Case-Insensitive String Replace

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

• 25^th January, 2000: Initial post