Janilabo | MSSL_ClosestPos() / MSSL_FurthestPos()

function MSSL_ClosestPos(trgt_pos: Integer; s, str: string): Integer;
var
  strL, o, p: Integer;
begin
  strL := Length(str);
  if ((Length(s) > strL) or (trgt_pos < 1) or (trgt_pos > strL)) then
    Exit;
  repeat
    p := PosEx(s, str, (o + 1));
    if (p > 0) then
    begin
      if (Result = 0) then
        Result := p
      else
        if (IAbs(trgt_pos - p) < IAbs(trgt_pos - Result)) then
          Result := p
        else
          Exit;
      o := p;
    end;
  until (p <= 0);
end;

function MSSL_FurthestPos(trgt_pos: Integer; s, str: string): Integer;
var
  strL, o, p: Integer;
begin
  strL := Length(str);
  if ((Length(s) > strL) or (trgt_pos < 1) or (trgt_pos > strL)) then
    Exit;
  repeat
    p := PosEx(s, str, (o + 1));
    if (p > 0) then
    begin
      if (Result = 0) then
        Result := p
      else
        if (IAbs(trgt_pos - p) > IAbs(trgt_pos - Result)) then
          Result := p;
      o := p;
    end;
  until (p <= 0);
end;

var
  str: string;

begin
  str := 'TEST is only a TEST... TEST!';
  WriteLn(MSSL_ClosestPos(Pos('...', str), 'TEST', str));
  WriteLn(MSSL_FurthestPos(Pos('...', str), 'TEST', str));
end.