Installation
============

Using the Vendored Argon2
-------------------------

.. code-block:: bash

  python -m pip install argon2-cffi

should be all it takes.

But since ``argon2-cffi`` vendors Argon2's C code by default, it can lead to complications depending on the platform.

The C code is known to compile and work on all common platforms (including x86, ARM, and PPC).
On x86, an SSE2_-optimized version is used.

If something goes wrong, please try to update your ``cffi``, ``pip`` and ``setuptools`` first:

.. code-block:: bash

  python -m pip install -U cffi pip setuptools


Overall this should be the safest bet because ``argon2-cffi`` has been specifically tested against the vendored version.


Wheels
^^^^^^

Binary `wheels <https://pythonwheels.com>`_ for macOS, Windows, and Linux are provided on PyPI_.
With a recent-enough ``pip`` and ``setuptools``, they should be used automatically.


Source Distribution
^^^^^^^^^^^^^^^^^^^

A working C compiler and `CFFI environment`_ are required.
If you've been able to compile Python CFFI extensions before, ``argon2-cffi`` should install without any problems.


Using a System-wide Installation of Argon2
------------------------------------------

If you set ``ARGON2_CFFI_USE_SYSTEM`` to ``1`` (and *only* ``1``), ``argon2-cffi`` will not build its bindings.
However binary wheels are preferred by ``pip`` and Argon2 gets installed along with ``argon2-cffi`` anyway.

Therefore you also have to instruct ``pip`` to use a source distribution:

.. code-block:: bash

  env ARGON2_CFFI_USE_SYSTEM=1 \
    python -m pip install --no-binary=argon2-cffi argon2-cffi

This approach can lead to problems around your build chain and you can run into incompatibilities between Argon2 and ``argon2-cffi`` if the latter has been tested against a different version.

**It is your own responsibility to deal with these risks if you choose this path.**

Available since version 18.1.0.


Override Automatic SSE2 Detection
---------------------------------

Usually the build process tries to guess whether or not it should use SSE2_-optimized code.
This can go wrong and is problematic for cross-compiling.

Therefore you can use the ``ARGON2_CFFI_USE_SSE2`` environment variable to control the process:

- If you set it to ``1``, ``argon2-cffi`` will build **with** SSE2 support.
- If you set it to ``0``, ``argon2-cffi`` will build **without** SSE2 support.
- If you set it to anything else, it will be ignored and ``argon2-cffi`` will try to guess.

Available since version 20.1.0.


.. _SSE2: https://en.wikipedia.org/wiki/SSE2
.. _PyPI: https://pypi.org/project/argon2-cffi/
.. _CFFI environment: https://cffi.readthedocs.io/en/latest/installation.html