bool haswon(int64_t board)
{
    int64_t y = board & (board >> 7);
    if (y & (y >> 2 * 7)) // check  diagonal
        return true;
    y = board & (board >> 8);
    if (y & (y >> 2 * 8)) // check horizontal -
        return true;
    y = board & (board >> 9);
    if (y & (y >> 2 * 9)) // check / diagonal
        return true;
    y = board & (board >> 1);
    if (y & (y >> 2))     // check vertical |
        return true;
    return false;
}

#include <iostream>
#include <bitset>

namespace tictactoe {

    constexpr std::size_t N = 3;

    using board = std::bitset<N*N>;

    constexpr char NOUGHT = 'O';
    constexpr char CROSS = 'X';

    bool curr_move_noughts = true;

    board combined() {
        return noughts | crosses;    // combined bit board for both players
    }

}

10000001
00000010
00000100
00000000
00000000
00000000
00000000
00000000

+---+---+---+
| 0 | 1 | 2 |
+---+---+---+
| 3 | 4 | 5 |
+---+---+---+
| 6 | 7 | 8 |
+---+---+---+

bool line_is_full (Board* p_board, char p_player, int p1, int p2, int p3)
{
  return (   (p_board [p1] == p_player)
          && (p_board [p2] == p_player)
          && (p_board [p3] == p_player));
}

bool board_has_win (Board* p_board, char p_player)
{
  return (   line_is_full (p_board, p_player, 0, 1, 2)
          || line_is_full (p_board, p_player, 3, 4, 5)
          || line_is_full (p_board, p_player, 6, 7, 8)

          || line_is_full (p_board, p_player, 0, 3, 6)
          || line_is_full (p_board, p_player, 1, 4, 7)
          || line_is_full (p_board, p_player, 2, 5, 8)

          || line_is_full (p_board, p_player, 0, 4, 8)

          || line_is_full (p_board, p_player, 2, 4, 6));
}

0 .... All three cells empty
 1 .... One O, two empty cells
 2 .... Two Os, one empty cell
 3 .... Three Os - O wins

 4 .... One X, two empty cells
 5 .... One X, one O, one empty cell
 6 .... One X, two Os
 7 .... Impossible

 8 .... Two Xs, one empty cell
 9 .... Two Xs, one O
10 .... Impossible
11 .... Impossible

12 .... Three Xs - X wins
13+ ... Impossible