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最近碰到了個新問題，記錄下來作為windows的磁碟操作那個系列的續篇吧。
一些時候我們的程式需要區分本機存放區裝置和USB存放裝置。在網上搜一搜一般會找到一個最直接的API，GetDriveType，其原型為UINT GetDriveType(LPCTSTR lpRootPathName)參數lpRootPathName是存放裝置的根目錄，例如C:\，傳回值即為裝置類型。
| Return code |
Description |
| DRIVE_REMOVABLE |
The drive has removable media; for example, a floppy drive, thumb drive, or flash card reader. |
| DRIVE_FIXED |
The drive has fixed media; for example, a hard drive or flash drive. |
或者採用一種稍微複雜一點的方法，使用我們第一節http://cutebunny.blog.51cto.com/301216/624027中介紹的GetDriveGeometry()函數，其輸出參數DISK_GEOMETRY
*pdg中的MediaType欄位代表裝置類型。typedef enum _MEDIA_TYPE{…RemovableMediaFixedMedia…}MEDIA_TYPE; 這兩個方法看似能方便快捷的解決我們的需求，但事實上當你使用GetDriveType()去擷取一塊移動硬碟的類型時，程式會坑爹的告訴你這塊移動硬碟的類型是DRIVE_FIXED，根本無法與本地磁碟區分開來。GetDriveGeometry()函數的結果也是如此。事實上，上述方法只對小容量的隨身碟有效，會返回給你DRIVE_REMOVABLE的結果；而對移動硬碟甚至是一塊稍大容量的隨身碟（比如我有一塊格式化為FAT32格式的4G
隨身碟），就無能為力了。 所以，我們必須採用別的思路了，這裡我介紹一種通過查看匯流排類型來區分本地磁碟和USB磁碟的方法。當然，其基礎還是我們那萬能的DeviceIoControl，不過這次的控制碼為IOCTL_STORAGE_QUERY_PROPERTY。同時對應的輸入參數為STORAGE_PROPERTY_QUERY結構，輸出參數為STORAGE_DEVICE_DESCRIPTOR結構體。typedef struct _STORAGE_PROPERTY_QUERY {
STORAGE_PROPERTY_ID PropertyId;
STORAGE_QUERY_TYPE QueryType;
UCHAR AdditionalParameters[1];
} STORAGE_PROPERTY_QUERY, *PSTORAGE_PROPERTY_QUERY;調用時需設定輸入參數中的欄位PropertyId = StorageDeviceProperty;QueryType = PropertyStandardQuery;以表明我們要查詢一個device descriptor，也就是說，只有指定這種類型，輸出參數才會得到STORAGE_DEVICE_DESCRIPTOR類型資料。typedef struct _STORAGE_DEVICE_DESCRIPTOR {
ULONG Version;
ULONG Size;
UCHAR DeviceType;
UCHAR DeviceTypeModifier;
BOOLEAN RemovableMedia;
BOOLEAN CommandQueueing;
ULONG VendorIdOffset;
ULONG ProductIdOffset;
ULONG ProductRevisionOffset;
ULONG SerialNumberOffset;
STORAGE_BUS_TYPE BusType;
ULONG RawPropertiesLength;
UCHAR RawDeviceProperties[1];
} STORAGE_DEVICE_DESCRIPTOR, *PSTORAGE_DEVICE_DESCRIPTOR;其中，BusType定義為typedef enum _STORAGE_BUS_TYPE {
BusTypeUnknown = 0x00,
BusTypeScsi,
BusTypeAtapi,
BusTypeAta,
BusType1394,
BusTypeSsa,
BusTypeFibre,
BusTypeUsb,
BusTypeRAID,
BusTypeiScsi,
BusTypeSas,
BusTypeSata,
BusTypeSd,
BusTypeMmc,
BusTypeMax,
BusTypeMaxReserved = 0x7F
} STORAGE_BUS_TYPE, *PSTORAGE_BUS_TYPE;明白了吧，如果匯流排類型為BusTypeUsb，就是找到了我們的USB移動硬碟了。但此時還需要解決一個問題，STORAGE_DEVICE_DESCRIPTOR可以理解為一個變長緩衝區，最後一個欄位RawDeviceProperties[1]是可以動態擴充的（windows
API經常有這種情況），那麼函數DeviceIoControl()中的參數nOutBufferSize應該填多少呢？這時我們需要藉助另一個資料結構STORAGE_DESCRIPTOR_HEADER，在我們不知道device
descriptor實際需要多大的緩衝區時，可以先把STORAGE_DESCRIPTOR_HEADER作為輸出參數以獲得device descriptor的緩衝區大小，其大小被存入header的size欄位中。typedef struct _STORAGE_DESCRIPTOR_HEADER {
ULONG Version;
ULONG Size;
} STORAGE_DESCRIPTOR_HEADER, *PSTORAGE_DESCRIPTOR_HEADER; 以下是具體代碼/******************************************************************************* Function: get the bus type of an disk* input: drive name (c:)* output: bus type* return: Succeed, 0* Fail, -1******************************************************************************/DWORD GetDriveTypeByBus(const CHAR *drive, WORD *type){ HANDLE hDevice; // handle to the drive to be examined BOOL result; // results flag DWORD readed; // discard results STORAGE_DESCRIPTOR_HEADER *pDevDescHeader; STORAGE_DEVICE_DESCRIPTOR *pDevDesc; DWORD devDescLength; STORAGE_PROPERTY_QUERY query; hDevice = CreateFile( drive, // drive to open GENERIC_READ | GENERIC_WRITE, // access to the drive FILE_SHARE_READ | FILE_SHARE_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); } query.PropertyId = StorageDeviceProperty; query.QueryType = PropertyStandardQuery; pDevDescHeader = (STORAGE_DESCRIPTOR_HEADER *)malloc(sizeof(STORAGE_DESCRIPTOR_HEADER)); if (NULL == pDevDescHeader) { return (DWORD)-1; } result = DeviceIoControl( hDevice, // device to be queried IOCTL_STORAGE_QUERY_PROPERTY, // operation to perform &query, sizeof query, // no input buffer pDevDescHeader, sizeof(STORAGE_DESCRIPTOR_HEADER), // output buffer &readed, // # bytes returned NULL); // synchronous I/O if (!result) //fail { fprintf(stderr, "IOCTL_STORAGE_QUERY_PROPERTY Error: %ld\n", GetLastError()); free(pDevDescHeader); (void)CloseHandle(hDevice); return DWORD(-1); } devDescLength = pDevDescHeader->Size; pDevDesc = (STORAGE_DEVICE_DESCRIPTOR *)malloc(devDescLength); if (NULL == pDevDesc) { free(pDevDescHeader); return (DWORD)-1; } result = DeviceIoControl( hDevice, // device to be queried IOCTL_STORAGE_QUERY_PROPERTY, // operation to perform &query, sizeof query, // no input buffer pDevDesc, devDescLength, // output buffer &readed, // # bytes returned NULL); // synchronous I/O if (!result) //fail { fprintf(stderr, "IOCTL_STORAGE_QUERY_PROPERTY Error: %ld\n", GetLastError()); free(pDevDescHeader); free(pDevDesc); (void)CloseHandle(hDevice); return DWORD(-1); } //printf("%d\n", pDevDesc->BusType); *type = (WORD)pDevDesc->BusType; free(pDevDescHeader); free(pDevDesc); (void)CloseHandle(hDevice); return 0;} 代碼說明：1． 調用CreateFile開啟並獲得裝置控制代碼。2． 在輸入參數STORAGE_PROPERTY_QUERY query中指定查詢類型。3． 以STORAGE_DESCRIPTOR_HEADER *pDevDescHeader為輸出參數，叫用作業碼為IOCTL_STORAGE_QUERY_PROPERTY的DeviceIoControl函數獲得輸出緩衝區大小。4． 按3中獲得的緩衝區大小為STORAGE_DEVICE_DESCRIPTOR *pDevDesc分配空間，以pDevDesc為輸出參數，叫用作業碼為IOCTL_STORAGE_QUERY_PROPERTY的DeviceIoControl函數獲得device
descriptor。5． 從device descriptor中獲得BusType。
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