CODEWITHSUNDEEP
c++c++11cryptography
Fabricio Franco
Fabricio Franco

Reputation: 23

Converting HEXA 64 bits numbers to int

I'm making a college job, a conversion between hexa numbers enclosed in a stringstream. I have a big hexa number (a private key), and I need to convert to int, to put in a map<int,int>. So when I run the code, the result of conversion is the same for all the two hexa values inserted, what is incorrect, it should be differente results after conversion. I think it's an int sizes stack problem, because when I insert short hexas, it works greatly. As shown below the hexa has 64 bits.

Any idea to get it working?

int main() 
{
    unsigned int x;   
    std::stringstream ss;
    ss << std::hex << "0x3B29786B4F7E78255E9F965456A6D989A4EC37BC4477A934C52F39ECFD574444";
    ss >> x;

    std::cout << "Saida" << x << std::endl;
    // output it as a signed type
    std::cout << "Result 1: " << static_cast<std::int64_t>(x) << std::endl;

    ss << std::hex << "0x3C29786A4F7E78255E9A965456A6D989A4EC37BC4477A934C52F39ECFD573344";
    ss >> x;
    std::cout << "Saida 2 " << x << std::endl;
    // output it as a signed type
    std::cout << "Result 2: " << static_cast<std::int64_t>(x) << std::endl;
}

Upvotes: 0

Views: 375

Answers (3)

Jeffrey
Jeffrey

Reputation: 11430

You need to process the input 16 characters at a time. Each character is 4 bits. The 16 first characters will give you an unsigned 64-bit value. (16x4 is 64)

Then you can put the fist value in a vector or other container and move on to the next 16 characters. If you have questions about string manipulation, search this site for similar questions.

Upvotes: 0

lokains
lokains

Reputation: 127

  1. Firstly, the HEX numbers in your examples do not fit into an unsigned int.
  2. You should clear the stream before loading the second HEX number there.
...
std::cout << "Result 1: " << static_cast<std::int64_t>(x) << std::endl;

ss.clear();
ss << std::hex << "0x3C29786A4F7E78255E9A965456A6D989A4EC37BC4477A934C52F39ECFD573344";
ss >> x;
...

Upvotes: 1

DevSolar
DevSolar

Reputation: 70333

Each hexadecimal digit equates to 4 bits (0xf -> 1111b). Those hex strings are both 64 x 4 = 256 bits long. You're looking at a range error.

Upvotes: 0

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