更新ctypes指针 [英] Update ctypes pointer in place

问题描述

出于各种原因，我想就地更新ctypes指针的值.换句话说，我想要的是修改指针对象包装的内部缓冲区.这是一种可能的方法:

For various reasons I would like to update the value of a ctypes pointer in place. In other words, what I want is to modify the internal buffer the pointer object wraps. Here is one possible approach:

from ctypes import *

a = pointer(c_int(123))
b = pointer(c_int(456))

memmove(addressof(a), addressof(b), sizeof(c_void_p))
a._objects.clear()
a._objects.update(b._objects)

现在 a.contents 将返回 c_long(456).但是，使用_objects属性似乎太在意实现细节了(这甚至会正确地起作用吗?).有没有更惯用的方法来做到这一点?

Now a.contents will return c_long(456). However, playing around with the _objects attribute seems like it's too concerned with the implementation details (will this even behave correctly?). Is there a more idiomatic way to do this?

推荐答案

由于eryksun尚未发布他的答案，所以我将在此处添加自己.这是应该这样做的方式:

Since eryksun hasn't posted up his answer I'll add it here my self. This is how it should be done:

from ctypes import *

a = pointer(c_int(123))
b = pointer(c_int(456))

tmp = pointer(a)[0]
tmp.contents = b.contents

现在 a.contents = c_int(456).关键是 tmp 与 a 共享一个缓冲区(这就是为什么您会找到 tmp._b_needsfree_ == 0 的原因).

Now a.contents = c_int(456). The key is that tmp shares a buffer with a (which is why you'll find tmp._b_needsfree_ == 0).

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