Calling C code from C# - stuck with a couple of issues

Question

I have some C code that and I trying to use from C#. Most of the conversion is done. I have a couple of issues though.

Part of the 'C' code looks like this.

typedef struct r_GetCPL {

  UInt8 Storage;
  UInt8 Key[16];             //(1) 

  UInt8 *Buff;               //(2)
  Array16 *CryptoKeyIDs;     //(3)

} REPLY_GETCPL;

alias defined in 'C'

typedef unsigned char      UInt8;
typedef unsigned short     UInt16;
typedef unsigned long      UInt32;
typedef unsigned long long UInt64;

typedef UInt8   Array8[8];
typedef UInt8   Array16[16];
typedef UInt8   Array32[32];
typedef UInt8   Array64[64];
typedef UInt8   Array128[128];

I am assuming I can replace the typedef with a direct struct definition. Is this fine? The equivalent C# struct I defined is,

public struct REPLY_GETCPL 
{
  Byte Storage;
  Byte[16] Key;          //(1) Is this right?

  UInt8 *Buff;           //(2)  What is the equivalent?
  Array16 *CryptoKeyIDs; //(3)  What is the equivalent?
}

Also, There are a couple of methods import that I am stuck at

void hex_print(char* data, UInt32 length);
DRMKLVItem *NewDRMKLVItem(UInt32 lenBuff, UInt32 cmdId);
RESULT DRMKLVLengthDecode(const UInt8 *s, UInt32 *pLen);

C#

//I think this one is defined right
[DllImport("DoremiSource.dll")]
public static extern void hex_print([MarshalAs(UnmanagedType.LPStr)]string data, UInt32 length);

//(How to convert the function return type?)
[DllImport("DoremiSource.dll")]
public static extern DRMKLVItem *NewDRMKLVItem(UInt32 lenBuff, UInt32 cmdId);  //(4)

//(How do i convert the function parameters here)
[DllImport("DoremiSource.dll", CharSet = CharSet.Ansi)]
public static extern int DRMKLVLengthDecode(const UInt8 *s, ref UInt32 pLen);  //(5)

Answer 1

You can use complex types and marshal them around between C and C#, you just have to know about the compilation option for the structure, then decorate a C# type like the following: (From MSDN)

[StructLayout(LayoutKind.Explicit, Size=16, CharSet=CharSet.Ansi)]
public class MySystemTime 
{
   [FieldOffset(0)]public ushort wYear; 
   [FieldOffset(2)]public ushort wMonth;
   [FieldOffset(4)]public ushort wDayOfWeek; 
   [FieldOffset(6)]public ushort wDay; 
   [FieldOffset(8)]public ushort wHour; 
   [FieldOffset(10)]public ushort wMinute; 
   [FieldOffset(12)]public ushort wSecond; 
   [FieldOffset(14)]public ushort wMilliseconds; 
}