init

    pub fn init(
        ring: *IoUring,
        allocator: Allocator,
        group_id: u16,
        buffer_size: u32,
        buffers_count: u16,
    ) !BufferGroup {
        const buffers = try allocator.alloc(u8, buffer_size * buffers_count);
        errdefer allocator.free(buffers);
        const heads = try allocator.alloc(u32, buffers_count);
        errdefer allocator.free(heads);

        const br = try setup_buf_ring(ring.fd, buffers_count, group_id, .{ .inc = true });
        buf_ring_init(br);

        const mask = buf_ring_mask(buffers_count);
        var i: u16 = 0;
        while (i < buffers_count) : (i += 1) {
            const pos = buffer_size * i;
            const buf = buffers[pos .. pos + buffer_size];
            heads[i] = 0;
            buf_ring_add(br, buf, i, mask, i);
        }
        buf_ring_advance(br, buffers_count);

        return BufferGroup{
            .ring = ring,
            .group_id = group_id,
            .br = br,
            .buffers = buffers,
            .heads = heads,
            .buffer_size = buffer_size,
            .buffers_count = buffers_count,
        };
    }