Call a C API from Python becomes more enjoyable with CFFI
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The document discusses integrating C libraries with Python using the C Foreign Function Interface (CFFI), highlighting its advantages over traditional methods for accessing low-level APIs like OpenGL and Vulkan. It covers practical examples of using CFFI to create wrappers around C functions, manage data structures, and compile C code from Python. The document also provides insights into using templates for generating C extensions and integrating with build systems.
![CTYPES
from ctypes import cdll, Structure, c_int, c_double
lib = cdll.LoadLibrary('./vector.so')
# ctypes Point structure
class Point(Structure):
_fields_ = [('x', c_int), ('y', c_int)]
# Initialize Point[2] argument
points_array = (Point * 2)((1, 2), (3, 4))
# Get vector_size from library
vector_size_fn = lib.vector_size
vector_size_fn.restype = c_double
# Call vector_size with ctypes
size = vector_size_fn(points_array)
print('out = {}'.format(size))](https://image.slidesharecdn.com/outcffi-170719145750/85/Call-a-C-API-from-Python-becomes-more-enjoyable-with-CFFI-16-320.jpg)
![ABI / IN-LINE
from cffi import FFI
ffi = FFI()
ffi.cdef("int printf(const char *format, ...);")
C = ffi.dlopen(None)
arg = ffi.new("char[]", "world")
C.printf("hello %sn", arg)](https://image.slidesharecdn.com/outcffi-170719145750/85/Call-a-C-API-from-Python-becomes-more-enjoyable-with-CFFI-18-320.jpg)
![OBJECTS
CFFI EXTENSION
def _new(ctype, **kwargs):
_type = ffi.typeof(ctype)
ptrs = {}
for k, v in kwargs.items():
# convert tuple pair to dict
ktype = dict(_type.fields)[k].type
if ktype.kind == 'pointer':
ptrs[k] = _cast_ptr(v, ktype)
init = dict(kwargs, **{k: v for k, (v, _) in ptrs.items()})
return ffi.new(_type.cname + '*', init)[0]](https://image.slidesharecdn.com/outcffi-170719145750/85/Call-a-C-API-from-Python-becomes-more-enjoyable-with-CFFI-34-320.jpg)
![BUILDING
ffi = FFI()
with open('shaderc.h') as f:
source = f.read()
ffi.set_source('_pyshaderc', source, libraries=['shaderc_combined'])
if __name__ == '__main__':
ffi.compile()](https://image.slidesharecdn.com/outcffi-170719145750/85/Call-a-C-API-from-Python-becomes-more-enjoyable-with-CFFI-39-320.jpg)
![SETUPTOOLS
INTEGRATION
setup(
...
cffi_modules=["_cffi_build/pyshaderc_build.py:ffi"]
)](https://image.slidesharecdn.com/outcffi-170719145750/85/Call-a-C-API-from-Python-becomes-more-enjoyable-with-CFFI-44-320.jpg)
Call a C API from Python becomes more enjoyable with CFFI
- 10. WHY ABI ?
- 11. CYTHON
- 14. CYTHON ABI / API
- 22. REBUILD
- 26. HOW IT WORKS ?
- 27. JINJA2 TEMPLATE
- 32. OBJECTS
- 35. FAST API MODE
- 36. SHADERC WRAPPER
- 40. USE
- 45. DEMO TIME !