system.access.violation

[swts]

hi,

i am using unmanaged code.while converting to managed code i use the function

 public static object ByteArrayToStructure(byte[] bytearray)
        {
            IntPtr ptr = IntPtr.Zero;
            try
            {
                ptr = Marshal.AllocHGlobal(bytearray.Length);
                Marshal.Copy(bytearray, 0, ptr, bytearray.Length);
                return (packet)Marshal.PtrToStructure(ptr, typeof(packet));
            }
            finally
            {
                if (ptr != IntPtr.Zero)
                {
                    Marshal.FreeHGlobal(ptr);
                }
            }
        }
 
 

i an getting the error or accessing a read or write protected area. the memory might be corrupt. how can i debug this error??
kindly help.

thanks in advance

[Plater]

Which line throws the exception?

[swts]

the function PtrToStructure flags an error.

[swts]

system.AccessViolationexception:Attempted to read or write protected memory.This is often an indication that other memory is corrupt.at System.runtime.interopservices.marshal .ptrtostructure.
this is the error

[Frinavale]

hi,

i am using unmanaged code.while converting to managed code i use the function

 public static object ByteArrayToStructure(byte[] bytearray)
        {
            IntPtr ptr = IntPtr.Zero;
            try
            {
                ptr = Marshal.AllocHGlobal(bytearray.Length);
                Marshal.Copy(bytearray, 0, ptr, bytearray.Length);
                return (packet)Marshal.PtrToStructure(ptr, typeof(packet));
            }
            finally
            {
                if (ptr != IntPtr.Zero)
                {
                    Marshal.FreeHGlobal(ptr);
                }
            }
        }
 
 

i an getting the error or accessing a read or write protected area. the memory might be corrupt. how can i debug this error??
kindly help.

thanks in advance

Make sure that your Structure ("Packet") matches the unmanaged "Packet" Structure.....if they don't match then the Marshal won't work.

-Frinny

[swts]

the functions worked fine when i tested it in the same application. but it flagged the error when i put the demarshalin function in the receiver side.however, i receive the byte array perfectly fine from the sender side. the same byte array is printed on the sender an receiver side.on passing the received byte array to the the function i get the exception

[Plater]

Hmm when they are in the same application, you are using some type of marshalling to get the bytes from that structure yes? Which would mean that .NET is aware of these bytes being special.
When they come from a socket stream that notification to .NET is not there maybe?

[swts]

this is the marshalling code:

public static byte[] StructureToBytesArray(object obj)
        {
            int len = Marshal.SizeOf(obj);
            byte[] arr = new byte[len];
            IntPtr ptr = Marshal.AllocHGlobal(len);
            Marshal.StructureToPtr(obj, ptr, true);
            Marshal.Copy(ptr, arr, 0, len);
            Marshal.FreeHGlobal(ptr);
            return arr;
        }

the same byte arrays are received on the receiver side as sent by the sender. the error occurs wen the byte array is being passed to the demarshalin function.all the functions are declared public in my code yet it flags write/read protected.since the byte arrays are received doesn tat imply tat receiver knows abt these byet arrays?so y does the error occur

[Plater]

What I ment was, when you use marshalling, the runtime agent goes "ok these bytes are special, i'll make a note of that and keep their memory address 'static' so it can be used later"
When it comes in over the socket that knowledge is not in existance. It seems like creating the IntPrt and Marshalling stuff *should* have notified the runtime that "hey, keep this memory address available", but it doesn't look like it.
Maybe there is more?

[swts]

ya tats right. wat else cud i change??any other method u suggest to recreate the packets at the receiver end?? wen i tried copying the byte array from the receive buffer to a new byte array an then passing this new array as an argument to dearshalli function it flagged "safearraytypemismatch".does this indicate any changes tat cud be made???