Writing Windows WDM Device Drivers

 // Complete successfully
 return CompleteIrp(Irp,STATUS_SUCCESS,0);
}
///////////////////////////////////////////////////////////////////////
//Wdm1Close:
//
//Description:
//Handle IRP_MJ_CLOSE requests
//
//Arguments:
//Pointer to our FDO
//Pointer to the IRP
//
//Return Value:
//This function returns STATUS_XXX
NTSTATUS Wdm1Close(IN PDEVICE_OBJECT fdo, IN PIRP Irp) {
 DebugPrintMsg('Close');
 // Complete successfully
 return CompleteIrp(Irp,STATUS_SUCCESS,0);
}
///////////////////////////////////////////////////////////////////////
//Wdm1Read:
//
//Description:
//Handle IRP_MJ_READ requests
//
//Arguments:
//Pointer to our FDO
//Pointer to the IRP
//IrpStack->Parameters.Read.xxx has read parameters
//User buffer at:AssociatedIrp.SystemBuffer(buffered I/O)
//MdlAddress(direct I/O)
//
//Return Value:
//This function returns STATUS_XXX
NTSTATUS Wdm1Read(IN PDEVICE_OBJECT fdo, IN PIRP Irp) {
 PIO_STACK_LOCATION IrpStack = IoGetCurrentIrpStackLocation(Irp);
 NTSTATUS status = STATUS_SUCCESS;
 LONG BytesTxd = 0;
 // Get call parameters
 LONGLONG FilePointer = IrpStack->Parameters.Read.ByteOffset.QuadPart;
 ULONG ReadLen = IrpStack->Parameters.Read.Length;
 DebugPrint('Read %d bytes from file pointer %d',(int)ReadLen,(int)FilePointer);
 // Get access to the shared buffer
 KIRQL irql;
 KeAcquireSpinLock(&BufferLock,&irql);
 // Check file pointer
 if (FilePointer<0) status = STATUS_INVALID_PARAMETER;
 if (FilePointer>=(LONGLONG)BufferSize) status = STATUS_END_OF_FILE;
 if (status==STATUS_SUCCESS) {
  // Get transfer count
  if ( ((ULONG)FilePointer)+ReadLen>BufferSize) {
   BytesTxd = BufferSize – (ULONG)FilePointer;
   if (BytesTxd<0) BytesTxd = 0;
  } else BytesTxd = ReadLen;
  // Read from shared buffer
  if (BytesTxd>0 && Buffer!=NULL) RtlCopyMemory(Irp->AssociatedIrp.SystemBuffer, Buffer+FilePointer, BytesTxd);
 }
 // Release shared buffer
 KeReleaseSpinlock(&BufferLock,irql);
 DebugPrint('Read: %d bytes returned',(int)BytesTxd);
 // Complete IRP
 return Completelrp(Irp.status.BytesTxd);
}
///////////////////////////////////////////////////////////////////////
//Wdm1Write: //
//Description:
//Handle IRP_MJ_WRITE requests
//
//Arguments:
//Pointer to our FDO
//Pointer to the IRP
//IrpStack->Parameters.Write.xxx has write parameters
//User buffer at:AssociatedIrp.SystemBuffer(buffered I/O)
//MdlAddress(direct I/O)
//
//Return Value:
//This function returns STATUS_XXX
NTSTATUS Wdm1Write(IN PDEVICE_OBJECT fdo, IN PIRP Irp) {
 PIO_STACK_LOCATION IrpStack = IoGetCurrentIrpStackLocation(Irp);
 NTSTATUS status = STATUS_SUCCESS;
 LONG BytesTxd = 0;
 // Get call parameters
 LONGLONG FilePointer = IrpStack->Parameters.Write.ByteOffset.QuadPart;
 ULONG WriteLen = IrpStack->Parameters.Write.Length;
 DebugPrint('Write %d bytes from file pointer %d',(int)WriteLen,(int)FilePointer);
 if (FilePointer<0) status = STATUS_INVALID_PARAMETER;
 else {
  // Get access to the shared buffer