Acrobat/Reader CosStringValue returns trash when file name consist of russian letters

Hello, I try to retrieve attachment name but in case when attachment name contains russian letters adobe functions returns trash.

Usage:

ACCB1 ASBool ACCB2 AdobePluginHelper::GetEmbeddedFiles(CosObj obj, CosObj value, void *clientData)
{
    auto adobe = CAdobePlugin::GetAdobeMethods();
    auto attachedFiles = (vector<string>*)clientData;

    PDFileAttachment fileAttachment = adobe->PdFileAttachmentFromCosObj(value);

    //Grab the file's name using the cos object dictionary and the File Specifcation String key. 
    ASTCount len = 0;
    std::string sFileName(adobe->CosStringValueFromCosObject(adobe->CosDictObjGet(value, adobe->AtomFromString("F")), &len));

    if (!sFileName.empty())
    {
        attachedFiles->push_back(sFileName);
    }

    return true;
}

void AdobePluginHelper::GetAttachedFiles(PDDoc document, vector<string>& attachedFiles)
{
    auto adobe = CAdobePlugin::GetAdobeMethods();

    PDNameTree nameTree = adobe->PdDocGetNameTree(document, adobe->AtomFromString("EmbeddedFiles"));
    
    if (adobe->PdNameTreeIsValid(nameTree))
    {
        //Apply the enum function to the nametree so it can iterate through, extracting the attachments.
        adobe->PdNameTreeEnum(nameTree, &GetEmbeddedFiles, &attachedFiles);
    }
}

char* Implementation::Adobe::CosStringValueFromCosObject(CosObj obj, ASTCount* nBytes)
{
    return CosStringValue(obj, nBytes);
}

CosObj Implementation::Adobe::CosDictObjGet(CosObj dict, ASAtom key)
{
    return CosDictGet(dict, key);
}

Original:

In other cases it works fine.