#380 Improve the multi volume rar file detection

[Kenji Mouri]

This is the first time for me to create a 7-Zip patch ticket. I am sorry if something is not suitable.

Some NanaZip users aren't able to extract multi volume rar files properly but WinRAR can handle it properly. (https://github.com/M2Team/NanaZip/issues/82) I have do some discovery and find the 7-Zip have that issue too. I have tried to do some modifications for CPP\7zip\Archive\Rar\RarVol.h and succeed to resolve the issue. I think I should share the way.

Here is the example of the files names for multi volume rar files we aren't able to extract properly.

• ANSYS_Products_2022_R1_x64_Multilingual.part1_Downloadly.ir.rar
• ANSYS_Products_2022_R1_x64_Multilingual.part2_Downloadly.ir.rar
• ANSYS_Products_2022_R1_x64_Multilingual.part3_Downloadly.ir.rar
• ANSYS_Products_2022_R1_x64_Multilingual.part4_Downloadly.ir.rar
• ANSYS_Products_2022_R1_x64_Multilingual.part5_Downloadly.ir.rar

And we can know there are some complex chars after the volume digit number. But 7-Zip's implementation is only suitable for something like "{Prefix}{Digit}.{Suffix}". I have modify the CVolumeName::InitName method. Here is the snippet.

bool InitName(const UString &name, bool newStyle = true)
  {
    _needChangeForNext = true;
    _after.Empty();
    UString base (name);
    const int dotPos = name.ReverseFind_Dot();

    int newPos = dotPos;
    for (; newPos != 0; newPos--)
        if (IsDigit(base[newPos - 1]))
            break;

    if (dotPos >= 0)
    {
      const UString ext (name.Ptr(dotPos + 1));
      if (ext.IsEqualTo_Ascii_NoCase("rar"))
      {
        _after += name.Ptr(newPos);
        base.DeleteFrom(newPos);
      }
      else if (ext.IsEqualTo_Ascii_NoCase("exe"))
      {
        _after += name.Ptr(newPos);
        base.DeleteFrom(newPos);
        _after.Replace(L".exe", L".rar");
      }
      else if (!newStyle)
      {
        if (ext.IsEqualTo_Ascii_NoCase("000") ||
            ext.IsEqualTo_Ascii_NoCase("001") ||
            ext.IsEqualTo_Ascii_NoCase("r00") ||
            ext.IsEqualTo_Ascii_NoCase("r01"))
        {
          _changed = ext;
          _before = name.Left(dotPos + 1);
          return true;
        }
      }
    }

    if (newStyle)
    {
      unsigned i = base.Len();

      for (; i != 0; i--)
        if (!IsDigit(base[i - 1]))
          break;

      if (i != base.Len())
      {
        _before = base.Left(i);
        _changed = base.Ptr(i);
        return true;
      }
    }

    _after.Empty();
    _before = base;
    _before += '.';
    _changed = "r00";
    _needChangeForNext = false;
    return true;
  }

I think it should have more elegant implementation to resolve this issue.

Kenji Mouri

[Igor Pavlov]

I' ll try to fix it.
Thanks!