我們在說DeviceIoControl函數時其第二個參數dwIoControlCode就是由CTL_CODE宏定義的,下邊我們可以瞭解一下CTL_CODE的內容。
CTL_CODE:用於建立一個唯一的32位系統I/O控制碼,這個控制碼包括4部分
組成:DeviceType(裝置類型,高16位(16-31位)),Access(訪問限制,14-15位),Function(功能2-13
位),Method(I/O訪問記憶體使用量方式)。
This macro creates a unique system I/O control code (IOCTL).
#define CTL_CODE(DeviceType, Function, Method, Access) (
((DeviceType) << 16) | ((Access) << 14) | ((Function) << 2) | (Method)
)
Parameters(參數)
-
DeviceType
-
Defines the type of device for the given IOCTL.
This parameter can be no bigger than a WORD value.
The values used by Microsoft are in the range 0-32767; the values 32768-65535 are reserved for use by OEMs and IHVs.
The following device types are defined by the system:
- FILE_DEVICE_BEEP
- FILE_DEVICE_CD_ROM
- FILE_DEVICE_CD_ROM_FILE_SYSTEM
- FILE_DEVICE_CONTROLLER
- FILE_DEVICE_DATALINK
- FILE_DEVICE_DFS
- FILE_DEVICE_DISK
- FILE_DEVICE_DISK_FILE_SYSTEM
- FILE_DEVICE_FILE_SYSTEM
- FILE_DEVICE_INPORT_PORT
- FILE_DEVICE_KEYBOARD
- FILE_DEVICE_MAILSLOT
- FILE_DEVICE_MIDI_IN
- FILE_DEVICE_MIDI_OUT
- FILE_DEVICE_MOUSE
- FILE_DEVICE_MULTI_UNC_PROVIDER
- FILE_DEVICE_NAMED_PIPE
- FILE_DEVICE_NETWORK
- FILE_DEVICE_NETWORK_BROWSER
- FILE_DEVICE_NETWORK_FILE_SYSTEM
- FILE_DEVICE_NULL
- FILE_DEVICE_PARALLEL_PORT
- FILE_DEVICE_PHYSICAL_NETCARD
- FILE_DEVICE_PRINTER
- FILE_DEVICE_SCANNER
- FILE_DEVICE_SERIAL_MOUSE_PORT
- FILE_DEVICE_SERIAL_PORT
- FILE_DEVICE_SCREEN
- FILE_DEVICE_SOUND
- FILE_DEVICE_DEVICE_STREAMS
- FILE_DEVICE_TAPE
- FILE_DEVICE_TAPE_FILE_SYSTEM
- FILE_DEVICE_TRANSPORT
- FILE_DEVICE_UNKNOWN
- FILE_DEVICE_VIDEO
- FILE_DEVICE_VIRTUAL_DISK
- FILE_DEVICE_WAVE_IN
- FILE_DEVICE_WAVE_OUT
- FILE_DEVICE_8042_PORT
- FILE_DEVICE_NETWORK_REDIRECTOR
- FILE_DEVICE_BATTERY
- FILE_DEVICE_BUS_EXTENDER
- FILE_DEVICE_MODEM
- FILE_DEVICE_VDM
- FILE_DEVICE_MASS_STORAGE
- FILE_DEVICE_SMB
- FILE_DEVICE_KS
- FILE_DEVICE_CHANGER
- FILE_DEVICE_SMARTCARD
- FILE_DEVICE_ACPI
- FILE_DEVICE_DVD
- FILE_DEVICE_FULLSCREEN_VIDEO
- FILE_DEVICE_DFS_FILE_SYSTEM
- FILE_DEVICE_DFS_VOLUME
The following device types are specific to Windows CE:
- FILE_DEVICE_HAL
- FILE_DEVICE_CONSOLE
- FILE_DEVICE_PSL
- FILE_DEVICE_SERVICE
-
Function
-
Defines an action within the device category.
Function codes 0-2047 are reserved for Microsoft; codes 2048-4095 are reserved for OEMs and IHVs.
A function code can be no larger then 4095.
-
Method
-
Defines the method codes for how buffers are passed for I/O and file system controls.
The following values are possible for this parameter:
- METHOD_BUFFERED
- METHOD_IN_DIRECT
- METHOD_OUT_DIRECT
- METHOD_NEITHER
This field is ignored by Windows CE. You should always use the
METHOD_BUFFERED value unless compatibility with Windows-based desktop
platforms is required using a different Method
value.
-
Access
-
Defines the access check value for any access.
The following table shows the possible flags for this parameter. The FILE_ACCESS_ANY is generally the correct value.
Flag |
Description |
FILE_ANY_ACCESS |
Request all access. |
FILE_READ_ACCESS |
Request read access. Can be used with FILE_WRITE_ACCESS. |
FILE_WRITE_ACCESS |
Request write access. Can be used with FILE_READ_ACCESS. |
Return Values(傳回值)
None.
Remarks(備忘)
The macro can be used for defining IOCTL and FSCTL function control
codes. All IOCTLs must be defined this way to ensure that values used
by Microsoft, OEMs, and IHVs do not overlap.
The following illustration shows the format of the resulting IOCTL.
參考自:http://msdn.microsoft.com/en-us/library/ms904001.aspx