C++ uint8_t to hex string

uint8_to_hex.cpp

#include <sstream>
#include <iostream>
#include <iomanip>

std::string uint8_to_hex_string(const uint8_t *v, const size_t s) {
  std::stringstream ss;

  ss << std::hex << std::setfill('0');

  for (int i = 0; i < s; i++) {
    ss << std::hex << std::setw(2) << static_cast<int>(v[i]);
  }

  return ss.str();
}

Hey thanks for this. It would be nice if you share hex_string_to_uint8_array.

not sure if this is what you need?
convert from string -> hex -> unit8_array

std::vector<uint8_t> convertToHexByte(string input)
{
ostringstream ret;
string strResult;
std::vector<uint8_t> byteList;
uint8_t byte;
for (string::size_type i = 0; i < input.length(); ++i)
{
ret << std::hex << std::setfill('0') << std::setw(2) << (int)input[i];
strResult = ret.str();
byte = (uint8_t) strtol(strResult.c_str(), nullptr, 10);
byteList.push_back(byte);
//reset ret
ret.str("");
ret.clear();
}
return byteList;
}

In this case what would const size_t s be?

size_t s is the size of the uint8_t array as in the length of it.

A version for C++20:

std::string convert(span<const uint8_t> data) {
    std::stringstream ss;
    ss << std::hex << std::setfill('0');

    std::ranges::for_each(data, [&](auto x) { ss << static_cast<int>(x); });

    return ss.str();
}