Way way back in the dark ages of Delphi XE2, I wrote a function to encode components of a URI. Now, this function has been updated for use on mobile platforms, by Nicolas Dusart, and I quote Nicolas:

I had to make some modifications on it to compile for the mobile platforms, as the strings are 0-based on these platforms.

I also modified it to escape non-ASCII characters using their UTF-8 encoding as the standards advices. For multi-bytes characters, each byte is percent-encoded as usual.

Here’s the code, maybe it could interests you and the future readers of that article 🙂

And here’s Nicolas’s updated function in all its glory:

function EncodeURIComponent(const ASrc: string): string;
const
  HexMap: string = '0123456789ABCDEF';

  function IsSafeChar(ch: Byte): Boolean;
  begin
    if (ch >= 48) and (ch <= 57) then Result := True    // 0-9
    else if (ch >= 65) and (ch <= 90) then Result := True  // A-Z
    else if (ch >= 97) and (ch <= 122) then Result := True  // a-z
    else if (ch = 33) then Result := True // !
    else if (ch >= 39) and (ch <= 42) then Result := True // '()*
    else if (ch >= 45) and (ch <= 46) then Result := True // -.
    else if (ch = 95) then Result := True // _
    else if (ch = 126) then Result := True // ~
    else Result := False;
  end;

var
  I, J: Integer;
  Bytes: TBytes;
begin
  Result := '';
    
  Bytes := TEncoding.UTF8.GetBytes(ASrc);
    
  I := 0;
  J := Low(Result);

  SetLength(Result, Length(Bytes) * 3); // space to %xx encode every byte

  while I < Length(Bytes) do
  begin
    if IsSafeChar(Bytes[I]) then
    begin
      Result[J] := Char(Bytes[I]);
      Inc(J);
    end
    else
    begin
      Result[J] := '%';
      Result[J+1] := HexMap[(Bytes[I] shr 4) + Low(ASrc)];
      Result[J+2] := HexMap[(Bytes[I] and 15) + Low(ASrc)];
      Inc(J,3);
    end;
    Inc(I);
  end;
    
  SetLength(Result, J-Low(ASrc));
end;

Many thanks, Nicolas 🙂