Python-ctypes-如何调用函数和访问结构字段？

我有一个C库：

智能字符串.h：

typedef struct SmartString {
    unsigned string_len;
    unsigned alloc_len;
    char *str;
    char *str_terminator;

} SmartString;

SmartString *SmartString_new(char *str);
... definitions of more functions ...

import ctypes
from ctypes import *

# Defining the python type that represents the C SmartString
# It must extend the 'Structure' class
# Structure, c_uint, c_char_p, etc. were imported from ctypes
class SmartString(Structure):
    _fields_=[("string_len",c_uint),
              ("alloc_len",c_uint),
              ("str",c_char_p),
              ("str_terminator", c_char_p)]


# Loading the C shared lib I've just compiled
smartstring_lib = ctypes.CDLL('SmartString.so')

# Defining pointer to the SmartString_new() function
SmartString_new = smartstring_lib.SmartString_new

# Declaring the function return type - a pointer to a SmartString object - just like in the C code
SmartString_new.restype = POINTER(SmartString)

# Declaring list of parameter types. In this case, the list contains only one item,
# as the function has only one parameter
SmartString_new.argtypes = [c_char_p]

# Calling the SmartString_new() function. Expecting to get a pointer to SmartString object into 'my_str'
# The API requires a MUTABLE string, so create_string_buffer() is used here
# The reference to this string is not saved, as I don't care if it is modified by the C code
my_str = SmartString_new(create_string_buffer('my nice string'))

# Printing fields of the dereferenced returned value (dereferencing is done using '.contents')
print my_str.contents.string_len
print my_str.contents.alloc_len
print my_str.contents.str
print my_str.contents.str_terminator

在名为smart_string.c的文件中可以找到该实现

我需要一个运行

SmartString\u new（）

函数和访问返回的结构指针字段的指南

谁能告诉我怎么做吗

---

谢谢

回答自己并与您分享知识：

首先，需要从C文件创建一个共享库：

gcc-shared-fpic smart_string.c-o SmartString.so

然后，使用以下Python代码（有关每个已完成操作的解释，请参阅注释）：

注意：

char*

，如上面的API所示，是一个C可编辑字符串，而

const char*

是一个只读字符串。因为C API需要

char*

而不是

const char*

，所以我们必须向它传递一个可变的字符串，这样它就可以被C代码编辑。默认情况下，Python字符串是不可变的。因此，我们在这里使用

create\u string\u buffer（）

函数

python\u smart\u string.py：

typedef struct SmartString {
    unsigned string_len;
    unsigned alloc_len;
    char *str;
    char *str_terminator;

} SmartString;

SmartString *SmartString_new(char *str);
... definitions of more functions ...

import ctypes
from ctypes import *

# Defining the python type that represents the C SmartString
# It must extend the 'Structure' class
# Structure, c_uint, c_char_p, etc. were imported from ctypes
class SmartString(Structure):
    _fields_=[("string_len",c_uint),
              ("alloc_len",c_uint),
              ("str",c_char_p),
              ("str_terminator", c_char_p)]


# Loading the C shared lib I've just compiled
smartstring_lib = ctypes.CDLL('SmartString.so')

# Defining pointer to the SmartString_new() function
SmartString_new = smartstring_lib.SmartString_new

# Declaring the function return type - a pointer to a SmartString object - just like in the C code
SmartString_new.restype = POINTER(SmartString)

# Declaring list of parameter types. In this case, the list contains only one item,
# as the function has only one parameter
SmartString_new.argtypes = [c_char_p]

# Calling the SmartString_new() function. Expecting to get a pointer to SmartString object into 'my_str'
# The API requires a MUTABLE string, so create_string_buffer() is used here
# The reference to this string is not saved, as I don't care if it is modified by the C code
my_str = SmartString_new(create_string_buffer('my nice string'))

# Printing fields of the dereferenced returned value (dereferencing is done using '.contents')
print my_str.contents.string_len
print my_str.contents.alloc_len
print my_str.contents.str
print my_str.contents.str_terminator

---

指定

SmartString\u new.argtypes=[c\u char\u p]

。您可能需要保留对

create\u string\u buffer（）

的引用

my_str[0]

是解除指针引用的另一种方法。