How to Get Printer Information in C++|How to convert char * to BSTR* in C++

In this blog post, we will discuss how to get printer information in C++. We will use the following code:

C++

STDMETHODIMP CSimpleCom::Get_PrinterInfo(BSTR* InfoBuffer)
{
	AFX_MANAGE_STATE(AfxGetStaticModuleState());

	// TODO: Add your dispatch handler code here
	try
	{
		int a = 0;
		char* str = (char*)memset(malloc(1), '\0', 1);
		a = EV_Get_PrinterInfo(str);
		if (a == 0)
		{
			int len = strlen(str) + 1;
			OLECHAR* wstr = new OLECHAR[len];
			MultiByteToWideChar(CP_ACP, 0, str, len, wstr, len + 1);
			*InfoBuffer = SysAllocString(wstr);
		}
		
	}
	catch (...)
	{

	}

	return S_OK;
}

Use code with caution. Learn more

Explanation:

The first thing we do is declare a function called Get_PrinterInfo(). This function takes a pointer to a BSTR string as its parameter. The BSTR string will be used to store the printer information.

Next, we use the AFX_MANAGE_STATE() macro to manage the state of the application. This macro is necessary when using ActiveX controls in MFC applications.

The next part of the code is the try block. This block of code will be executed as long as there are no errors.

Inside the try block, we first declare a variable called a and initialize it to 0. The variable a will be used to store the return value of the EV_Get_PrinterInfo() function.

Next, we use the memset() function to allocate memory for the string str and initialize it with null characters. The str string will be used to store the printer information in a character array.

We then call the EV_Get_PrinterInfo() function. This function gets the printer information and stores it in the string str.

The next step is to check the value of a. If a is equal to 0, then the printer information was successfully retrieved. Otherwise, an error occurred.

If the printer information was successfully retrieved, we then declare a variable called len and initialize it to the length of the string str plus 1. The len variable will be used to determine the size of the wide character string that will be created.

Next, we declare a variable called wstr and initialize it to a new OLECHAR array of size len. The wstr array will be used to store the wide character string that represents the printer information.

We then use the MultiByteToWideChar() function to convert the string str to a wide character string. The MultiByteToWideChar() function takes the following parameters:

• The code page to use for the conversion. In this case, we are using the default code page, which is CP_ACP.
• The flags to use for the conversion. In this case, we are not using any flags.
• The pointer to the character array that contains the string to be converted.
• The length of the character array.
• The pointer to the wide character array that will receive the converted string.
• The size of the wide character array.

The MultiByteToWideChar() function will convert the string str to a wide character string and store it in the wstr array.

Finally, we set the value of the pointer InfoBuffer to the value of the function SysAllocString(). The SysAllocString() function allocates memory for a BSTR string and sets its value to the wide character string wstr.

The catch block catches any exceptions that are thrown by the try block.

The last line of the function returns the value S_OK, which indicates that the function was successful.

Conclusion:

This blog post has discussed how to get printer information in C++. The code that we discussed can be used to get the printer information from any printer that is installed on the system.