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# Source code for astropy.nddata.bitmask

    """
    A module that provides functions for manipulating bit masks and data quality
    (DQ) arrays.

    """

    import numbers
    import warnings

    import numpy as np

    __all__ = [
        "BitFlagNameMap",
        "InvalidBitFlag",
        "bitfield_to_boolean_mask",
        "extend_bit_flag_map",
        "interpret_bit_flags",
    ]

    _ENABLE_BITFLAG_CACHING = True
    _SUPPORTED_FLAGS = int(np.bitwise_not(0, dtype="uint64", casting="unsafe"))

    def _is_bit_flag(n):
        """
        Verifies if the input number is a bit flag (i.e., an integer number that is
        an integer power of 2).

        Parameters
        ----------
        n : int
            A positive integer number. Non-positive integers are considered not to
            be "flags".

        Returns
        -------
        bool
            ``True`` if input ``n`` is a bit flag and ``False`` if it is not.

        """
        if n < 1:
            return False

        return n.bit_count() == 1

    def _is_int(n):
        return (isinstance(n, numbers.Integral) and not isinstance(n, bool)) or (
            isinstance(n, np.generic) and np.issubdtype(n, np.integer)
        )

    class InvalidBitFlag(ValueError):
        """Indicates that a value is not an integer that is a power of 2."""

    class BitFlag(int):
        """Bit flags: integer values that are powers of 2."""

        def __new__(cls, val, doc=None):
            if isinstance(val, tuple):
                if doc is not None:
                    raise ValueError("Flag's doc string cannot be provided twice.")
                val, doc = val

            if not (_is_int(val) and _is_bit_flag(val)):
                raise InvalidBitFlag(
                    f"Value '{val}' is not a valid bit flag: bit flag value must be "
                    "an integral power of two."
                )

            s = int.__new__(cls, val)
            if doc is not None:
                s.__doc__ = doc
            return s

    class BitFlagNameMeta(type):
        def __new__(cls, name, bases, members):
            for k, v in members.items():
                if not k.startswith("_"):
                    v = BitFlag(v)

            attr = [k for k in members.keys() if not k.startswith("_")]
            attrl = list(map(str.lower, attr))

            if _ENABLE_BITFLAG_CACHING:
                cache = {}

            for b in bases:
                for k, v in b.__dict__.items():
                    if k.startswith("_"):
                        continue
                    kl = k.lower()
                    if kl in attrl:
                        idx = attrl.index(kl)
                        raise AttributeError(
                            f"Bit flag '{attr[idx]:s}' was already defined."
                        )
                    if _ENABLE_BITFLAG_CACHING:
                        cache[kl] = v

            members = {
                k: v if k.startswith("_") else BitFlag(v) for k, v in members.items()
            }

            if _ENABLE_BITFLAG_CACHING:
                cache.update(
                    {k.lower(): v for k, v in members.items() if not k.startswith("_")}
                )
                members = {"_locked": True, "__version__": "", **members, "_cache": cache}
            else:
                members = {"_locked": True, "__version__": "", **members}

            return super().__new__(cls, name, bases, members)

        def __setattr__(cls, name, val):
            if name == "_locked":
                return super().__setattr__(name, True)

            else:
                if name == "__version__":
                    if cls._locked:
                        raise AttributeError("Version cannot be modified.")
                    return super().__setattr__(name, val)

                err_msg = f"Bit flags are read-only. Unable to reassign attribute {name}"
                if cls._locked:
                    raise AttributeError(err_msg)

            namel = name.lower()
            if _ENABLE_BITFLAG_CACHING:
                if not namel.startswith("_") and namel in cls._cache:
                    raise AttributeError(err_msg)

            else:
                for b in cls.__bases__:
                    if not namel.startswith("_") and namel in list(
                        map(str.lower, b.__dict__)
                    ):
                        raise AttributeError(err_msg)
                if namel in list(map(str.lower, cls.__dict__)):
                    raise AttributeError(err_msg)

            val = BitFlag(val)

            if _ENABLE_BITFLAG_CACHING and not namel.startswith("_"):
                cls._cache[namel] = val

            return super().__setattr__(name, val)

        def __getattr__(cls, name):
            if _ENABLE_BITFLAG_CACHING:
                flagnames = cls._cache
            else:
                flagnames = {k.lower(): v for k, v in cls.__dict__.items()}
                flagnames.update(
                    {k.lower(): v for b in cls.__bases__ for k, v in b.__dict__.items()}
                )
            try:
                return flagnames[name.lower()]
            except KeyError:
                raise AttributeError(f"Flag '{name}' not defined")

        def __getitem__(cls, key):
            return cls.__getattr__(key)

        def __add__(cls, items):
            if not isinstance(items, dict):
                if not isinstance(items[0], (tuple, list)):
                    items = [items]
                items = dict(items)

            return extend_bit_flag_map(
                cls.__name__ + "_" + "_".join(list(items)), cls, **items
            )

        def __iadd__(cls, other):
            raise NotImplementedError(
                "Unary '+' is not supported. Use binary operator instead."
            )

        def __delattr__(cls, name):
            raise AttributeError(
                f"{cls.__name__}: cannot delete {cls.mro()[-2].__name__} member."
            )

        def __delitem__(cls, name):
            raise AttributeError(
                f"{cls.__name__}: cannot delete {cls.mro()[-2].__name__} member."
            )

        def __repr__(cls):
            return f"<{cls.mro()[-2].__name__} '{cls.__name__}'>"

    class BitFlagNameMap(metaclass=BitFlagNameMeta):
        """
        A base class for bit flag name maps used to describe data quality (DQ)
        flags of images by provinding a mapping from a mnemonic flag name to a flag
        value.

        Mapping for a specific instrument should subclass this class.
        Subclasses should define flags as class attributes with integer values
        that are powers of 2. Each bit flag may also contain a string
        comment following the flag value.

        Examples
        --------
            >>> from astropy.nddata.bitmask import BitFlagNameMap
            >>> class ST_DQ(BitFlagNameMap):
            ...     __version__ = '1.0.0'  # optional
            ...     CR = 1, 'Cosmic Ray'
            ...     CLOUDY = 4  # no docstring comment
            ...     RAINY = 8, 'Dome closed'
            ...
            >>> class ST_CAM1_DQ(ST_DQ):
            ...     HOT = 16
            ...     DEAD = 32

        """

    def extend_bit_flag_map(cls_name, base_cls=BitFlagNameMap, **kwargs):
        """
        A convenience function for creating bit flags maps by subclassing an
        existing map and adding additional flags supplied as keyword arguments.

        Parameters
        ----------
        cls_name : str
            Class name of the bit flag map to be created.

        base_cls : BitFlagNameMap, optional
            Base class for the new bit flag map.

        **kwargs : int
            Each supplied keyword argument will be used to define bit flag
            names in the new map. In addition to bit flag names, ``__version__`` is
            allowed to indicate the version of the newly created map.

        Examples
        --------
            >>> from astropy.nddata.bitmask import extend_bit_flag_map
            >>> ST_DQ = extend_bit_flag_map('ST_DQ', __version__='1.0.0', CR=1, CLOUDY=4, RAINY=8)
            >>> ST_CAM1_DQ = extend_bit_flag_map('ST_CAM1_DQ', ST_DQ, HOT=16, DEAD=32)
            >>> ST_CAM1_DQ['HOT']  # <-- Access flags as dictionary keys
            16
            >>> ST_CAM1_DQ.HOT  # <-- Access flags as class attributes
            16

        """
        new_cls = BitFlagNameMeta.__new__(
            BitFlagNameMeta, cls_name, (base_cls,), {"_locked": False}
        )
        for k, v in kwargs.items():
            try:
                setattr(new_cls, k, v)
            except AttributeError as e:
                if new_cls[k] != int(v):
                    raise e

        new_cls._locked = True
        return new_cls

    def interpret_bit_flags(bit_flags, flip_bits=None, flag_name_map=None):
        """
        Converts input bit flags to a single integer value (bit mask) or `None`.

        When input is a list of flags (either a Python list of integer flags or a
        string of comma-, ``'|'``-, or ``'+'``-separated list of flags),
        the returned bit mask is obtained by summing input flags.

        .. note::
            In order to flip the bits of the returned bit mask,
            for input of `str` type, prepend '~' to the input string. '~' must
            be prepended to the *entire string* and not to each bit flag! For
            input that is already a bit mask or a Python list of bit flags, set
            ``flip_bits`` for `True` in order to flip the bits of the returned
            bit mask.

        Parameters
        ----------
        bit_flags : int, str, list, None
            An integer bit mask or flag, `None`, a string of comma-, ``'|'``- or
            ``'+'``-separated list of integer bit flags or mnemonic flag names,
            or a Python list of integer bit flags. If ``bit_flags`` is a `str`
            and if it is prepended with '~', then the output bit mask will have
            its bits flipped (compared to simple sum of input flags).
            For input ``bit_flags`` that is already a bit mask or a Python list
            of bit flags, bit-flipping can be controlled through ``flip_bits``
            parameter.

            .. note::
                When ``bit_flags`` is a list of flag names, the ``flag_name_map``
                parameter must be provided.

            .. note::
                Only one flag separator is supported at a time. ``bit_flags``
                string should not mix ``','``, ``'+'``, and ``'|'`` separators.

        flip_bits : bool, None
            Indicates whether or not to flip the bits of the returned bit mask
            obtained from input bit flags. This parameter must be set to `None`
            when input ``bit_flags`` is either `None` or a Python list of flags.

        flag_name_map : BitFlagNameMap
             A `BitFlagNameMap` object that provides mapping from mnemonic
             bit flag names to integer bit values in order to translate mnemonic
             flags to numeric values when ``bit_flags`` that are comma- or
             '+'-separated list of menmonic bit flag names.

        Returns
        -------
        bitmask : int or None
            Returns an integer bit mask formed from the input bit value or `None`
            if input ``bit_flags`` parameter is `None` or an empty string.
            If input string value was prepended with '~' (or ``flip_bits`` was set
            to `True`), then returned value will have its bits flipped
            (inverse mask).

        Examples
        --------
            >>> from astropy.nddata.bitmask import interpret_bit_flags, extend_bit_flag_map
            >>> ST_DQ = extend_bit_flag_map('ST_DQ', CR=1, CLOUDY=4, RAINY=8, HOT=16, DEAD=32)
            >>> "{0:016b}".format(0xFFFF & interpret_bit_flags(28))
            '0000000000011100'
            >>> "{0:016b}".format(0xFFFF & interpret_bit_flags('4,8,16'))
            '0000000000011100'
            >>> "{0:016b}".format(0xFFFF & interpret_bit_flags('CLOUDY,RAINY,HOT', flag_name_map=ST_DQ))
            '0000000000011100'
            >>> "{0:016b}".format(0xFFFF & interpret_bit_flags('~4,8,16'))
            '1111111111100011'
            >>> "{0:016b}".format(0xFFFF & interpret_bit_flags('~(4+8+16)'))
            '1111111111100011'
            >>> "{0:016b}".format(0xFFFF & interpret_bit_flags('~(CLOUDY+RAINY+HOT)',
            ... flag_name_map=ST_DQ))
            '1111111111100011'
            >>> "{0:016b}".format(0xFFFF & interpret_bit_flags([4, 8, 16]))
            '0000000000011100'
            >>> "{0:016b}".format(0xFFFF & interpret_bit_flags([4, 8, 16], flip_bits=True))
            '1111111111100011'

        """
        has_flip_bits = flip_bits is not None
        flip_bits = bool(flip_bits)
        allow_non_flags = False

        if _is_int(bit_flags):
            return ~int(bit_flags) if flip_bits else int(bit_flags)

        elif bit_flags is None:
            if has_flip_bits:
                raise TypeError(
                    "Keyword argument 'flip_bits' must be set to 'None' when "
                    "input 'bit_flags' is None."
                )
            return None

        elif isinstance(bit_flags, str):
            if has_flip_bits:
                raise TypeError(
                    "Keyword argument 'flip_bits' is not permitted for "
                    "comma-separated string lists of bit flags. Prepend '~' to "
                    "the string to indicate bit-flipping."
                )

            bit_flags = str(bit_flags).strip()

            if bit_flags.upper() in ["", "NONE", "INDEF"]:
                return None

            # check whether bitwise-NOT is present and if it is, check that it is
            # in the first position:
            bitflip_pos = bit_flags.find("~")
            if bitflip_pos == 0:
                flip_bits = True
                bit_flags = bit_flags[1:].lstrip()
            else:
                if bitflip_pos > 0:
                    raise ValueError("Bitwise-NOT must precede bit flag list.")
                flip_bits = False

            # basic check for correct use of parenthesis:
            while True:
                nlpar = bit_flags.count("(")
                nrpar = bit_flags.count(")")

                if nlpar == 0 and nrpar == 0:
                    break

                if nlpar != nrpar:
                    raise ValueError("Unbalanced parentheses in bit flag list.")

                lpar_pos = bit_flags.find("(")
                rpar_pos = bit_flags.rfind(")")
                if lpar_pos > 0 or rpar_pos < (len(bit_flags) - 1):
                    raise ValueError(
                        "Incorrect syntax (incorrect use of parenthesis) in bit flag list."
                    )

                bit_flags = bit_flags[1:-1].strip()

            if sum(k in bit_flags for k in "+,|") > 1:
                raise ValueError(
                    "Only one type of bit flag separator may be used in one "
                    "expression. Allowed separators are: '+', '|', or ','."
                )

            if "," in bit_flags:
                bit_flags = bit_flags.split(",")

            elif "+" in bit_flags:
                bit_flags = bit_flags.split("+")

            elif "|" in bit_flags:
                bit_flags = bit_flags.split("|")

            else:
                if bit_flags == "":
                    raise ValueError(
                        "Empty bit flag lists not allowed when either bitwise-NOT "
                        "or parenthesis are present."
                    )
                bit_flags = [bit_flags]

            if flag_name_map is not None:
                try:
                    int(bit_flags[0])
                except ValueError:
                    bit_flags = [flag_name_map[f] for f in bit_flags]

            allow_non_flags = len(bit_flags) == 1

        elif hasattr(bit_flags, "__iter__"):
            if not all(_is_int(flag) for flag in bit_flags):
                if flag_name_map is not None and all(
                    isinstance(flag, str) for flag in bit_flags
                ):
                    bit_flags = [flag_name_map[f] for f in bit_flags]
                else:
                    raise TypeError(
                        "Every bit flag in a list must be either an "
                        "integer flag value or a 'str' flag name."
                    )

        else:
            raise TypeError("Unsupported type for argument 'bit_flags'.")

        bitset = set(map(int, bit_flags))
        if len(bitset) != len(bit_flags):
            warnings.warn("Duplicate bit flags will be ignored")

        bitmask = 0
        for v in bitset:
            if not _is_bit_flag(v) and not allow_non_flags:
                raise ValueError(
                    f"Input list contains invalid (not powers of two) bit flag: {v}"
                )
            bitmask += v

        if flip_bits:
            bitmask = ~bitmask

        return bitmask

    def bitfield_to_boolean_mask(
        bitfield,
        ignore_flags=0,
        flip_bits=None,
        good_mask_value=False,
        dtype=np.bool_,
        flag_name_map=None,
    ):
        """
        bitfield_to_boolean_mask(bitfield, ignore_flags=None, flip_bits=None, \
    good_mask_value=False, dtype=numpy.bool_)
        Converts an array of bit fields to a boolean (or integer) mask array
        according to a bit mask constructed from the supplied bit flags (see
        ``ignore_flags`` parameter).

        This function is particularly useful to convert data quality arrays to
        boolean masks with selective filtering of DQ flags.

        Parameters
        ----------
        bitfield : ndarray
            An array of bit flags. By default, values different from zero are
            interpreted as "bad" values and values equal to zero are considered
            as "good" values. However, see ``ignore_flags`` parameter on how to
            selectively ignore some bits in the ``bitfield`` array data.

        ignore_flags : int, str, list, None (default = 0)
            An integer bit mask, `None`, a Python list of bit flags, a comma-,
            or ``'|'``-separated, ``'+'``-separated string list of integer
            bit flags or mnemonic flag names that indicate what bits in the input
            ``bitfield`` should be *ignored* (i.e., zeroed), or `None`.

            .. note::
                When ``bit_flags`` is a list of flag names, the ``flag_name_map``
                parameter must be provided.

            | Setting ``ignore_flags`` to `None` effectively will make
              `bitfield_to_boolean_mask` interpret all ``bitfield`` elements
              as "good" regardless of their value.

            | When ``ignore_flags`` argument is an integer bit mask, it will be
              combined using bitwise-NOT and bitwise-AND with each element of the
              input ``bitfield`` array (``~ignore_flags & bitfield``). If the
              resultant bitfield element is non-zero, that element will be
              interpreted as a "bad" in the output boolean mask and it will be
              interpreted as "good" otherwise. ``flip_bits`` parameter may be used
              to flip the bits (``bitwise-NOT``) of the bit mask thus effectively
              changing the meaning of the ``ignore_flags`` parameter from "ignore"
              to "use only" these flags.

            .. note::

                Setting ``ignore_flags`` to 0 effectively will assume that all
                non-zero elements in the input ``bitfield`` array are to be
                interpreted as "bad".

            | When ``ignore_flags`` argument is a Python list of integer bit
              flags, these flags are added together to create an integer bit mask.
              Each item in the list must be a flag, i.e., an integer that is an
              integer power of 2. In order to flip the bits of the resultant
              bit mask, use ``flip_bits`` parameter.

            | Alternatively, ``ignore_flags`` may be a string of comma- or
              ``'+'``(or ``'|'``)-separated list of integer bit flags that should
              be added (bitwise OR) together to create an integer bit mask.
              For example, both ``'4,8'``, ``'4|8'``, and ``'4+8'`` are equivalent
              and indicate that bit flags 4 and 8 in the input ``bitfield``
              array should be ignored when generating boolean mask.

            .. note::

                ``'None'``, ``'INDEF'``, and empty (or all white space) strings
                are special values of string ``ignore_flags`` that are
                interpreted as `None`.

            .. note::

                Each item in the list must be a flag, i.e., an integer that is an
                integer power of 2. In addition, for convenience, an arbitrary
                **single** integer is allowed and it will be interpreted as an
                integer bit mask. For example, instead of ``'4,8'`` one could
                simply provide string ``'12'``.

            .. note::
                Only one flag separator is supported at a time. ``ignore_flags``
                string should not mix ``','``, ``'+'``, and ``'|'`` separators.

            .. note::

                When ``ignore_flags`` is a `str` and when it is prepended with
                '~', then the meaning of ``ignore_flags`` parameters will be
                reversed: now it will be interpreted as a list of bit flags to be
                *used* (or *not ignored*) when deciding which elements of the
                input ``bitfield`` array are "bad". Following this convention,
                an ``ignore_flags`` string value of ``'~0'`` would be equivalent
                to setting ``ignore_flags=None``.

            .. warning::

                Because prepending '~' to a string ``ignore_flags`` is equivalent
                to setting ``flip_bits`` to `True`, ``flip_bits`` cannot be used
                with string ``ignore_flags`` and it must be set to `None`.

        flip_bits : bool, None (default = None)
            Specifies whether or not to invert the bits of the bit mask either
            supplied directly through ``ignore_flags`` parameter or built from the
            bit flags passed through ``ignore_flags`` (only when bit flags are
            passed as Python lists of integer bit flags). Occasionally, it may be
            useful to *consider only specific bit flags* in the ``bitfield``
            array when creating a boolean mask as opposed to *ignoring* specific
            bit flags as ``ignore_flags`` behaves by default. This can be achieved
            by inverting/flipping the bits of the bit mask created from
            ``ignore_flags`` flags which effectively changes the meaning of the
            ``ignore_flags`` parameter from "ignore" to "use only" these flags.
            Setting ``flip_bits`` to `None` means that no bit flipping will be
            performed. Bit flipping for string lists of bit flags must be
            specified by prepending '~' to string bit flag lists
            (see documentation for ``ignore_flags`` for more details).

            .. warning::
                This parameter can be set to either `True` or `False` **ONLY** when
                ``ignore_flags`` is either an integer bit mask or a Python
                list of integer bit flags. When ``ignore_flags`` is either
                `None` or a string list of flags, ``flip_bits`` **MUST** be set
                to `None`.

        good_mask_value : int, bool (default = False)
            This parameter is used to derive the values that will be assigned to
            the elements in the output boolean mask array that correspond to the
            "good" bit fields (that are 0 after zeroing bits specified by
            ``ignore_flags``) in the input ``bitfield`` array. When
            ``good_mask_value`` is non-zero or ``numpy.True_`` then values in the
            output boolean mask array corresponding to "good" bit fields in
            ``bitfield`` will be ``numpy.True_`` (if ``dtype`` is ``numpy.bool_``)
            or 1 (if ``dtype`` is of numerical type) and values of corresponding
            to "bad" flags will be ``numpy.False_`` (or 0). When
            ``good_mask_value`` is zero or ``numpy.False_`` then the values
            in the output boolean mask array corresponding to "good" bit fields
            in ``bitfield`` will be ``numpy.False_`` (if ``dtype`` is
            ``numpy.bool_``) or 0 (if ``dtype`` is of numerical type) and values
            of corresponding to "bad" flags will be ``numpy.True_`` (or 1).

        dtype : data-type (default = ``numpy.bool_``)
            The desired data-type for the output binary mask array.

        flag_name_map : BitFlagNameMap
             A `BitFlagNameMap` object that provides mapping from mnemonic
             bit flag names to integer bit values in order to translate mnemonic
             flags to numeric values when ``bit_flags`` that are comma- or
             '+'-separated list of menmonic bit flag names.

        Returns
        -------
        mask : ndarray
            Returns an array of the same dimensionality as the input ``bitfield``
            array whose elements can have two possible values,
            e.g., ``numpy.True_`` or ``numpy.False_`` (or 1 or 0 for integer
            ``dtype``) according to values of to the input ``bitfield`` elements,
            ``ignore_flags`` parameter, and the ``good_mask_value`` parameter.

        Examples
        --------
            >>> from astropy.nddata import bitmask
            >>> import numpy as np
            >>> dqarr = np.asarray([[0, 0, 1, 2, 0, 8, 12, 0],
            ...                     [10, 4, 0, 0, 0, 16, 6, 0]])
            >>> flag_map = bitmask.extend_bit_flag_map(
            ...     'ST_DQ', CR=2, CLOUDY=4, RAINY=8, HOT=16, DEAD=32
            ... )
            >>> bitmask.bitfield_to_boolean_mask(dqarr, ignore_flags=0,
            ...                                  dtype=int)
            array([[0, 0, 1, 1, 0, 1, 1, 0],
                   [1, 1, 0, 0, 0, 1, 1, 0]])
            >>> bitmask.bitfield_to_boolean_mask(dqarr, ignore_flags=0,
            ...                                  dtype=bool)
            array([[False, False,  True,  True, False,  True,  True, False],
                   [ True,  True, False, False, False,  True,  True, False]]...)
            >>> bitmask.bitfield_to_boolean_mask(dqarr, ignore_flags=6,
            ...                                  good_mask_value=0, dtype=int)
            array([[0, 0, 1, 0, 0, 1, 1, 0],
                   [1, 0, 0, 0, 0, 1, 0, 0]])
            >>> bitmask.bitfield_to_boolean_mask(dqarr, ignore_flags=~6,
            ...                                  good_mask_value=0, dtype=int)
            array([[0, 0, 0, 1, 0, 0, 1, 0],
                   [1, 1, 0, 0, 0, 0, 1, 0]])
            >>> bitmask.bitfield_to_boolean_mask(dqarr, ignore_flags=6, dtype=int,
            ...                                  flip_bits=True, good_mask_value=0)
            array([[0, 0, 0, 1, 0, 0, 1, 0],
                   [1, 1, 0, 0, 0, 0, 1, 0]])
            >>> bitmask.bitfield_to_boolean_mask(dqarr, ignore_flags='~(2+4)',
            ...                                  good_mask_value=0, dtype=int)
            array([[0, 0, 0, 1, 0, 0, 1, 0],
                   [1, 1, 0, 0, 0, 0, 1, 0]])
            >>> bitmask.bitfield_to_boolean_mask(dqarr, ignore_flags=[2, 4],
            ...                                  flip_bits=True, good_mask_value=0,
            ...                                  dtype=int)
            array([[0, 0, 0, 1, 0, 0, 1, 0],
                   [1, 1, 0, 0, 0, 0, 1, 0]])
            >>> bitmask.bitfield_to_boolean_mask(dqarr, ignore_flags='~(CR,CLOUDY)',
            ...                                  good_mask_value=0, dtype=int,
            ...                                  flag_name_map=flag_map)
            array([[0, 0, 0, 1, 0, 0, 1, 0],
                   [1, 1, 0, 0, 0, 0, 1, 0]])
            >>> bitmask.bitfield_to_boolean_mask(dqarr, ignore_flags='~(CR+CLOUDY)',
            ...                                  good_mask_value=0, dtype=int,
            ...                                  flag_name_map=flag_map)
            array([[0, 0, 0, 1, 0, 0, 1, 0],
                   [1, 1, 0, 0, 0, 0, 1, 0]])

        """
        bitfield = np.asarray(bitfield)
        if not np.issubdtype(bitfield.dtype, np.integer):
            raise TypeError("Input bitfield array must be of integer type.")

        ignore_mask = interpret_bit_flags(
            ignore_flags, flip_bits=flip_bits, flag_name_map=flag_name_map
        )

        if ignore_mask is None:
            if good_mask_value:
                mask = np.ones_like(bitfield, dtype=dtype)
            else:
                mask = np.zeros_like(bitfield, dtype=dtype)
            return mask

        # filter out bits beyond the maximum supported by the data type:
        ignore_mask = ignore_mask & _SUPPORTED_FLAGS

        # invert the "ignore" mask:
        ignore_mask = np.bitwise_not(
            ignore_mask, dtype=bitfield.dtype.type, casting="unsafe"
        )

        mask = np.empty_like(bitfield, dtype=np.bool_)
        np.bitwise_and(bitfield, ignore_mask, out=mask, casting="unsafe")

        if good_mask_value:
            np.logical_not(mask, out=mask)

        return mask.astype(dtype=dtype, subok=False, copy=False)