.. _codec-registry:

Codec registry and support functions
====================================

.. c:function:: int PyCodec_Register(PyObject *search_function)

   Register a new codec search function.

   As a side effect, this tries to load the :mod:`!encodings` package, if not yet
   done, to make sure that it is always first in the list of search functions.

.. c:function:: int PyCodec_Unregister(PyObject *search_function)

   Unregister a codec search function and clear the registry's cache.
   If the search function is not registered, do nothing.
   Return 0 on success. Raise an exception and return -1 on error.

   .. versionadded:: 3.10

.. c:function:: int PyCodec_KnownEncoding(const char *encoding)

   Return ``1`` or ``0`` depending on whether there is a registered codec for
   the given *encoding*.  This function always succeeds.

.. c:function:: PyObject* PyCodec_Encode(PyObject *object, const char *encoding, const char *errors)

   Generic codec based encoding API.

   *object* is passed through the encoder function found for the given
   *encoding* using the error handling method defined by *errors*.  *errors* may
   be ``NULL`` to use the default method defined for the codec.  Raises a
   :exc:`LookupError` if no encoder can be found.

.. c:function:: PyObject* PyCodec_Decode(PyObject *object, const char *encoding, const char *errors)

   Generic codec based decoding API.

   *object* is passed through the decoder function found for the given
   *encoding* using the error handling method defined by *errors*.  *errors* may
   be ``NULL`` to use the default method defined for the codec.  Raises a
   :exc:`LookupError` if no decoder can be found.


Codec lookup API
----------------

In the following functions, the *encoding* string is looked up converted to all
lower-case characters, which makes encodings looked up through this mechanism
effectively case-insensitive.  If no codec is found, a :exc:`KeyError` is set
and ``NULL`` returned.

.. c:function:: PyObject* PyCodec_Encoder(const char *encoding)

   Get an encoder function for the given *encoding*.

.. c:function:: PyObject* PyCodec_Decoder(const char *encoding)

   Get a decoder function for the given *encoding*.

.. c:function:: PyObject* PyCodec_IncrementalEncoder(const char *encoding, const char *errors)

   Get an :class:`~codecs.IncrementalEncoder` object for the given *encoding*.

.. c:function:: PyObject* PyCodec_IncrementalDecoder(const char *encoding, const char *errors)

   Get an :class:`~codecs.IncrementalDecoder` object for the given *encoding*.

.. c:function:: PyObject* PyCodec_StreamReader(const char *encoding, PyObject *stream, const char *errors)

   Get a :class:`~codecs.StreamReader` factory function for the given *encoding*.

.. c:function:: PyObject* PyCodec_StreamWriter(const char *encoding, PyObject *stream, const char *errors)

   Get a :class:`~codecs.StreamWriter` factory function for the given *encoding*.


Registry API for Unicode encoding error handlers
------------------------------------------------

.. c:function:: int PyCodec_RegisterError(const char *name, PyObject *error)

   Register the error handling callback function *error* under the given *name*.
   This callback function will be called by a codec when it encounters
   unencodable characters/undecodable bytes and *name* is specified as the error
   parameter in the call to the encode/decode function.

   The callback gets a single argument, an instance of
   :exc:`UnicodeEncodeError`, :exc:`UnicodeDecodeError` or
   :exc:`UnicodeTranslateError` that holds information about the problematic
   sequence of characters or bytes and their offset in the original string (see
   :ref:`unicodeexceptions` for functions to extract this information).  The
   callback must either raise the given exception, or return a two-item tuple
   containing the replacement for the problematic sequence, and an integer
   giving the offset in the original string at which encoding/decoding should be
   resumed.

   Return ``0`` on success, ``-1`` on error.

.. c:function:: PyObject* PyCodec_LookupError(const char *name)

   Lookup the error handling callback function registered under *name*.  As a
   special case ``NULL`` can be passed, in which case the error handling callback
   for "strict" will be returned.

.. c:function:: PyObject* PyCodec_StrictErrors(PyObject *exc)

   Raise *exc* as an exception.

.. c:function:: PyObject* PyCodec_IgnoreErrors(PyObject *exc)

   Ignore the unicode error, skipping the faulty input.

.. c:function:: PyObject* PyCodec_ReplaceErrors(PyObject *exc)

   Replace the unicode encode error with ``?`` or ``U+FFFD``.

.. c:function:: PyObject* PyCodec_XMLCharRefReplaceErrors(PyObject *exc)

   Replace the unicode encode error with XML character references.

.. c:function:: PyObject* PyCodec_BackslashReplaceErrors(PyObject *exc)

   Replace the unicode encode error with backslash escapes (``\x``, ``\u`` and
   ``\U``).

.. c:function:: PyObject* PyCodec_NameReplaceErrors(PyObject *exc)

   Replace the unicode encode error with ``\N{...}`` escapes.

   .. versionadded:: 3.5


Codec utility variables
-----------------------

.. c:var:: const char *Py_hexdigits

   A string constant containing the lowercase hexadecimal digits: ``"0123456789abcdef"``.

   .. versionadded:: 3.3