CTL_CODE说明
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(shù)）
DeviceTypeThis 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 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.
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.
The following table shows the possible flags for this parameter. The FILE_ACCESS_ANY is generally the correct value.
| 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（返回值）
None.
Remarks（備注）
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.
?
舉例說明一下：
我定義兩個IOCTL,一個用于對設備的讀，一個用于對設備的寫
#define ATST2004_IOCTL_READ CTL_CODE(FILE_DEVICE_UNKNOWN, 0x800, METHOD_BUFFERED, FILE_READ_DATA)
#define ATST2004_IOCTL_WRITE CTL_CODE(FILE_DEVICE_UNKNOWN, 0x801, METHOD_BUFFERED, FILE_WRITE_DATA)
在VC中使用不需要進行處理，假如我要在VB中使用這兩個IOCTL，就需要進行查值計算了，計算后定義如下：
Private Const ATST2004_IOCTL_READ = &H226000
Private Const ATST2004_IOCTL_WRITE = &H22A004
關于Method（I/O訪問內(nèi)存使用方式），我們下篇在說。
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