Construct stringstream from char

Question

I implemented the following code, which does what it's supposed to, but I think that it can / should be simplified.

Basically, I need to create a vector of numbers, each containing one of the digits found in testString. Is there any way to construct the stringstream directly from a char (i. e. testString[i])? I'd rather not involve C-style functions, like atoi, if it can be done in a C++ way.

#include <iostream>
#include <string>
#include <sstream>
#include <vector>

int main ()
{
    std::string testString = "abc123.bla";
    std::string prefix = "abc";

    std::vector<unsigned short> digits;

    if (0 == testString.find(prefix))
    {
        for (size_t i = prefix.size(); i < testString.find("."); ++i)
        {
            int digit;
            std::stringstream digitStream;
            digitStream << testString[i];
            digitStream >> digit;
            digits.emplace_back(digit);
        }
    }

    for (std::vector<unsigned short>::iterator digit = digits.begin(); digit < digits.end(); ++digit)
    {
        std::cout << *digit << std::endl;
    }

    return 0;
}

Answer 1

Assuming testString[i] is between '0' and '9', just do:

digits.emplace_back(testString[i] - '0');