windows的磁盘操作之五——获取物理磁盘上的所有逻辑分区号

本节讨论与上一节相反的操作，根据物理驱动器号获取该磁盘上的所有分区号。DeviceIoControl函数并没有提供操作码来直接完成此操作，所以需要稍微绕个圈子来实现这项功能。

大体思路为，先通过GetLogicalDrives函数获得系统中所有分区号，然后过滤掉非硬盘分区（例如软驱、光驱），再过滤掉不属于指定物理磁盘的分区，最后剩下的就是我们所需要的分区号了。

代码如下

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

* Function: get disk's drive letters from physical number

*           e.g. 0-->{C, D, E} (disk0 has 3 drives, C:, D: and E:)

* input: phyDriveNumber, disk's physical number

* output: letters, letters array

* return: Succeed, the amount of letters

*         Fail, -1

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

DWORD GetPartitionLetterFromPhysicalDrive(DWORD phyDriveNumber, CHAR **letters)

{

    DWORD mask;

    DWORD driveType;

    DWORD bmLetters;

    DWORD diskNumber;

    CHAR path[DISK_PATH_LEN];

    CHAR letter;

    DWORD letterNum;

    WORD i;

    CHAR *p;

    bmLetters = GetLogicalDrives();

    if (0 == bmLetters)

    {

        return (DWORD)-1;

    }

    letterNum = 0;

    for (i = 0; i < sizeof(DWORD) * 8; i++)

    {

        mask = 0x1u << i;

        if ((mask & bmLetters) == 0)        //get one letter

        {

            continue;

        }

        letter = (CHAR)(0x41 + i);    //ASCII change

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

        driveType = GetDriveType(path);

        if (driveType != DRIVE_FIXED)

        {

            bmLetters &= ~mask;     //clear this bit

            continue;

        }

        diskNumber = GetPhysicalDriveFromPartitionLetter(letter);

        if (diskNumber != phyDriveNumber)

        {

            bmLetters &= ~mask;     //clear this bit

            continue;

        }

        letterNum++;

    }

    //build the result

    *letters = (CHAR *)malloc(letterNum);

    if (NULL == *letters)

    {

        return (DWORD)-1;

    }

    p = *letters;

    for (i = 0; i < sizeof(DWORD) * 8; i++)