c2py23 0.4.0

Wrap C99 code to Python via the buffer protocol

c2py23

All code in this repository was generated by DeepSeek V4 and other large language models, in collaboration with jonwright.

Wrap C99 functions as Python C extensions via the buffer protocol. One compiled .so works on Python 2.7 through 3.15 with no recompilation. Zero copies, zero allocations. No numpy required.

Install

pip install c2py23

Requires PyYAML and a C99 compiler (gcc, clang, or MSVC on Windows).

Quick Start

Create a C function:

/* arraysum.c */
#include <stdint.h>
int array_sum(const double *a, const double *b, double *out, intptr_t n) {
    for (intptr_t i = 0; i < n; i++) out[i] = a[i] + b[i];
    return n;
}

Write the interface file:

# arraysum.c2py
module: arraysum
source: [arraysum.c]

functions:
  - py_sig: "array_sum(a: buffer, b: buffer, out: buffer) -> int"
    checks:
      - "a.format == 'd'"
      - "b.format == 'd'"
      - "out.format == 'd'"
    c_overloads:
      - sig: "array_sum(const double *a, const double *b, double *out, intptr_t n) -> int"
        map: {a: "a.ptr", b: "b.ptr", out: "out.ptr", n: "a.n"}

Build and use:

c2py23 build arraysum.c2py
python3 -c "
import ctypes, sys; sys.path.insert(0, '.')
import arraysum
a = (ctypes.c_double * 4)(1, 2, 3, 4)
b = (ctypes.c_double * 4)(5, 6, 7, 8)
r = (ctypes.c_double * 4)(0, 0, 0, 0)
arraysum.array_sum(a, b, r)
print(list(r))  # [6.0, 8.0, 10.0, 12.0]
"

Usage

c2py23 build file.c2py                       # parse + generate + compile
c2py23 build file.c2py --generate-only       # generate wrapper .c only
c2py23 build wrapper.c --compile-only -s src.c -I inc/
                                              # compile existing wrapper
c2py23 build file.c2py --asan                # compile with address sanitizer
c2py23 generate file.c2py -o wrapper.c       # generate without building

Supported Platforms

Linux (x86_64, gcc) and Windows (x64, MSVC/MinGW). 32-bit not supported.

Examples

The GitHub repository includes build examples (not in the PyPI sdist):

• examples/kissfft_wrap/ — real + complex FFT over float buffers
• examples/lz4_wrap/ — compress/decompress over byte buffers
• examples/simd_dispatch/ — CPU feature dispatch (SSE2/AVX2/AVX-512, NEON, Altivec)
• examples/threading_bench/ — GIL release, free-threading, OpenMP
• examples/wheel_demo/ — multi-platform wheel packaging
• examples/cmake_demo/, examples/meson_demo/ — build system integration

Documentation

• docs/specification.md — full .c2py grammar, supported types, architecture
• docs/user_guide.md — thread safety, wheel packaging, GIL release
• AGENTS.md — contributor guide, CI workflows, coding standards
• audit/ — LLM peer review toolchain

License

MIT. See LICENSE.