Ctypes wstring通过引用传递

问题描述

如何在python中创建unicode缓冲区，将ref传递给C ++函数并获取wstring并在python中使用它？

How can I create a unicode buffer in python, pass by ref to a C++ function and get the wstring back and use it in python ?

c ++代码：

extern "C" {
void helloWorld(wstring &buffer)
    {
        buffer = L"Hello world";
    }
}

python代码：

import os
import json

from ctypes import *

lib = cdll.LoadLibrary('./libfoo.so')

lib.helloWorld.argtypes = [pointer(c_wchar_p)]

buf = create_unicode_buffer("")
lib.helloWorld(byref(buf))

str = cast(buf, c_wchar_p).value
print(str)

我收到此错误：

lib.helloWorld.argtypes = [pointer(c_wchar_p)]
TypeError: _type_ must have storage info

我缺少什么？

推荐答案

您不能使用 wstring 。是 ctypes 而不是 cpptypes 。使用 wchar_t *，size_t 将缓冲区传递给C ++，而不是 wstring 。

You can't use a wstring. It's ctypes not cpptypes. Use a wchar_t*,size_t to pass the buffer to C++, not wstring.

示例DLL：

#include <iostream>
#include <string>
#include <stdlib.h>
using namespace std;

#define API __declspec(dllexport)

extern "C" {
API void helloWorld(wchar_t* buffer, size_t length)
    {
        // Internally use wstring to manipulate buffer if you want
        wstring buf(buffer);
        wcout << buf.c_str() << "\n";
        buf += L"(modified)";
        wcsncpy_s(buffer,length,buf.c_str(),_TRUNCATE);
    }
}

示例用法：

>>> from ctypes import *
>>> x=CDLL('x')
>>> x.helloWorld.argtypes = c_wchar_p,c_size_t
>>> x.helloWorld.restype = None
>>> s = create_unicode_buffer('hello',30)
>>> x.helloWorld(s,len(s))
hello
>>> s.value
'hello(modified)'

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