Windows disk operation 4-obtain the physical disk number based on the Logical Partition Number

 

In section 1, we talked about two types of disk device names:

For physical drive x, the format is \. \ PhysicalDriveX. The number starts from 0, for example

Name	Description
\. \ PhysicalDrive0	Open the first physical drive
\\. \ PhysicalDrive2	Open the third physical drive

 

For logical partitions (volumes), the format is \. \ X:, for example

Name	Description
\. \:	Open drive)
\. \ C:	Open disk C (logical partition of disk)

 

How to find the physical drive numbers 0, 1, 2 ...... And logical partition numbers C, D, E ...... What is the relationship between them? This section describes how to obtain a physical drive letter by using a logical partition number. The next section describes how to identify the logical Partition Number contained by a physical drive number. Of course, there will certainly be other ways to implement the same function. You are welcome to add this.

First, we need to make it clear that the physical drive letter and the logical partition number should be one-to-many. For example, disk0 may contain three partitions: C, D, and E. So the function GetPhysicalDriveFromPartitionLetter discussed below returns a separate integer number. DeviceIoControl provides the operation code IOCTL_STORAGE_GET_DEVICE_NUMBER, which allows you to conveniently obtain the type and number of the device that is enabled.

The Code is as follows:

/*************************************** ***************************************

* Function: get disk's physical number from its drive letter

* E.g. C --> 0 (C: is on disk0)

* Input: letter, drive letter

* Output: N/

* Return: Succeed, disk number

* Fail,-1

**************************************** **************************************/

DWORD GetPhysicalDriveFromPartitionLetter (CHAR letter)

{

HANDLE hDevice; // handle to the drive to be examined

BOOL result; // results flag

DWORD readed; // discard results

STORAGE_DEVICE_NUMBER number; // use this to get disk numbers

 

CHAR path [DISK_PATH_LEN];

Sprintf (path, "\\\\\ % c:", letter );

HDevice = CreateFile (path, // drive to open

GENERIC_READ | GENERIC_WRITE, // access to the drive

File_cmd_read | file_cmd_write, // share mode

NULL, // default security attributes

OPEN_EXISTING, // disposition

0, // file attributes

NULL); // do not copy file attribute

If (hDevice = INVALID_HANDLE_VALUE) // cannot open the drive

{

Fprintf (stderr, "CreateFile () Error: % ld \ n", GetLastError ());

Return DWORD (-1 );

}

 

Result = DeviceIoControl (

HDevice, // handle to device

IOCTL_STORAGE_GET_DEVICE_NUMBER, // dwIoControlCode

NULL, // lpInBuffer

0, // nInBufferSize

& Number, // output buffer

Sizeof (number), // size of output buffer

& Readed, // number of bytes returned

NULL // OVERLAPPED structure

);

If (! Result) // fail

{

Fprintf (stderr, "IOCTL_STORAGE_GET_DEVICE_NUMBER Error: % ld \ n", GetLastError ());

(Void) CloseHandle (hDevice );

Return (DWORD)-1;

}

// Printf ("% d \ n", number. DeviceType, number. DeviceNumber, number. PartitionNumber );

 

(Void) CloseHandle (hDevice );

Return number. DeviceNumber;

}

 

Code Analysis:

1. Generate a device name based on the Partition Number.

2. Call CreateFile to open the device and obtain the device handle.

3. Call the DeviceIoControl function whose operation code is IOCTL_STORAGE_GET_DEVICE_NUMBER. The output is the struct variable STORAGE_DEVICE_NUMBER.

Struct STORAGE_DEVICE_NUMBER is defined

Typedef struct _ STORAGE_DEVICE_NUMBER {

DEVICE_TYPE DeviceType;

ULONG DeviceNumber;

ULONG PartitionNumber;

} STORAGE_DEVICE_NUMBER, * PSTORAGE_DEVICE_NUMBER;

The DeviceNumber is the physical disk number we need.

4. Return DeviceNumber.

 

This article is from the "bunny Technology Workshop" blog