我正在尝试使用 DeviceIoControl IOCTL_STORAGE_EJECT_MEDIA 弹出我的 CD Rom 驱动器，但出现访问冲突写入位置错误

Question

我正在尝试通过单击按钮弹出我的 CD Rom 驱动器。按下按钮时，CD Rom 驱动器之前是正确弹出的，但现在它给我一个错误：“0xC0000005：访问冲突写入位置 0x00000000。”我不确定为什么会收到此错误。我的代码如下，我的光驱是D盘：

#include <windows.h>
#include <tchar.h>
#include <stdio.h>

#define BUTTON                  3456
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
DWORD dwBytes;
HANDLE hCdRom;

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_CREATE:
    {
        HWND hwndButton = CreateWindow(
            L"BUTTON",  // Predefined class; Unicode assumed 
            L"EJECT",   // Button text 
            WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,  // Styles 
            180,         // x position 
            200,        // y position 
            100,        // Button width
            100,        // Button height
            hWnd,     // Parent window
            (HMENU)BUTTON,       // No menu.
            (HINSTANCE)GetWindowLongPtr(hWnd, GWLP_HINSTANCE),
            NULL);      // Pointer not needed.
    }
    
    case WM_COMMAND:
    {
        switch (LOWORD(wParam))
        {
        case BUTTON:
            hCdRom = CreateFile(L"\\.\D:",
                GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);

            if (hCdRom == INVALID_HANDLE_VALUE)
            {
                wsprintf(NULL, L"Error: %d", GetLastError());    //Getting error: Exception thrown at 0x746FFA6F (user32.dll) in Project.exe: 0xC0000005: Access violation writing location 0x00000000.
                return 1;
            }

            DeviceIoControl(hCdRom, IOCTL_STORAGE_EJECT_MEDIA, NULL, 0, NULL, 0, &dwBytes, NULL);

            if (hCdRom == 0)
            {
                wsprintfW(NULL, L"Error: %d", GetLastError());
                return 1;
            }
            MessageBox(NULL, L"Please insert a CD ROM in the CD tray.", L"CD ROM Drive", 0);

            CloseHandle(hCdRom);
    
            break;
        }
    }
}

有没有人遇到过这个错误并且知道如何修复它？

Answer 1

因为MessageBox一直处于阻塞状态，所以CloseHandle没有被调用。第二次按下按钮时，CreateFile会再次打开光驱句柄，之前的句柄没有关闭，拒绝访问

您可以简单地删除这一行：

MessageBox(NULL, L"Please insert a CD ROM in the CD tray.", L"CD ROM Drive", 0);

但正确的方法是添加 DefWindowProcA 函数以确保所有消息都得到处理。

Calls the default window procedure to provide default processing for any window messages that an application does not process. This function ensures that every message is processed. DefWindowProc is called with the same parameters received by the window procedure.

这样修改，

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_CREATE:
    {
        HWND hwndButton = CreateWindow(
            L"BUTTON",  // Predefined class; Unicode assumed 
            L"EJECT",   // Button text 
            WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,  // Styles 
            180,         // x position 
            200,        // y position 
            100,        // Button width
            100,        // Button height
            hWnd,     // Parent window
            (HMENU)BUTTON,       // No menu.
            (HINSTANCE)GetWindowLongPtr(hWnd, GWLP_HINSTANCE),
            NULL);      // Pointer not needed.
    }

    case WM_COMMAND:
    {
        switch (LOWORD(wParam))
        {
        case BUTTON:
            hCdRom = CreateFile(L"\\.\D:",
                GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);

            if (hCdRom == INVALID_HANDLE_VALUE)
            {
                wsprintf(NULL, L"Error: %d", GetLastError());    //Getting error: Exception thrown at 0x746FFA6F (user32.dll) in Project.exe: 0xC0000005: Access violation writing location 0x00000000.
                return 1;
            }

            DeviceIoControl(hCdRom, IOCTL_STORAGE_EJECT_MEDIA, NULL, 0, NULL, 0, &dwBytes, NULL);

            if (hCdRom == 0)
            {
                wsprintfW(NULL, L"Error: %d", GetLastError());
                return 1;
            }
            MessageBox(NULL, L"Please insert a CD ROM in the CD tray.", L"CD ROM Drive", 0);

            CloseHandle(hCdRom);

            break;
        }
    }
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}

已更新：

#include <tchar.h>
#include <windows.h>
#include <mmsystem.h> // for MCI functions

// Link to winmm.lib (usually included in project settings)
#pragma comment(lib, "winmm")

void ControlCdTray(TCHAR drive, DWORD command)
{
    // Not used here, only for debug
    MCIERROR mciError = 0;

    // Flags for MCI command
    DWORD mciFlags = MCI_WAIT | MCI_OPEN_SHAREABLE | 
        MCI_OPEN_TYPE | MCI_OPEN_TYPE_ID | MCI_OPEN_ELEMENT;

    // Open drive device and get device ID
    TCHAR elementName[] = { drive };
    MCI_OPEN_PARMS mciOpenParms = { 0 };
    mciOpenParms.lpstrDeviceType = (LPCTSTR)MCI_DEVTYPE_CD_AUDIO;
    mciOpenParms.lpstrElementName = elementName;    
    mciError = mciSendCommand(0, 
        MCI_OPEN, mciFlags, (DWORD_PTR)&mciOpenParms);

    // Eject or close tray using device ID
    MCI_SET_PARMS mciSetParms = { 0 };
    mciFlags = MCI_WAIT | command; // command is sent by caller
    mciError = mciSendCommand(mciOpenParms.wDeviceID, 
        MCI_SET, mciFlags, (DWORD_PTR)&mciSetParms);
    
    // Close device ID
    mciFlags = MCI_WAIT;
    MCI_GENERIC_PARMS mciGenericParms = { 0 };
    mciError = mciSendCommand(mciOpenParms.wDeviceID, 
        MCI_CLOSE, mciFlags, (DWORD_PTR)&mciGenericParms);
}

// Eject drive tray
void EjectCdTray(TCHAR drive)
{
    ControlCdTray(drive, MCI_SET_DOOR_OPEN);
}

// Retract drive tray
void CloseCdTray(TCHAR drive)
{
    ControlCdTray(drive, MCI_SET_DOOR_CLOSED);
}

int _tmain(int argc, _TCHAR* argv[])
{
    EjectCdTray(TEXT('D')); // drive letter hardcoded
    //CloseCdTray(TEXT('D'));

    return 0;
}