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Case-Insensitive String Replace

, 25 Jan 2000
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Function to replace all occurences of a string within another, ignoring the case

Introduction

This is a simple function that acts like CString::Replace(), except that the case of the string to search for is ignored.

The whole code follows:

// instr:  string to search in.
// oldstr: string to search for, ignoring the case.
// newstr: string replacing the occurrences of oldstr.
CString ReplaceNoCase( LPCTSTR instr, LPCTSTR oldstr, LPCTSTR newstr )
{
	CString output( instr );

	// lowercase-versions to search in.
	CString input_lower( instr );
	CString oldone_lower( oldstr );
	input_lower.MakeLower();
	oldone_lower.MakeLower();

	// search in the lowercase versions,
	// replace in the original-case version.
	int pos=0;
	while ( (pos=input_lower.Find(oldone_lower,pos))!=-1 ) {

		// need for empty "newstr" cases.
		input_lower.Delete( pos, lstrlen(oldstr) );	
		input_lower.Insert( pos, newstr );

		// actually replace.
		output.Delete( pos, lstrlen(oldstr) );
		output.Insert( pos, newstr );
	}

	return output;
}

The function's implementation is rather simple: it creates several copies of the strings. If you need a memory- and speed- optimized replace function, this one is probably not the best for you. Anyway, in my project, it worked just well.

Please feel free to ask any questions you have by e-mail: keim@zeta-software.de.

History

  • 25th January, 2000: Initial post

License

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

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About the Author

Uwe Keim
Chief Technology Officer Zeta Producer Desktop CMS
Germany Germany
Uwe does programming since 1989 with experiences in Assembler, C++, MFC and lots of web- and database stuff and now uses ASP.NET and C# extensively, too. He has also teached programming to students at the local university.
 
In his free time, he does climbing, running and mountain biking. Recently he became a father of a cute boy.
 
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Comments and Discussions

 
GeneralEndlich !!! Pinmemberplattenbomber15-May-10 1:36 
GeneralRe: Endlich !!! PinmvpUwe Keim15-May-10 2:09 
GeneralMy vote of 1 PinmemberHoria Tudosie24-Nov-09 4:36 
GeneralA more simple alternative... Pinmemberskjpatel30-May-08 4:37 
Questionwhy this code not work in UNICODE,_UNICODE setting? PinmemberPankaj.Jain13-Jun-07 21:46 
GeneralMore Efficient Version Pinmemberpwensing28-Apr-06 8:49 
While I was making some slight modifications to this for a project I was working on, I made some modifications that ended up working faster. The basic gist is that instead of performing the replace in the old string and the new string, I keep some extra track of positions so that I only need to do the replace in the main string. There was about a 27% gain in speed with this version compared to the original when I tested it (I ran it on a fairly large string 1000 times for each function). Sorry for the minor differences in parameters and such, this way suited my needs better.
 
void newReplace2(CString& mainStr, CString& oldStr, CString& newStr)
{
//Prevent infinite loop when user tries to replace nothing.
if (oldStr != "")
{
int oldLen = oldStr.GetLength(), newLen = newStr.GetLength();
int nPos = 0, lastPos = 0, newPos = 0, posDiff = 0;
 
//Copies of the main string and the string to be replaced that
//are made lower case
CString mainStr_low(mainStr);
CString oldStr_low(oldStr);
mainStr_low.MakeLower();
oldStr_low.MakeLower();
 
while ((nPos = mainStr_low.Find(oldStr_low, nPos)) != -1)
{
//Calc number of characters between last match and
//new match
posDiff = nPos - lastPos;

//Determine the position of the match in the string
//to be returned
newPos += posDiff;
 
//Do the replace in the main string that will be
//returned.
mainStr.Delete(newPos, oldLen);
mainStr.Insert(newPos, newStr);
 
//Skip the rest of the old string
nPos += oldLen;
//Skip the new position to the end of the new string
//To keep it inline with the position in the old
//string
newPos += newLen;
//Needed to determine posDiff above
lastPos = nPos;
}
}
}

GeneralThanks for the code PinmemberCode4Food15-Nov-05 17:38 
QuestionIncludes/Namespaces? PinmemberDarth_Sulfur5-Sep-05 14:28 
AnswerRe: Includes/Namespaces? PinmemberChristian Graus5-Sep-05 14:40 
GeneralRe: Includes/Namespaces? PinmemberDarth_Sulfur6-Sep-05 10:09 
GeneralRe: Includes/Namespaces? PinmemberChristian Graus6-Sep-05 11:08 
GeneralRe: Includes/Namespaces? PinmemberDarth_Sulfur7-Sep-05 11:27 
GeneralRe: Includes/Namespaces? PinmemberChristian Graus7-Sep-05 12:47 
GeneralRe: Includes/Namespaces? PinmemberDarth_Sulfur8-Sep-05 13:22 
GeneralRe: Includes/Namespaces? PinmemberChristian Graus8-Sep-05 13:27 
QuestionBug correction? Pinmemberpetermcwerner28-Jul-05 1:35 
AnswerRe: Bug correction? PinmemberAberAber26-Nov-13 18:22 
GeneralBug PinsussPeter Werner27-Jul-05 8:18 
Generalwhy MakeLower() can not work PinmemberDavid 200817-Mar-04 6:30 
GeneralBug PinsussWicket_19-Feb-03 20:53 
GeneralRe: Bug Pinsusswicket_19-Feb-03 20:56 
Generala little optimization PinmemberKarstenK15-Apr-02 21:17 
GeneralRe: a little optimization PinsitebuilderUwe Keim15-Apr-02 21:23 
GeneralGood but a little bit slow PinmemberBraulio Díez22-Nov-01 22:33 

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