Representing only a set of bits in a binary number

@tricky,

This is my testbench code....

 stim_proc: process
  
  begin
  
    wait for 10 ns;
    reset_n_i <= '1';
   
    wait for 15 ns;
    enable_i <= '1';
    tdc_i <= "0000111111111111111111111000000001111111111111100000000111111000";
    
    wait for 100 ns;
    tdc_i <= "0000000011111111111000000000111111100000111110000011110000111000";
    wait for 1 ms;
    reset_n_i <= '0';
  
    wait for 1 ms;
    reset_n_i <= '1';
    wait for 1 ms;
    enable_i <= '0';
    wait for 1 ms;
    enable_i <= '1';
    wait for 1 ms;
    assert False report "End simulation!" severity Failure;
  end process;
  p_check_tdc_out: process(reset_n_i, clk_128meg_i)
  begin
    if (reset_n_i = '0') then
     tdc_fall_s <= (others => '0');
     tdc_rise_fall_s <= (others => '0');
     tdc_rise_s <= (others => '0');
    elsif (clk_128meg_i'event and clk_128meg_i = '1') then
      if (enable_i = '1') then
      this_loop: loop 
       if (unsigned(tdc_i(cnt_s) and tdc_i(cnt_s + 1)) = '0') then
          tdc_fall_s <= std_logic_vector(unsigned(tdc_fall_s) + 1);
       elsif (unsigned(tdc_i(cnt_s) and tdc_i(cnt_s + 1)) = '1') then
          tdc_rise_fall_s <= std_logic_vector(unsigned(tdc_rise_fall_s) + 1);
          if(unsigned(tdc_i(cnt_s+1) and tdc_i(cnt_s + 2)) = '0') then
             exit this_loop;
          end if;
       end if; 
       cnt_s <= cnt_s + 1;          
      end loop this_loop;
       tdc_rise_s <= std_logic_vector(unsigned(tdc_fall_s) + unsigned(tdc_rise_fall_s));
      else
         tdc_fall_s <= (others => '0');
         tdc_rise_fall_s <= (others => '0');
         tdc_rise_s <= (others => '0');
      end if;
     end if;
  end process;
  
  p_check_tdcmodule: process(clk_128meg_i)
  begin
    if (clk_128meg_i'event and clk_128meg_i = '0') then
      assert rise_o = tdc_rise_s report "Wrong output: Rise time is not calculated properly" severity error;
      assert rise_fall_o = tdc_rise_fall_s report "Wrong output : Rise time - fall time is not calculated properly" severity error;
    end if;
  end process;
end beh;

What I need to do I need to check for the binary digits 0 and 1 and should stop the operation of checking when the next 0 after the first set of 1s arrive. Please help me to solve the issue