Re: Interesting problem: serializing in with MFC CArchive, reading out using C# BinaryReader

From: Luis Barreira (lbarreira_at_isa.pt)
Date: 01/27/05 

Date: Thu, 27 Jan 2005 18:32:38 -0000

A few months ago I had the same problem. I solved it by looking into the MFC
source code and converting the needed code to C#:

public class MFCStringReader : System.IO.BinaryReader
{
  public MFCStringReader(Stream s) : base(s)
  {
  }

  public MFCStringReader(Stream s, Encoding e) : base(s, e)
  {
  }

  public string ReadCString()
  {
    string str = "";
    int nConvert = 1; // if we get ANSI, convert

    UInt32 nNewLen = ReadStringLength();
    if (nNewLen == unchecked((UInt32)(-1)))
    {
      nConvert = 1 - nConvert;
      nNewLen = ReadStringLength();
      if (nNewLen == unchecked((UInt32)(-1)))
        return str;
    }

    // set length of string to new length
    UInt32 nByteLen = nNewLen;
    nByteLen += (UInt32)(nByteLen * (1 - nConvert)); // bytes to read

    // read in the characters
    if (nNewLen != 0)
    {
      // read new data
      byte[] byteBuf = ReadBytes((int)nByteLen);

      // convert the data if as necessary
      StringBuilder sb = new StringBuilder();
      if (nConvert != 0)
      {
        for (int i = 0; i < nNewLen; i++)
          sb.Append((char)byteBuf[i]);
      }
      else
      {
        for (int i = 0; i < nNewLen; i++)
          sb.Append((char)(byteBuf[i*2] + byteBuf[i*2+1] * 256));
      }

      str = sb.ToString();
    }

    return str;
  }

  private UInt32 ReadStringLength()
  {
    UInt32 nNewLen;

    // attempt BYTE length first
    byte bLen = ReadByte();

    if (bLen < 0xff)
      return bLen;

    // attempt WORD length
    UInt16 wLen = ReadUInt16();
    if (wLen == 0xfffe)
    {
      // UNICODE string prefix (length will follow)
      return unchecked((UInt32)(-1));
    }
    else if (wLen == 0xffff)
    {
      // read DWORD of length
      nNewLen = ReadUInt32();
      return nNewLen;
    }
    else
      return wLen;
  }
}

"Airjoe" <airjoe@newsgroup.nospam> wrote in message
news:OuuiBRs4EHA.2180@TK2MSFTNGP10.phx.gbl...
> Hello,
>
> I am planning to write a C# application that needs to read binary files
> created with MFC serialization.
>
> Have you made any progress on solving your issues? If so any information
> would be appreciated
>
> Thanks,
>
> J
> "RP2001" <ratcharit@gmail.com> wrote in message
> news:7ec191d7.0411111405.419feb80@posting.google.com...
>> I've serialized in various variables of various types (mainly CString,
>> int, double) into an instantiated MFC CArchive class and saved it as a
>> binary file.
>>
>> I am able to open the binary file and read out the individual
>> variables fine with an MFC application. However I cannot read the
>> binary file correctly with a C#.NET application, where I'm using the
>> BinaryReader Class. Doing some debugging I noticed that the problem
>> occured at this C# line of code:
>>
>> my_variable_of_type_CString =
>> instantiated_CSharp_binaryreader.ReadString();
>>
>> When this line of code execute, the binary reads out the ENTIRE
>> remainder of the file. So I thought is this one of those hairy, good
>> old string termination issues, but I've checked the byte representing
>> the string termination and it's there.
>>
>> Another strange thing that I noticed is that the first ASCII character
>> that is suppose to be there as part of the string being read out, is
>> not being interpreted.
>>
>> Two other things I want to point out that is specific to my situation
>> and it is that the string being read out from the binary file has two
>> consecutive carriage returns and line feeds ("\r\n\r\n"). Also I'm
>> trying to read out two string consecutively. Could these two aspects
>> attribute to the problem?
>>
>> Example, when I use the Studio.NET debugger to see what is contained
>> in my_variable_of_type_CString, I get something like this:
>>
>> my_variable_of_type_CString = "ew York City\vNext String to be read
>> out\0\0\0 . . . (garbage until the end of file"
>>
>> Any help will be GREATLY appreciated. Thanks in advance.
>>
>> -RP
>
>

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