added writing function

    IVAS_QUATERNION *pQuaternion      /* i  : head-tracking data             */

)

{

    float w, x, y, z;

    float posx, posy, posz;

    int32_t read_values;

    posx = 0.0f;

    posy = 0.0f;

    posz = 0.0f;

    read_values = fscanf( headRotWriter->trajFile, "%f,%f,%f,%f,%f,%f,%f", &w, &x, &y, &z, &posx, &posy, &posz );

    if ( ( read_values != 4 ) && ( read_values != 7 ) ) /* Allow either orientation (4) or orientation+position (4+3) */

    {

        if ( feof( headRotWriter->trajFile ) )

        {

            rewind( headRotWriter->trajFile );

            headRotWriter->fileRewind = true;

            return HeadRotationFileWriting( headRotWriter, pQuaternion );

        }

        return IVAS_ERR_FAILED_FILE_PARSE;

    }

    ( headRotWriter->frameCounter )++;

    pQuaternion->w = w;

    pQuaternion->x = x;

    pQuaternion->y = y;

    pQuaternion->z = z;

    fprintf(headRotWriter->trajFile, "%f %f %f %f\r\n", pQuaternion->w, pQuaternion->x, pQuaternion->y, pQuaternion->z);

    return IVAS_ERR_OK;

}