Cython-将宽字符串（wchar_t *）转换为Python 3 unicode对象 [英] Cython - convert wide string (wchar_t *) to Python 3 unicode object

问题描述

我正在使用Cython将C库包装到Pyhon 3，并且我正在寻找一种将wchar_t字符串转换为要从函数返回的python对象的方法。在此问题中有一个答案，但是它涉及将字符串编码为多字节str，然后将其解码回unicode。我希望有更直接的解决方案。我尝试从Python C API使用 PyUnicode_FromWideChar ，但是我我遇到了段错误。这是我的.pyx代码：

I'm wrapping a C library to Pyhon 3 using Cython and i'm looking for a way of converting wchar_t string to python object which i want to return from a function. There's an answer in this question, but it involves encoding the string as multibyte str, and decoding it back to unicode. I hope for more straightforward solution. I tried using PyUnicode_FromWideChar from Python C API, but i'm getting a segfault. Here's my .pyx code:

from cpython.ref cimport PyObject 
from libc.stddef cimport wchar_t

cdef extern from "Python.h":
    PyObject* PyUnicode_FromWideChar(wchar_t *w, Py_ssize_t size)

cdef extern from "../../src/my_c_lib.h":
    wchar_t * myObjToStr(wchar_t * result, size_t size, myObj * obj)


cdef class MyClass:
    cdef myObj * ptr
    ...
    def to_str(self):
        cdef wchar_t buf[64]

        cdef wchar_t * result = myObjToStr(buf, 64, self.ptr)
        if result is NULL:
            raise Exception("Error converting object to string.")

        cdef PyObject * pystr = PyUnicode_FromWideChar(result, 64)
        return <object>pystr

结果实际上是指向<$的指针c $ c> buf 。怎么了有没有编码/解码的另一种方法吗？

result is actually the pointer to buf. What's wrong with this? Is there another way without encoding/decoding?

编辑：我发现 PyUnicode_FromWideChar（）返回NULL，但是为什么？我检查了结果是有效的wchar_t *字符串。

I found that PyUnicode_FromWideChar() returns NULL, but why? I checked, that result is a valid wchar_t * string.

推荐答案

使用-1作为 PyUnicode_FromWideChar（result，-1）的第二个参数（以便该函数在内部使用wcslen），解决了此问题。

Using -1 as second argument to PyUnicode_FromWideChar(result, -1)(so that the function uses wcslen internally), fixed the problem.

所以 PyUnicode_FromWideChar 确实是 前进的方式。

So PyUnicode_FromWideChar really is the way to go.

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