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ctypeslib2 - FFI toolkit, relies on clang

Project description

# ctypeslib with libclang

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[Quick usage guide](docs/ctypeslib_2.0_Introduction.ipynb) in the docs/ folder.

## Status update

  • 2021-02:
    • Thanks for the pull requests
    • Note: libclang-xx-dev must be installed for stddef and other reasons.
    • bump to libclang-11
  • 2018-01-03: master branch works with libclang-5.0 HEAD, python clang from pypi, python3
  • 2017-05-01: master branch works with libclang-4.0 HEAD

## Installation

On Ubuntu, libclang libraries are installed with versions. This library tries to load a few different versions to help you out. (__init__.py) But if you encounter a version compatibility issue, you might have to fix the problem using one of the following solutions:

  1. Install libclang-11-dev to get libclang.so (maybe)
  2. OR create a link to libclang-11.so.1 named libclang.so
  3. OR hardcode a call to clang.cindex.Config.load_library_file(‘libclang-10.so.1’) in your code

### Pypi

Stable Distribution is available through PyPi at https://pypi.python.org/pypi/ctypeslib2/

sudo pip install ctypeslib2

### Setting up clang >= 3.7 dependency

See the LLVM Clang instructions at http://apt.llvm.org/ or use your distribution’s packages.

## Examples

Look at test/test_example_script.py

## Other example

Source file:

$ cat t.c struct my_bitfield { long a:3; long b:4; unsigned long long c:3; unsigned long long d:3; long f:2; };

Run c-to-python script:

clang2py t.c

Output:

# -- coding: utf-8 -- # # TARGET arch is: [] # WORD_SIZE is: 8 # POINTER_SIZE is: 8 # LONGDOUBLE_SIZE is: 16 # import ctypes

class struct_my_bitfield(ctypes.Structure):
_pack_ = True # source:False _fields_ = [ (‘a’, ctypes.c_int64, 3), (‘b’, ctypes.c_int64, 4), (‘c’, ctypes.c_int64, 3), (‘d’, ctypes.c_int64, 3), (‘f’, ctypes.c_int64, 2), (‘PADDING_0’, ctypes.c_int64, 49)]
__all__ =
[‘struct_my_bitfield’]

## Other example with headers:

Source file:

$ cat test-stdbool.c #include <stdbool.h>

typedef struct s_foo { bool bar1; bool bar2; bool bar3; } foo;

Run c-to-python script (with any relevant include folder):

clang2py –clang-args=”-I/usr/include/clang/4.0/include” test-stdbool.c

Output:

# -- coding: utf-8 -- # # TARGET arch is: [‘-I/usr/include/clang/4.0/include’] # WORD_SIZE is: 8 # POINTER_SIZE is: 8 # LONGDOUBLE_SIZE is: 16 # import ctypes

class struct_s_foo(ctypes.Structure):
_pack_ = True # source:False _fields_ = [ (‘bar1’, ctypes.c_bool), (‘bar2’, ctypes.c_bool), (‘bar3’, ctypes.c_bool),]

foo = struct_s_foo __all__ = [‘struct_s_foo’, ‘foo’]

## _pack_ and PADDING explanation

clang2py test/data/test-record.c

This outputs:

# …

class struct_Node2(Structure):
_pack_ = True # source:False _fields_ = [ (‘m1’, ctypes.c_ubyte), (‘PADDING_0’, ctypes.c_ubyte * 7), (‘m2’, POINTER_T(struct_Node)),]

# …

The PADDING_0 field is added to force the ctypes memory Structure to align fields offset with the definition given by the clang compiler.

The [_pack_](https://docs.python.org/3/library/ctypes.html#ctypes.Structure._pack_) attribute forces the alignment on 0 bytes, to ensure all fields are as defined by this library, and not per the compiler used by the host python binary

The objective of this, is to be able to produce cross-architecture python code, that can read memory structures from a different architecture (like reading a memory dump from a different architecture)

## Usage

usage: clang2py [-h] [-c] [-d] [–debug] [-e] [-k TYPEKIND] [-i] [-l DLL]
[-m module] [–nm NM] [-o OUTPUT] [-p DLL] [-q] [-r EXPRESSION] [-s SYMBOL] [-t TARGET] [-v] [-V] [-w W] [-x] [–show-ids SHOWIDS] [–max-depth N] [–clang-args CLANG_ARGS] files [files …]

Version 2.3.0. Generate python code from C headers

positional arguments:
files source filenames. stdin is not supported
optional arguments:
-h, --help show this help message and exit
-c, --comments include source doxygen-style comments
-d, --doc include docstrings containing C prototype and source file location
--debug setLevel to DEBUG
-e, --show-definition-location
 include source file location in comments
-k TYPEKIND, --kind TYPEKIND
 kind of type descriptions to include: a = Alias, c = Class, d = Variable, e = Enumeration, f = Function, m = Macro, #define s = Structure, t = Typedef, u = Union default = ‘cdefstu’
-i, --includes include declaration defined outside of the sourcefiles
-l DLL, --include-library DLL
 library to search for exported functions. Add multiple times if required
-m module, --module module
 Python module(s) containing symbols which will be imported instead of generated
--nm NM nm program to use to extract symbols from libraries
-o OUTPUT, --output OUTPUT
 output filename (if not specified, standard output will be used)
-p DLL, --preload DLL
 dll to be loaded before all others (to resolve symbols)
-q, --quiet Shut down warnings and below
-r EXPRESSION, --regex EXPRESSION
 regular expression for symbols to include (if neither symbols nor expressions are specified,everything will be included)
-s SYMBOL, --symbol SYMBOL
 symbol to include (if neither symbols nor expressions are specified,everything will be included)
-t TARGET, --target TARGET
 target architecture (default: x86_64-Linux)
-v, --verbose verbose output
-V, --version show program’s version number and exit
-w W add all standard windows dlls to the searched dlls list
-x, --exclude-includes
 Parse object in sources files only. Ignore includes
--show-ids SHOWIDS
 Don’t compute cursor IDs (very slow)
--max-depth N Limit cursor expansion to depth N
--clang-args CLANG_ARGS
 clang options, in quotes: –clang-args=”-std=c99 -Wall”

Cross-architecture: You can pass target modifiers to clang. For example, try –clang-args=”-target x86_64” or “-target i386-linux” to change the target CPU arch.

## Inner workings for memo

  • clang2py is a script that calls ctypeslib/ctypeslib/clang2py.py
  • clang2py.py is mostly the old xml2py.py module forked to use libclang.
  • clang2py.py calls ctypeslib/ctypeslib/codegen/codegenerator.py
  • codegenerator.py calls ctypeslib/ctypeslib/codegen/clangparser.py
  • clangparser.py uses libclang’s python binding to access the clang internal representation of the C source code.
    • It then translate each child of the AST tree to python objects as listed in typedesc.
  • codegenerator.py then uses these python object to generate ctypes-based python source code.
Because clang is capable to handle different target architecture, this fork
{is/should be} able to produce cross-platform memory representation if needed.

## Credits

This fork of ctypeslib is mainly about using the libclang1>=3.7 python bindings to generate python code from C source code, instead of gccxml.

the original ctypeslib contains these packages:
  • ctypeslib.codegen - a code generator
  • ctypeslib.contrib - various contributed modules
  • ctypeslib.util - assorted small helper functions
  • ctypeslib.test - unittests

This fork of ctypeslib is heavily patched for clang. - https://github.com/trolldbois/ctypeslib is based on rev77594 of the original ctypeslib. - git-svn-id: http://svn.python.org/projects/ctypes/trunk/ctypeslib@775946015fed2-1504-0410-9fe1-9d1591cc4771

The original ctypeslib is written by - author=”Thomas Heller”, - author_email=”theller@ctypes.org”,

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