how to extract binary data from stringstream variable in c++?

Question

I am new in C++, I usually use C. But now, I just find a good library that compress some information, with a special algorithm that it is very useful to my project. Then this library gave me as an answer: binary data which lives in a stringstream object. Since it is binary data, there are some bytes that are not an ASCII character. So what I want to do is extract the data and got their hexadecimal representation. How I can do it? I have the following code:

stringstream ss; \\variable in which I got the result from the library
bitset1.write(ss); \\with this instruction I got the binary information from the library

From there I try the following things:

1) Just print:

cout << hex << ss;

2) Use the str method.

cout << hex << ss.str();

3) Use the read buffer method.

cout << hex << ss.rdbuf();

So, I think I am missing something, or maybe a lot, someone can help me?

thb · Accepted Answer · 2012-06-19 18:52:27Z

2

If a shortcut exists, I do not know it. However, this does what you want:

std::cout << std::hex << std::setfill('0');
const std::string s = ss.str();
const size_t slen = s.length();
for (size_t i = 0; i < slen; ++i) {
    const unsigned char c = s[i];
    const unsigned int n = c;
    std::cout << std::setw(2) << n;
}
std::cout << "\n";

The key is to use a non-char integer type for output, since the stream insertion operator << treats char specially.

edited Jun 19, 2012 at 18:52

answered Jun 18, 2012 at 2:47

thb

14.6k3 gold badges43 silver badges71 bronze badges

Sign up to request clarification or add additional context in comments.

7 Comments

ildjarn Over a year ago

Calling ss.str() repeatedly is abysmal for efficiency. Call it once and cache it.

user1462592 Over a year ago

@thb it works perfectly well thanks a lot, also I just callit once ss.str(). Now, i just will like to know how to do the invers process if I have a string how I load a StringStream variable?

ildjarn Over a year ago

@user1462592 : std::stringstream ss(my_string_object); It's not like documentation isn't readily available...

user1462592 Over a year ago

@ildjarn well in did the question is: how to load a String that has hexadecimal representation of a binary data to a stringstream

ildjarn Over a year ago

@user1462592 : I showed exactly how in the comment you just replied to.

|

Collectives™ on Stack Overflow

how to extract binary data from stringstream variable in c++?

1 Answer 1

7 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

7 Comments

Your Answer

Sign up or log in

Post as a guest

Related