Thread: Reading REG_MULTI_SZ strings

So exactly what do you want to know? You could do something like this:

Code:

int split_multi_strings(const char *regvalue, char *outputarr[], int maxstrings)
{
     const char *ptr = regvalue;
     int count, len;
     for(;;)
     {
         len = strlen(ptr);
         if (len == 0 || count == maxstrings-1)
             break;
         outputarr[count] = ptr;
         count++;
         ptr += len;
      }
      // len != 0 means we didn't get to the end of regvalue, so 
      // we need more space for strings.  
      if (len != 0)
         return -count;
      return count; 
}

That's of course, only one variant of solution.

Note: I haven't compiled and/or tested the above code, so there may be both syntactical and logical errors in it. It's your task to validate it.

--
Mats

Yes, that's how it is described on the MS web-site at least, so either you, I and the MS website are right, or that's not how it's stored! My bet is that we're right!

So, to write it back again, you need to do the opposite of the splitting function I just posted, build a string from the components, and finish it with an extra zero. Actually, I think the code I posted needs a "ptr += len+1" instead of "ptr += len".

--
Mats

for(; ; ) is an infinite loop - same as while(1).

You can disable smilies on the post, but I know what you meant.

--
Mats

I've already explained the for-statement (probably just crossing you posting while I was typing). Maxstrings is the number of elements in your outputarray. Note that we're just copying the location of the string inside the original buffer, so you may need to use a different buffer to overwrite the original data. [Although if you just want to remove the LAST entry, you can just put a zero in the first character of that string].

--
Mats

No, it's not the actual number of strings - it is the number of elements in your array to recieve the split-out values.
So if we have "string1\0string2\0string3\0final strings\0\0" in the registry, then we could do this:

Code:

#define MAXSTRINGS 20
int main()
{
    char buffer[1000];
    DWORD size = sizeof(buffer);
    char *strings[MAXSTRINGS];
    LONG res; 
    int count; 
    int i;
... 
// Code that opens the registry, etc. 
...     
    res = RegQueryValueEx(hKey, L"ValueName",0, &type, buffer, &size);
    if (res > 0)
    {
       count = split_multi_strings(buffer, strings, MAXSTRINGS); 
       if (count < 0) 
       {
          printf("Too many strings in registry, need more space: %d is not enough\n"
            "displaying what we got so far\n", MAXSTRINGS);
          count = -count; 
       }
       for(i = 0; i < count; i++)
       {
           printf("%03d: %s\n", i, strings[i]);
        }
    } else 
         // deal with errors. 
    ...
}

--
Mats

Originally Posted by BobS0327

Code:

            dwReturn = RegQueryValueEx(
                hKey,           
                TEXT("DependOnService"),
                0,              
                &dwType,        
                lpBuffer,      
                &dwSize        
                );
            if( dwReturn == ERROR_SUCCESS ) {
                register LPTSTR p = LPTSTR(lpBuffer);
                for(; *p; p += _tcslen(p) + 1) 
                    printf("%s\n",p);
            }

This isn't reliable, there's no guarantee the returned data is null terminated so you're potentially off into the weeds and dead faster than you can say Steve Irwin. If you don't want to check for proper termination yourself use RegGetValue if you can target Vista, or SHQueryValueEx elsewhere. Another alternative if you're only querying one value is to use SHRegGetUSValue or SHGetValueand forget about all the opening and closing malarky.

Originally Posted by adeyblue

This isn't reliable, there's no guarantee the returned data is null terminated so you're potentially off into the weeds and dead faster than you can say Steve Irwin. If you don't want to check for proper termination yourself use RegGetValue if you can target Vista, or SHQueryValueEx elsewhere. Another alternative if you're only querying one value is to use SHRegGetUSValue or SHGetValueand forget about all the opening and closing malarky.

I'm not sure I understand what you mean by there's no guarantee that a REG_MULTI_SZ will be null terminated. This MSDN link indicates that a REG_MULTI_SZ is null terminated.

EDIT On second thought, I can see how that can possibly happen. For example, an incompetent programmer badly forming a REG_MULTI_SZ string and then writing it out to the key.

EDIT1 So, if you want to code defensively against incompetency in the above example, just increase dwSize by one.