gdb调试MySQL时，查看内存值，很多时候显示为8进制值
利用log协助调试时，log无法直接打印这些8进制的值，调试对比起来很不方便
下面参考了HexDump，实现很简单的OctDump功能，目的是打印格式与gdb调试所显示的格式相同

#include <iostream>
#include <string>
#include <cstring>
#include <cctype>

using namespace std;

std::string ToOct(const std::string& str1)
{
  std::string str2;

  for (char c : str1)
  {
    if (std::isprint(c))
    {
      str2.push_back(c);
    }
    else
    {
      str2.push_back('\\');
      str2.push_back((char)(((c & 0xc0) >> 6) + '0'));
      str2.push_back((char)(((c & 0x38) >> 3) + '0'));
      str2.push_back((char)((c & 0x07) + '0'));
    }
  }

  return str2;
}

int main()
{
  int v[4] = {1, 20, 3, 9};
  std::string str1((char*)(&v[0]), 16);

  std::string str2 = ToOct(str1);

  cout << "\"" << str2 << "\"" << endl;

  const char* cstr = "abc24, #";
  char* mstr = (char*)calloc(8, sizeof(char));
  memcpy(mstr, cstr, std::min<int>(8, strlen(cstr)));
  std::string str3 = ToOct(std::string(mstr, 8));
  cout << "\"" << str3 << "\"" << endl;
  free(mstr);
}