C++ char conversion

Question

I googled it for 2 hours now, and i can't find an answer for my problem: i need to get a registry REG_SZ value and pass it to a char*.

char host_val[1024]; DWORD hostVal_size = 1024; char* hostName; DWORD dwType = REG_SZ; RegOpenKeyEx(//no problem here); if( RegQueryValueEx( hKey, TEXT("HostName"), 0, &dwType, (LPBYTE)&host_val, &hostVal_size ) == ERROR_SUCCESS ) { //hostName = host_val; }

How should i do this conversion hostName = host_val?

What's the problem exactly? to convert char array of fixed lenth to char *? — SingerOfTheFall
– SingerOfTheFall, Commented Sep 7, 2012 at 6:04

user4815162342 · Accepted Answer · 2012-09-07 06:16:12Z

The resulting host_val is a possibly non-null-terminated string (see "Remarks"), so you should copy it to a newly allocated string with memcpy, and ensure it's null-terminated:

hostName = new char[hostVal_size + 1]; // host_val may or may not be null-terminated memcpy(hostName, host_val, hostVal_size); hostName[hostVal_size] = '\0';

You will need to delete[] the hostName later.

the value in my registry is an IP address, say, 192.168.1.219. Using RegQueryValueEx that value is passed to host_val, but after using your code all that is copied to hostName is 1.

AndersK · Accepted Answer · 2012-09-07 06:29:25Z

3

use the ANSI version of the function

RegQueryValueExA

that way you don't need to convert.

answered Sep 7, 2012 at 6:29

AndersK

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Comments

WhozCraig · Accepted Answer · 2012-09-07 07:54:27Z

If you're compiling with Unicode you're copying a Unicode string (that is possibly NOT terminated) into a narrow char buffer. the first character in the unicode string will be 0x3100 (accounting for the endianness on your machine, which is likely little-endian, and the fact that you said the IP address is 192....)

That value stuffed into the char[] array will report back as a single-char-null-terminated string. You have two options.

Use RegQueryValueExA, everything else stays the same, or
Change your char[] array to a wchar_t[] array, do what you're currently doing, then convert to narrow using WideCharToMultiByte(docs are in the SDK).

For obvious reasons, I'd take the former of those two options.

if i use RegQueryValueExA i get an error C2664: 'RegQueryValueExA' : cannot convert parameter 2 from 'const wchar_t [9]' to 'LPCSTR'
Take out the TEXT() macro wrapper, for your string literals on that call.

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