[Mono-list] (no subject) (Robert Jordan)

[tcmichals]

Also you can do the following:
[StructLayout(LayoutKind.Sequential, Pack = 1, CharSet = CharSet.Ansi), 
Serializable]

public struct tttString

{

unsafe public fixed byte Text[128];//ASCII or UNICODE string

}

then you use size of etc...


"David Abrames" <abramesd at kmbs.konicaminolta.us> wrote in message 
news:HMEDIMBMEHHCFFHNGGAGKEBJCMAA.abramesd at kmbs.konicaminolta.us...
>> David Abrames wrote:
>> > I have the following structure in Windows:
>> >
>> > typedef struct {
>> > BYTE FAR *myBtyeArray;
>> > } MYSTRUCTURE;
>> >
>> > In .NET this structure is defined like this:
>> >
>> > [StructLayout(LayoutKind.Sequential, Size = 4, Pack = 1)]
>> > public class MYSTRUCTURE {
>> > public byte[] myByteArray;
>> > }
>> >
>> > which works OK. I then compiled the code successfully on Mono
>> 1.1.16.1 but
>> > when I run my program I get the following error:
>> >
>> > ** ERROR ** Structure field of type byte[] can't be marshaled
>> as LPArray.
>> > I have read several postings and articles about marshaling but I do not
>> > understand what the underlying problem is.  This structure is used in a
>> > function call where the called function will return a pointer
>> to an array of
>> > bytes. How should this be marshaled?
>>
>> 1) If the size of the array is constant, you can use this:
>>
>> [StructLayout(LayoutKind.Sequential, Size = 4)]
>> public class MYSTRUCTURE
>> {
>> [MarshalAs(UnmanagedType.LPArray, SizeConst = 100)]
>>          public byte[] myByteArray;
>> }
>>
>>
>> 2) If it's dynamic, you have to marshal manually:
>>
>> [StructLayout(LayoutKind.Sequential, Size = 4)]
>> public class MYSTRUCTURE
>> {
>>          public IntPtr myByteArray;
>> }
>>
>>
>> After the p/invoke call, which definitely needs to
>> somehow return the size of the array, use
>> System.Runtime.InteropServices.Copy:
>>
>> MYSTRUCTURE s = new MYSTRUCTURE ();
>>
>> // pinvoke call ...
>>
>> byte bytes[] = new byte[theSize];
>> Marshal.Copy (s.myByteArray, bytes, 0, theSize);
>>
>> Robert
>
> Dear Robert,
>
> Thank you very much for the reply.  After reading your explanation and 
> going
> back to the docs I now understand what is going on.  The underlying 
> problem
> is that the Mono Marshaller cannot determine the amount of memory needed 
> to
> hold the contents of the byte[] returned by p/invoke call.  So I have to
> either tell it at compile time or have some way in figuring it out at
> runtime.
>
> Thanks again.
>
> David Abrames
>
>
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