Non-MFC String Class for ATL

Download demo project - 22 Kb

Download source files - 6 Kb

Introduction

When writing ATL components, I have found that one of the hardest things for Windows programmers to overcome is the dependency on the MFC library. For dates and strings, MFC simplifies the programmer's job by handling memory allocations and type conversions within its class encapsulation. However, with that simplification comes the price of having to distribute the MFC DLL's with your component.

This article focuses on the issues surrounding the use of strings in an ATL component. If you don't include MFC support in your ATL component, you obviously won't have the CString available to use. There have been several articles published that address this issue. Several of the ones that I have read are:

• NonMFC:CString (posted on www.worldofatl.com) - This article provides a new CString class based on the standard template library (STL).
• Add MFC's CString to ATL w/ No MFC dependencies (by K. Shane Triem (www.codeguru.com) - This article illustrates how to use a Visual Studio macro to extract the CString class source code from the MFC library and then use this class in your ATL component.

CCOMString

While both of these articles are viable alternatives to the MFC CString class, I wanted a class that would compile under both ANSI and Unicode and had no dependencies whatsoever: neither MFC or STL. My alternative was to write a string handling class entitled CCOMString which is based entirely on Visual C++'s TCHAR datatype.

The TCHAR datatype is defined as follows:

• As a char when _MBCS is defined in your program.
• As a wchar_t when _UNICODE is defined in your program.
• As a char when neither _MBCS or _UNICODE is defined in your program.

Therefore, by using the TCHAR datatype, CCOMString is compatible with both ANSI and Unicode compile modes. Please note that there is one caveat to this class in its present state of development: it does not currently include exception handling for the memory allocation functions. I am currently trapping any memory allocation errors with the ATLASSERT macro, but these will compile away in Release mode (I'm still researching a way to handle these errors without adding the exception handling overhead to the class).

The current version of the CCOMString includes the following functionality. Please note, if there are any functions in the CCOMString class that you download that are not listed in the text below, they are considered to be undocumented and, therefore, possibly untest as well:

Constructors

CCOMString() - Constructs an empty string.

CCOMString(CCOMString&) - Constructs a string from another CCOMString.

CCOMString(LPCTSTR) - Constructs a string from a LPCTSTR (i.e., const TCHAR*).

CCOMString(BSTR) - Constructs a string from a BSTR.

CCOMString(TCHAR, int) - Constructs a string from a character repeated an indicated number of times.

Assignment Operations

operator=(CCOMString&) - Copies another CCOMString object to the CCOMString object.

operator=(LPCTSTR) - Copies a LPCTSTR to the CCOMString object.

operator=(BSTR) - Copies a BSTR to the CCOMString object.

operator LPCTSTR() - Returns a const TCHAR* from the CCOMString object.

TCHAR* GetString() - Obtains a pointer to the string contained in the CCOMString object.

BSTR AllocSysString() - Allocates a BSTR from the CCOMString object.

Concatenation

<code>operator+=(CCOMString&) - Concatenates a CCOMString object to the end of the CCOMString object.

operator+=(LPCTSTR) - Concatenates a const TCHAR* to the end of the CCOMString object.

operator+=(BSTR) - Concatenates a BSTR to the end of the CCOMString object.

operator+=(TCHAR) - Concatenates a TCHAR to the end of the CCOMString object.

operator+(CCOMString&, CCOMString&) - Concatenates two CCOMString objects together.

operator+(CCOMString&, LPCTSTR) - Concatenates a CCOMString object and a const TCHAR* together.

operator+(LPCTSTR, CCOMString&) - Concatenates a const TCHAR* and CCOMString object together.

operator+(CCOMString&, BSTR) - Concatenates a CCOMString object and a BSTR together.

operator+(BSTR, CCOMString&) - Concatenates a BSTR and a CCOMString object together.

Accessors for the String as an Array

GetLength() - Returns the length of the CCOMString string as an integer.

IsEmpty() - Returns TRUE or FALSE depending on whether or not the CCOMString string is empty.

Empty() - Sets the CCOMString string to an empty string (i.e., _T("")).

GetAt(int) - Returns a TCHAR character from the CCOMString string at the specified location.

operator[] (int) - Same functionality as GetAt(int).

SetAt(int, TCHAR) - Sets the character at the specified location of the CCOMString string to the specified character.

Conversions

MakeUpper() - Converts the CCOMString string into all uppercase characters.

MakeLower() - Converts the CCOMString string into all lowercase characters.

MakeReverse() - Reverses the sequence of the characters contained in the CCOMString string.

TrimLeft() - Removes all spaces from the left-hand side of the CCOMString string.

TrimRight() - Removes all spaces from the right-hand side of the CCOMString string.

Searching

Find(TCHAR) - Returns the first position in the CCOMString string of the specified character.

Find(TCHAR, int nStart) - Returns the first position after the nStart position in the CCOMString string of the specified character.

Find(LPCTSTR lpszSub) - Returns the first position in the CCOMString string of the specified character string.

Find(LPCTSTR lpszSub, int nStart) - Returns the first position after the nStart position in the CCOMString string of the specified character string.

Extraction

Mid(int) - Returns a CCOMString object containing the character starting at the specified position to the end of the CCOMString string.

Mid(int, int) - Returns a CCOMString object containing the character starting at the specified position and extending for the specified length of the CCOMString string.

Left(int nCount) - Returns nCount characters starting at the left-hand side of the CCOMString string.

Right(int nCount) - Returns nCount characters starting at the right-hand side of the CCOMString string.

Replacing

Replace(TCHAR chOld, TCHAR chNew) - Replaces all the chOld characters in the CCOMString string with the chNew character.

Replace(LPCTSTR lpszOld, LPCTSTR lpszNew) - Replaces all the lpszOld strings in the CCOMString string with the lpszNew string.

Comparison

Compare(CCOMString&) - Compares the current CCOMString string with the specified CCOMString string and returns zero if equal and non-zero if not equal. This comparision is case sensitive.

Compare(LPCTSTR) - Compares the current CCOMString string with the specified const TCHAR* and returns zero if equal and non-zero if not equal. This comparision is case sensitive.

operator==(const CCOMString&, const CCOMString&) - Same functionality as Compare(CCOMString&).

operator==(const CCOMString&, LPCTSTR) - Same functionality as Compare(LPCTSTR).

operator==(LPCTSTR, const CCOMString&) - Same functionality as Compare(LPCTSTR).

operator!=(const CCOMString&, const CCOMString&) - Compares the current CCOMString string with the specified CCOMString string and returns zero if not equal and non-zero if equal. This comparision is case sensitive.

operator!=(const CCOMString&, LPCTSTR) - Compares the current CCOMString string with the specified const TCHAR* and returns zero if not equal and non-zero if equal.This comparision is case sensitive.

operator!=(LPCTSTR, const CCOMString&) - Same functionality as operator !=(const CCOMString&, LPCTSTR).

CompareNoCase(CCOMString&) - Compares the current CCOMString string with the specified CCOMString string and returns zero if equal and non-zero if not equal. This comparision is not case sensitive.

CompareNoCase(LPCTSTR) - Compares the current CCOMString string with the specified const TCHAR* and returns zero if equal and non-zero if not equal. This comparision is not case sensitive.

Formatting

Format(LPCTSTR, ...) - Formats the string similar to the C function printf().

History

28 June 2000 - memory leak fix in source

12 August 2000 - updated source ZIP file

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about operator >> in string class mingtotti 19:10 20 Apr '07   i want to reload the operator >> in this string class, but how can i avoid buffer overrun? Sign In·View Thread·PermaLink Pretty class! Sergey Kolomenkin 14:17 3 Jun '05   Your class is very usefull. I used it in a number of projects, when I couldn't use MFC. It was great! But I didn't found some useful methods from MFC CString (trimming with a character set, FormatV, etc). I also found a bug in Format method. When the result buffer was equal to the allocated one, then no terminating null character is added. There is also impossible to support mixed Unicode/Non-unicode code. It would be great if we could use CCOMString, CCOMStringA, CCOMStringW together! Thanks a lot for your code! An author of the article "Task Manager Extension 2.0" Sign In·View Thread·PermaLink Updated CCOMString Sergey Kolomenkin 13:01 12 Jun '05   Here you can get modified version of CCOMString class. http://reinhard.at.tut.by/files/String_new.zip[^] This is the code prom my project. It was modified from the very old version of CCOMString, but it is very common to yours. We did the same things! But mine has no bug with Format() and has some more useful CString methods. Merge these classes at your own! I hope that Paul will update his CCOMString. P.S. You've also got my five. Sign In·View Thread·PermaLink 2.67/5 (2 votes) Are there leaks in the class? bigZidane 22:15 16 Mar '05   I tried add a loop in demo application and i see memory usage increased gradually. I added Sleep() for each loop but the memory usage still increased. Any suggestion to remove leaks? Nghi~a nghiado@psv.com.vn Sign In·View Thread·PermaLink Re: Are there leaks in the class? bigZidane 17:10 17 Mar '05   I think we need to call Empty() and free(m_pszString) in CCOMString::~CCOMString() CCOMString::~CCOMString() { Empty(); free(m_pszString); } Sign In·View Thread·PermaLink C2558 Error with VS.2003 ? balbi21 21:48 17 Oct '04   Hi there, I tried to compile the demo-source with VS.net 2003, but the compiler says: error C2558: class 'CCOMString' : no copy constructor available or copy constructor is declared 'explicit' But in the source, I think, there is a copy-constructor and the possibility to make assignements with operator=... Is there any up to date version of this files with the many updates/bugfixing discussed in this threads here? The page of the author doesn't exist anymore, i think. best regards, Bjoern M. Albrecht Sign In·View Thread·PermaLink Re: C2558 Error with VS.2003 ? Tim Musschoot 2:34 25 Oct '04   Modify the copy constructor like this: CCOMString::CCOMString(const CCOMString& str) { m_pszString = NULL; int nLen = str.GetLength(); AllocString(nLen); _tcsncpy(m_pszString, (LPCTSTR) str, nLen); } Just add the "const" declaration to the argument specification. I did not test it yet, but it helps resolving the compiler error. At least this one Sign In·View Thread·PermaLink 2.00/5 (1 vote) best aming99 23:37 14 Mar '04   AllocString(nRetVal); _tcsncpy(m_pszString, pszTemp, nRetVal); m_pszString[nRetVal]=0; Sign In·View Thread·PermaLink CCOMString::Format aming99 23:07 14 Mar '04   used _vsntprintf(...) .. how to write to POSIX ?? thx Sign In·View Thread·PermaLink Convertion from CCOMString olvsh 7:36 19 Dec '03   Could someone please help with a piece of code to convert CCOMString back into BSTR? Sorry, I'm a beginner. Sign In·View Thread·PermaLink Re: Convertion from CCOMString olvsh 8:12 19 Dec '03   I've already figured out myself. Sign In·View Thread·PermaLink CCOMString::TrimLeft() Ralph Hosking 15:34 7 Dec '03   In order to avoid an error in memmove() for example 'The instruction at "0x7800ffe7" referenced memory at "0x0097c000". The memory could not be "read".' the last parameter of memmove 'Number of bytes of characters to copy' must be the remaining string length not the original. void CCOMString::TrimLeft() {      LPTSTR lpsz = m_pszString;      while (_istspace(*lpsz))           lpsz = _tcsinc(lpsz);      if (lpsz != m_pszString)      {           // original //          memmove(m_pszString, lpsz, (GetLength()+1) * sizeof(TCHAR));           // new - move the remaining string length, not the original length           // length shown as separate variable for clarity           int nLen = (GetLength() + 1) - (lpsz - m_pszString);           memmove(m_pszString, lpsz, nLen * sizeof(TCHAR));      } } Sign In·View Thread·PermaLink Added FindReverse - here's the code John Simmons / outlaw programmer 6:06 31 Mar '03   // added by JMS - 03/31/2003 // returns the zero-based index into our string int CCOMString::ReverseFind(LPCTSTR lpszSub) { return ReverseFind(lpszSub, _tcslen(lpszSub)); } // added by JMS - 03/31/2003 // returns the zero-based index into our string int CCOMString::ReverseFind(LPCTSTR lpszSub, int nStart) { // we're gonna need this several times, but there's no point in calling it // more than once. int nLength = GetLength(); // compensate for the reverse direction of the find nStart = nLength - nStart; // make sure we're not gonna be wasting our time if (_tcslen(lpszSub) <= 0 || nStart > nLength || nStart < 0) { return -1; } // Create a new string so we can reverse it without taking a chance on munging // up the original. We already know the length of the string being searched, // so we don't need to retrieve it again - just reverse the string for the // search CComString newStr(m_pszString); newStr.MakeReverse(); // Create a new substring to find. We do this so we can reverse it in // preparation for the search. We're also gonna need the size of this substring // to help calculate the correct position. CComString newSub(lpszSub); int nSubLength = newSub.GetLength(); newSub.MakeReverse(); // now we're ready to search LPTSTR lpsz = _tcsstr(newStr + nStart, newSub); int nResult = (lpsz == NULL) ? -1 : (int)(lpsz - newStr); // if the search resulted in a hit, we need to re-calculate the resulting // position for use with the unreversed version of the string. if (nResult != -1) { nResult = nLength - (nSubLength + nResult) + 1; } return nResult; } ------- signature starts "...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001 Please review the Legal Disclaimer in my bio. ------- signature ends Sign In·View Thread·PermaLink PocketPC 2002 Version John Simmons / outlaw programmer 5:06 31 Mar '03   I think I've come up with a version of this class that will compile under PocketPC 2K2. ------- signature starts "...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001 Please review the Legal Disclaimer in my bio. ------- signature ends Sign In·View Thread·PermaLink concatenation error when using long string Anonymous 21:04 17 Nov '02   I get garbage text when i concate long lines of text. Sign In·View Thread·PermaLink 2.00/5 (1 vote) Is CCOMString COM code? Anonymous 9:37 27 Sep '02   Hi folks! I use the class in a Tokenizer class I've written, and (after some modifications proposed in a previous thread) it works fine. But why is it called CCOMString ( I mean the "COM" )? I don't know that much about COM, but normally you have a reference counter, which is increased, if a) the COM object is constructed or b) the object is copied or used by another object. I don't find that concept in CCOMString class, so I'm a bit curious what the name means. Best regards Andreas Haferburg Sign In·View Thread·PermaLink Yet another string? Why? Vagif Abilov 5:22 27 Jul '02   I don't want to kill the idea (well, actually I do), but why not using WTL strings with VC 6.0? And in VS.Net MFC and ATL share common CString implementation. VC framework is already full of string implementations (CString, CComBSTR, _bstr_t, STL strings), so I don't see the point of adding yet another one. Vagif Abilov MCP (Visual C++) Oslo, Norway Sign In·View Thread·PermaLink 5.00/5 (1 vote) Re: Yet another string? Why? Tim Smith 5:50 27 Jul '02   Back when we started our latest project, there just didn't exist a solid string class that met our needs. We needed to be able to use UNICODE and MBCS strings in the same build. That killed CString, CComBSTR, and _bstr_t. Then the problems with STLPort and bugs in VC6 strings made STL string unusable. Not to mention that STL strings don't support mixed string styles well. The support them, but just don't mix as well as we needed. Thus we created our own. If we started the project today, we would use the ATL strings since they seem to be not only full featured, but can mix W and A strings in the same application easily. So, there are valid reasons to re-invent implementations. We had to re-write STL's hash_map since it made implementation decisions that relegated it to a limited set of problems. We improved performance by 4 fold with our implementation that was specifically tailored for our needs. Just because there exists a solution in a problem set doesn't mean that solution fully covers the problem set. Tim Smith "Programmers are always surrounded by complexity; we can not avoid it... If our basic tool, the language in which we design and code our programs, is also complicated, the language itself becomes part of the problem rather that part of the solution." Hoare - 1980 ACM Turing Award Lecture Sign In·View Thread·PermaLink Re: Yet another string? Why? Vagif Abilov 10:02 27 Jul '02   OK, that explains it. I thought the code was new. But since it's probably older than first WTL implementation, you had all reasons to come up with this solution. Great code. I was just curious about practical aspects. Best regards and thanks for sharing your code. Vagif Abilov MCP (Visual C++) Oslo, Norway Sign In·View Thread·PermaLink Terrible and bugsful code!!! Anonymous 22:21 23 Jul '02   I spent a lot of time trying to debug it and in vain. Even destructor don't frees allocated memory! Sign In·View Thread·PermaLink Re: Terrible and bugsful code!!! Jerry Brown 10:53 24 Jul '02   Make these changes: 1) CCOMString::~CCOMString(){      if (m_bAllocated){           free (m_pszString);      }; } 2) Remove the function and header for ReAllocString 3) Change all other occurences of ReAllocString to AllocString 4) Change AllocString: void CCOMString::AllocString(int nLen){      ATLASSERT(nLen >= 0);      if (m_bAllocated){           m_pszString = (TCHAR*) realloc(m_pszString, (nLen+1) * sizeof(TCHAR));      }else{           m_pszString = (TCHAR*) malloc((nLen+1) * sizeof(TCHAR));      }      m_bAllocated=true;      m_pszString[nLen] = '\0';      } 5) Add      m_bAllocated=false; to the top of every constructor 6) Add   bool m_bAllocated; to the protected section of the header 7) Have yourself a great coding day with a great string class that includes perl style concatenation Sign In·View Thread·PermaLink 2.00/5 (1 vote) Re: Terrible and bugsful code!!! bigZidane 17:31 17 Mar '05   I changed a bit in demo application to test leaks in CCOMString. After the loop i don't see the memory is released all. I think we still have leaks in CCOMString class. void main() long i = 0; CCOMString zTotal; while (TRUE) { CCOMString zTest; zTest+=_T("1234567890"); zTest+=_T("QWERASDFZXCVTYUIFGHJVNBMO[P]K;'M.,/"); zTest+=_T("qwertyuiop[]\asdfghjkl;'zxcvbnm,./"); zTest+=_T("~!@#$%^&*()_+"); zTotal+=zTest; i++; zTest.Empty(); if (i == 10000) { zTotal.Empty(); break; } Sleep(1000); } Any suggestion? Sign In·View Thread·PermaLink string compare with wild card cym 23:11 16 Jun '02   is there a method or anyone has done similar, to compare a string with another string consists of wild card characters? e.g. "house" is equal to "hou*" cheers, cym Sign In·View Thread·PermaLink Re: string compare with wild card real name 23:40 16 Jun '02   there is more general solution: try search this server for "regular expresion"s t! Sign In·View Thread·PermaLink Re: string compare with wild card real name 23:44 16 Jun '02   or see http://www.codeproject.com/string/wildcmp.asp t! Sign In·View Thread·PermaLink

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