Char array to hex string C++

Question

I searched char* to hex string before but implementation I found adds some non-existent garbage at the end of hex string. I receive pa

Answer 1

I've found good example here Display-char-as-Hexadecimal-String-in-C++:

  std::vector<char> randomBytes(n);
  file.read(&randomBytes[0], n);

  // Displaying bytes: method 1
  // --------------------------
  for (auto& el : randomBytes)
    std::cout << std::setfill('0') << std::setw(2) << std::hex << (0xff & (unsigned int)el);
  std::cout << '\n';

  // Displaying bytes: method 2
  // --------------------------
  for (auto& el : randomBytes)
    printf("%02hhx", el);
  std::cout << '\n';
  return 0;

Method 1 as shown above is probably the more C++ way:

Cast to an unsigned int
Use std::hex to represent the value as hexadecimal digits
Use std::setw and std::setfill from <iomanip> to format
Note that you need to mask the cast int against 0xff to display the least significant byte:
(0xff & (unsigned int)el).

Otherwise, if the highest bit is set the cast will result in the three most significant bytes being set to ff.

Answer 2

The simplest:

int main()
{
    const char* str = "hello";
    for (const char* p = str; *p; ++p)
    {
        printf("%02x", *p);
    }
    printf("\n");
    return 0;
}

Answer 3

You could use std::hex

Eg.

std::cout << std::hex << packet;

Answer 4

Here is something:

char const hex_chars[16] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

for( int i = data; i < data_length; ++i )
{
    char const byte = data[i];

    string += hex_chars[ ( byte & 0xF0 ) >> 4 ];
    string += hex_chars[ ( byte & 0x0F ) >> 0 ];
}

Answer 5

Using boost:

#include <boost/algorithm/hex.hpp>

std::string s("tralalalala");
std::string result;
boost::algorithm::hex(s.begin(), s.end(), std::back_inserter(result));

Answer 6

You can try this code for converting bytes from packet to a null-terminated string and store to "string" variable for processing.

const int buffer_size = 2048;
// variable for storing buffer as printable HEX string
char data[buffer_size*2];
// receive message from socket
int ret = recvfrom(sock, buffer, sizeofbuffer, 0, reinterpret_cast<SOCKADDR *>(&from), &size);
// bytes converting cycle
for (int i=0,j=0; i<ret; i++,j+=2){ 
    char res[2]; 
    itoa((buffer[i] & 0xFF), res, 16);
        if (res[1] == 0) {
            data[j] = 0x30; data[j+1] = res[0];
        }else {
            data[j] = res[0]; data[j + 1] = res[1];
        }
}
// Null-Terminating the string with converted buffer
data[(ret * 2)] = 0;

When we send message with hex bytes 0x01020E0F, variable "data" had char array with string "01020e0f".