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Case-Insensitive String Replace

, 25 Jan 2000 CPOL
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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 2:36 
GeneralRe: Endlich !!! PinmvpUwe Keim15-May-10 3:09 
GeneralMy vote of 1 PinmemberHoria Tudosie24-Nov-09 5:36 
GeneralA more simple alternative... Pinmemberskjpatel30-May-08 5:37 
Questionwhy this code not work in UNICODE,_UNICODE setting? PinmemberPankaj.Jain13-Jun-07 22:46 
GeneralMore Efficient Version Pinmemberpwensing28-Apr-06 9:49 
GeneralThanks for the code PinmemberCode4Food15-Nov-05 18:38 
QuestionIncludes/Namespaces? PinmemberDarth_Sulfur5-Sep-05 15:28 
AnswerRe: Includes/Namespaces? PinmemberChristian Graus5-Sep-05 15:40 
GeneralRe: Includes/Namespaces? PinmemberDarth_Sulfur6-Sep-05 11:09 
GeneralRe: Includes/Namespaces? PinmemberChristian Graus6-Sep-05 12:08 
GeneralRe: Includes/Namespaces? PinmemberDarth_Sulfur7-Sep-05 12:27 
GeneralRe: Includes/Namespaces? PinmemberChristian Graus7-Sep-05 13:47 
GeneralRe: Includes/Namespaces? PinmemberDarth_Sulfur8-Sep-05 14:22 
GeneralRe: Includes/Namespaces? PinmemberChristian Graus8-Sep-05 14:27 
QuestionBug correction? Pinmemberpetermcwerner28-Jul-05 2:35 
I needed a case insensitive string replace and made a Google search for a CString algorithm. This was the only place I found. I have no speed problem as I am searching relatively short strings (database entries with up to 15 characters - not speed critical).
 
However, the original code gets into an endless loop in the following examples:
 
inst = "nnn"
oldstr = "n"
newstr = "N"
output should be "NNN"
 

inst = "can"
oldstr = "n"
newstr = "nnot"
output should be "cannot"
 
Please test the following version. I think it solves the problems but I have not tested all the possibilities:
 
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;
for (;;)
{
pos=input_lower.Find(oldone_lower,pos);
if (pos == -1)
break;
 
// 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 );
 
pos += strlen(newstr);
 
}
 
return output;
}

 
Peter M.C. Werner
www.cadelec.com
AnswerRe: Bug correction? PinmemberAberAber26-Nov-13 19:22 
GeneralBug PinsussPeter Werner27-Jul-05 9:18 
Generalwhy MakeLower() can not work PinmemberDavid 200817-Mar-04 7:30 
GeneralBug PinsussWicket_19-Feb-03 21:53 
GeneralRe: Bug Pinsusswicket_19-Feb-03 21:56 
Generala little optimization PinmemberKarstenK15-Apr-02 22:17 
GeneralRe: a little optimization PinsitebuilderUwe Keim15-Apr-02 22:23 
GeneralGood but a little bit slow PinmemberBraulio Díez22-Nov-01 23:33 

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