cmagic.py

# -*- coding: utf-8 -*-
"""C magic.

This is a very simple magic for compiling and importing C code with ctypes.

This derives from biteymagic.py, by Bradley Froehle:
https://gist.github.com/bfroehle/3458310

You must provide the function names you would like exported.

Example usage:

>>> %%c foo
int foo(int x)
{
  return x*2;
}

>>> foo(4)

It doesn't do nearly as many interesting things as bitey, and could benefit
from integration with a parser such as:

https://bitbucket.org/eliben/pycparser
"""
#-----------------------------------------------------------------------------
# Copyright (C) 2013, Continuum Analytics
#
# Distributed under the terms of the Modified BSD License.
#-----------------------------------------------------------------------------

from __future__ import print_function

import ctypes
import imp
import io
import os
import pipes
import subprocess
import sys
from distutils.sysconfig import get_config_var, get_python_inc

try:
    import hashlib
except ImportError:
    import md5 as hashlib

from IPython.core.magic import (Magics, magics_class, line_magic,
                                cell_magic, line_cell_magic)

@magics_class
class CMagics(Magics):
    """Magics for C, a simple compile-and-import Tool"""

    @cell_magic
    def c(self, line, cell):
        """Compile single C function code and wrap/import using ctypes.

        Usage, in cell mode::

            %%c <function names to export>
            <C code>

        The user is responsible for using ctypes to handle function calls.
        """
        code = cell if cell.endswith('\n') else cell+'\n'

        fun_names = line.split()

        lib_dir = os.path.join(self.shell.ipython_dir, 'cmagic')
        key = line, code, sys.version_info, sys.executable
        if not os.path.exists(lib_dir):
            os.makedirs(lib_dir)

        module_name = "_c_magic_" + \
                      hashlib.md5(str(key).encode('utf-8')).hexdigest()
        c_name = module_name+'.c'
        o_name = module_name+'.o'
        # sorry Windows users :(, I don't know how to fix this default
        lib_name = module_name + '.so'

        c_path = os.path.join(lib_dir, c_name)
        o_path = os.path.join(lib_dir, o_name)
        lib_path = os.path.join(lib_dir, lib_name)

        if not os.path.exists(c_path):
            with io.open(c_path, 'w', encoding='utf-8') as f:
                f.write(code)

        if not os.path.exists(lib_path):
            try:
                startupinfo = None
                if os.name == 'nt':
                    # Avoid a console window in Microsoft Windows.
                    startupinfo = subprocess.STARTUPINFO()
                    startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW

                cc = get_config_var('CC')
                cflags = get_config_var('CFLAGS')
                ccshared = get_config_var('CCSHARED')
                ldshared = get_config_var('LDSHARED')
                python_inc = get_python_inc()

                cmd = cc.split() + ['-c', '-I', python_inc] + \
                    ccshared.split() + cflags.split() + [c_name]
                subprocess.check_output(cmd,
                                        stderr=subprocess.STDOUT,
                                        cwd=lib_dir,
                                        startupinfo=startupinfo)

                cmd = ldshared.split() +['-o', lib_name, o_name]
                subprocess.check_output(cmd,
                                        stderr=subprocess.STDOUT,
                                        cwd=lib_dir,
                                        startupinfo=startupinfo)

            except subprocess.CalledProcessError as e:
                print(e.output, file=sys.stderr)
                print("ERROR: command `%s` failed." %
                      ' '.join(map(pipes.quote, e.cmd)),
                      file=sys.stderr)
                return

        lib = ctypes.CDLL(lib_path)

        for fun_name in fun_names:
            fun = getattr(lib, fun_name)

        self.shell.push({fun_name:fun})


def load_ipython_extension(ip):
    """Load the extension in IPython."""
    ip.register_magics(CMagics)