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Question

I have wrote a program to detect usb drive whenever it is inserted. I want to know all the partitions on the usb. If my drive has one partition (example E:/ ), then the program detects successfully. But if the usb drive has two partition (example: E: , F: ) then only first partition E: is detected but I do not know how to detect F: or other partitions of the usb. On inserting a usb drive, DBT_DEVICEARRIVAL is triggered.

case DBT_DEVICEARRIVAL:
            
            if (b->dbcc_devicetype == DBT_DEVTYP_VOLUME)
            {
                
                PDEV_BROADCAST_HDR lpdbh = (PDEV_BROADCAST_HDR)lParam;
                PDEV_BROADCAST_VOLUME vol = (PDEV_BROADCAST_VOLUME)lParam;
                char drive = FirstDriveFromMask(vol->dbcv_unitmask);                
            }

The function FirstDriveFromMask() can detect first encountered partition from mask. How do I detect the other partitions from the usb drive.

char FirstDriveFromMask(ULONG unitmask)// (usb has drive e:, f: )unitmask I receive is 48. Output is E
{
    for (char i = 0; i < 26; ++i, unitmask >>= 1)
        if (unitmask & 0x1)
            return i + 'A';
    return 0;
}

Answer 1

The following function could be helpful:

std::string DrivesFromMask(ULONG unitmask)
{
    char i;
    std::string drv = "";
    for (i = 0; i < 26 && unitmask; ++i)
    {
        if (unitmask & 0x1)
        {
            drv += i + 'A';
        }
        unitmask = unitmask >> 1;
    }
    return drv;
}

And then read each drive letter in std::string .