failed string/values from registry enum call - string

Question

Hello and thanks in advance.
my problem today is i'm getting back "garbage" for the strings for a registry key value name, and value data. this appears to be a problem on all registry values within a key/folder except for the last value, though sometimes I am able to read the name of the first value (but still not the data)
what I'm trying to do is be able to display the value name and value data that are in a single, possibly variable, registry key (I dont care about subkeys at this point)
I'm trying to do this with windows unicode strings, WCHAR * and LPWSTR types.
the "garbage" i see for the problem strings is a repeated series of non-english characters, which messes up the subsequent wcout displays.
in the registry editor display, the values i'm attempting to read have REG_SZ type data, which I understand to be a string.
probably my biggest problem is i cannot find a clear guide on simply how to do exactly what I'm trying to do, look inside a registry key, and list the value names and value data. any help would be greatly appreciated. I am new to unicode strings and the windows api. my environment is windows xp sp3, visual c++ 2010 express.
#include <stdio.h>
#include <iostream> /* for std::wcin and wcout */
#include <windows.h>
#include <stdlib.h>
#include <string.h>
#include <process.h>
#include "conio.h"
#
include "stdafx.h"
int _tmain(int argc, _TCHAR* argv[])
{
int return_val;
DWORD error;
HKEY hkey;
BYTE iterations = 0;
/* 1. first, open key (folder) */
return_val = RegOpenKeyExW(HKEY_LOCAL_MACHINE, L"HARDWARE\\DEVICEMAP\\VIDEO", 0, KEY_READ, &hkey);
/* check how the open went */
if(return_val != ERROR_SUCCESS)
{
std::wcout << L"error opening the key: " << return_val << std::endl;
}
else
{
std::wcout << L"it's cool" << std::endl;
/* 1.a. query the key (optional) */
LPTSTR className = new WCHAR[255];
DWORD classNameSize = MAX_PATH;
DWORD subKey = 0;
DWORD maxSubKey;
DWORD maxClass;
DWORD value;
DWORD maxValue;
DWORD maxValueData;
DWORD securityDescriptor;
FILETIME ftLastWriteTime;
DWORD sectionNameSize;
return_val = RegQueryInfoKey(hkey, className, &classNameSize, NULL,
&subKey, &maxSubKey, &maxClass, &value, &maxValue,
&maxValueData, &securityDescriptor, &ftLastWriteTime);
std::wcout << L"query return: " << return_val << std::endl;
std::wcout << L"class name: " << className << L", (size): " << classNameSize << std::endl;
std::wcout << L"subkey: " << subKey << L", max: " << maxSubKey << L", maxClass: " << maxClass << std::endl;
std::wcout << L"Value: " << value << L", maxval: " << maxValue << L", maxvaldata: " << maxValueData << std::endl;
std::wcout << L"Sec descrpt: " << securityDescriptor << std::endl << std::endl;
/* now enumerate the strings in the key */
int count = 0;
DWORD valuename_size = 16, type_return = 0, data_size = 102;
LPWSTR valuename = new WCHAR[valuename_size];//maxValue
LPWSTR data = new WCHAR[data_size];//maxValueData>>1
/* 2. the outer loop grabs the values one at a time (the data within the key/folder) */
do {
iterations++; /* just for debugging */
return_val = RegEnumValue(hkey, count, valuename, &valuename_size, 0, &type_return, (LPBYTE)data, &data_size);
/* return of RegEnumValue */
std::wcout << L"RegEnumValue return val: " << return_val << std::endl;
/* double check sizes */
std::wcout << L"size: valname_size: " << valuename_size << L", data_size: " << data_size << std::endl;
if(return_val == ERROR_SUCCESS || return_val == ERROR_MORE_DATA)
{
/* to try and avoid bad strings */
if(type_return == REG_DWORD || count == 0)
std::wcout << L"Value - " << valuename << L", Type: " << type_return << L" Data - " << (BYTE)(*data) << std::endl;
else
std::wcout << L"Value - " << valuename << L", Type: " << type_return << L" Data - " << data << std::endl;
}
//data = REG_SZ;
count++;
} while (return_val != ERROR_NO_MORE_ITEMS && count < value);
}
/* just to check my code */
std::wcout << L"iterations: " << iterations << std::endl;
/* to "pause" during debugging */
std::wcin >> input;
return 0;
}
this version based in part on the commentors help seems to work how I want, and I'm posting this for others to reference. What wasnt clear to me is that when getting the number of characters back for the valuename did not include a null terminating character (of course) but also that the size of buffer you pass into it needs to include that, so if you get back 16 and you input 16, thats why it would return 234, (not fair that the input follows diferent constraints than the output but life's not fair), you then need to input 17 for the string size
/* now enumerate the strings in the key */
int count = 0;
DWORD valuename_size, type_return = 0, data_size;
LPWSTR valuename;
BYTE *data;
/* 2. the outer loop grabs the values one at a time (the data within the key/folder) */
do {
valuename_size = maxValue;
data_size = maxValueData;
iterations++; /* just for debugging */
return_val = RegEnumValue(hkey, count, NULL, &valuename_size, 0, &type_return, NULL, &data_size); /* value name */
//return_val = RegEnumValue(hkey, count, NULL, NULL, 0, &type_return, NULL, &data_size); /* value data */
valuename = new WCHAR[valuename_size+1];
data = new BYTE[data_size]; /* data_size is in BYTES, of any type */
valuename[0] = L'\0'; /* if the string returned is still invalid, this will help make sure wcout doesnt mess up */
return_val = RegEnumValue(hkey, count, valuename, &valuename_size, 0, &type_return, (LPBYTE)data, &data_size); /* value name */
//return_val = RegEnumValue(hkey, count, NULL, NULL, 0, &type_return, (LPBYTE)data, &data_size); /* value data */
/* return of RegEnumValue */
std::wcout << L"RegEnumValue return val: " << return_val << std::endl;
/* double check sizes */
std::wcout << L"size: valname_size: " << valuename_size << L", data_size: " << data_size << L", Type: " << type_return << std::endl;
if(return_val == ERROR_MORE_DATA /*&& type_return == REG_DWORD*/)
{
/* try again? */
delete valuename;//free(valuename);
delete data;
/* double the "global" max number of WORDs for the string (including null termination) */
maxValue <<= 1;
valuename_size = maxValue;
maxValueData <<= 1;
data_size = maxValueData;
/* doublecheck */
std::wcout << L"new val size before enum: " << valuename_size << L", new data size before enum: " << data_size << std::endl;
return_val = RegEnumValue(hkey, count, NULL, &valuename_size, 0, &type_return, NULL, &data_size); /* value name */
/* the return version of valuename_size is the number of characters, not including the null terminating character */
valuename = new WCHAR[valuename_size+1];
data = new BYTE[data_size];
valuename[0] = L'\0'; /* if the string returned is still invalid, this will help make sure wcout doesnt mess up */
return_val = RegEnumValue(hkey, count, valuename, &valuename_size, 0, &type_return, (LPBYTE)data, &data_size); /* value name */
std::wcout << std::endl << L"return: " << return_val << L", Val size: " << valuename_size << L", data_size: " << data_size << std::endl << std::endl;
}
if(return_val == ERROR_SUCCESS)
{
valuename[valuename_size] = L'\0'; /* null terminate the string before printing */
/* I only care about string data */
if (type_return == REG_SZ)
{
data[data_size] = 0; /* null terminate the string before printing */
std::wcout << L"Value - " << valuename << L", Type: " << type_return << L" Data - " << (LPWSTR)data << std::endl;
}
}
count++;
} while (return_val != ERROR_NO_MORE_ITEMS && count < value);
}
/* just to check my code */
std::wcout << L"iterations: " << iterations << std::endl;
/* to "pause" during debugging */
std::wcin >> input;
return 0;
}

Answer 1

A few obvious problems:
When you call RegEnumValue, valuename_size and data_size should contain the size of the buffers, but they only do so for the first value. For the second value and beyond they contain the results of the previous call.
String values in the registry are not guaranteed to be NULL terminated. You need to explicitly terminate strings (using the returned length) before using them. Note that since you're using unicode you need to divide the byte length by two to get the length in code units. These comments only apply to values, not names.
You assume that any value that isn't a DWORD is a string. What about binary values?