hex.cpp

#include <iostream>
#include <string>

namespace utils {
size_t sprintHex(char *out, size_t outSize, const uint8_t *bytes, size_t size) {
  size_t i = 0;
  // 2 hex chars + 1 null terminator
  if (outSize < (size * 2 + 1)) {
    return 0;
  }
  while (i < (size * 2)) {
    // consider endianness
    uint8_t byte = bytes[i / 2];
    uint8_t nibble = (i % 2 == 0) ? (byte >> 4) : (byte & 0x0F);
    out[i++] = (nibble < 10) ? ('0' + nibble) : ('a' + nibble - 10);
  }
  out[i] = '\0';
  return i;
};

std::string toHex(const uint8_t *bytes, size_t size) {
  auto sizeNeeded = size * 2 + 1;
  auto res = std::string(sizeNeeded, '\0');
  auto len = sprintHex(const_cast<char*>(res.data()), sizeNeeded, bytes, size);
  return res;
};

}

int main() {
  uint8_t bytes[] = {0x01, 0x02, 0x03, 0xb4};
  std::cout << utils::toHex(bytes, sizeof(bytes)) << std::endl;
  return 0;
}