c++中将一长串字符转换为uint32_t或uint64_t

Question

I want to convert a string containing alphanumeric characters into either uint32_t or uint64_t. Tried doing the following. But, I am getting "terminate called after throwing an instance of 'std::out_of_range' " error. Also, when the string is smaller in length, for example : string s = "hello", it works, but what if I want to convert a longer string into uint32_t or uint64_t.

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

std::string string_to_hex(const std::string& in) {
    std::stringstream ss;
    ss << std::hex << std::setfill('0');
    for (size_t i = 0; i < in.size(); ++i) {
        ss << std::setw(2) << static_cast<unsigned int>(static_cast<unsigned char>(in[i]));
    }

    return ss.str(); 
}

int main() {
   std::string s = "hello world, this 123";
   std::string hex_str = string_to_hex(s);
   uint32_t value = std::stoul(hex_str , nullptr, 16);
   cout<<value<<endl; 
}

Okay, so according to the comments given, is the following the best way to do it?

int main()
{
    std::string s = "hello world, this 123";
    std::hash<std::string> hashed_name;
    uint32_t value = hashed_name(s);
    cout<<value<<endl;

    return 0;
}

Answer 1

This, strictly speaking, does what you need:

#include <iostream>
#include <string>
#include <unordered_map>

class Converter
{
public:
  static int StringToInt(const std::string& s)
  {
    auto it = cache.find(s);
    if (it != cache.end())
      return it->second;
    cache[s] = count;
    lookup[count++] = s;
  }
  static std::string IntToString(unsigned i)
  {
    auto it = lookup.find(i);
    if (it != lookup.end())
      return it->second;
    return "";
  }
private:
  static inline unsigned count = 0;
  static inline std::unordered_map<std::string, int> cache;
  static inline std::unordered_map<int, std::string> lookup;
};

int main() {
  std::string s = "hello world, this 123";
  int  value = Converter::StringToInt(s);
  std::cout << value << std::endl;
  std::string s2 = Converter::IntToString(value);
  std::cout << s2 << std::endl;
  int  value2 = Converter::StringToInt("hello world, this 123");
  std::cout << value2 << std::endl;

}

Answer 2

Your issue is that the resultant hex_str is a MASSIVE number. Specifically: 0x68656c6c6f20776f726c642c207468697320313233

You are converting every character to a two-digit hex value (ie one byte). Strings of size 4 (8 if using 64 bit int) or more is going to result in a number way too large to fit in your resultant uint32_t or uint64_t

See this GDB printout of your program

As Remy mentioned in the comments, look into hash algorithms.