如何使用ctypes的为ByteArray传递到一个C函数，它接受一个char *作为它的参数？ [英] How can I use ctypes to pass a byteArray into a C function that takes a char* as its argument?

问题描述

我已经创建了一个在C函数，它接受一个int的大小和一个char *缓冲区作为参数。我想用ctypes的从蟒蛇调用这个函数，并传递一个Python的字节数组。我知道，首先你必须编译C文件到共享库（.so文件），并使用ctypes的调用该函数。这里的code我有这么远。

I have created a function in C which takes an int size and a char *buffer as arguments. I would like to use ctypes to call this function from python and pass in a python byteArray. I know that first you must compile the C file into a shared library (.so file) and use ctypes to call that function. Here's the code I have so far.

encrypt.c：

encrypt.c:

#include <stdio.h>
void encrypt(int size, unsigned char *buffer);
void decrypt(int size, unsigned char *buffer);

void encrypt(int size, unsigned char *buffer){
    for(int i=0; i<size; i++){
        unsigned char c = buffer[i];
        printf("%c",c);
    }
}
void decrypt(int size, unsigned char *buffer){
    for(int i=0; i<size; i++){
        unsigned char c = buffer[i];
        printf("%c",c);
    }
}

和这里的蟒蛇文件：

import ctypes

encryptPy = ctypes.CDLL('/home/aradhak/Documents/libencrypt.so')
hello = "hello"
byteHello = bytearray(hello)
encryptPy.encrypt(5,byteHello)
encryptPy.decrypt(5,byteHello)

基本上，我想打电话从蟒蛇的C法，通过一条巨蟒字节数组，并将它通过遍历数组并打印每个元素

Basically I want to call the C method from python, pass through a python byte array, and have it iterate through the array and print each element

推荐答案

您所需要的最低（Python 2里）是：

The minimum you need (Python 2) is:

hello = "hello"
encryptPy.encrypt(5,hello)
encryptPy.decrypt(5,hello)

不过，这是好事，声明参数类型和返回值也是如此。全程式：

But it is good to declare the argument types and return values as well. Full program:

#!python2
import ctypes

encryptPy = ctypes.CDLL('/home/aradhak/Documents/libencrypt.so')

encryptPy.encrypt.argtypes = (ctypes.c_int,ctypes.c_char_p)
encryptPy.encrypt.restype = None
encryptPy.decrypt.argtypes = (ctypes.c_int,ctypes.c_char_p)
encryptPy.decrypt.restype = None

hello = "hello"
encryptPy.encrypt(len(hello),hello)
encryptPy.decrypt(len(hello),hello)

注意，传递一个Python字节字符串时，考虑缓冲区不变。在这种情况下，你只正在阅读的缓冲区，但如果你需要允许C函数突变字符串使用：

Note that when passing a python byte string, consider the buffer immutable. In this case you only are reading the buffer, but if you need to allow the C function to mutate the string use:

hello = ctypes.create_string_buffer(5,'hello')

本作品为好，但将长度为6终止空将包括在内。

This works as well, but will be length 6. A terminating null will be included.

hello = ctypes.create_string_buffer('hello')

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