How to marshal complex data structures - DOTNET

This is a discussion on How to marshal complex data structures - DOTNET ; Hi, I'm using Pinvoke and C# interop to interface to a C DLL. The DLL function signiture is as follows: int fun(char *name, my_id_t *id, my_buffer_t *buffer); The user defined types (in C) are as follows: struct my_id_t { unsigned ...

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How to marshal complex data structures

  1. Default How to marshal complex data structures

    Hi,

    I'm using Pinvoke and C# interop to interface to a C DLL. The DLL function
    signiture is as follows:

    int fun(char *name, my_id_t *id, my_buffer_t *buffer);


    The user defined types (in C) are as follows:


    struct my_id_t
    {
    unsigned char guid[16];
    }

    struct my_subbuffer_t
    {
    int format;
    }

    struct my_buffer_t
    {
    int count;
    my_subbuffer_t **bufferArray;
    }

    So I'm having trouble with the 3rd argument---my_buffer_t.

    This is what I've got so far in C#:

    [StructLayout(LayoutKind.Sequential)]
    public class my_id_t
    {
    [MarshalAs(UnManagedType.ByValArray, SizeConst=16)]
    public byte[] myGuid;
    }

    [StructLayout(LayoutKind.Sequential)]
    public class my_subbuffer_t
    {
    public int format;
    }

    [StructLayout(LayoutKind.Sequential)]
    public class my_buffer_t
    {
    public int count;
    my_subbuffer_t [] buffers;
    }





  2. Default Re: How to marshal complex data structures

    Oops, forgot to add the pinvoke signiture:

    [DllImport("mylib.dll")]

    public static extern int fun(string name, my_id_t id, my_buffer_t buffer);

    So when I run my code, the buffer is corrupted/invalid memory.

    Can you guys help out with some code or point my in the right direction?

    Thanks!
    JW


    "James Whetstone" <jameswhetstone@comcast.net> wrote in message
    news:t7WdnSN0HqWVMlvYnZ2dnUVZ_qqrnZ2d@comcast.com...
    > Hi,
    >
    > I'm using Pinvoke and C# interop to interface to a C DLL. The DLL
    > function signiture is as follows:
    >
    > int fun(char *name, my_id_t *id, my_buffer_t *buffer);
    >
    >
    > The user defined types (in C) are as follows:
    >
    >
    > struct my_id_t
    > {
    > unsigned char guid[16];
    > }
    >
    > struct my_subbuffer_t
    > {
    > int format;
    > }
    >
    > struct my_buffer_t
    > {
    > int count;
    > my_subbuffer_t **bufferArray;
    > }
    >
    > So I'm having trouble with the 3rd argument---my_buffer_t.
    >
    > This is what I've got so far in C#:
    >
    > [StructLayout(LayoutKind.Sequential)]
    > public class my_id_t
    > {
    > [MarshalAs(UnManagedType.ByValArray, SizeConst=16)]
    > public byte[] myGuid;
    > }
    >
    > [StructLayout(LayoutKind.Sequential)]
    > public class my_subbuffer_t
    > {
    > public int format;
    > }
    >
    > [StructLayout(LayoutKind.Sequential)]
    > public class my_buffer_t
    > {
    > public int count;
    > my_subbuffer_t [] buffers;
    > }
    >
    >
    >
    >




  3. Default Re: How to marshal complex data structures

    I think the fact that you are using formatted classes instead of
    structs in your code require you to flag the parameter with the
    InAttribute and OutAttribute ( [In, Out] ). Otherwise it would
    default to In only.



    On Feb 4, 11:18 pm, "James Whetstone" <jameswhetst...@comcast.net>
    wrote:
    > Oops, forgot to add the pinvoke signiture:
    >
    > [DllImport("mylib.dll")]
    >
    > public static extern int fun(string name, my_id_t id, my_buffer_t buffer);
    >
    > So when I run my code, the buffer is corrupted/invalid memory.
    >
    > Can you guys help out with some code or point my in the right direction?
    >
    > Thanks!
    > JW
    >
    > "James Whetstone" <jameswhetst...@comcast.net> wrote in message
    >
    > news:t7WdnSN0HqWVMlvYnZ2dnUVZ_qqrnZ2d@comcast.com...
    >
    >
    >
    > > Hi,

    >
    > > I'm using Pinvoke and C# interop to interface to a C DLL. The DLL
    > > function signiture is as follows:

    >
    > > int fun(char *name, my_id_t *id, my_buffer_t *buffer);

    >
    > > The user defined types (in C) are as follows:

    >
    > > struct my_id_t
    > > {
    > > unsigned char guid[16];
    > > }

    >
    > > struct my_subbuffer_t
    > > {
    > > int format;
    > > }

    >
    > > struct my_buffer_t
    > > {
    > > int count;
    > > my_subbuffer_t **bufferArray;
    > > }

    >
    > > So I'm having trouble with the 3rd argument---my_buffer_t.

    >
    > > This is what I've got so far in C#:

    >
    > > [StructLayout(LayoutKind.Sequential)]
    > > public class my_id_t
    > > {
    > > [MarshalAs(UnManagedType.ByValArray, SizeConst=16)]
    > > public byte[] myGuid;
    > > }

    >
    > > [StructLayout(LayoutKind.Sequential)]
    > > public class my_subbuffer_t
    > > {
    > > public int format;
    > > }

    >
    > > [StructLayout(LayoutKind.Sequential)]
    > > public class my_buffer_t
    > > {
    > > public int count;
    > > my_subbuffer_t [] buffers;
    > > }- Hide quoted text -

    >
    > - Show quoted text -




  4. Default Re: How to marshal complex data structures

    Thanks for the suggestion. I just tried it by adding

    [In, Out] to the parameter on the Pinvoke siginiture. So it looked like
    this:

    public static extern int fun(string name, my_id_t id, [In,Out]my_buffer_t
    buffer);

    I also changed the class to a struct and changed the pinvoke signiture to
    this:

    public static extern int fun(string name, my_id_t id, [In,Out] ref
    my_buffer_t buffer);

    But that didn't work either. Any other thoughts or comments?

    Cheers,
    JW

    "TDC" <NOtcarvinSPAM@lycos.com> wrote in message
    news:1170685614.384106.283150@h3g2000cwc.googlegroups.com...
    >I think the fact that you are using formatted classes instead of
    > structs in your code require you to flag the parameter with the
    > InAttribute and OutAttribute ( [In, Out] ). Otherwise it would
    > default to In only.
    >
    >
    >
    > On Feb 4, 11:18 pm, "James Whetstone" <jameswhetst...@comcast.net>
    > wrote:
    >> Oops, forgot to add the pinvoke signiture:
    >>
    >> [DllImport("mylib.dll")]
    >>
    >> public static extern int fun(string name, my_id_t id, my_buffer_t
    >> buffer);
    >>
    >> So when I run my code, the buffer is corrupted/invalid memory.
    >>
    >> Can you guys help out with some code or point my in the right direction?
    >>
    >> Thanks!
    >> JW
    >>
    >> "James Whetstone" <jameswhetst...@comcast.net> wrote in message
    >>
    >> news:t7WdnSN0HqWVMlvYnZ2dnUVZ_qqrnZ2d@comcast.com...
    >>
    >>
    >>
    >> > Hi,

    >>
    >> > I'm using Pinvoke and C# interop to interface to a C DLL. The DLL
    >> > function signiture is as follows:

    >>
    >> > int fun(char *name, my_id_t *id, my_buffer_t *buffer);

    >>
    >> > The user defined types (in C) are as follows:

    >>
    >> > struct my_id_t
    >> > {
    >> > unsigned char guid[16];
    >> > }

    >>
    >> > struct my_subbuffer_t
    >> > {
    >> > int format;
    >> > }

    >>
    >> > struct my_buffer_t
    >> > {
    >> > int count;
    >> > my_subbuffer_t **bufferArray;
    >> > }

    >>
    >> > So I'm having trouble with the 3rd argument---my_buffer_t.

    >>
    >> > This is what I've got so far in C#:

    >>
    >> > [StructLayout(LayoutKind.Sequential)]
    >> > public class my_id_t
    >> > {
    >> > [MarshalAs(UnManagedType.ByValArray, SizeConst=16)]
    >> > public byte[] myGuid;
    >> > }

    >>
    >> > [StructLayout(LayoutKind.Sequential)]
    >> > public class my_subbuffer_t
    >> > {
    >> > public int format;
    >> > }

    >>
    >> > [StructLayout(LayoutKind.Sequential)]
    >> > public class my_buffer_t
    >> > {
    >> > public int count;
    >> > my_subbuffer_t [] buffers;
    >> > }- Hide quoted text -

    >>
    >> - Show quoted text -

    >
    >




  5. Default Re: How to marshal complex data structures

    > public static extern int fun(string name, my_id_t id, [In,Out] ref
    > my_buffer_t buffer);


    The above should work. How did you allocate memory for buffer?

    Did you allocate memory for my_buffer_t and the array my_subbuffer_t?

    If so, you may want to try to lay out your structs explicitely rather than
    sequentially to avoid implicit packing alignment issues of struct members.



  6. Default Re: How to marshal complex data structures


    So I'm allocating memory for my_buffer_t like this:

    my_buffer_t buf = new my_buffer_t();
    buf.count = 1;

    buf.buffers = new my_subbuffer_t[1];

    buf.buffers[0].format = 100;

    Does this look right? I don't need to allocate on the unmanaged heap,
    right?

    I'll try using an explicit layout. Thanks for the suggestions.

    JW


    "Michael Phillips, Jr." <mphillips53@nospam.jun0.c0m> wrote in message
    news:%23W65BDXSHHA.4404@TK2MSFTNGP03.phx.gbl...
    >> public static extern int fun(string name, my_id_t id, [In,Out] ref
    >> my_buffer_t buffer);

    >
    > The above should work. How did you allocate memory for buffer?
    >
    > Did you allocate memory for my_buffer_t and the array my_subbuffer_t?
    >
    > If so, you may want to try to lay out your structs explicitely rather than
    > sequentially to avoid implicit packing alignment issues of struct members.
    >




  7. Default Re: How to marshal complex data structures

    Okay,

    So this is what I've got implemented now:


    [StructLayout(LayoutKind.Sequential)]
    public class my_subbuffer_t
    {
    public int format;
    }

    [StructLayout(LayoutKind.Sequential)]
    public class my_buffer_t
    {
    public int count;
    public my_subbuffer_t [] buffers;
    }

    [DllImport("mylib.dll")]
    public static extern int fun(string name, my_id_t id, [In, Out] ref
    my_buffer_t buffer);

    my_buffer_t buf;

    buf.buffers = new my_subbuffers_t[1];
    buf.buffers[0].format = 100;
    buf.count=1;

    string name="Jimbo";
    my_id_t id = new my_id_t();

    fun(name,id,ref buf);

    So now I get the following runtime error:
    Invalid managed/unmanaged type combination (this value type must be paired
    with Struct).

    Best,
    JW








    "Michael Phillips, Jr." <mphillips53@nospam.jun0.c0m> wrote in message
    news:%23W65BDXSHHA.4404@TK2MSFTNGP03.phx.gbl...
    >> public static extern int fun(string name, my_id_t id, [In,Out] ref
    >> my_buffer_t buffer);

    >
    > The above should work. How did you allocate memory for buffer?
    >
    > Did you allocate memory for my_buffer_t and the array my_subbuffer_t?
    >
    > If so, you may want to try to lay out your structs explicitely rather than
    > sequentially to avoid implicit packing alignment issues of struct members.
    >




  8. Default Re: How to marshal complex data structures

    Sorry,

    that wasn't quite right...I've changed the "classes" to "structs" like so:

    [StructLayout(LayoutKind.Sequential)]
    public struct my_subbuffer_t
    {
    public int format;
    }
    [StructLayout(LayoutKind.Sequential)]
    public class my_buffer_t
    {
    public int count;
    public my_subbuffer_t [] buffers;
    }

    ....

    Thanks for takin' the time,
    JW


    "James Whetstone" <jameswhetstone@comcast.net> wrote in message
    news:TqudnZ9izd2ouVXYnZ2dnUVZ_v-tnZ2d@comcast.com...
    > Okay,
    >
    > So this is what I've got implemented now:
    >
    >
    > [StructLayout(LayoutKind.Sequential)]
    > public class my_subbuffer_t
    > {
    > public int format;
    > }
    >
    > [StructLayout(LayoutKind.Sequential)]
    > public class my_buffer_t
    > {
    > public int count;
    > public my_subbuffer_t [] buffers;
    > }
    >
    > [DllImport("mylib.dll")]
    > public static extern int fun(string name, my_id_t id, [In, Out] ref
    > my_buffer_t buffer);
    >
    > my_buffer_t buf;
    >
    > buf.buffers = new my_subbuffers_t[1];
    > buf.buffers[0].format = 100;
    > buf.count=1;
    >
    > string name="Jimbo";
    > my_id_t id = new my_id_t();
    >
    > fun(name,id,ref buf);
    >
    > So now I get the following runtime error:
    > Invalid managed/unmanaged type combination (this value type must be paired
    > with Struct).
    >
    > Best,
    > JW
    >
    >
    >
    >
    >
    >
    >
    >
    > "Michael Phillips, Jr." <mphillips53@nospam.jun0.c0m> wrote in message
    > news:%23W65BDXSHHA.4404@TK2MSFTNGP03.phx.gbl...
    >>> public static extern int fun(string name, my_id_t id, [In,Out] ref
    >>> my_buffer_t buffer);

    >>
    >> The above should work. How did you allocate memory for buffer?
    >>
    >> Did you allocate memory for my_buffer_t and the array my_subbuffer_t?
    >>
    >> If so, you may want to try to lay out your structs explicitely rather
    >> than sequentially to avoid implicit packing alignment issues of struct
    >> members.
    >>

    >
    >




  9. Default Re: How to marshal complex data structures

    So to clarify, all my classes are now structs.
    Thanks,
    JW

    "James Whetstone" <jameswhetstone@comcast.net> wrote in message
    news:ZLSdnc1YYIQmuVXYnZ2dnUVZ_revnZ2d@comcast.com...
    > Sorry,
    >
    > that wasn't quite right...I've changed the "classes" to "structs" like so:
    >
    > [StructLayout(LayoutKind.Sequential)]
    > public struct my_subbuffer_t
    > {
    > public int format;
    > }
    > [StructLayout(LayoutKind.Sequential)]
    > public class my_buffer_t
    > {
    > public int count;
    > public my_subbuffer_t [] buffers;
    > }
    >
    > ...
    >
    > Thanks for takin' the time,
    > JW
    >
    >
    > "James Whetstone" <jameswhetstone@comcast.net> wrote in message
    > news:TqudnZ9izd2ouVXYnZ2dnUVZ_v-tnZ2d@comcast.com...
    >> Okay,
    >>
    >> So this is what I've got implemented now:
    >>
    >>
    >> [StructLayout(LayoutKind.Sequential)]
    >> public class my_subbuffer_t
    >> {
    >> public int format;
    >> }
    >>
    >> [StructLayout(LayoutKind.Sequential)]
    >> public class my_buffer_t
    >> {
    >> public int count;
    >> public my_subbuffer_t [] buffers;
    >> }
    >>
    >> [DllImport("mylib.dll")]
    >> public static extern int fun(string name, my_id_t id, [In, Out] ref
    >> my_buffer_t buffer);
    >>
    >> my_buffer_t buf;
    >>
    >> buf.buffers = new my_subbuffers_t[1];
    >> buf.buffers[0].format = 100;
    >> buf.count=1;
    >>
    >> string name="Jimbo";
    >> my_id_t id = new my_id_t();
    >>
    >> fun(name,id,ref buf);
    >>
    >> So now I get the following runtime error:
    >> Invalid managed/unmanaged type combination (this value type must be
    >> paired with Struct).
    >>
    >> Best,
    >> JW
    >>
    >>
    >>
    >>
    >>
    >>
    >>
    >>
    >> "Michael Phillips, Jr." <mphillips53@nospam.jun0.c0m> wrote in message
    >> news:%23W65BDXSHHA.4404@TK2MSFTNGP03.phx.gbl...
    >>>> public static extern int fun(string name, my_id_t id, [In,Out] ref
    >>>> my_buffer_t buffer);
    >>>
    >>> The above should work. How did you allocate memory for buffer?
    >>>
    >>> Did you allocate memory for my_buffer_t and the array my_subbuffer_t?
    >>>
    >>> If so, you may want to try to lay out your structs explicitely rather
    >>> than sequentially to avoid implicit packing alignment issues of struct
    >>> members.
    >>>

    >>
    >>

    >
    >




  10. Default Re: How to marshal complex data structures

    Do you now get the expected result(i.e., no interop errors)?




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