remove USB
http://www.codeproject.com/Articles/13839/How-to-Prepare-a-USB-Drive-for-Safe-Removal
这个例子应该可以解释一切了
.获取设备Handle
根据卷的驱动器类型和DOS设备名，使用Windows API枚举所有磁盘，包括软盘、光盘，或者其他设备。
//----------------------------------------------------------------------
// returns the device instance handle of a storage volume or 0 on error
//----------------------------------------------------------------------
DEVINST GetDrivesDevInstByDeviceNumber(long DeviceNumber, UINT DriveType, char* szDosDeviceName)
{
bool IsFloppy = (strstr(szDosDeviceName, "\\Floppy") != NULL);
GUID* guid;
switch (DriveType) {
case DRIVE_REMOVABLE:
if ( IsFloppy ) {
guid = (GUID*)&GUID_DEVINTERFACE_FLOPPY;
} else {
guid = (GUID*)&GUID_DEVINTERFACE_DISK;
}
break;
case DRIVE_FIXED:
guid = (GUID*)&GUID_DEVINTERFACE_DISK;
break;
case DRIVE_CDROM:
guid = (GUID*)&GUID_DEVINTERFACE_CDROM;
break;
default:
return 0;
}
// Get device interface info set handle for all devices attached to system
HDEVINFO hDevInfo = SetupDiGetClassDevs(guid, NULL, NULL, DIGCF_PRESENT | DIGCF_DEVICEINTERFACE);
if (hDevInfo == INVALID_HANDLE_VALUE) {
return 0;
}
// Retrieve a context structure for a device interface of a device information set
DWORD dwIndex = 0;
long res;
BYTE Buf[1024];
PSP_DEVICE_INTERFACE_DETAIL_DATA pspdidd = (PSP_DEVICE_INTERFACE_DETAIL_DATA)Buf;
SP_DEVICE_INTERFACE_DATA spdid;
SP_DEVINFO_DATA spdd;
DWORD dwSize;
spdid.cbSize = sizeof(spdid);
while ( true ) {
res = SetupDiEnumDeviceInterfaces(hDevInfo, NULL, guid, dwIndex, &spdid);
if ( !res ) {
break;
}
dwSize = 0;
SetupDiGetDeviceInterfaceDetail(hDevInfo, &spdid, NULL, 0, &dwSize, NULL); // check the buffer size
if ( dwSize!=0 && dwSize<=sizeof(Buf) ) {
pspdidd->cbSize = sizeof(*pspdidd); // 5 Bytes!
ZeroMemory(&spdd, sizeof(spdd));
spdd.cbSize = sizeof(spdd);
long res = SetupDiGetDeviceInterfaceDetail(hDevInfo, &spdid, pspdidd, dwSize, &dwSize, &spdd);
if ( res ) {
// in case you are interested in the USB serial number:
// the device id string contains the serial number if the device has one,
// otherwise a generated id that contains the '&' char...
/*
DEVINST DevInstParent = 0;
CM_Get_Parent(&DevInstParent, spdd.DevInst, 0);
char szDeviceIdString[MAX_PATH];
CM_Get_Device_ID(DevInstParent, szDeviceIdString, MAX_PATH, 0);
printf("DeviceId=%s\n", szDeviceIdString);
*/
// open the disk or cdrom or floppy
HANDLE hDrive = CreateFile(pspdidd->DevicePath, 0, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, 0, NULL);
if ( hDrive != INVALID_HANDLE_VALUE ) {
// get its device number
STORAGE_DEVICE_NUMBER sdn;
DWORD dwBytesReturned = 0;
res = DeviceIoControl(hDrive, IOCTL_STORAGE_GET_DEVICE_NUMBER, NULL, 0, &sdn, sizeof(sdn), &dwBytesReturned, NULL);
if ( res ) {
if ( DeviceNumber == (long)sdn.DeviceNumber ) { // match the given device number with the one of the current device
CloseHandle(hDrive);
SetupDiDestroyDeviceInfoList(hDevInfo);
return spdd.DevInst;
}
}
CloseHandle(hDrive);
}
}
}
dwIndex++;
}
SetupDiDestroyDeviceInfoList(hDevInfo);
return 0;
}
2.Remove Usb Device的主程序
本例中usb的盘符为G盘
char DriveLetter = 'G';
DriveLetter &= ~0x20; // uppercase
if ( DriveLetter < 'A' || DriveLetter > 'Z' ) {
return 1;
}
char szRootPath[] = "X:\\"; // "X:\" -> for GetDriveType
szRootPath[0] = DriveLetter;
char szDevicePath[] = "X:"; // "X:" -> for QueryDosDevice
szDevicePath[0] = DriveLetter;
char szVolumeAccessPath[] = "\\\\.\\X:"; // "\\.\X:" -> to open the volume
szVolumeAccessPath[4] = DriveLetter;
long DeviceNumber = -1;
2.1 open the storage volume
HANDLE hVolume = CreateFile(szVolumeAccessPath, 0, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, NULL, NULL);
if (hVolume == INVALID_HANDLE_VALUE) {
return 1;
}
2.2 get the volume's device number
STORAGE_DEVICE_NUMBER sdn;
DWORD dwBytesReturned = 0;
long res = DeviceIoControl(hVolume, IOCTL_STORAGE_GET_DEVICE_NUMBER, NULL, 0, &sdn, sizeof(sdn), &dwBytesReturned, NULL);
if ( res ) {
DeviceNumber = sdn.DeviceNumber;
}
CloseHandle(hVolume);
if ( DeviceNumber == -1 ) {
return 1;
}
2.3 get the drive type
UINT DriveType = GetDriveType(szRootPath);
2.4 get the dos device name
char szDosDeviceName[MAX_PATH];
res = QueryDosDevice(szDevicePath, szDosDeviceName, MAX_PATH);
if ( !res ) {
return 1;
}
2.5 get the device instance handle
DEVINST DevInst = GetDrivesDevInstByDeviceNumber(DeviceNumber, DriveType, szDosDeviceName);
if ( DevInst == 0 ) {
return 1;
}
PNP_VETO_TYPE VetoType = PNP_VetoTypeUnknown;
WCHAR VetoNameW[MAX_PATH];
VetoNameW[0] = 0;
bool bSuccess = false;
2.6 get drives's parent
DEVINST DevInstParent = 0;
res = CM_Get_Parent(&DevInstParent, DevInst, 0);
for ( long tries=1; tries<=3; tries++ ) { // sometimes we need try more than one times...
VetoNameW[0] = 0;
// CM_Query_And_Remove_SubTree doesn't work for restricted users
//res = CM_Query_And_Remove_SubTreeW(DevInstParent, &VetoType, VetoNameW, MAX_PATH, CM_REMOVE_NO_RESTART); // CM_Query_And_Remove_SubTreeA is not implemented under W2K!
//res = CM_Query_And_Remove_SubTreeW(DevInstParent, NULL, NULL, 0, CM_REMOVE_NO_RESTART); // with messagebox (W2K, Vista) or balloon (XP)
res = CM_Request_Device_EjectW(DevInstParent, &VetoType, VetoNameW, MAX_PATH, 0);
//res = CM_Request_Device_EjectW(DevInstParent, NULL, NULL, 0, 0); // with messagebox (W2K, Vista) or balloon (XP)
bSuccess = (res==CR_SUCCESS && VetoType==PNP_VetoTypeUnknown);
if ( bSuccess ) {
break;
}
Sleep(500); // required to give the next tries a chance!
}