string replace with unicode

[rattata]

I really have problems to translate standard c replace functions to wide char replace. additionally, when i want to use secure functions (_s) everything messes up.

What would be the wchar equivalent of this code:

char* replace(const char *str, const char *oldstr, const char *newstr, int *count)
{
   const char *tmp = str;
   char *result;
   int   found = 0;
   int   length, reslen;
   int   oldlen = strlen(oldstr);
   int   newlen = strlen(newstr);
   int   limit = (count != NULL && *count > 0) ? *count : -1; 

   tmp = str;
   while ((tmp = strstr(tmp, oldstr)) != NULL && found != limit)
      found++, tmp += oldlen;
   
   length = strlen(str) + found * (newlen - oldlen);
   if ( (result = (char *)malloc(length+1)) == NULL) {
      fprintf(stderr, "Not enough memory\n");
      found = -1;
   } else {
      tmp = str;
      limit = found; /* Countdown */
      reslen = 0; /* length of current result */ 
      /* Replace each old string found with new string  */
      while ((limit-- > 0) && (tmp = strstr(tmp, oldstr)) != NULL) {
         length = (tmp - str); /* Number of chars to keep intouched */
         strncpy(result + reslen, str, length); /* Original part keeped */ 
         strcpy(result + (reslen += length), newstr); /* Insert new string */
         reslen += newlen;
         tmp += oldlen;
         str = tmp;
      }
      strcpy(result + reslen, str); /* Copies last part and ending nul char */
   }
   if (count != NULL) *count = found;
   return result;
}

BTW, my source string is a global LPCWSTR, so I don't need the first parameter in my function - and I do NOT want a counter

[kbw]

You'd replace the strxxx functions with wcsxxx.
And you'd replace malloc(length+1) with malloc(2*(length+1)).
And of course, change chars to wchar_ts.

You should note that string lengths are unsiged, and these days are of type size_t.

[rattata]

my code compiles, but doesn't work - btw: is the above c char replace function correct? didn't test it.

Please check my code

////////////////////////////////////////////////////////////////////////////////
bool CMyString::Replace(LPCWSTR pszOldStr, LPCWSTR pszNewStr) 
{
	TRACE_FUNC("Entering CMyString::Replace");

	if (!ISVALIDSTRING(pszOldStr) || !ISVALIDSTRING(pszNewStr) || GetLength() == 0)
		return false;
	
	LPCWSTR		pszString	= NULL;
	LPCWSTR		pszTemp		= m_StrBuff.Ptr();
	LPWSTR		pszResult	= NULL;
	DWORD		dwFound		= 0;
	DWORD		dwOldLen	= (DWORD)wcslen(pszOldStr);
	DWORD		dwNewLen	= (DWORD)wcslen(pszNewStr);
	DWORD		dwLen, dwResLen;

	while (NULL != (pszTemp=wcsstr(pszTemp, pszOldStr)))
		++dwFound, pszTemp+=dwOldLen;
   
	dwLen = ((DWORD)wcslen(m_StrBuff.Ptr()))+dwFound*(dwNewLen - dwOldLen);

	if (NULL == (pszResult=(LPWSTR)malloc(2*(dwLen+1))))
	{
		return false; // not enough memory
	} 
	else
	{
		pszTemp=m_StrBuff.Ptr();
		dwResLen=0; // length of result
      
		// replace old strings with new strings
		while ((pszTemp=wcsstr(pszTemp, pszOldStr)) != NULL) 
		{
			dwLen=(pszTemp-m_StrBuff.Ptr()); // number of chars to keep 
			//wcsncpy(pszResult+dwResLen, m_StrBuff.Ptr(), dwLen);
			wcsncpy_s(pszResult+dwResLen, dwLen, m_StrBuff.Ptr(), (DWORD)wcslen(m_StrBuff.Ptr())); // original part
			//wcscpy(pszResult+(dwResLen+=dwLen), pszNewStr);
			wcscpy_s(pszResult+(dwResLen+=dwLen), dwLen, pszNewStr); // insert new 
			dwResLen+=dwNewLen;
			pszTemp+=dwOldLen;
			pszString = pszTemp;
		}
		//wcscpy(pszResult + dwResLen, pszTemp);
		wcscpy_s(pszResult + dwResLen, dwLen, pszString); // copy last part 
		CreateCopy(pszResult); // writes content from pszResult in m_StrBuff
	}
	return true;
}

[kbw]

LPCWSTR pszTemp = m_StrBuff.Ptr(); What's this?

You haven't done a straight conversion have you?. If you have a debugger, step thru the code to see what's wrong. If not, use trace statements.

[rattata]

m_strBuff is the internal global buffer, where my source string is in. Ptr() gives me LPCWSTR address of it

Stepped through it, got runtime error

Microsoft Visual C++ Debug Library
---------------------------
Debug Assertion Failed!

Program: C:\Windows\system32\MsiExec.exe
File: f:\dd\vctools\crt_bld\self_x86\crt\src\tcsncpy_s.inl
Line: 62

Expression: (L"Buffer is too small" && 0)

For information on how your program can cause an assertion
failure, see the Visual C++ documentation on asserts.

(Press Retry to debug the application)
---------------------------
Abort   Retry   Ignore   
---------------------------

on line 36 (see above thread post)

[rattata]

It worked fine with the "unsafe" functions.

So I guess I'm using the *_s functions wrong...

somebody correct syntax for me?

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[Disch]

Since you're using C++, why don't you use strings instead of char arrays? Then you don't have to worry about this kind of thing and the syntax is simpler.

wstring Replace(const wstring& orig,const wstring& fnd, const wstring& repl)
{
    ret = orig;
    size_t pos = 0;

    while(true)
    {
        pos = ret.find(fnd,pos);
        if(pos == wstring::npos)  // no more instances found
            break;

        ret.replace(pos,pos+fnd.size(),repl);  // replace old string with new string
        pos += repl.size();
    }

    return ret;
}

Usage:

wstring foo = L"This is a test.  Is this a test?";

foo = Replace(foo,L"is",L"WOW");  //replace "is" with "WOW"

// foo is now L"ThWOW WOW a test.  Is thWOW a test?" 

[rattata]

Yep, STD would be nice.
But, sadly, I'm not allowed to do it, almost the whole project is coded from scratch

[Disch]

almost the whole project is coded from scratch

But you are using the C standard lib... so why can't you use the C++ standard lib?

Is this some kind of school thing?

EDIT: Also...

kbw wrote:

And you'd replace malloc(length+1) with malloc(2*(length+1)).

You should actually use malloc(sizeof(wchar_t)*(length+1)); because sizeof(wchar_t) might be larger than 2 (it's 4 on *nix, for example).

[rattata]

It's not school, I must take what somebody created before (CMyString class)

so, I had to write my own replace function.

BTW: How can I do a replace with ""(nothing), in other words delete the substr from it?

No one who can tell me the correct usage of the _s functions in the above example please?
It works with the deprecated functions, but I need the _s to suppress the VS 2010 deprecation warnings

[coder777]

Well, you're using those _s functions in a correct way.

But look at line 38: wcscpy_s(pszResult+(dwResLen+=dwLen), dwLen, pszNewStr); // insert new you add dwLen to dwResLen and later on line 39 you do it again. I guess that's a problem without understanding all you did...

[rattata]

With the following code the replacement works, I can step through it, no error

////////////////////////////////////////////////////////////////////////////////
bool CMyString::Replace(LPCWSTR pszOldStr, LPCWSTR pszNewStr) 
{
	TRACE_FUNC("Entering CMyString::Replace");

	if (!ISVALIDSTRING(pszOldStr) || !ISVALIDSTRING(pszNewStr) || GetLength() == 0)
	{
		SetLastError(ERROR_INVALID_PARAMETER);
		return false;
	}
	
	LPCWSTR		pszString	= NULL;
	LPCWSTR		pszTemp		= CMyString::m_StrBuff.Ptr();
	LPWSTR		pszResult	= NULL;
	DWORD		dwFound		= 0;
	DWORD		dwOldLen	= (DWORD)wcslen(pszOldStr);
	DWORD		dwNewLen	= (DWORD)wcslen(pszNewStr);
	DWORD		dwLen, dwResLen;

	while (NULL != (pszTemp=wcsstr(pszTemp, pszOldStr)))
		++dwFound, pszTemp+=dwOldLen;
   
	dwLen = ((DWORD)wcslen(m_StrBuff.Ptr()))+dwFound*(dwNewLen-dwOldLen);

	if (NULL == (pszResult=(LPWSTR)malloc((sizeof(wchar_t))*(dwLen+1))))
	{
		return false; // not enough memory
	} 
	else
	{
		pszTemp=m_StrBuff.Ptr();
		dwResLen=0; // length of result
      
		// replace old strings with new strings
		while (NULL != (pszTemp=wcsstr(pszTemp, pszOldStr))) 
		{
			dwLen=(pszTemp-m_StrBuff.Ptr()); // number of chars to keep 
			//wcsncpy(pszResult+dwResLen, m_StrBuff.Ptr(), dwLen);
			wcsncpy_s(pszResult+dwResLen, wcslen(pszResult), m_StrBuff.Ptr(), dwLen); // original part
			//wcscpy(pszResult+(dwResLen+=dwLen), pszNewStr);cmd

			wcscpy_s(pszResult+(dwResLen+=dwLen), wcslen(pszResult), pszNewStr); // insert new 
			dwResLen+=dwNewLen;
			pszTemp+=dwOldLen;
			pszString=pszTemp;
		}
		//wcscpy(pszResult+dwResLen, pszString);
		
		wcscpy_s(pszResult+dwResLen, wcslen(pszResult), pszString); // copy last part 
		CreateCopy(pszResult); // writes content from pszResult in m_StrBuff
	}

	return true;
}

BUT when my code is finished, it gives me this error

Microsoft Visual C++ Debug Library
---------------------------
Debug Assertion Failed!

Program: C:\WINDOWS\system32\MsiExec.exe
File: f:\dd\vctools\crt_bld\self_x86\crt\src\dbgheap.c
Line: 1322

Expression: _CrtIsValidHeapPointer(pUserData)

For information on how your program can cause an assertion
failure, see the Visual C++ documentation on asserts.

(Press Retry to debug the application)
---------------------------
Abbrechen   Wiederholen   Ignorieren   
---------------------------

Please some expert give me a hint

[kbw]

Use Disch's Replace function to implement yours. There's no point asking for advice and then not taking it. Just because the advice is free, doesn't mean it's incorrect.

[rattata]

Please read carefully: Like I told before, I'm not allowed to take that STD string class.

[kbw]

I did see that, but I can't see why you're not using the C++ standard library, but happily use the C standard library when implementing a C++ object.

[Disch]

can't see why you're not using the C++ standard library, but happily use the C standard library when implementing a C++ object

+1 to this.

The only reason I can fathom for standard lib code to be forbidden would be if this was a school assignment, which you already said it wasn't.

But whatever. *shrug* If you want to do it the hard way, you can. But then you have to wrestle with problems/bugs like the one you're having now.

[coder777]

What about the line 42 (now) and that ominous (dwResLen+=dwLen)?

I'd say that'll be good for a crash?