一本在讲述USB驱动程式的书 及其范例原码

				// Control.cpp -- IOCTL handlers for memtest driver
				// Copyright (C) 1999, 2000 by Walter Oney
				// All rights reserved
				
				#include "stddcls.h"
				#include "driver.h"
				#include "ioctls.h"
				
				VOID DoMemoryTest(char* poolname, POOL_TYPE pooltype);
				
				///////////////////////////////////////////////////////////////////////////////
				
				#pragma PAGEDCODE
				
				NTSTATUS DispatchControl(PDEVICE_OBJECT fdo, PIRP Irp)
					{							// DispatchControl
					PAGED_CODE();
					PDEVICE_EXTENSION pdx = (PDEVICE_EXTENSION) fdo->DeviceExtension;
				
					NTSTATUS status = IoAcquireRemoveLock(&pdx->RemoveLock, Irp);
					if (!NT_SUCCESS(status))
						return CompleteRequest(Irp, status, 0);
					ULONG info = 0;
				
					PIO_STACK_LOCATION stack = IoGetCurrentIrpStackLocation(Irp);
					ULONG cbin = stack->Parameters.DeviceIoControl.InputBufferLength;
					ULONG cbout = stack->Parameters.DeviceIoControl.OutputBufferLength;
					ULONG code = stack->Parameters.DeviceIoControl.IoControlCode;
				
					switch (code)
						{						// process request
				
					case IOCTL_DO_TEST:				// code == 0x800
						{						// IOCTL_DO_TEST
						DoMemoryTest("PagedPool", PagedPool);
						DoMemoryTest("NonPagedPool", NonPagedPool);
						break;
						}						// IOCTL_DO_TEST
				
					default:
						status = STATUS_INVALID_DEVICE_REQUEST;
						break;
				
						}						// process request
				
					IoReleaseRemoveLock(&pdx->RemoveLock, Irp);
					return CompleteRequest(Irp, status, info);
					}							// DispatchControl
				
				///////////////////////////////////////////////////////////////////////////////
				
				#pragma LOCKEDCODE
				
				VOID DoMemoryTest(char* poolname, POOL_TYPE pooltype)
					{							// DoMemoryTest
					DbgPrint(DRIVERNAME " - Beginning test for %s\n", poolname);
				
					ULONG npages = 512 * 1024 * 1024 / PAGE_SIZE;	// start with 512 MB
					ULONG delta = npages / 2;
					ULONG biggest = 0;
				
					// Determine, to within 64 KB, the largest contiguous allocation from
					// this pool
				
					while (delta > 64 * 1024 / PAGE_SIZE)
						{						// determine largest allocation
						PVOID p = ExAllocatePoolWithTagPriority(pooltype, npages * PAGE_SIZE - 512, 'YENO', LowPoolPriority);
						if (p)
							ExFreePool(p);
				
						if (p)
							{					// success
							DbgPrint(DRIVERNAME " - Allocated %8.8X bytes okay\n", npages * PAGE_SIZE - 512);
							if (npages > biggest)
								biggest = npages;
							npages += delta;
				
							}					// success
						else
							{					// failure
							DbgPrint(DRIVERNAME " - Unable to allocate %8.8X bytes\n", npages * PAGE_SIZE - 512);
							npages -= delta;
							}					// failure
				
						delta /= 2;
						}						// determine largest allocation
					
					DbgPrint(DRIVERNAME " - **** Largest allocation from %s was %8.8X bytes (%8.8X pages) ****\n",
						poolname, biggest * PAGE_SIZE - 512, biggest);
					}							// DoMemoryTest