ActiveX C++控制 WriteFile 在 4 次尝试后失败

Question

我有一个用 C++ 编写的 ActiveX HTML 对象。该代码用于打印到蓝牙打印机。我能够成功调用代码 4 次（如下所示），然后“WriteFile”函数开始返回“0”。当我关闭浏览器并再次打开它时，它可以再尝试 4 次...所以这肯定看起来像内存泄漏或其他什么，但不幸的是我对 C++ 不太擅长...所以我在这里一些帮助:)

BOOL RegGetValue(HKEY hRootKey, LPCTSTR lpSubKey, LPCTSTR lpValueName, LPDWORD lpType, LPBYTE lpData, LPDWORD lpcbDataLen)
{
    LRESULT lResult = -1;
    HKEY hKey = NULL;
    lResult =RegOpenKeyEx(hRootKey, lpSubKey, 0, 0, &hKey);
    int e = GetLastError();
    if (lResult == ERROR_SUCCESS)
    {
        lResult = RegQueryValueEx(hKey, lpValueName, NULL, lpType, lpData, lpcbDataLen);
        e = GetLastError();
        RegCloseKey(hKey);
    }
    return (lResult == ERROR_SUCCESS);
}

#define MSS_PORTS_BASE _T("Software\\Microsoft\\Bluetooth\\Serial\\Ports")



bool FindBluetoothPort(TCHAR name[16])
{
    HKEY hKey, hRoot;
    TCHAR szPort[20] = _T(""), szPortString[20];
    DWORD len, dwIndex=0;
    bool bFound=false;

    INT i = 0, rc;
    DWORD dwNSize;
    DWORD dwCSize;
    TCHAR szClass[256];
    TCHAR szName[MAX_PATH];
    FILETIME ft;

    hRoot = HKEY_LOCAL_MACHINE;


    if (RegOpenKeyEx (hRoot, MSS_PORTS_BASE, 0, 0, &hKey) != ERROR_SUCCESS)
    {   rc = GetLastError();
        return 0;
    }

    dwNSize = dim(szName);
    dwCSize = dim(szClass);
    rc = RegEnumKeyEx (hKey, i, szName, &dwNSize, NULL, szClass, &dwCSize, &ft);
    while (rc == ERROR_SUCCESS)
    {
        // how many children
        TCHAR szCurrentKey[MAX_PATH];
        wcscpy(szCurrentKey, MSS_PORTS_BASE);
        wcscat(szCurrentKey, TEXT("\\"));
        wcscat(szCurrentKey, szName);
        wcscat(szCurrentKey, TEXT("\\"));

        len = sizeof(szPort);
        if(RegGetValue(hRoot, szCurrentKey, _T("Port"), NULL, (LPBYTE)szPort, &len))
        {
            wsprintf(szPortString, _T("%s:"), szPort);
            bFound = true;
            break;
        }


        dwNSize = dim(szName);
        rc = RegEnumKeyEx(hKey, ++i, szName, &dwNSize, NULL, NULL, 0, &ft);
    }
    if(bFound)
    _tcscpy(name, szPortString);
    return bFound;
}











WriteFile(
    HANDLE hFile,
    __in_bcount(nNumberOfBytesToWrite) LPCVOID lpBuffer,
    DWORD nNumberOfBytesToWrite,
    LPDWORD lpNumberOfBytesWritten,
    LPOVERLAPPED lpOverlapped
    );








void CHSMBTPrintXCtrl::PrintLabel(void)
{
    //MessageBox(TEXT("Started"), TEXT("HSMBTPrintX"), MB_OK);
    TCHAR g_szComPort[16];
    char szout[900];

    TCHAR comPort[16];
    HANDLE   hCom;
    unsigned long bytesWritten;
    int counter;

    for (counter = 0; counter < 900; counter++)
        szout[counter] = NULL;

    AFX_MANAGE_STATE(AfxGetStaticModuleState());


    if (!FindBluetoothPort(g_szComPort))
    {
        MessageBox(TEXT("No Port Found"), TEXT("HSMBTPrintX"), MB_OK);
        return;
    }

    //Try at least 3 times to get a valid handle
    for(counter = 0; counter < 2; ++counter)
    {
        hCom = CreateFile(g_szComPort,GENERIC_READ|GENERIC_WRITE,0,0,OPEN_EXISTING,0,0);
        if (hCom)
            break;
    }

    if (hCom == NULL)
    {
        MessageBox(TEXT("Could not open file to print"), TEXT("HSMBTPrintX"), MB_OK);
        return;
    }   

    CT2CA date(COleDateTime::GetCurrentTime().Format(L"%m/%d/%y"));
    CT2CA time(COleDateTime::GetCurrentTime().Format(L"%H:%M"));

    if (m_actionParameter == "SKUTagPrint") {
        CT2CA department (m_departmentParameter);
        CT2CA sku (m_skuParameter);

        for (counter = 0; counter < 900; counter++)
            szout[counter] = NULL;  

        strcpy(szout, "^XA\n");
        strcat(szout, "SomeTextHere");
        //more strcat lines here

        if(WriteFile(hCom,szout,900,&bytesWritten,NULL)==0) {
            MessageBox(TEXT("Unable to write file"), TEXT("HSMBTPrintX"), MB_OK);
            return;
        }
    }
    // MessageBox(m_barcodeParameter, TEXT("HSMBTPrintX"), MB_OK);
    // Create text to send to printer


    FireLabelPrinted();
    return;
}

// HTML

<object id="HSMBTPrintX1" width="350" height="350"
                    classid="CLSID:68D05400-18A6-4B39-B3FF-A17D77C1EDDF"
                    codebase=".\..\HSMBTPrintX.ocx#1,0,0,1" style="display:none;">
            </object>

            <script type="text/javascript" for="HSMBTPrintX1" event="LabelPrinted()">
               alert('Label(s) successfully printed.');
            </script>

// Javascript

HSMBTPrintX1.sizeParameter = document.getElementById("tdSize").innerText;
HSMBTPrintX1.actionParameter = "SKUTagPrint";

HSMBTPrintX1.PrintLabel();

Answer 1

您需要将 CreateFile() 与 CloseHandle() 相匹配，否则可能会发生奇怪的事情，请参阅：http://msdn.microsoft.com/en-us/library/aa363858(v=vs.85).aspx