如何在Cython中包装C结构以便在Python中使用？

Question

为了获得一些学习经验,我试图在Cython中包含SDL(1.2.14)的一些部分,用于Python 3.2的扩展.

我有一个问题,弄清楚如何将C结构直接包装到Python中,能够直接访问其属性,如:

struct_name.attribute

例如,我想采用struct SDL_Surface:

typedef struct SDL_Rect {
    Uint32 flags
    SDL_PixelFormat * format
    int w, h
    Uint16 pitch
    void * pixels
    SDL_Rect clip_rect
    int refcount
} SDL_Rect;

并且能够在python中使用它:

import SDL
# initializing stuff

Screen = SDL.SetVideoMode( 320, 480, 32, SDL.DOUBLEBUF )

# accessing SDL_Surface.w and SDL_Surface.h
print( Screen.w, ' ', Screen.h )

目前,我已将SDL_SetVideoMode和SDL_Surface包装在一个名为SDL.pyx的文件中

cdef extern from 'SDL.h':
    # Other stuff

    struct SDL_Surface:
        unsigned long flags
        SDL_PixelFormat * format
        int w, h
        # like past declaration...

    SDL_Surface * SDL_SetVideoMode(int, int, int, unsigned )


cdef class Surface(object):
    # not sure how to implement       


def SetVideoMode(width, height, bpp, flags):
    cdef SDL_Surface * screen = SDL_SetVideoMode  

    if not screen:
        err = SDL_GetError()
        raise Exception(err)

    # Possible way to return?...
    return Surface(screen)

我该如何实现SDL.Surface？

Answer 1

在简单的情况下，如果 struct 是不透明的，则简单如下：

cdef extern from "foo.h":
    struct spam:
        pass

当您想要访问成员时，有几个选项，文档中详细介绍了这些选项：

http://docs.cython.org/src/userguide/external_C_code.html#styles-of-struct-union-and-enum-declaration