Split big text files in smaller ones in X++

static void KlForSplitFile(Args _args)
{
    #File
    AsciiIO             inFile, outFile;
    container           rec;
    int                 cnt = 0, fileNum    = 0;
    FileName            outFileName;
    FileIOPermission    filePermissionOrig, outFilePermission;
    Set                 permissionSet = new set(types::Class);

    // settings begin
    // input file
    str                 _inFileName = @"C:\temp\testsplit\testsplit.csv";
    // max number of lines
    int                 _maxrec = 20000;
    //settings end
    ;

    //
    // first loop to create the permission set
    //

    // assert permission for read
    new FileIOPermission(_inFileName, #io_read).assert();

    // create new asciiIo for the file we are reading in
    inFile  = new AsciiIo(_inFileName,#io_read);

    // read file to check how many files will be created
    while(inFile.read())
    {
        if(cnt == _maxrec || cnt == 0)
        {
            // 1 more file
            filenum++;
            // create filename
            outFileName = strfmt('%1_%2.csv',
            substr(_inFileName,1,strlen(_inFileName) - 4), fileNum);
            // create permission
            outFilePermission = new FileIOPermission(outFileName,#io_write);
            // add permission to set
            permissionset.add(outFilePermission);
            // reset line counter
            cnt = 0;
        }
        // 1 more line
        cnt++;
    }

    // also add fileIn permission to set
    filePermissionOrig =  new FileIOPermission(_inFileName, #io_read);
    permissionset.add(filePermissionOrig);
    // revert permission assertion
    CodeAccessPermission::revertAssert();

    // assert permissions for set
    CodeAccessPermission::assertMultiple(permissionset);

    //
    // loop file again and split
    //

    // reset counters
    fileNum = 0;
    cnt     = 0;

    // create new asciiIo for the file we are reading in
    inFile  = new AsciiIo(_inFileName,#io_read);

    // read file to check how many files will be created
    // read ahead
    rec = inFile.read();
    while(rec)
    {
        if(cnt == _maxrec || cnt == 0)
        {
            // 1 more file
            filenum++;
            // create filename
            outFileName = strfmt('%1_%2.csv',
            substr(_inFileName,1,strlen(_inFileName) - 4), fileNum);
            outFile = new AsciiIO(outFileName,#io_write);
            // reset line counter
            cnt = 0;
        }
        // 1 more line
        cnt++;
        // write to split file
        outFile.writeExp(rec);
        // read next line
        rec = inFile.read();
    }

    // revert permission assertion
    CodeAccessPermission::revertAssert();

    info('done');
}