Uncompressing using unrar.dll P/Invoke what do I do wrong?

[Oliver]

Hello !

I am trying to get the unrar.dll working in C#... it seems that I correctly
imported the functions as the first 2 function work without problem
(RAROpenArchive & RARGetDLLVersion)... however always if I want to execute
the RARReadHeader Function I get "Object reference not set to an instance
of an object"

What do I wrong, I used the unrar.dll documentation and I really dont find
any mistakes but why do I always get this error message and why do i only
get it by calling the function RARReadHeader?

Thanks in advance,
Oliver

------------------------- Code -------------------------------


using System;
using System.Runtime.InteropServices;

namespace Unrar
{
/// <summary>
/// Summary description for Class1.
/// </summary>
class Class1
{
public const int ERAR_END_ARCHIVE = 10;
public const int ERAR_NO_MEMORY = 11;
public const int ERAR_BAD_DATA = 12;
public const int ERAR_BAD_ARCHIVE = 13;
public const int ERAR_UNKNOWN_FORMAT = 14;
public const int ERAR_EOPEN = 15;
public const int ERAR_ECREATE = 16;
public const int ERAR_ECLOSE = 17;
public const int ERAR_EREAD = 18;
public const int ERAR_EWRITE = 19;
public const int ERAR_SMALL_BUF = 20;

public const int RAR_OM_LIST = 0;
public const int RAR_OM_EXTRACT = 1;

public const int RAR_SKIP = 0;
public const int RAR_TEST = 1;
public const int RAR_EXTRACT = 2;

public const int RAR_VOL_ASK = 0;
public const int RAR_VOL_NOTIFY = 1;

public enum RarOperations
{
OP_EXTRACT = 0,
OP_TEST = 1,
OP_LIST = 2
}

public struct RARHeaderData
{
public string ArcName;
public string FileName;
public uint Flags;
public uint PackSize;
public uint UnpSize;
public uint HostOS;
public uint FileCRC;
public uint FileTime;
public uint UnpVer;
public uint Method;
public uint FileAttr;
public string CmtBuf;
public uint CmtBufSize;
public uint CmtSize;
public uint CmtState;
}

public struct RAROpenArchiveData
{
public string ArcName;
public uint OpenMode;
public uint OpenResult;
public string CmtBuf;
public uint CmtBufSize;
public uint CmtSize;
public uint CmtState;
}

public struct RAROpenArchiveDataEx
{
public string ArcName;
public string ArcNameW;
public uint OpenMode;
public uint OpenResult;
public string CmtBuf;
public uint CmtBufSize;
public uint CmtSize;
public uint CmtState;
public uint Flags;
public uint Reserved;
}
public struct RARHeaderDataEx
{
public string ArcName;
public string ArcNameW;
public string FileName;
public string FileNameW;
public uint Flags;
public uint PackSize;
public uint PackSizeHigh;
public uint UnpSize;
public uint UnpSizeHigh;
public uint HostOS;
public uint FileCRC;
public uint FileTime;
public uint UnpVer;
public uint Method;
public uint FileAttr;
public string CmtBuf;
public uint CmtBufSize;
public uint CmtSize;
public uint CmtState;
public uint Reserved;
};


[DllImportAttribute("unrar.dll")]
public static extern IntPtr RAROpenArchive (ref
RAROpenArchiveData ArchiveData);
[DllImportAttribute("unrar.dll")]
public static extern int RARCloseArchive(IntPtr hArcData);
[DllImportAttribute("unrar.dll")]
public static extern int RARReadHeader (IntPtr hArcData, ref
RARHeaderData HeaderData);
[DllImportAttribute("unrar.dll")]
public static extern IntPtr RAROpenArchiveEx(ref
RAROpenArchiveDataEx ArchiveData);
[DllImportAttribute("unrar.dll")]
public static extern int RARReadHeaderEx(IntPtr hArcData, ref
RARHeaderDataEx HeaderData);
[DllImportAttribute("unrar.dll")]
public static extern int RARProcessFile(IntPtr hArcData, int
Operation, string DestPath, string DestName);
[DllImportAttribute("unrar.dll")]
public static extern int RARGetDllVersion();


static void Main(string[] args)
{
IntPtr lHandle;
int iStatus;
RARHeaderData uHeader=new RARHeaderData();
RAROpenArchiveData uRAR=new RAROpenArchiveData();

uRAR.ArcName = "D:\\adddas.rar";
uRAR.CmtBuf = string.Empty.PadLeft(16384,' ');
uRAR.CmtBufSize = 16384;
uRAR.OpenMode=RAR_OM_LIST;

Console.WriteLine("DLL Version: {0}",RARGetDllVersion());

lHandle = RAROpenArchive(ref uRAR);
Console.WriteLine("OpenResult: {0}",uRAR.OpenResult);
Console.WriteLine("CmtState: {0}",uRAR.CmtState);


iStatus=RARReadHeader(lHandle, ref uHeader);
Console.WriteLine("Status: {0}",iStatus);

iStatus = RARCloseArchive(lHandle);
Console.WriteLine("Status: {0}",iStatus);
}
}
}

 

[Chris R. Timmons]

Hello !

I am trying to get the unrar.dll working in C#... it seems that
I correctly imported the functions as the first 2 function work
without problem (RAROpenArchive & RARGetDLLVersion)... however
always if I want to execute the RARReadHeader Function I get
"Object reference not set to an instance of an object"

What do I wrong, I used the unrar.dll documentation and I really
dont find any mistakes but why do I always get this error
message and why do i only get it by calling the function
RARReadHeader?

Oliver,

The RARHeaderData structure has two string parameters which are
supposed to represent fixed length arrays of characters (e.g. "char
arcName[260];" in C). When using P/Invoke, a string instead of a
character array is typically used. However, the fixed-length nature
of the string must be explicitly stated using the MarshalAs
attribute:

public struct RARHeaderData
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
public string ArcName;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
public string FileName;
...
}

I added these two attributes and ran your code. It seemed to work
OK.

Hope this helps.

Chris.

 

[Oliver]

Hi Chris!!!

Thank you very much for you help! That was exactly which was missing.
Didn't know how I could make them fixed size since string ArcName[260] or
similar didnt work!

So thanks for taking the time to test it and give me the correct answer. I
really appreciate that! I sat 4 hours and searched the internet but didnt
find any answer to this

Thanks,
Oliver

 

[gcl]

How did you get the info for that RAR stuffs like its api
calls?

 

[Chris R. Timmons]

How did you get the info for that RAR stuffs like its api
calls?

http://www.rarlab.com/rar_add.htm


Chris.