Windows NT Driver >> Pascal >> File
DO_NEITHER_IO
參考資訊:
1. Source Code
2. delphidriverdevelopmentkit
基本上,Microsoft沒有定義DO_NEITHER_IO這個Flag,而Neither I/O的意思就是Neither Buffered Nor Direct I/O,因此,當沒有設定DO_BUFFERED_IO或DO_DIRECT_IO Flag時,就會使用Neither的方式,使用這種方式時,I/O Manager會將User Buffer的指標,透過操作後,傳遞給驅動程式使用,因此,驅動程式可以直接存取User Buffer的資料,所以存取速度可以得到很大的改善,對於有速度要求的驅動程式來說,建議使用Neither的方式,不過,關於User Buffer指標的存取問題上,會遇到更多需要面對的問題,如:指標的有效性以及多次存取的同步問題,因此,在選擇使用上,更需要考量到這些額外付出的代價是否值得使用,因為,驅動程式以及User Application雙方都需要很嚴謹的看待這塊共用的Buffer。
Microsoft的說明網頁:
using-neither-buffered-nor-direct-i-o
記憶體指標:
IRP | Buffer | Length |
---|---|---|
IRP_MJ_READ | (Irp) UserBuffer |
(IrpStack) Parameters.Read.Length |
IRP_MJ_WRITE | (Irp) UserBuffer |
(IrpStack) Parameters.Write.Length |
main.pas
unit main; interface uses DDDK; const DEV_NAME = '\Device\MyDriver'; SYM_NAME = '\DosDevices\MyDriver'; function _DriverEntry(pOurDriver:PDriverObject; pOurRegistry:PUnicodeString):NTSTATUS; stdcall; implementation var szBuf: array[0..255] of char; function IrpOpen(pOurDevice:PDeviceObject; pIrp:PIrp):NTSTATUS; stdcall; begin DbgPrint('IRP_MJ_CREATE', []); Result:= STATUS_SUCCESS; pIrp^.IoStatus.Information:= 0; pIrp^.IoStatus.Status:= Result; IoCompleteRequest(pIrp, IO_NO_INCREMENT); end; function IrpRead(pOurDevice:PDeviceObject; pIrp:PIrp):NTSTATUS; stdcall; var len: ULONG; begin DbgPrint('IRP_MJ_READ', []); len:= strlen(@szBuf[0])+1; memcpy(pIrp^.UserBuffer, @szBuf[0], len); Result:= STATUS_SUCCESS; pIrp^.IoStatus.Information:= len; pIrp^.IoStatus.Status:= Result; IoCompleteRequest(pIrp, IO_NO_INCREMENT); end; function IrpWrite(pOurDevice:PDeviceObject; pIrp:PIrp):NTSTATUS; stdcall; var len: ULONG; psk: PIoStackLocation; begin DbgPrint('IRP_MJ_WRITE', []); psk:= IoGetCurrentIrpStackLocation(pIrp); len:= psk.Parameters.Write.Length; memcpy(@szBuf[0], pIrp^.UserBuffer, len); DbgPrint('Address: 0x%x, Length: %d', [pIrp^.UserBuffer, len]); Result:= STATUS_SUCCESS; pIrp^.IoStatus.Information:= len; pIrp^.IoStatus.Status:= Result; IoCompleteRequest(pIrp, IO_NO_INCREMENT); end; function IrpClose(pOurDevice:PDeviceObject; pIrp:PIrp):NTSTATUS; stdcall; begin DbgPrint('IRP_MJ_CLOSE', []); Result:= STATUS_SUCCESS; pIrp^.IoStatus.Information:= 0; pIrp^.IoStatus.Status:= Result; IoCompleteRequest(pIrp, IO_NO_INCREMENT); end; procedure Unload(pOurDriver:PDriverObject); stdcall; var szSymName: TUnicodeString; begin RtlInitUnicodeString(@szSymName, SYM_NAME); IoDeleteSymbolicLink(@szSymName); IoDeleteDevice(pOurDriver^.DeviceObject); end; function _DriverEntry(pOurDriver:PDriverObject; pOurRegistry:PUnicodeString):NTSTATUS; stdcall; var suDevName: TUnicodeString; szSymName: TUnicodeString; pOurDevice: PDeviceObject; begin RtlInitUnicodeString(@suDevName, DEV_NAME); RtlInitUnicodeString(@szSymName, SYM_NAME); Result:= IoCreateDevice(pOurDriver, 0, @suDevName, FILE_DEVICE_UNKNOWN, 0, FALSE, pOurDevice); if NT_SUCCESS(Result) then begin pOurDriver^.MajorFunction[IRP_MJ_CREATE]:= @IrpOpen; pOurDriver^.MajorFunction[IRP_MJ_READ] := @IrpRead; pOurDriver^.MajorFunction[IRP_MJ_WRITE] := @IrpWrite; pOurDriver^.MajorFunction[IRP_MJ_CLOSE] := @IrpClose; pOurDriver^.DriverUnload := @Unload; pOurDevice^.Flags:= pOurDevice^.Flags and not DO_DEVICE_INITIALIZING; Result:= IoCreateSymbolicLink(@szSymName, @suDevName); end; end; end.
IrpFile()收到IRP_MJ_WRITE時,Driver複製User Buffer的內容到szBuffer,而收到IRP_MJ_READ時,將szBuffer內容又複製回User Buffer,完成暫存的功能,IoStatus.Information的數值就是ReadFile()或WriteFile()完成的長度。
app.pas
program main; {$APPTYPE CONSOLE} uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, DIALOGS; var fd: DWORD; ret: DWORD; len: DWORD; szBuf: array[0..255] of char; begin fd:= CreateFile('\\.\MyDriver', GENERIC_READ or GENERIC_WRITE, FILE_SHARE_READ, Nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0); if (fd <> INVALID_HANDLE_VALUE) then begin StrCopy(szBuf, 'I am error'); len:= strlen(szBuf)+1; WriteLn(Output, Format('WR: %s, %d', [szBuf, len])); WriteFile(fd, szBuf, len, ret, Nil); ReadFile(fd, szBuf, len, ret, Nil); WriteLn(Output, Format('RD: %s, %d', [szBuf, ret])); CloseHandle(fd); end else begin WriteLn(Output, 'failed to open mydriver'); end; end.
結果