How can I get IntPtr pointer from object

Question

I'm working on a finger-print device, the manufacture (Upek) gave me a c++ BSAPI.dll so I need to use wrappers to get this to work in .net.

I'm able to work with it all from in-memory, I could grab and match the finger prints.

Now I'm stuck trying to get the data out to a file and then loading it back in to memory and get the IntPtr.

Here there's a c++ sample on how to export and import from a file. but I don't know how to read it.

Any help is appreciated Thanks all

---

This is what I have and works great:

Now I need two things 1. Take that bufBIR save it to a database. 2. Take the data I saved and pass it in to the abs_verify.

How can this be done?

Answer 1

Here is C# code I got (I think from the BIOAPI sample code) a long time ago to interface with BioAPI. The DoMarshall method returns an IntPtr pointing to allocated memory large enough to hold the array.

I have not worked with Managed C++, so I am not sure what changes are needed, but maybe it will point you in the right direction. I was working with UPEK at the time. I hope this helps...

    [Serializable]
[StructLayout(LayoutKind.Sequential)]
public class BioAPI_DATA 
{
    public uint Length = 0;
    public byte[] Data = null;
    public BioAPI_DATA() {}
    public BioAPI_DATA(uint length, byte[] data) { Length = length; Data = data; }

    public IntPtr DoMarshal(ref int size)
    {
        IntPtr ptr;
        IntPtr ptrData = IntPtr.Zero;
        int ofs = 0;

        size = Marshal.SizeOf(Type.GetType("System.Int32")) + 
               Marshal.SizeOf(Type.GetType("System.IntPtr"));

        ptr = Marshal.AllocCoTaskMem( size );
        Marshal.WriteInt32(ptr, ofs, (int) Length);
        ofs += Marshal.SizeOf(Type.GetType("System.Int32"));
        if (Data != null) 
        {
            ptrData = Marshal.AllocCoTaskMem( Data.Length );
            Marshal.Copy(Data, 0, ptrData, Data.Length);
        }
        Marshal.WriteIntPtr(ptr, ofs, ptrData);
        return ptr;
    }

    public void DoUnmarshal(IntPtr ptr, ref int size, bool fDeleteOld)
    {
        int ofs = 0;
        size = Marshal.SizeOf(Type.GetType("System.Int32")) + 
               Marshal.SizeOf(Type.GetType("System.IntPtr"));
        Length =  (uint) Marshal.ReadInt32( ptr, ofs );
        ofs += Marshal.SizeOf(Type.GetType("System.Int32"));

        if (Length == 0) 
        {
            if (Data != null) Data = null;
            return;
        }

        IntPtr ptr2 = Marshal.ReadIntPtr(ptr, ofs);

        if (Data == null || Data.Length != Length) Data = new byte[Length];
        Marshal.Copy(ptr2, Data, 0, (int) Length);
        if (fDeleteOld)  { if (ptr != IntPtr.Zero) Marshal.FreeCoTaskMem( ptr ); }
    }
}