static void UpdateInvertLoop(mod_channel *ch)
{
    static const unsigned char pt_tab_invloop[16] =
    {
        0x00, 0x05, 0x06, 0x07, 0x08, 0x0A, 0x0B, 0x0D,
        0x0F, 0x13, 0x16, 0x1A, 0x20, 0x2B, 0x40, 0x80
    };

    ch->invloop_delay += pt_tab_invloop[ch->invloop_speed];
    if (ch->invloop_delay >= 128)
    {
        ch->invloop_delay = 0;

        if (ch->sample > 0)
        {
            MODULE_SAMPLE *s = &source->samples[ch->sample - 1];

            if (s->loop_length >= 4)
            {
                ch->invloop_offset++;
                if (ch->invloop_offset >= s->loop_end)
                {
                    ch->invloop_offset = s->loop_start;
                }

                source->sample_data[s->offset + ch->invloop_offset] ^= 0xFF;
            }
        }
    }

    return;
}

static void effecte_invertloop(mod_channel *ch)
{
    if (mod_tick == 0)
    {
        ch->invloop_speed = ch->param & 0x0F;

        UpdateInvertLoop(ch);
    }

    return;
}

static void update_effect(mod_channel *ch)
{
    if (mod_tick > 0)
    {
        UpdateInvertLoop(ch);
    }

    effect_routines[ch->command](ch);

    return;
}

static void update_channel(mod_channel *ch)
{
    aflags = 0;
    if (mod_tick == 0)
    {
        if (pattern_delay_2 == 0)
        {
            read_note(ch);
        }

        /* if a sample number is found */
        if (ch->sample > 0)
        {
            MODULE_SAMPLE *s = &source->samples[ch->sample - 1];
            ch->invloop_offset = s->loop_start;
        }

        /* ... */
    }

    /* ... */

    update_effect(ch);

    /* ... */

    return;
}