检测USB设备的插入和拔出

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1.需求
需要一个DLL，它可以自动检测USB设备插入和拔出，并以回调函数的方法告诉调用DLL的应用程序。

2.预研
2.1参考文档
（1）关于“Registering for DeviceNotification”（官方文档）
地址：https://msdn.microsoft.com/en-us/library/aa363432(VS.85).aspx
（2）关于“Detecting Media Insertionor Removal”（官方文档）
地址：https://msdn.microsoft.com/en-us/library/aa363215(v=vs.85).aspx
（3）stackoverflow中的一个问答“Detecting USBInsertion / Removal Events in Windows using C++”
地址：http://stackoverflow.com/questions/4078909/detecting-usb-insertion-removal-events-in-windows-using-c
（4）codeproject中的一个实例“Detecting whendrives are added or removed”
（包含代码和demo，参考价值很高！）
地址：http://www.codeproject.com/Articles/19264/Detecting-when-drives-are-added-or-removed

3.实现

下面是一个DEMO的代码，但它不是DLL（DLL的DEMO，以后再写）。这个实例的主要代码来自csdn论坛的一个问答（地址：http://bbs.csdn.net/topics/390112567），非常感谢版主同学“VisualEleven”！

#include <tchar.h>#include <string>#include <iostream>#include <Windows.h>#include <dbt.h>/*------------------------------------------------------------------FirstDriveFromMask( unitmask )DescriptionFinds the first valid drive letter from a mask of drive letters.The mask must be in the format bit 0 = A, bit 1 = B, bit 2 = C, and so on. A valid drive letter is defined when the corresponding bit is set to 1.Returns the first drive letter that was found.--------------------------------------------------------------------*/char FirstDriveFromMask(ULONG unitmask){char i;for (i = 0; i < 26; ++i){if (unitmask & 0x1)break;unitmask = unitmask >> 1;}return(i + 'A');}LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam){PDEV_BROADCAST_HDR lpdb = (PDEV_BROADCAST_HDR)lParam;PDEV_BROADCAST_VOLUME lpdbv = (PDEV_BROADCAST_VOLUME)lpdb;TCHAR szMsg[80];char driveName;    switch(uMsg)    {    case WM_DEVICECHANGE:switch(wParam ){case DBT_DEVICEARRIVAL:driveName = FirstDriveFromMask(lpdbv->dbcv_unitmask);sprintf(szMsg, "USB Drive %c: has inserted.\n", driveName);printf("%s\r\n", szMsg);MessageBox(hWnd, szMsg, TEXT("WM_DEVICECHANGE"), MB_OK);break;case DBT_DEVICEREMOVECOMPLETE:driveName = FirstDriveFromMask(lpdbv->dbcv_unitmask);sprintf(szMsg, "USB Drive %c: has removed.\n", driveName);printf("%s\r\n", szMsg);MessageBox(hWnd, szMsg, TEXT("WM_DEVICECHANGE"), MB_OK );break;default:;}        break;default:;    }    return DefWindowProc(hWnd, uMsg, wParam, lParam);}int _tmain(int argc, TCHAR* argv[], TCHAR* envp[]){    TCHAR szClassName[] = _T("MyApp");    WNDCLASS wndcls = {0};    wndcls.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);    wndcls.hCursor = (HCURSOR)LoadCursor(NULL, IDC_ARROW);    wndcls.hIcon = (HICON)LoadIcon(NULL, IDI_APPLICATION);    wndcls.lpfnWndProc = WndProc;    wndcls.lpszClassName = szClassName;    if(!RegisterClass(&wndcls))    {        printf("RegisterClass Failed!\r\n");        return 0;    }    HWND hWnd = CreateWindow(szClassName, szClassName, WS_OVERLAPPEDWINDOW, CW_USEDEFAULT,        CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, NULL, NULL);    if(NULL == hWnd)    {        printf("CreateWindow Failed!\r\n");        return 0;    }    ShowWindow(hWnd, SW_HIDE);    UpdateWindow(hWnd);    MSG msg;    while(GetMessage(&msg, NULL, NULL, NULL))    {        TranslateMessage(&msg);        DispatchMessage(&msg);    }    return 0;}

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