rw.c

ReactOS是一些高手根据Windows XP的内核编写出的类XP。内核实现机理和API函数调用几乎相同。甚至可以兼容XP的程序。喜欢研究系统内核的人可以看一看。

/*
 * COPYRIGHT:        See COPYING in the top level directory
 * PROJECT:          ReactOS kernel
 * FILE:             services/fs/minix/rw.c
 * PURPOSE:          Minix FSD
 * PROGRAMMER:       David Welch ([e-mail])
 * UPDATE HISTORY:
 */

/* INCLUDES *****************************************************************/

#include <ntddk.h>
#include <string.h>
#include <ntos/minmax.h>

#define NDEBUG
#include <debug.h>

#include "minix.h"

/* FUNCTIONS ****************************************************************/

NTSTATUS STDCALL
MinixWrite(PDEVICE_OBJECT DeviceObject, PIRP Irp)
{
   DPRINT("MinixWrite(DeviceObject %x Irp %x)\n",DeviceObject,Irp);

   Irp->IoStatus.Status = STATUS_UNSUCCESSFUL;
   Irp->IoStatus.Information = 0;
   return(STATUS_UNSUCCESSFUL);
}

static NTSTATUS MinixReadFilePage(PDEVICE_OBJECT DeviceObject,
				  PMINIX_DEVICE_EXTENSION DeviceExt,
				  PMINIX_FSCONTEXT FsContext,
				  ULONG Offset,
				  PVOID* Buffer)
{
   NTSTATUS Status;
   ULONG i;
   ULONG DiskOffset;

   *Buffer = ExAllocatePool(NonPagedPool, 4096);

   for (i=0; i<4; i++)
     {
	Status = MinixReadBlock(DeviceObject,
				DeviceExt,
				&FsContext->inode,
				Offset + (i * BLOCKSIZE),
				&DiskOffset);
	MinixReadSector(DeviceObject,
			DiskOffset / BLOCKSIZE,
			(*Buffer) + (i * BLOCKSIZE));
     }
   return(STATUS_SUCCESS);
}

NTSTATUS STDCALL
MinixRead(PDEVICE_OBJECT DeviceObject, PIRP Irp)
{
   ULONG Length;
   PVOID Buffer;
   ULONG Offset;
   ULONG CurrentOffset;
   PIO_STACK_LOCATION Stack = IoGetCurrentIrpStackLocation(Irp);
   PFILE_OBJECT FileObject = Stack->FileObject;
   MINIX_DEVICE_EXTENSION* DeviceExt = DeviceObject->DeviceExtension;
   PMINIX_FSCONTEXT FsContext = (PMINIX_FSCONTEXT)FileObject->FsContext;
   unsigned int i;
   PVOID DiskBuffer;

   DPRINT("MinixRead(DeviceObject %x, Irp %x)\n",DeviceObject,Irp);

   Length = Stack->Parameters.Read.Length;
   Buffer = MmGetSystemAddressForMdl(Irp->MdlAddress);
   Offset = Stack->Parameters.Read.ByteOffset.u.LowPart;

   DPRINT("Length %d Buffer %x Offset %x\n",Length,Buffer,Offset);

   CurrentOffset=Offset;

   DPRINT("inode->i_size %d\n",inode->i_size);

   if (Offset > FsContext->inode.i_size)
     {
	Irp->IoStatus.Status = STATUS_UNSUCCESSFUL;
	Irp->IoStatus.Information = 0;
	IoCompleteRequest(Irp,IO_NO_INCREMENT);
	return(STATUS_UNSUCCESSFUL);
     }
   if ((Offset+Length) > FsContext->inode.i_size)
     {
	Length = FsContext->inode.i_size - Offset;
     }

   if ((Offset%PAGE_SIZE)!=0)
     {
	CurrentOffset = Offset - (Offset%PAGE_SIZE);

	MinixReadFilePage(DeviceObject,
			  DeviceExt,
			  FsContext,
			  CurrentOffset,
			  &DiskBuffer);

	memcpy(Buffer,
	       DiskBuffer+(Offset%PAGE_SIZE),
	       min(PAGE_SIZE - (Offset%PAGE_SIZE),Length));

	ExFreePool(DiskBuffer);

	DPRINT("(BLOCKSIZE - (Offset%BLOCKSIZE)) %d\n",
	       (BLOCKSIZE - (Offset%BLOCKSIZE)));
	DPRINT("Length %d\n",Length);
	CurrentOffset = CurrentOffset + PAGE_SIZE;
	Buffer = Buffer + PAGE_SIZE - (Offset%PAGE_SIZE);
	Length = Length - min(PAGE_SIZE - (Offset%PAGE_SIZE),Length);
	DPRINT("CurrentOffset %d Buffer %x Length %d\n",CurrentOffset,Buffer,
	       Length);
     }
   for (i=0;i<(Length/PAGE_SIZE);i++)
     {
	CHECKPOINT;

	DPRINT("Length %d\n",Length);

	MinixReadFilePage(DeviceObject,
			  DeviceExt,
			  FsContext,
			  CurrentOffset,
			  &DiskBuffer);
	memcpy(Buffer, DiskBuffer, PAGE_SIZE);

	ExFreePool(DiskBuffer);

	CurrentOffset = CurrentOffset + PAGE_SIZE;
	Buffer = Buffer + PAGE_SIZE;
     }
   if ((Length%PAGE_SIZE) > 0)
     {
	CHECKPOINT;

	DPRINT("Length %x Buffer %x\n",(Length%PAGE_SIZE),Buffer);

	MinixReadFilePage(DeviceObject,
			  DeviceExt,
			  FsContext,
			  CurrentOffset,
			  &DiskBuffer);

	memcpy(Buffer, DiskBuffer, (Length%PAGE_SIZE));

	ExFreePool(DiskBuffer);

     }

   Irp->IoStatus.Status = STATUS_SUCCESS;
   Irp->IoStatus.Information = Length;
   IoCompleteRequest(Irp,IO_NO_INCREMENT);
   return(STATUS_SUCCESS);
}