the dll function 
                fixed (Int16* pMsg_bit = msg_bit, pOut_bit = out_bit) encoder (pMsg_bit, pOut_bit);
                //Console.WriteLine ("Testing ends");  -->  here comes the error
//--> after executing this function if u keep a breakpoint and try to get the values in out_bit array i can get the values, but if u try to write it in console it gives an error : Attempted to read or write protected memory. This is often an indication that other memory is corrupt
            }
            //commented these lines coz it doesnt work
            //for (i = 0; i < 2*44; i++)
            //{
                // I need the value from out_bit array               
               //Console.Write (out_bit[i]);
            //}
             

        }
    }
}

hope to hear for u guys soon....

[Frinavale]

Hi guys...

I am having a typical problem in using one of the native dll in C#

I'll explain what am trying to do, I've a dll written in C language which i am trying to include in my C# project, the solutions builds fine but once i try to run the program it gives an exception as "Attempted to read or write protected memory. This is often an indication that other memory is corrupt" I am passing two integer pointer variables as the parameters, one as input and the other stores the output, the function jus changes the format of the data from input. I tried using break points and tried to read the data in the immediate window and for my surprise i can get the values in the immediate window, but when am trying to write that into the console window it gives an error, not only the value if i try to write anything in the console or try to execute any statement after the function call it gives an error, I tried lots of solutions those were available in the net, like changing the compiler option and all.. but nothing works.. it wud b gud if anyone cud give me a solution for this... thanx in advance...

here goes the source code
...

hope to hear for u guys soon....

Have you throughly tested your C code?
C code handles memory differently than .NET does. Make sure that all of your memory allocations are properly handled in the C code.

-Frinny

[Plater]

C# really doesn't do pointers very well.....

You could try to rewrite the DLL to have function such that

public static extern byte[] encoder (byte[] msg_bits);

or something similar, is a working def for it. encoder() will take in the message as a byte array (pretty much what your int16 pointer would be pointing too) and return the msg encoded as another byte[].

Have you taken a look at System.Security .Authentication and System.Security .Cryptography ? Many algorithms have already been implemented.