void nvme_io_wait(uint64_t *iocqb_copy)
{
    uint64_t val;

    do{
        val = *(uint64_t *) iocqb_copy;

    }while(val == 0);

    *(uint64_t *) iocqb_copy = 0; // Overwrite the old entry
}

void nvme_io_savetail(uint32_t io_tail_val, volatile char* nvme_iotail, uint32_t old_tail_val)
{
    uint8_t val = (uint8_t) io_tail_val;
    uint32_t val_new = val;
    volatile char *iocqb_copy = nvme_iocqb;

    *nvme_iotail = val; // Save the tail for the next command

    *((volatile uint32_t *) ((char *) nvme_base + 0x1008)) = val_new; // Write the new tail value

    // Check completion queue
    old_tail_val = (old_tail_val << 4); // Each entry is 16 bytes
    old_tail_val = old_tail_val + 8;    // Add 8 for DW3

    iocqb_copy += old_tail_val;

    nvme_io_wait(iocqb_copy);
}

/*
 * copy data from ssd partition to the partition data buffer
 */
char *copy_data_from_ssd_partition(uint32_t starting_sector, uint32_t num_blocks)
{
    uint32_t cdw0 = 0x00000002; // CDW0 CID 0, PRP used (15:14 clear), FUSE normal (bits 9:8 clear), command read (0x02)
    uint32_t cdw1 = 1;  // CDW1 NSID
    uint32_t cdw10_11 = starting_sector;        // CDW10_11
    uint32_t cdw12 = num_blocks - 1; /* num of logical blocks to be read */

    char *nvme_iosqb_ptr = nvme_iosqb;
    uint32_t tmp, io_tail_val = 0;

    // Build the command at the expected location in the Submission ring
    io_tail_val = *nvme_iotail; // Get the current io tail value

    io_tail_val *= 64;          // Quick multiply by 64

    nvme_iosqb_ptr += io_tail_val;

    // Build the structure
    *(uint32_t *) nvme_iosqb_ptr = cdw0;    // CDW0
    *(uint32_t *) (nvme_iosqb_ptr + 4) = cdw1;  // CDW1
    *(uint32_t *) (nvme_iosqb_ptr + 8) = 0; // CDW2
    *(uint32_t *) (nvme_iosqb_ptr + 12) = 0;    // CDW3
    *(uint64_t *) (nvme_iosqb_ptr + 16) = 0;    // CDW4-5
    *(uint64_t *) (nvme_iosqb_ptr + 24) = (uint64_t) partition_data_buffer; // CDW6-7
    *(uint64_t *) (nvme_iosqb_ptr + 32) = 0;    // CDW8-9
    *(uint64_t *) (nvme_iosqb_ptr + 40) = cdw10_11; // CDW10_11
    *(uint32_t *) (nvme_iosqb_ptr + 48) = cdw12;    // CDW12
    *(uint32_t *) (nvme_iosqb_ptr + 52) = 0;    // CDW13
    *(uint32_t *) (nvme_iosqb_ptr + 56) = 0;    // CDW14
    *(uint32_t *) (nvme_iosqb_ptr + 60) = 0;    // CDW15


    // Start the read command by updating the tail doorbell
    io_tail_val = 0;
    io_tail_val = *nvme_iotail; // Get the current io tail value
    tmp = io_tail_val;  // Save the old io tail value for reading from the completion ring
    io_tail_val++;          // Add 1 to it

    if(io_tail_val>= 64)
        io_tail_val = 0;

    nvme_io_savetail(io_tail_val, nvme_iotail, tmp);

    return partition_data_buffer;
}

/*
 * paste data from the partition data buffer into the ssd partition.
 */
void paste_data_into_ssd_partition(uint32_t starting_sector, uint32_t num_blocks)
{
    uint32_t cdw0 = 0x00000001; // CDW0 CID 0, PRP used (15:14 clear), FUSE normal (bits 9:8 clear), command write (0x01)
    uint32_t cdw1 = 1;  // CDW1 NSID
    uint32_t cdw10_11 = starting_sector;        // CDW10_11
    uint32_t cdw12 = num_blocks - 1; /* num logical blocks to be written */


    char *nvme_iosqb_ptr = nvme_iosqb;
    uint32_t tmp, io_tail_val = 0;

    // Build the command at the expected location in the Submission ring
    io_tail_val = *nvme_iotail; // Get the current io tail value

    io_tail_val *= 64;          // Quick multiply by 64
                            //
    nvme_iosqb_ptr += io_tail_val;

    // Build the structure
    *(uint32_t *) nvme_iosqb_ptr = cdw0;    // CDW0
    *(uint32_t *) (nvme_iosqb_ptr + 4) = cdw1;  // CDW1
    *(uint32_t *) (nvme_iosqb_ptr + 8) = 0; // CDW2
    *(uint32_t *) (nvme_iosqb_ptr + 12) = 0;    // CDW3
    *(uint64_t *) (nvme_iosqb_ptr + 16) = 0;    // CDW4-5
    *(uint64_t *) (nvme_iosqb_ptr + 24) = (uint64_t) partition_data_buffer; // CDW6-7
    *(uint64_t *) (nvme_iosqb_ptr + 32) = 0;    // CDW8-9
    *(uint64_t *) (nvme_iosqb_ptr + 40) = cdw10_11; // CDW10_11
    *(uint32_t *) (nvme_iosqb_ptr + 48) = cdw12;    // CDW12
    *(uint32_t *) (nvme_iosqb_ptr + 52) = 0;    // CDW13
    *(uint32_t *) (nvme_iosqb_ptr + 56) = 0;    // CDW14
    *(uint32_t *) (nvme_iosqb_ptr + 60) = 0;    // CDW15
                                //

    // Start the write command by updating the tail doorbell
    io_tail_val = 0;
    io_tail_val = *nvme_iotail; // Get the current io tail value
    tmp = io_tail_val;  // Save the old io tail value for reading from the completion ring
    io_tail_val++;          // Add 1 to it

    if(io_tail_val>= 64)
        io_tail_val = 0;

    nvme_io_savetail(io_tail_val, nvme_iotail, tmp);
}