ALPHABETS_SPECIAL = r'''`-=[]\;',./~!@#$%^&*()_+{}|:"<>?'''

    ALPHABETS_FULL = ALPHABETS_BIG + ALPHABETS_SMALL \

        + ALPHABETS_NUM + ALPHABETS_SPECIAL

    ALPHABETS_ALPHANUM = ALPHABETS_BIG + ALPHABETS_SMALL + ALPHABETS_NUM

    ALPHABETS_BIG_SMALL = ALPHABETS_BIG + ALPHABETS_SMALL

    ALPHABETS_ALPHANUM_BIG = ALPHABETS_BIG + ALPHABETS_NUM

    ALPHABETS_ALPHANUM_SMALL = ALPHABETS_SMALL + ALPHABETS_NUM

    def gen_password(self, length, alphabet=ALPHABETS_FULL):

        assert len(alphabet) <= 256, alphabet

        l = []

        while len(l) < length:

            i = ord(os.urandom(1))

            if i < len(alphabet):

                l.append(alphabet[i])

        return ''.join(l)

def get_crypt_password(password):

    """

    Cryptographic function used for password hashing based on pybcrypt

    or Python's own OpenSSL wrapper on windows

    :param password: password to hash

    """

    if is_windows:

        return hashlib.sha256(password).hexdigest()

    elif is_unix:

        import bcrypt

        return bcrypt.hashpw(safe_str(password), bcrypt.gensalt(10))

    else:

        raise Exception('Unknown or unsupported platform %s'

                        % __platform__)

def check_password(password, hashed):

    """

    Checks matching password with it's hashed value, runs different

    implementation based on platform it runs on

    :param password: password

    :param hashed: password in hashed form

    """

    if is_windows:

        return hashlib.sha256(password).hexdigest() == hashed

    elif is_unix:

        import bcrypt

        try:

            return bcrypt.checkpw(safe_str(password), safe_str(hashed))

        except ValueError as e:

            # bcrypt will throw ValueError 'Invalid hashed_password salt' on all password errors

            log.error('error from bcrypt checking password: %s', e)

            return False

    else:

        raise Exception('Unknown or unsupported platform %s'

                        % __platform__)

def _cached_perms_data(user_id, user_is_admin, user_inherit_default_permissions,

                       explicit, algo):

    RK = 'repositories'

    GK = 'repositories_groups'

    UK = 'user_groups'

    GLOBAL = 'global'

    PERM_WEIGHTS = Permission.PERM_WEIGHTS

    permissions = {RK: {}, GK: {}, UK: {}, GLOBAL: set()}

    def _choose_perm(new_perm, cur_perm):

        new_perm_val = PERM_WEIGHTS[new_perm]

        cur_perm_val = PERM_WEIGHTS[cur_perm]

        if algo == 'higherwin':

            if new_perm_val > cur_perm_val:

                return new_perm

            return cur_perm

        elif algo == 'lowerwin':

            if new_perm_val < cur_perm_val:

                return new_perm

            return cur_perm

    #======================================================================

    # fetch default permissions

    #======================================================================

    default_user = User.get_by_username('default', cache=True)

    default_user_id = default_user.user_id

    default_repo_perms = Permission.get_default_perms(default_user_id)

    default_repo_groups_perms = Permission.get_default_group_perms(default_user_id)

    default_user_group_perms = Permission.get_default_user_group_perms(default_user_id)

    if user_is_admin:

        #==================================================================

        # admin users have all rights;

        # based on default permissions, just set everything to admin

        #==================================================================

        permissions[GLOBAL].add('hg.admin')