windows的磁盘操作之一――基本概念

最近项目中需要在windows系统下与磁盘打交道，用了一个礼拜时间，弄懂了一些基本的概念，记录于此，并以项目中的部分代码作为范例。

首先说明一点，本文中使用的不是cmd命令行，基于以下几点原因：

1．在C/C++中调用系统命令会存在处理的种种不方便，需要大量额外的代码去分析命令执行结果。

2．windows命令行远不如linux的shell来的强大。

3．效率。

当然，如果不考虑编码，仅作为系统下一种应用工具的话，DiskPart是既安全又便利的选择。

 

我们先来看几个主要的使用频繁的函数。

在windows下与磁盘打交道最主要的API就是 DeviceIoControl了，以下是从MSDN中直接拷贝出来的对该函数的说明。此函数确实太重要也太强大了，建议大家耐着性子先将它的说明看完，当然，本文后续例子中会大量用到此函数，可随时返回此节参阅。

DeviceIoControl Function

Sends a control code directly to a specified device driver, causing the corresponding device to perform the corresponding operation.

BOOL WINAPI DeviceIoControl(

 __in           HANDLE hDevice,

 __in           DWORD dwIoControlCode,

 __in           LPVOID lpInBuffer,

 __in           DWORD nInBufferSize,

 __out          LPVOID lpOutBuffer,

 __in           DWORD nOutBufferSize,

 __out          LPDWORD lpBytesReturned,

 __in           LPOVERLAPPED lpOverlapped

);

Parameters

hDevice

A handle to the device on which the operation is to be performed. The device is typically a volume, directory, file, or stream. To retrieve a device handle, use the CreateFile function. For more information, see Remarks.

dwIoControlCode

The control code for the operation. This value identifies the specific operation to be performed and the type of device on which to perform it.

For a list of the control codes, see Remarks. The documentation for each control code provides usage details for the lpInBuffer, nInBufferSize, lpOutBuffer, and nOutBufferSize parameters.

lpInBuffer

A pointer to the input buffer that contains the data required to perform the operation. The format of this data depends on the value of the dwIoControlCode parameter.

This parameter can be NULL if dwIoControlCode specifies an operation that does not require input data.

nInBufferSize

The size of the input buffer, in bytes.

lpOutBuffer

A pointer to the output buffer that is to receive the data returned by the operation. The format of this data depends on the value of the dwIoControlCode parameter.

This parameter can be NULL if dwIoControlCode specifies an operation that does not return data.

nOutBufferSize

The size of the output buffer, in bytes.

lpBytesReturned

A pointer to a variable that receives the size of the data stored in the output buffer, in bytes.

If the output buffer is too small to receive any data, the call fails, GetLastError returns ERROR_INSUFFICIENT_BUFFER, and lpBytesReturned is zero.

If the output buffer is too small to hold all of the data but can hold some entries, some drivers will return as much data as fits. In this case, the call fails, GetLastError returns ERROR_MORE_DATA, and lpBytesReturned indicates the amount of data received. Your application should call DeviceIoControl again with the same operation, specifying a new starting point.

If lpOverlapped is NULL, lpBytesReturned cannot be NULL. Even when an operation returns no output data and lpOutBuffer is NULL, DeviceIoControl makes use of lpBytesReturned. After such an operation, the value of lpBytesReturned is meaningless.

If lpOverlapped is not NULL, lpBytesReturned can be NULL. If this parameter is not NULL and the operation returns data, lpBytesReturned is meaningless until the overlapped operation has completed. To retrieve the number of bytes returned, call GetOverlappedResult. If hDevice is associated with an I/O completion port, you can retrieve the number of bytes returned by calling GetQueuedCompletionStatus.

lpOverlapped

A pointer to an OVERLAPPED structure.

If hDevice was opened without specifying FILE_FLAG_OVERLAPPED, lpOverlapped is ignored.

If hDevice was opened with the FILE_FLAG_OVERLAPPED flag, the operation is performed as an overlapped (asynchronous) operation. In this case, lpOverlapped must point to a valid OVERLAPPED structure that contains a handle to an event object. Otherwise, the function fails in unpredictable ways.

For overlapped operations, DeviceIoControl returns immediately, and the event object is signaled when the operation has been completed. Otherwise, the function does not return until the operation has been completed or an error occurs.

Return Value

If the operation completes successfully, the return value is nonzero.

If the operation fails or is pending, the return value is zero. To get extended error information, call GetLastError.

Remarks

To retrieve a handle to the device, you must call the CreateFile function with either the name of a device or the name of the driver associated with a device. To specify a device name, use the following format:

\\.\ DeviceName

DeviceIoControl can accept a handle to a specific device. For example, to open a handle to the logical drive A: with CreateFile, specify \\.\a:. Alternatively, you can use the names \\.\PhysicalDrive0, \\.\PhysicalDrive1, and so on, to open handles to the physical drives on a system.

You should specify the FILE_SHARE_READ and FILE_SHARE_WRITE access flags when calling CreateFile to open a handle to a device driver. However, when you open a communications resource, such as a serial port, you must specify exclusive access. Use the other CreateFile parameters as follows when opening a device handle:

·         The fdwCreate parameter must specify OPEN_EXISTING.

·         The hTemplateFile parameter must be NULL.

·         The fdwAttrsAndFlags parameter can specify FILE_FLAG_OVERLAPPED to indicate that the returned handle can be used in overlapped (asynchronous) I/O operations.

Requirements

Client	Requires Windows Vista, Windows XP, Windows 2000 Professional, or Windows NT Workstation.
Server	Requires Windows Server 2008, Windows Server 2003, Windows 2000 Server, or Windows NT Server.
Header	Declared in Winbase.h; include Windows.h.
Library	Use Kernel32.lib.
DLL	Requires Kernel32.dll.

 

该函数实现对设备的访问，包括获取信息，发送命令，交换数据等。可以利用该接口函数向指定的设备驱动发送正确的控制码及数据，分析它的响应，执行程序设计人员想要的功能。磁盘操作只是它强大功能中的一小部分。

该函数最重要的两个参数是 hDevice和 dwIoControlCode.

 

控制码 dwIoControlCode决定了操作类型，与磁盘相关的控制码有

IOCTL_DISK_CREATE_DISK    利用CREATE_DISK结构中的信息对指定磁盘和磁盘分区进行初始化。

IOCTL_DISK_DELETE_DRIVE_LAYOUT    从主引导记录中删除引导信息，所以磁盘将会被从头到尾的格式化。扇区0中的分区信息也就不复存在了。

IOCTL_DISK_FORMAT_TRACKS    格式化指定的、连续的软盘磁道。如果需要更多的功能请使用IOCTL_DISK_FORMAT_TRACKS_EX。

IOCTL_DISK_FORMAT_TRACKS_EX    格式化指定的、连续的软盘磁道。

IOCTL_DISK_GET_CACHE_INFORMATION    返回磁盘的高速缓存配置数据

IOCTL_DISK_GET_DRIVE_GEOMETRY_EX    返回物理磁盘的扩展信息。包括：类型、柱面数量、每柱面磁道数、每磁道扇区数和每扇区字节数等。

IOCTL_DISK_GET_DRIVE_LAYOUT_EX    返回各分区的扩展信息以及这些分区的特性。更多信息请参照DRIVE_LAYOUT_INFORMATION_EX结构。

IOCTL_DISK_GET_LENGTH_INFO    返回指定磁盘/卷/分区的大小信息

IOCTL_DISK_GET_PARTITION_INFO_EX    返回指定分区的扩展信息。包括：分区类型、大小和种类。更多信息请参照PARTITION_INFORMATION_EX结构。

IOCTL_DISK_GROW_PARTITION    扩大指定分区。

IOCTL_DISK_IS_WRITABLE    确定指定磁盘是否可写。

IOCTL_DISK_PERFORMANCE    启用并获取磁盘性能统计

IOCTL_DISK_PERFORMANCE_OFF    关闭磁盘性能统计

IOCTL_DISK_REASSIGN_BLOCKS    使磁盘设备影射一块区域做为它的备用存储块公用池（spare block pool）。

IOCTL_DISK_SET_CACHE_INFORMATION    设置磁盘的配置信息

IOCTL_DISK_SET_DRIVE_LAYOUT_EX    根据给定的磁盘信息对磁盘进行分区。

IOCTL_DISK_SET_PARTITION_INFO_EX    设置指定分区的分区信息。包括AT和EFI (Extensible Firmware Interface)分区的布局信息。

IOCTL_DISK_UPDATE_PROPERTIES    使缓冲的分区表无效并重新获取一份。

IOCTL_DISK_VERIFY    对指定磁盘进行逻辑格式化

 

另一个参数 hDevice指向要操作的设备句柄，调用函数 CreateFile获得。 CreateFile函数原型为

HANDLE WINAPI CreateFile(

 __in           LPCTSTR lpFileName,

 __in           DWORD dwDesiredAccess,

 __in           DWORD dwShareMode,

 __in           LPSECURITY_ATTRIBUTES lpSecurityAttributes,

 __in           DWORD dwCreationDisposition,

 __in           DWORD dwFlagsAndAttributes,

 __in           HANDLE hTemplateFile

);

lpFileName为需要打开设备的名称，对于磁盘来说，可能为以下几种形式：

对于物理驱动器x，形式为 \\.\PhysicalDriveX ，编号从0开始，例如

名称	含义
\\.\PhysicalDrive0	打开第一个物理驱动器
\\.\PhysicalDrive2	打开第三个物理驱动器

对于逻辑分区（卷），形式为 \\.\X: ，例如

名称	含义
\\.\A:	打开A盘（软驱）
\\.\C:	打开C盘（磁盘逻辑分区）

 

最后复制一段MSDN上的示例代码作为本节的结束，该示例获取磁盘的详细信息（包括柱面、磁道、扇区等统计信息）并打印出来。

 

/* The code of interest is in the subroutine GetDriveGeometry. The

   code in main shows how to interpret the results of the call. */

 

#include <windows.h>

#include <winioctl.h>

#include <stdio.h>

 

BOOL GetDriveGeometry(DISK_GEOMETRY *pdg)

{

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

 BOOL bResult;                  // results flag

 DWORD junk;                   // discard results

 

 hDevice = CreateFile(TEXT("\\\\.\\PhysicalDrive0"), // drive

                    0,                // no access to the drive

                    FILE_SHARE_READ | // share mode

                    FILE_SHARE_WRITE,

                    NULL,             // default security attributes

                    OPEN_EXISTING,   // disposition

                    0,                // file attributes

                    NULL);            // do not copy file attributes

 

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

 {

    return (FALSE);

 }

 

 bResult = DeviceIoControl(hDevice, // device to be queried

      IOCTL_DISK_GET_DRIVE_GEOMETRY, // operation to perform

                             NULL, 0, // no input buffer

                            pdg, sizeof(*pdg),     // output buffer

                            &junk,                 // # bytes returned

                            (LPOVERLAPPED) NULL); // synchronous I/O

 

 CloseHandle(hDevice);

 

 return (bResult);

}

 

int main(int argc, char *argv[])

{

 DISK_GEOMETRY pdg;            // disk drive geometry structure

 BOOL bResult;                 // generic results flag

 ULONGLONG DiskSize;           // size of the drive, in bytes

 

 bResult = GetDriveGeometry (&pdg);

 

 if (bResult)

 {

    printf("Cylinders = %I64d\n", pdg.Cylinders);

    printf("Tracks/cylinder = %ld\n", (ULONG) pdg.TracksPerCylinder);

    printf("Sectors/track = %ld\n", (ULONG) pdg.SectorsPerTrack);

    printf("Bytes/sector = %ld\n", (ULONG) pdg.BytesPerSector);

 

    DiskSize = pdg.Cylinders.QuadPart * (ULONG)pdg.TracksPerCylinder *

      (ULONG)pdg.SectorsPerTrack * (ULONG)pdg.BytesPerSector;

    printf("Disk size = %I64d (Bytes) = %I64d (Gb)\n", DiskSize,

           DiskSize / (1024 * 1024 * 1024));

 }

 else

 {

    printf ("GetDriveGeometry failed. Error %ld.\n", GetLastError ());

 }

 

 return ((int)bResult);

}