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CString-clone Using Standard C++

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7 Dec 2011CPOL4 min read 3.9M   14.1K   227   568
A Drop-In replacement for CString that builds on the Standard C++ Library's basic_string template

Introduction

As much as I use and appreciate the Standard C++ Library, I've never liked its string template - basic_string<>. At times, it seems the designers went out of their way to make it difficult to use.

On the other hand, I've always loved the ease of use of MFC's CString class. It checks for NULL pointers, implicitly converts to const TCHAR*, and has some very handy member functions (Format, Load, etc.) that make string programming a breeze. But of course, I don't want to use MFC anymore. In fact, I don't want to rely on any proprietary library because I want portability.

Therefore I decided to combine the best of both worlds and create:

CStdString

This is a class (a template instantiation actually) that derives from from basic_string<TCHAR>. To the basic_string it adds the entire CString API. You get CString ease of use with 100% basic_string compatibility. In short, a CStdString object is a basic_string that (with very few exceptions (noted below) it is also a drop-in replacement for CString. The best part of this is that both APIs (basic_string and CString) are well known and well documented.

I originally submitted this article to another code site (which shall remain nameless :)) a few years ago. I like CodeProject so much I thought I'd submit it here too. I have used this class in almost every professional project I've done over the past 4 years. It has proven to be the single most useful piece of code I've ever written. It is also extensively debugged. I hope you like it. If you ever have any problems with it, please e-mail me. I'm happy to help.

I provided a simple source application here to prove some of the CString functions work but it's really just a token. The list of sample projects out there that use CString and/or basic_string is massive.

Features

  • Drop in Replacement for CString (see below for exceptions)
  • Two instantiations available at all times -- wchar_t-based version CStdStringW and char-based version CStdStringA. The name CStdString is just a typedef of one of these two.
  • Safely checks for NULL string pointer inputs (like CString) in all functions
  • Extra constructors and assignment operators to automatically convert between wide (wchar_t-based) and thin (char-based) strings for you.
  • Implicit conversion to c_str(). The C++ committee doesn't like this but I sure do.
  • Builds on several platforms, including Windows, Unix and Linux. Works with several implementations of the Standard C++ Library, including Dinkumware, GNU, CodeWarrior, and STLPort.
  • Win32 builds give you some extra goodies like UNICODE/MBCS conversion macros (just like MFCs) as well as member functions for persisting CStdString objects to and from DCOM IStreams.
  • Makes no use of any implementation details of the base class template (basic_string)
  • The derived template adds no member data to basic_string and adds no virtual functions

There are a couple of issues about this code of that I should point out.

CString Compatibility

I was unable to exactly reproduce the CString API. There are a two functions that both CString and basic_string; share, but implement differently. In these cases, I felt it best to make CStdString behave like basic_string (the base class) rather than CString. To be specific.

  • CStdString::operator[] returns characters by value (unlike CString which returns them by reference)
  • The constructor that takes a character and a count takes them in the order (count, value) which is the opposite of the order CString declares them. That's the order that basic_string<>; needs and it was impossible to implement both versions.

There were also two CString functions I could not implement at all -- LockBuffer and UnlockBuffer.

Deriving From basic_string<>

The template I wrote derives from basic_string, a class template without a virtual destructor. Any introductory text to C++ will tell you that it is dangerous to derive from a class without a virtual destructor. It can lead to behavior that is undefined. So if you were to code the following (deleting a CStdStringA through a pointer to the base class), you would technically get undefined behavior:

C++
// assign DERIVED object to  BASE pointer
std::string* pstr = new CStdStringA("Hi"); 

// delete  DERIVED through BASE class pointer -- UNDEFINED
delete pstr;   

Personally, I don't think this is much of an issue. I mean really how often do you actually do this with string objects? I have rarely (if ever) needed to dynamically allocate a string object on the heap. And if I ever do, I won't using a base-class pointer. So if you don't do this, you'll never have to worry. In fact, even if you do code this way, I doubt you'll have any problems with CStdString. I can tell you that at least with Microsoft Visual C++, even the above code runs just fine with no errors or memory leaks. I doubt many other compilers would give you problems either. However my doubt does not impose reality on the C++ world. Caveat Emptor.

History

  • 7 Dec 2011: Updated source code.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


Written By
Web Developer
United States United States
I've been a software developer since 1990.

While my main page is out of date (and I have therefore blanked it), you can read about the CStdString pages here

http://home.earthlink.net/~jmoleary/stdstring.htm

Comments and Discussions

 
QuestionKudos and update: Pin
studleylee6-Jan-22 16:36
studleylee6-Jan-22 16:36 
AnswerRe: Kudos and update: Pin
Joe O'Leary31-Jul-23 9:29
Joe O'Leary31-Jul-23 9:29 
QuestionSuggested fixes for g++ warnings. Pin
Member 132459945-Oct-18 7:35
Member 132459945-Oct-18 7:35 
AnswerRe: Suggested fixes for g++ warnings. Pin
Joe O'Leary12-Sep-20 17:47
Joe O'Leary12-Sep-20 17:47 
NewsVS 2017 v15.7 no longer uses _USE in locale, but use_facet (as it should) Pin
Member 1382128010-May-18 8:42
Member 1382128010-May-18 8:42 
GeneralRe: VS 2017 v15.7 no longer uses _USE in locale, but use_facet (as it should) Pin
wheelman570z4-Oct-18 7:09
professionalwheelman570z4-Oct-18 7:09 
QuestionI've used this for years Thanks Joe!!!!! Pin
studleylee9-Mar-18 13:24
studleylee9-Mar-18 13:24 
QuestionWhat abaut performance? Pin
_Reinhard23-Apr-16 1:07
_Reinhard23-Apr-16 1:07 
AnswerRe: What abaut performance? Pin
Joe O'Leary5-May-17 5:31
Joe O'Leary5-May-17 5:31 
QuestionHow to build it on Linux (Ubuntu)? Pin
hao le vu6-Jul-15 23:04
hao le vu6-Jul-15 23:04 
GeneralMy vote of 5 Pin
pasztorpisti24-Aug-13 8:43
pasztorpisti24-Aug-13 8:43 
QuestionAbout Stephen Hewitt's GetBuffer Question Pin
FeiluHang15-Apr-13 1:25
FeiluHang15-Apr-13 1:25 
AnswerRe: About Stephen Hewitt's GetBuffer Question Pin
Joe O'Leary17-Apr-13 16:10
Joe O'Leary17-Apr-13 16:10 
GeneralMy vote of 5 Pin
Michael Haephrati8-Jan-13 11:42
professionalMichael Haephrati8-Jan-13 11:42 
GeneralMy vote of 5 Pin
Dave Calkins15-Nov-12 3:20
Dave Calkins15-Nov-12 3:20 
SuggestionThank you! Pin
user_user_user12-Nov-12 22:23
user_user_user12-Nov-12 22:23 
Question[My vote of 2] Weak Pin
xComaWhitex11-Oct-12 18:16
xComaWhitex11-Oct-12 18:16 
AnswerRe: [My vote of 2] Weak Pin
Joe O'Leary11-Oct-12 18:40
Joe O'Leary11-Oct-12 18:40 
GeneralRe: [My vote of 2] Weak Pin
xComaWhitex11-Oct-12 18:45
xComaWhitex11-Oct-12 18:45 
Btw it's Qt not QT. QT is Quicktime. Qt isn't an acronym. Where is Hungarian notation anywhere in Qt? now, I don't know about internal, as I don't mess with that. Just saying, it's useable outside of Qt too, if you actually wrote a class that performed the same functionality. Why would I bother rewriting code you wrote? That's your job not mine. I personally have no use for the code. I'm not saying your code is bad as I haven't used it. I've only glanced over it and gave my opinions.
GeneralRe: [My vote of 2] Weak Pin
Joe O'Leary11-Oct-12 18:49
Joe O'Leary11-Oct-12 18:49 
AnswerRe: [My vote of 2] Weak Pin
Stephen Hewitt11-Oct-12 22:58
Stephen Hewitt11-Oct-12 22:58 
GeneralRe: [My vote of 2] Weak Pin
xComaWhitex11-Oct-12 23:07
xComaWhitex11-Oct-12 23:07 
GeneralRe: [My vote of 2] Weak Pin
Stephen Hewitt11-Oct-12 23:21
Stephen Hewitt11-Oct-12 23:21 
GeneralRe: [My vote of 2] Weak Pin
xComaWhitex11-Oct-12 23:24
xComaWhitex11-Oct-12 23:24 
AnswerRe: [My vote of 2] Weak Pin
Dave Calkins15-Nov-12 3:19
Dave Calkins15-Nov-12 3:19 

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