C++ 中无符号字符的 ostream 运算符重载

Question

Given:

typedef struct { char val[SOME_FIXED_SIZE]; } AString;
typedef struct { unsigned char val[SOME_FIXED_SIZE]; } BString;

I want to add ostream operator << available for AString and BString .

std::ostream & operator<<(std::ostream &out, const AString &str)
{ 
   out.write(str.val, SOME_FIXED_SIZE);
   return out;
}

If I do the same for BString , the compiler complains about invalid conversion from 'const unsigned char*' to 'const char*' . The ostream.write does not have const unsigned char* as argument.

It seems << itself accepts the const unsigned char , so I try something like this

std::ostream & operator<<(std::ostream &out, const BString &str)
{ 
    for (int i=0; i<SOME_FIXED_SIZE; i++)
    {
        out<<str.val[i];
    }
    return out;
}

Can someone tell me if this is right/good practice or there are some better ways? welcome any comments!

Answer 1

The simplest and cleanest solution is to create an std::string , eg:

out << std::string(str.val, str.val + sizeof(str.val));

However, the question is: do you want formatted or unformatted output? For unformatted output, as ugly as it is, I'd just use a reinterpret_cast .

Answer 2

Have you thought about casting it to char* :

std::ostream & operator<<(std::ostream &out, const BString &str)
{ 
   out.write(reinterpret_cast<char*>(str.val), sizeof(str.val));
   return out;
}