Another registry class

SteveKing, 25 Apr 2003

A registry class with overloaded operators to use registry values like normal variables

Download source files - 4 Kb

Introduction

In many projects I need to store simple strings, DWORDS or for window position CRect's in the registry. I know there are many registry classes out there, so why one more?

The answer: simplicity. I want to write to the registry as easy as assigning a value to a variable. Like an eeprom variable in neuron controllers (those of you who use those controllers know what I mean). So I wrote exactly such a class.

Usage

So, how to use this class - or better classes. I wrote a separate class for CString, DWORD, CRect and CPoint.

// initialize the variables
CRegString mystring("Software\\Company\\Subkey\\MyString", "defaultvalue");
CRegRect   myrect("Software\\Company\\Subkey\\MyRect", CRect(1,1,1,1));
CRegDWORD  myword("Software\\Company\\Subkey\\mydword", 100, 
                     TRUE, HKEY_LOCAL_MACHINE);
CRegPoint  mypoint("Software\\Company\\Subkey\\mypoint");

// now use those variables
CString str = mystring;     //if registry does not exist, the default value is used
mystring = "TestValue";     //"TestValue" is stored in the registry
mystring += "!";            //now the registry value MyString contains "TestValue!"
myrect = CRect(100,200,300,400);    //store in the registry
LPRECT lpR = (LPRECT)myrect;
myword = GetTickCounts();   //just an example
mypoint = CPoint(0,0);

As you can see, once the CRegXXX object knows to which registry key/value it is assigned to you can use it like any other variable!

To avoid too much access to the registry the value is cached. Writes occur only if the new value is different than the current value. Reads occur only once in the constructor. Since such a cached behaviour could lead to some problems, you can force reads and writes to the registry with the methods read() and write(). To disable the cache and force the class to always access the registry just set that in the constructor. the constructor for the CRegDWORD looks like this:

/**
* Constructor.
* @param key the path to the key, including the key. 
*            example: "Software\\Company\\SubKey\\MyValue"
* @param def the default value used when the key does not exist or 
*            a read error occured
* @param force set to TRUE if no cache should be used, i.e. always read and write 
*              directly from/to registry
* @param base a predefined base key like HKEY_LOCAL_MACHINE. see the SDK 
*             documentation for more information.
*/
CRegDWORD(CString key, DWORD def = 0, BOOL force = FALSE, 
          HKEY base = HKEY_CURRENT_USER);

The classes CRegString, CRegRect and CRegPoint have similar constructors. See the header files for details.

Not all methods of the "base" classes are overloaded. So if you want to, for example, use some methods of the CString class you have to typecast the CRegString to a CString first:

int l = ((CString)mystring).GetLength();
((CString)mystring).Trim();

Please note that in the second line where the Trim() is used that the changed string is NOT written to the registry!

And please: keep your complaints about "not again a registry class" and the like for yourselves. If you don't like it, don't use it!

Update

2. April 2003 :
1. added classes for use without MFC: CRegStdString, CRegStdDWORD
2. now compiles for UNICODE too
9. July 2002 :
1. Corrected a bug found by Hans Dietrich
2. Extended the classes with two methods: removeKey() and removeValue()

Daniel Andersson wrote a templatized version of this class. See his article here.

License

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

About the Author

SteveKing

	Software Developer
	Switzerland

---

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Comments and Discussions

My vote of 5

despana5-Feb-13 11:29

despana

5-Feb-13 11:29

Awesome!

Bug for Unicode projects?

rh_20-Apr-07 2:26

rh_

20-Apr-07 2:26

Hello,

I think there is a bug if you want to use this class in Unicode projects. Line 497 should read

if (RegSetValueEx(m_hKey, m_key.c_str(), 0, REG_SZ, (BYTE *)m_value.c_str(), (DWORD)(m_value.size()+1)*sizeof(TCHAR))==ERROR_SUCCESS)<br />

The "sizeof(TCHAR)" is necessary if TCHAR is not 1 byte.
Am I correct?

Modified to read REG_MULTI_SZ correctly

Douglas R. Keesler23-Dec-06 4:54

Douglas R. Keesler

23-Dec-06 4:54

As is, this class will only return the first null terminated string portion of a multi-string registry entry. I have modified the class so that the CRegString() method will automatically determine whether entry is regular string or multi-string and return it correctly. Multi-strings are returned as vertical bar or pipe-delimited strings (eg. "string-a|string-b"). Here is the code modification:

CString	CRegString::read()
{
	ASSERT(m_key != _T(""));
	if (RegOpenKeyEx(m_base, m_path, 0, KEY_EXECUTE, &m_hKey)==ERROR_SUCCESS)
	{
		int size = 0;
		DWORD type;
		RegQueryValueEx(m_hKey, m_key, NULL, &type, NULL, (LPDWORD) &size);
		TCHAR* pStr = new TCHAR[size];

	//////////////////////////////////////////////////////////////////////
        //      MULTI-STRING CODE MODIFICATION BEGINS HERE
        //////////////////////////////////////////////////////////////////////

		if(type==REG_MULTI_SZ)
		{
			delete [] pStr;
			RegCloseKey(m_hKey);
			TCHAR szResult[512] = _T("\0"); //512 is max regsz entry

			if(RegMultiRead(m_base, m_path.GetBuffer(), m_key.GetBuffer(),szResult,512)==0)
			{
				m_read=TRUE;
				m_value = CString(szResult);
			}
			else
			{
				m_read=FALSE;
				m_value = m_defaultvalue;
			}

			m_path.ReleaseBuffer();
			m_key.ReleaseBuffer();
			return m_value;	
		}

          //////////////////////////////////////////////////////////////////
          //         END OF MULTI-STRING CODE MODIFICATION
          //////////////////////////////////////////////////////////////////

		if (RegQueryValueEx(m_hKey, m_key, NULL, &type, (BYTE*) pStr,(LPDWORD) &size)==ERROR_SUCCESS)
		{
			
			m_value = CString(pStr);
			delete [] pStr;
			ASSERT(type==REG_SZ);
			m_read = TRUE;
			RegCloseKey(m_hKey);
			return m_value;
		}
		else
		{
			delete [] pStr;
			RegCloseKey(m_hKey);
			return m_defaultvalue;
		}
	}
	return m_defaultvalue;
}

And then you must add the corresponding new method to the CRegString class:

////////////////////////////////////////////////////////////
//     MULTI-STRING CODE MODIFICATION:  NEW METHOD
////////////////////////////////////////////////////////////
DWORD CRegString::RegMultiRead(HKEY hHive, LPTSTR szKey, LPTSTR szValue, LPTSTR szResult, size_t iResultSize)
{
       long lRet = 0;
       HKEY  hKey; 

       if (lRet = RegOpenKeyEx(hHive,szKey,0,KEY_EXECUTE,&hKey) == ERROR_SUCCESS)
       {
              DWORD dwType = 0;
              DWORD dwSize = iResultSize;
              DWORD dwCapacity = iResultSize;
              LPTSTR szData = new TCHAR[iResultSize+4*sizeof(TCHAR)]; 

              lRet = RegQueryValueEx(hKey,szValue,NULL,&dwType,(LPBYTE)szData,&dwSize);

              if( (lRet != ERROR_SUCCESS) || (dwSize > dwCapacity) || dwType != REG_MULTI_SZ )
              {
                     RegCloseKey(hHive);
                     delete[] szData;
                     return dwSize;
              }

              LPTSTR  szToken = NULL;
              LPTSTR  szTmp = new TCHAR[dwCapacity];
              _tcscpy (szTmp, _T("\0")); 

              // Grab the first null-terminated string
              szToken = szData;
              while( szToken != NULL )
              {
                     // Copy the string out
                     _tcscat (szTmp, szToken);

                     // Increment the token to the next string
                     szToken = szToken + _tcslen (szToken) + sizeof(TCHAR);

                     // If the next string isn't null, append a pipe
                     // to the target string.
                     if (_tcslen (szToken) > 0)
                           _tcscat (szTmp, _T("|"));
                     else
                           szToken = NULL;
              }

              _tcscpy(szResult, szTmp);     
              delete[] szData;
              delete[] szTmp;
              RegCloseKey(hKey);
              RegCloseKey(hHive);
       }
       else
              return lRet;      

       return 0;
}
////////////////////////////////////////////////////////////////
//   END OF MULTI-STRING CODE MODIFICATION
////////////////////////////////////////////////////////////////

In business, if two people always agree, one of them is unnecessary.

tab ctrl

locoone2-Sep-06 13:29

locoone

2-Sep-06 13:29

ok ive never used a tab control before i have no clue as to go about it. could someone give me a sample as to how to put a control on a tab all im going to use is check boxs and a few edits.

thanks in advance.

Nice...

HumanJHawkins14-Jun-06 11:39

HumanJHawkins

14-Jun-06 11:39

This is very useful. Very easy to use and powerful.

The only trouble I have with it is that if I try to read a non-existant key, it should either return null, or give an error indicating that there is no key. Returning the default value can be confusing as this is data that might then be mishandled.

Perhaps returning the default value on non-keys could be an option that could be turned on or off?

Anyway, this is very helpful.

Thanks!

unicode for registry

raycadarena13-Feb-06 18:45

raycadarena

13-Feb-06 18:45

Hi all!;)
I want to read and write to registry use unicode character but i don't know how to do D'Oh! | :doh:

. Who can help me? Confused | :confused:

Thanks a lot. Blush | :O

Need error handling

CharlieG28-Jul-05 6:08

CharlieG

28-Jul-05 6:08

As I'm learning, nothing in life is certain, esp. so with Windows. This class, since it writes to something VERY important should be throwing exceptions. Might just add those and send to the author.

later....

C. Gilley
Will program for food...
Whoever said children were cheaper by the dozen... lied.

Very nice, thank you a lot!

Alex Chirokov4-Jul-05 16:47

Alex Chirokov

4-Jul-05 16:47

Just wanted you to know that it is excellent class.

Sincerely,
Alex Chirokov

Constructor / read problem

Bob Stanneveld13-Apr-05 3:08

Bob Stanneveld

13-Apr-05 3:08

Hello,

I'm using you little registry class library and I must say that it does the job almost perfect! I found a little "feature" which I don't know if it's there on purpose or as a surprise..

This "feature" is in the constructor / read method of the CRegBase derived classes. This is what happens:
I call the constructor with a default value. The registry value / key don't exist yet. The read function returns the default value. The variable m_value doesn't change! So after the constructor finished the object has an invalid default value. (Not the one I specified.)

The code now looks like this:

<br />
// constructor<br />
m_value = "";<br />
m_defaultvalue = def;<br />
m_force = force;<br />
m_base = base;<br />
m_read = FALSE;<br />
key.TrimLeft(_T("\\"));<br />
m_path = key.Left(key.ReverseFind(_T('\\')));<br />
m_path.TrimRight(_T("\\"));<br />
m_key = key.Right(key.GetLength() - key.ReverseFind(_T('\\')));<br />
m_key.Trim(_T("\\"));<br />
read();<br />
<br />
// read method<br />
ASSERT(m_key != _T(""));<br />
if (RegOpenKeyEx(m_base, m_path, 0, KEY_EXECUTE, &m_hKey)==ERROR_SUCCESS)<br />
{ <br />
  int size = 0;<br />
  DWORD type;<br />
  RegQueryValueEx(m_hKey, m_key, NULL, &type, NULL, (LPDWORD) &size);<br />
  TCHAR* pStr = new TCHAR[size];<br />
  if (RegQueryValueEx(m_hKey, m_key, NULL, &type, (BYTE*) pStr,(LPDWORD) &size)==ERROR_SUCCESS)<br />
  {<br />
   m_value = CString(pStr);<br />
   delete [] pStr;<br />
   ASSERT(type==REG_SZ);<br />
   m_read = TRUE;<br />
   RegCloseKey(m_hKey);<br />
   return m_value;<br />
  } <br />
  else<br />
  {<br />
   delete [] pStr;<br />
   RegCloseKey(m_hKey);<br />
   return m_defaultvalue;<br />
  }<br />
 }<br />
// Note: the variable m_value is not changed here!<br />
return m_defaultvalue;<br />

And I think that the code should look like this:

<br />
// constructor<br />
m_value = "";<br />
m_defaultvalue = def;<br />
m_force = force;<br />
m_base = base;<br />
m_read = FALSE;<br />
key.TrimLeft(_T("\\"));<br />
m_path = key.Left(key.ReverseFind(_T('\\')));<br />
m_path.TrimRight(_T("\\"));<br />
m_key = key.Right(key.GetLength() - key.ReverseFind(_T('\\')));<br />
m_key.Trim(_T("\\"));<br />
// Option 1, change this line to m_value = read()<br />
read();<br />
<br />
// read method<br />
ASSERT(m_key != _T(""));<br />
if (RegOpenKeyEx(m_base, m_path, 0, KEY_EXECUTE, &m_hKey)==ERROR_SUCCESS)<br />
{ <br />
  int size = 0;<br />
  DWORD type;<br />
  RegQueryValueEx(m_hKey, m_key, NULL, &type, NULL, (LPDWORD) &size);<br />
  TCHAR* pStr = new TCHAR[size];<br />
  if (RegQueryValueEx(m_hKey, m_key, NULL, &type, (BYTE*) pStr,(LPDWORD) &size)==ERROR_SUCCESS)<br />
  {<br />
   m_value = CString(pStr);<br />
   delete [] pStr;<br />
   ASSERT(type==REG_SZ);<br />
   m_read = TRUE;<br />
   RegCloseKey(m_hKey);<br />
   return m_value;<br />
  } <br />
  else<br />
  {<br />
   delete [] pStr;<br />
   RegCloseKey(m_hKey);<br />
   // Option 2 modify the function as follows<br />
   // Note: no value returned here!<br />
  }<br />
 }<br />
// and modify this line<br />
return (m_value = m_defaultvalue);<br />

I think that option 2 is the better option, because that way m_value is always changed, which I thinkt is the purpose of the read() method.

Besides that, it's a great class! Big Grin | :-D

I also got the blogging virus..[^]

error C2039: 'Trim' : is not a member of 'CString'

qiek4-Nov-04 5:07

qiek

4-Nov-04 5:07

and sure Trim is not a member of CString, then...

Re: error C2039: 'Trim' : is not a member of 'CString'

EvanTao30-Nov-04 0:03

EvanTao

30-Nov-04 0:03

I think that maybe it's a bug.

I think that it maybe should like this:
m_key.TrimLeft(_T("\\"));

And i believe it is right with trimleft().

Re: error C2039: 'Trim' : is not a member of 'CString'

Alex Chirokov4-Jul-05 16:52

Alex Chirokov

4-Jul-05 16:52

Trim is now a member of the old MFC CString class, but here is what google found:
"The trimChars can be either a string of the characters or an integer array of characters that will be trimmed from both ends"
so instead of

string.Trim()

i used

string.TrimLeft();
string.TrimRight();

so far it works,

Sincerely,
Alex Chirokov

Re: error C2039: 'Trim' : is not a member of 'CString'

Douglas R. Keesler23-Dec-06 5:30

Douglas R. Keesler

23-Dec-06 5:30

Yes, Trim is a valid CString function... BUT.. it returns the result rather than changing the object directly. So the line MyString.trim(), while being valid code, will have no effect as the result is lost... It needs to be written CString szTrimmed = MyString.Trim(), and now the result of the Trim() operation is captured in the szTrimmed variable.

Trim operates on both ends of the string as opposed to TrimLeft and TrimRight which operate on only one end -- so if MyString = "*****Important String!!!!!!", you could use szTrimmed = MyString.Trim("*!"); and the result would be "Important String".

The important point here is that the reason there is data loss in the example code, is because he didn't assign a variable to catch the returned result of the Trim operation.

In business, if two people always agree, one of them is unnecessary.

export registry as text file programmatically

yamei14-Oct-04 12:28

yamei

14-Oct-04 12:28

The .reg file saved by RegSaveKey() is a binary file.
How to export registry as an ASCII text file?

Linker error wtih removeKey()

JR Cooper7-Oct-04 13:34

JR Cooper

7-Oct-04 13:34

Hello,

No problem when I use removeValue(),
however; when I use removeKey() I get linker errors?

How do I fix the linker errors, or how can
I remove keys without using removeKey()?

Linking...
maindoc.obj : error LNK2001: unresolved external symbol __imp__SHDeleteKeyA@8
../../Apps/Debug/SPMNotify.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

VC++ 6.0 SP5
Thanks,
Jacques

Re: Linker error wtih removeKey()

mnowok12-Oct-04 0:07

mnowok

12-Oct-04 0:07

Just add Shlwapi.lib import library to your VS 5 project (Project/Settings/Settings for all configurations/Link/Object/library modules).

i can write to the registry, yaay!

asmotritsky19-Jun-04 23:33

asmotritsky

19-Jun-04 23:33

thanks for posting this outstanding code!

Use in DLL that does not use MFC

ltang724-Apr-04 19:01

ltang7

24-Apr-04 19:01

Is there any way to use this registry class in program that does not support MFC?
I would like to use this registry class in an existing DLL that does not support MFC. I think it is rather difficult to make that DLL to support MFC, so I would like to see if there is any way to use this class with no support of MFC.
I am definitely open to the suggestion on how to change a DLL to support MFC with minimum effort.

Thanks,
LT

"Simple" is great!

XeonSniper13-Apr-04 17:40

XeonSniper

13-Apr-04 17:40

This is one heck of a class library!
keep up the great work! Smile | :)

loading .reg file programmatically

bruno leclerc18-Mar-04 1:14

bruno leclerc

18-Mar-04 1:14

Hi,
Do you know how to load an entire .reg file programmatically?
I didn't see that anywhere ?
Thanks.

CRegStdDWORD instead of CRegStdWORD

ujohnc0016-Mar-04 10:11

ujohnc00

16-Mar-04 10:11

Thought this little bit may be of use for some.

The class declares CRegStdWORD instead of CRegStdDWORD as you (and I) would expect. Those programs referencing CRegStdDWORD will not compile. Since I did not want to change a lot of the code, adding this line to the end of registry.h provides a quick fix:

typedef CRegStdWORD CRegStdDWORD;

Thanks for the great class!

Great! thank you

PMartos18-Dec-03 9:14

PMartos

18-Dec-03 9:14

This was exactly what I was looking for. thanks a lot for writing it.

Felicidades :)

C++17-Dec-03 8:41

C++

17-Dec-03 8:41

Congratulations Smile | :)

; is just what I was looking for, thanks a lot.

People say that I am a perverse person, but are not truth because I have the heart of a boy.... I have it in a bottle with formol in my writing-desk.

Bug?

Igor Vigdorchik16-Dec-03 9:29

Igor Vigdorchik

16-Dec-03 9:29

Hi,
I am getting the following linker error:
error LNK2001: unresolved external symbol "public: class CRegStdWORD & __thiscall CRegStdWORD::operator=(unsigned long)" (??4CRegStdWORD@@QAEAAV0@K@Z)
Debug/StickyNotes.exe : fatal error LNK1120: 1 unresolved externals.
Looks like CRegStdWORD::operator=(DWORD d) is not defined.
Is it a bug or a feature? Or am I missing something?

With respect,
Igor.

Re: Bug?

Jonas Nordlund5-Feb-04 23:50

Jonas Nordlund

5-Feb-04 23:50

Yes, I'm getting the same thing when trying to link to the CRegistry code, part of another DLL. Frown | :(

Looks like it isn't exported for some reason. Help? Smile | :)

error LNK2001: unresolved external symbol "public: class CRegStdWORD & __thiscall CRegStdWORD::operator=(unsigned long)" (??4CRegStdWORD@@QAEAAV0@K@Z)