Convert uint64_t to std::string

Question

How can I transfer uint64_t value to std::string? I need to construct the std::string containing this value For example something like this:

void genString(uint64_t val)
{
      std::string str;
      //.....some code for str 
      str+=(unsigned int)val;//????
}

Thank you

Solution 1

use either boost::lexical_cast or std::ostringstream

e.g.:

str += boost::lexical_cast<std::string>(val);

or

std::ostringstream o;
o << val;
str += o.str();

Solution 2

In C++ 11 you may just use:

std::to_string()

it's defined in header

http://www.cplusplus.com/reference/string/to_string/

Solution 3

I use something like this code below. Because it's a template it will work with any type the supports operator<< to a stream.

#include <sstream>

template <typename T>
std::string tostring(const T& t)
{
    std::ostringstream ss;
    ss << t;
    return ss.str();
}

for example

uint64_t data = 123;
std::string mystring = tostring(data);

Solution 4

string genString(uint64_t val)
{
   char temp[21];
   sprintf(temp, "%z", val);
   return temp;
}

View more solutions

Comments

[YAKOVM]

Can you give me the code example how to use std::ostringstream?

[Flexo]

@yakov - added examples for both. You'll need either #include <boost/lexical_cast.hpp> or #include <sstream> depending on which solution you use.

[Seth Carnegie]

To whomever may use this in the future, make sure to make your buffer big enough. Also you could make that buffer static if you wanted to add a little more efficiency.

[Flexo]

@Seth - is static (and hence not reentrant) really faster than changing the stack pointer increase at entering the function from n to n + 21?

[Flexo]

@Seth - gcc 4.4 with -O3 on ia32 gives me the exact opposite behaviour. static makes it consistently (slightly) slower (more than the error) on 100 repetitions of a 10,000,000 call loop. Seems like premature optimisation to me. The main chance in the local version is subl $72, %esp vs subl $52, %esp, an O(1) change.

[Flexo]

@nmi - I don't think %z is correct - I get test.cc:10:29: warning: conversion lacks type at end of format and test.cc:10:29: warning: too many arguments for format with gcc

[Liosan]

Downvoted since by now, the standard C++11 solution should be used - std::to_string.