代码我也放在了gist上 https://gist.github.com/hit9/7244344

foolib.c:

typedef struct post {
    char *x;
    char *y;
    int x_z;
} post_t;


void
foo (post_t *o, char *src)
{
    int i=0;

    char *p = src;
    int len = strlen(src);

    for (; *p != '\0'; i++, p++) {
        if (*p == 'x') {
            o->x = p;
            o->x_z = len-i;
        }
    }
    o->y=src;
}

test.py:

from ctypes import *

foolib = CDLL("./foolib.so")

class Post(Structure):
    _fields_ = (
        ("x", c_void_p),
        ("y", c_void_p),
        ("x_z", c_int),
    )

o = Post()

s = "iooxooiddfggggggggggggvd"

foolib.foo(byref(o), create_string_buffer(s))

print o.x_z

print string_at(o.x, o.x_z)
print string_at(o.y, len(s))

其中，foolib.c用来生成一个动态链接库 foolib.so

打印结果为何是:

foo ➤ python test.py                                                                                                                   
21
ooiddfggggggggggggvd
ooiddfggggggggggggvd

而不是

21
iooxooiddfggggggggggggvd
ooiddfggggggggggggvd

呢?