从文件读取文本到 unsigned char 数组

我希望使用 OpenSSL 来加密文件中的文本，并且在加密之前需要将文本放在 unsigned char 数组中。从文件读取文本到无符号字符数组的最简单方法是什么？

Your question is tagged both C and C++ _{(which isn't constructive)}. I will give an answer for C++.

#include <fstream>
#include <iterator>
#include <vector>

using namespace std;

int main()
{
    ifstream in("filename.txt"); //open file
    in >> noskipws;  //we don't want to skip spaces        
    //initialize a vector with a pair of istream_iterators
    vector<unsigned char> v((istream_iterator<unsigned char>(in)), 
                            (istream_iterator<unsigned char>()));
    ...
}