hex.h

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*/
 
#ifndef ROUTER_SRC_REST_MRS_SRC_HELPER_STRING_HEX_H_
#define ROUTER_SRC_REST_MRS_SRC_HELPER_STRING_HEX_H_
 
#include <cassert>
#include <cstdint>
#include <iomanip>
#include <sstream>
#include <stdexcept>
#include <type_traits>
 
namespace helper {
namespace string {
 
class DefaultHex {
 public:
  void operator()(std::ostringstream &os) {
    os << std::setfill('0') << std::setw(2) << std::hex;
  }
 
  template <typename ValueType>
  int operator()(const ValueType &v) {
    return v;
  }
};
 
class CStringHex {
 public:
  void operator()(std::ostringstream &os) {
    os << std::setfill('0') << std::setw(2) << std::hex;
  }
 
  int operator()(const char &v) { return (int)static_cast<uint8_t>(v); }
};
 
template <typename Container, typename Transform = DefaultHex>
std::string hex(const Container &c) {
  std::ostringstream os;
  Transform trans;
  auto end = std::end(c);
  auto it = std::begin(c);
  static_assert(sizeof(decltype(*it)) == 1);
 
  for (; it != end; ++it) {
    trans(os);
    os << trans(*it);
  }
  return os.str();
}
 
inline bool get_unhex_character(const char c, uint8_t *out) {
  static_assert('0' < 'A');
  static_assert('A' < 'a');
  static_assert('0' < '9');
 
  if (c > 'f') return false;
 
  if (c >= 'a') {
    *out = c - 'a' + 10;
    return true;
  }
 
  if (c > 'F') return false;
 
  if (c >= 'A') {
    *out = c - 'A' + 10;
    return true;
  }
 
  if (c > '9') return false;
 
  if (c >= '0') {
    *out = c - '0';
    return true;
  }
 
  return false;
}
 
inline bool get_unhex_character_or_throw(const char c, uint8_t *out) {
  if (get_unhex_character(c, out)) return true;
 
  throw std::runtime_error("Invalid character in hexadecimal value.");
 
  return false;
}
 
using HexConverter = bool (*)(const char c, uint8_t *out);
 
inline uint8_t unhex_character(const char c) {
  uint8_t result;
  if (!get_unhex_character(c, &result))
    throw std::runtime_error("Invalid character in hexadecimal value.");
  return result;
}
 
template <HexConverter converter, typename IT1, typename IT2>
bool get_hex_skip(IT1 &it, const IT2 &end, uint8_t *out) {
  bool result;
  do {
    if (it == end) return false;
    result = converter(*it, out);
    ++it;
  } while (!result);
  return result;
}
 
template <typename Container,
          HexConverter converter = get_unhex_character_or_throw>
Container unhex(const std::string &h) {
  Container result;
  uint8_t v1, v2;
 
  for (auto i = h.begin(); i != h.end();) {
    if (!get_hex_skip<converter>(i, h.end(), &v2)) break;
    if (!get_hex_skip<converter>(i, h.end(), &v1)) break;
    uint8_t v = v2 * 16 + v1;
    result.push_back(v);
  }
  return result;
}
 
}  // namespace string
}  // namespace helper
 
#endif  // ROUTER_SRC_REST_MRS_SRC_HELPER_STRING_HEX_H_