convert hex string to int values in C++

boost::lexical_cast is quite handy to convert between string and numerical types. However, sometimes you need more. for example, when you want to convert a string "0x0A" to its int value 0x0A(10), or vice versa. you are out of luck. The following code comes handy for this purpose.

#pragma once
#include <string>
#include <sstream>
#include <iomanip>

// the following routines convert dec/hex string literal to size_t values

namespace numeric_conversion
    template <typename T, bool is_hex>
    size_t string_to_size_t(const std::basic_string<T>& s)
        std::basic_istringstream<T> ss(s, std::ios_base::in);

        size_t size(0);
        ss >> (is_hex ? std::hex : std::dec )>>size;
        return size;

    template <typename T>
    size_t hexstring_to_size_t(const std::basic_string<T>& s)
        return string_to_size_t<T, true>(s);

    template <typename T>
    size_t hexstring_to_size_t(const T* s)
        return string_to_size_t<T, true>(std::basic_string<T>(s));

    template <typename T>
    size_t decstring_to_size_t(const std::basic_string<T>& s)
        return string_to_size_t<T, false>(s);

    template <typename T>
    size_t decstring_to_size_t(const T* s)
        return string_to_size_t<T, false>(std::basic_string<T>(s));


    template <int N>
    std::wstring to_hex_string(size_t i, bool map_0_to_empty)
        if(map_0_to_empty && (0 == i)) return L"";

        std::wstringstream wss;
        wss << L"0x"/*std::showbase*/ << std::hex << std::setw(N) << std::setfill(L'0') << i;

        return wss.str();

Test code:
#include <iostream>
int main()
	using namespace std;
	using namespace numeric_conversion;
	wcout << L"convert string with base: 0x0a = " << hexstring_to_size_t(L"0x0a") << endl;
	wcout << L"convert string with base no base: 0a = " << hexstring_to_size_t(L"0a") << endl;	
	wcout << L"convert value to hex string: 0a = " << to_hex_string<2>(10, true);


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  • Wendi  On May 30, 2014 at 6:20 am

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