ParagonIE_Sodium_Core_X25519::fe_cswap

    public static function fe_cswap(
        ParagonIE_Sodium_Core_Curve25519_Fe $f,
        ParagonIE_Sodium_Core_Curve25519_Fe $g,
        $b = 0
    ) {
        $f0 = (int) $f[0];
        $f1 = (int) $f[1];
        $f2 = (int) $f[2];
        $f3 = (int) $f[3];
        $f4 = (int) $f[4];
        $f5 = (int) $f[5];
        $f6 = (int) $f[6];
        $f7 = (int) $f[7];
        $f8 = (int) $f[8];
        $f9 = (int) $f[9];
        $g0 = (int) $g[0];
        $g1 = (int) $g[1];
        $g2 = (int) $g[2];
        $g3 = (int) $g[3];
        $g4 = (int) $g[4];
        $g5 = (int) $g[5];
        $g6 = (int) $g[6];
        $g7 = (int) $g[7];
        $g8 = (int) $g[8];
        $g9 = (int) $g[9];
        $b = -$b;
        $x0 = ($f0 ^ $g0) & $b;
        $x1 = ($f1 ^ $g1) & $b;
        $x2 = ($f2 ^ $g2) & $b;
        $x3 = ($f3 ^ $g3) & $b;
        $x4 = ($f4 ^ $g4) & $b;
        $x5 = ($f5 ^ $g5) & $b;
        $x6 = ($f6 ^ $g6) & $b;
        $x7 = ($f7 ^ $g7) & $b;
        $x8 = ($f8 ^ $g8) & $b;
        $x9 = ($f9 ^ $g9) & $b;
        $f[0] = $f0 ^ $x0;
        $f[1] = $f1 ^ $x1;
        $f[2] = $f2 ^ $x2;
        $f[3] = $f3 ^ $x3;
        $f[4] = $f4 ^ $x4;
        $f[5] = $f5 ^ $x5;
        $f[6] = $f6 ^ $x6;
        $f[7] = $f7 ^ $x7;
        $f[8] = $f8 ^ $x8;
        $f[9] = $f9 ^ $x9;
        $g[0] = $g0 ^ $x0;
        $g[1] = $g1 ^ $x1;
        $g[2] = $g2 ^ $x2;
        $g[3] = $g3 ^ $x3;
        $g[4] = $g4 ^ $x4;
        $g[5] = $g5 ^ $x5;
        $g[6] = $g6 ^ $x6;
        $g[7] = $g7 ^ $x7;
        $g[8] = $g8 ^ $x8;
        $g[9] = $g9 ^ $x9;
    }