Python ctype中的指针和数组

I have a DLL containing a C function with a prototype like this:

我有一个DLL包含一个C函数，它的原型是这样的:

int c_read_block(uint32 addr, uint32 *buf, uint32 num);

int c_read_block(uint32 addr, uint32 *buf, uint32 num);

I want to call it from Python using ctypes. The function expects a pointer to a chunk of memory, into which it will write the results. I don't know how to construct and pass such a chunk of memory. The ctypes documentation isn't much help.

我想使用ctype从Python中调用它。该函数期望指向内存块的指针，并将其写入结果。我不知道如何构造并传递这样一块内存。ctypes文档并没有多大帮助。

Constructing an array and passing it "byref", like this:

构造一个数组并通过它“byref”，如下所示:

    cresult = (c_ulong * num)()
    err = self.c_read_block(addr, byref(cresult), num)

Gives this error message:

让这个错误信息:

ArgumentError: argument 3: <type 'exceptions.TypeError'>: expected LP_c_ulong instance instead of pointer to c_ulong_Array_2

参数3: :期望的LP_c_ulong实例，而不是指向c_ulong_Array_2的指针

I guess that is because the Python ulong array is nothing like a c uint32 array. Should I use create_char_string. If so, how do I persuade Python to "cast" that buffer to an LP_c_ulong?

我猜那是因为Python ulong数组与c uint32数组完全不同。我应该使用create_char_string。如果是，我如何说服Python将该缓冲区“cast”到LP_c_ulong?

2 个解决方案

#1

You can cast with the cast function :)

您可以使用cast功能:)

>>> import ctypes
>>> x = (ctypes.c_ulong*5)()
>>> x
<__main__.c_ulong_Array_5 object at 0x00C2DB20>
>>> ctypes.cast(x, ctypes.POINTER(ctypes.c_ulong))
<__main__.LP_c_ulong object at 0x0119FD00>
>>>

#2

-1

There is a typo in the solution. In order to get a pointer to an array of ulongs you need to cast to a POINTER(list of ulong)

解决方案中有一个错误。为了获得指向ulongs数组的指针，你需要将它转换为一个指针(ulong列表)

In [33]: ptr = ctypes.cast(x, ctypes.POINTER(ctypes.c_ulong*5))
In [34]: ptr
Out[34]: <__main__.LP_c_ulong_Array_5 at 0x23e2560>

#1