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Goals
-----
The interface is based on `LuaJIT's FFI`_, and follows a few principles:
* The goal is to call C code from Python without learning a 3rd language:
existing alternatives require users to learn domain specific language
(Cython_, SWIG_) or API (ctypes_). The CFFI design requires users to know
only C and Python, minimizing the extra bits of API that need to be learned.
* Keep all the Python-related logic in Python so that you don't need to
write much C code (unlike `CPython native C extensions`_).
* The preferred way is to work at the level of the API (Application
Programming Interface): the C compiler is called from the declarations
you write to validate and link to the C language constructs.
Alternatively, it is also possible to work at the ABI level
(Application Binary Interface), the way ctypes_ work.
However, on non-Windows platforms, C libraries typically
have a specified C API but not an ABI (e.g. they may
document a "struct" as having at least these fields, but maybe more).
* Try to be complete. For now some C99 constructs are not supported,
but all C89 should be, including macros (and including macro "abuses",
which you can `manually wrap`_ in saner-looking C functions).
* Attempt to support both PyPy and CPython, with a reasonable path
for other Python implementations like IronPython and Jython.
* Note that this project is **not** about embedding executable C code in
Python, unlike `Weave`_. This is about calling existing C libraries
from Python.
* There is no C++ support. Sometimes, it is reasonable to write a C
wrapper around the C++ code and then call this C API with CFFI.
Otherwise, look at other projects. I would recommend cppyy_, which
has got some similarities (and also works efficiently on both CPython
and PyPy).
.. _`LuaJIT's FFI`: http://luajit.org/ext_ffi.html
.. _`Cython`: http://www.cython.org
.. _`SWIG`: http://www.swig.org/
.. _`CPython native C extensions`: http://docs.python.org/extending/extending.html
.. _`native C extensions`: http://docs.python.org/extending/extending.html
.. _`ctypes`: http://docs.python.org/library/ctypes.html
.. _`Weave`: http://wiki.scipy.org/Weave
.. _`cppyy`: http://cppyy.readthedocs.io/en/latest/
.. _`manually wrap`: overview.html#abi-versus-api
Get started by reading `the overview`__.
.. __: overview.html
Comments and bugs
-----------------
The best way to contact us is on the IRC ``#pypy`` channel of
``irc.freenode.net``. Feel free to discuss matters either there or in
the `mailing list`_. Please report to the `issue tracker`_ any bugs.
As a general rule, when there is a design issue to resolve, we pick the
solution that is the "most C-like". We hope that this module has got
everything you need to access C code and nothing more.
--- the authors, Armin Rigo and Maciej Fijalkowski
.. _`issue tracker`: https://bitbucket.org/cffi/cffi/issues
.. _`mailing list`: https://groups.google.com/forum/#!forum/python-cffi
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