What is the fastest way of stripping non alphanumeric characters from a string in Delphi7?

Question

The characters allowed are A to Z, a to z, 0 to 9. The least amount of code or a single function would be best as the system is time critical on response to input.

Answer 1

uses JclStrings;

  S := StrKeepChars('mystring', ['A'..'Z', 'a'..'z', '0'..'9']);