Convert C++ std::string to UTF-16-LE encoded string

Question

I've been searching for hours today and just can't find anything that works out for me. The one I've just had a look at, with no luck, is "How to convert UTF-8 encoded std::string to UTF-16 std::string".

My question is, with a brief explanation:

I want to make a valid NTLM hash in std C++, and I'm using OpenSSL's library to create the hash using its MD4 routines. I know how to do that, so does anyone know how to convert the std::string into a UTF-16 LE encoded string which I can pass to the MD4 functions to get a correct digest?

So, can I have a std::string which holds the char type, and convert it to a UTF16-LE encoded variable length std::string_type? Whether that be std::u16string, or std::wstring?

And would I use s.c_str() or s.data() and would the length() function report correctly in both cases?

Answer 1

Apologies, firsthand... this will be an ugly reply with some long code. I ended up using the following function, while effectively compiling in iconv into my windows application file by file :)

Hope this helps.

char* conver(const char* in, size_t in_len, size_t* used_len)
{
    const int CC_MUL = 2; // 16 bit
    setlocale(LC_ALL, "");
    char* t1 = setlocale(LC_CTYPE, "");
    char* locn = (char*)calloc(strlen(t1) + 1, sizeof(char));
    if(locn == NULL)
    {
        return 0;
    }

    strcpy(locn, t1);
    const char* enc = strchr(locn, '.') + 1;

#if _WINDOWS
    std::string win = "WINDOWS-";
    win += enc;
    enc = win.c_str();
#endif

    iconv_t foo = iconv_open("UTF-16LE", enc);

    if(foo == (void*)-1)
    {
        if (errno == EINVAL)
        {
            fprintf(stderr, "Conversion from %s is not supported\n", enc);
        }
        else
        {
            fprintf(stderr, "Initialization failure:\n");
        }
        free(locn);
        return 0;
    }

    size_t out_len = CC_MUL * in_len;
    size_t saved_in_len = in_len;
    iconv(foo, NULL, NULL, NULL, NULL);
    char* converted = (char*)calloc(out_len, sizeof(char));
    char *converted_start = converted;
    char* t = const_cast<char*>(in);
    int ret = iconv(foo,
                    &t,
                    &in_len,
                    &converted,
                    &out_len);
    iconv_close(foo);
    *used_len = CC_MUL * saved_in_len - out_len;

    if(ret == -1)
    {
        switch(errno)
        {
        case EILSEQ:
            fprintf(stderr,  "EILSEQ\n");
            break;
        case EINVAL:
            fprintf(stderr,  "EINVAL\n");
            break;
        }

        perror("iconv");
        free(locn);
        return 0;
    }
    else
    {
        free(locn);
        return converted_start;
    }
}