How to convert Byte Array to hex string in visual c++?

Question

Declaration of a method are following:

//some.h
void TDES_Decryption(BYTE *Data, BYTE *Key, BYTE *InitalVector, int Length);

I am calling t

Answer 1

Using stringstream, sprintf and other functions in the loop is simply not C++. It's horrible for performance and these kind of functions usually get called a lot (unless you're just writing some things into the log).

Here's one way of doing it. Writing directly into the std::string's buffer is discouraged because specific std::string implementation might behave differently and this will not work then but we're avoiding one copy of the whole buffer this way:

#include 
#include 
#include 

std::string bytes_to_hex_string(const std::vector &input)
{
  static const char characters[] = "0123456789ABCDEF";

  // Zeroes out the buffer unnecessarily, can't be avoided for std::string.
  std::string ret(input.size() * 2, 0);

  // Hack... Against the rules but avoids copying the whole buffer.
  char *buf = const_cast(ret.data());

  for (const auto &oneInputByte : input)
  {
    *buf++ = characters[oneInputByte >> 4];
    *buf++ = characters[oneInputByte & 0x0F];
  }
  return ret;
}

int main()
{
  std::vector bytes = { 34, 123, 252, 0, 11, 52 };
  std::cout << "Bytes to hex string: " << bytes_to_hex_string(bytes) << std::endl;
}