delphi - strip out all non standard text characers from string

Question

I need to strip out all non standard text characers from a string. I need remove all non ascii and control characters (except line feeds/carriage returns).

Answer 1

Here's a version that doesn't build the string by appending char-by-char, but allocates the whole string in one go. It requires going over the string twice, once to count the "good" char, once to effectively copy those chars, but it's worth it because it doesn't do multiple reallocations:

function StripNonAscii(s:string):string;
var Count, i:Integer;
begin
  Count := 0;
  for i:=1 to Length(s) do
    if ((s[i] >= #32) and (s[i] <= #127)) or (s[i] in [#10, #13]) then
      Inc(Count);
  if Count = Length(s) then
    Result := s // No characters need to be removed, return the original string (no mem allocation!)
  else
    begin
      SetLength(Result, Count);
      Count := 1;
      for i:=1 to Length(s) do
        if ((s[i] >= #32) and (s[i] <= #127)) or (s[i] in [#10, #13]) then
        begin
          Result[Count] := s[i];
          Inc(Count);
        end;
    end;
end;