从 WCHAR 转换为 const unsigned char

Question

I am a wix application packager. I am quite new to C++ and I am stuck with the below issue.

In my code, I am trying to convert wchar to const unsigned char . I have tried quite a few solutions that I got on the Internet, but I am unable to do it.

WCHAR szabc[888] = L"Example";

const unsigned char* pText = (const unsigned char*)szabc;

For your reference, the value of szabc is hard-coded, but ideally it is fetched as user input during installation of my code. szabc needs to be converted to const unsigned char as operator= doesn't seem to be working for conversion.

I am not getting any compilation error, but when I run this code, only the first character of szabc is being assigned to pText , I want the whole value of szabc to be assigned to pText .

As the value of pText is a user account password in a real time scenario, and it will be passed to a method which encrypts the value of the password.

Answer 1

Since you neglected to mention your OS, I am assuming it is Windows. You need WideCharToMultiByte or the standard wcstombs functions.

Note that both will determine the target encoding using system settings, so results will vary across computers. If possible, convert to UTF-8 or tell your users to stay away from special characters.

Answer 2

operator= cannot assign a value to a variable of an unrelated type. Which is why you cannot assign a WCHAR[] directly to an unsigned char* .

However, the real problem is with how the pointed data is being interpreted . You have a 16-bit Unicode string, and you are trying to pass it to a method that clearly wants a null-terminated 8-bit string instead.

On Windows, WCHAR is 2 bytes, and so the 2nd byte in your Unicode string is 0x00 , eg:

WCHAR szabc[] = {L'E', L'x', L'a', L'm', L'p', L'l', L'e', L'\0'};

Has the same memory layout as this:

BYTE szabc[] = {'E', 0x00, 'x', 0x00, 'a', 0x00, 'm', 0x00, 'p', 0x00, 'l', 0x00, 'e', 0x00, '\0', 0x00};

This is why the method appears to see only 1 "character". It stops reading when it encounters the 1st 0x00 byte.

Thus, a simple pointer type-cast will not suffice. You will need to either:

• use an 8-bit string to begin with, eg:

   CHAR szabc[888] = "Example"; unsigned char* pText = (unsigned char*)szabc; // use pText as needed...

• convert the Unicode data at runtime, using WideCharToMultiByte() or equivalent, eg:

   WCHAR szabc[888] = L"Example"; int len = WideCharToMultiByte(CP_ACP, 0, szabc, -1, NULL, 0, NULL, NULL); CHAR szConverted = new char[len]; WideCharToMultiByte(CP_ACP, 0, szabc, -1, szConverted, len, NULL, NULL); unsigned char* pText = (unsigned char*)szConverted; // use pText as needed... delete[] szConverted;