text: #include <IO/WriteHelpers.h>
  #include <inttypes.h>
  #include <Common/hex.h>
  
  
  namespace DB
  {
  
  template <typename IteratorSrc, typename IteratorDst>
  void formatHex(IteratorSrc src, IteratorDst dst, const size_t num_bytes)
  {
      size_t src_pos = 0;
      size_t dst_pos = 0;
      for (; src_pos < num_bytes; ++src_pos)
      {
          writeHexByteLowercase(src[src_pos], &dst[dst_pos]);
          dst_pos += 2;
      }
  }
  
  void formatUUID(const UInt8 * src16, UInt8 * dst36)
  {
      formatHex(&src16[0], &dst36[0], 4);
      dst36[8] = '-';
      formatHex(&src16[4], &dst36[9], 2);
      dst36[13] = '-';
      formatHex(&src16[6], &dst36[14], 2);
      dst36[18] = '-';
      formatHex(&src16[8], &dst36[19], 2);
      dst36[23] = '-';
      formatHex(&src16[10], &dst36[24], 6);
  }
  
  /** Function used when byte ordering is important when parsing uuid
   *  ex: When we create an UUID type
   */
  void formatUUID(std::reverse_iterator<const UInt8 *> src16, UInt8 * dst36)
  {
      formatHex(src16 + 8, &dst36[0], 4);
      dst36[8] = '-';
      formatHex(src16 + 12, &dst36[9], 2);
      dst36[13] = '-';
      formatHex(src16 + 14, &dst36[14], 2);
      dst36[18] = '-';
      formatHex(src16, &dst36[19], 2);
      dst36[23] = '-';
      formatHex(src16 + 2, &dst36[24], 6);
  }
  
  
  void writeException(const Exception & e, WriteBuffer & buf, bool with_stack_trace)
  {
      writeBinary(e.code(), buf);
      writeBinary(String(e.name()), buf);
      writeBinary(e.displayText(), buf);
  
      if (with_stack_trace)
          writeBinary(e.getStackTraceString(), buf);
      else
          writeBinary(String(), buf);
  
      bool has_nested = false;
      writeBinary(has_nested, buf);
  }
  }
  