Python ctypes的byref和pointer有啥区别
2014-01-20 20:04
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byref(n)返回的相当于C的指针右值&n,本身没有被分配空间:
>>> from ctypes import *
>>> n = c_int(0)
>>> p = byref(n)
>>> pp = byref(p)
Traceback (most recent call last):
File "<pyshell#4>", line 1, in <module>
pp = byref(p)
TypeError: byref() argument must be a ctypes instance, not 'CArgObject'
pointer返回的相当于指针左值T* p=&n,可以改变,可以取地址:
>>> from ctypes import *
>>> n = c_int(0)
>>> q = pointer(n)
>>> q.contents = c_int(1)
>>> qq = byref(q)
>>> dir(qq)
['__class__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_obj']
>>> type(qq)
<class 'CArgObject'> #'CArgObject'是什么对象???
>>> qq
<cparam 'P' (010AD238)>
>>> q
<__main__.LP_c_long object at 0x010AD210>
>>> q.contents
c_long(1)
对于T**参数,通常你得构造一个pointer,然后byref传进去
以__开头并以__结束的属性(__class__、__dir__ 等)都是为内置方法(built-in method),唯独_obj不是
>>> qq._obj
<__main__.LP_c_long object at 0x010B8120>
>>> q
<__main__.LP_c_long object at 0x010B8120>
由以上执行代码可知,二维指针qq的_obj属性就是该二维指针的首地址,即指向q指针的地址
PS: addressof返回一个Python整数,不能直接传给C那边
>>> from ctypes import *
>>> n = c_int(0)
>>> p = byref(n)
>>> pp = byref(p)
Traceback (most recent call last):
File "<pyshell#4>", line 1, in <module>
pp = byref(p)
TypeError: byref() argument must be a ctypes instance, not 'CArgObject'
pointer返回的相当于指针左值T* p=&n,可以改变,可以取地址:
>>> from ctypes import *
>>> n = c_int(0)
>>> q = pointer(n)
>>> q.contents = c_int(1)
>>> qq = byref(q)
>>> dir(qq)
['__class__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_obj']
>>> type(qq)
<class 'CArgObject'> #'CArgObject'是什么对象???
<cparam 'P' (010AD238)>
>>> q
<__main__.LP_c_long object at 0x010AD210>
>>> q.contents
c_long(1)
对于T**参数,通常你得构造一个pointer,然后byref传进去
以__开头并以__结束的属性(__class__、__dir__ 等)都是为内置方法(built-in method),唯独_obj不是
>>> qq._obj
<__main__.LP_c_long object at 0x010B8120>
>>> q
<__main__.LP_c_long object at 0x010B8120>
由以上执行代码可知,二维指针qq的_obj属性就是该二维指针的首地址,即指向q指针的地址
PS: addressof返回一个Python整数,不能直接传给C那边
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