cpypes 0.0.1

IPC implementation of ctypes API

cpypes

cpypes is a drop-in substitute for ctypes that runs the compiled code in a separate process.

This provides separation between the Python process and the process running the compiled code, which could allow you to debug the compiled code more easily, or even run it on a separate machine!

Quick Start

pip install cpypes

>>> import cpypes

>>> libc = cpypes.CDLL("libc.so.6")
>>> dst = cpypes.create_string_buffer(10)
>>> libc.strncpy(dst, b"Hello, world!", 5)
-1783489504
>>> dst.value
b'Hello'

By default, cpypes starts up a server for itself. You can also start the server manually and then use

cpypes.connect(("127.0.0.1", 5555))

to connect to it (you should do right after importing it). The server is typically installed at .venv/cpypes/server/main. To start it listening on a port, run

.venv/cpypes/server/main 5555

Use Case Examples

• You write a C library (.so) and want to write unit tests for the public functions. You can write the unit tests in Python, run them with pytest, and run the library under valgrind!

• Say you have a .so on an embedded Linux device that you want to test out. You can run the cpypes server on the embedded device (you'll need to compile the server for that architecture, and make sure the embedded device has libffi on it) and then connect to it with cpypes running on your laptop!

Requirements

cpypes currently supports only Linux.

cpypes requires make, gcc, and libffi-dev to build the server.

Caveats

Because it runs the compiled code in a separate process, cpypes is inherently unsuitable for some applications. For example, running printf in cpypes will always write to the server's standard output rather than the current process's (which, incidentally, will most likely cause a fatal error for cpypes). You can certainly use file descriptors in the server; you just need to make sure you don't try to use the client's file descriptors in the server's context, or anything equivalent.

Coming Soon

• Option to start server under valgrind.

• Support for more types.