Wsrtjtyk

I have a c++ string with embedded '' characters.

I have a function replaceAll() which should replace all occurrences of a pattern with another pattern. For "normal" strings it works fine. However, when I try to find the '' character my function does not work and I don't know why. replaceAll seems to be failing on string::find() which doesn't make sense to me.

// Replaces all occurrences of the text 'from' to the text 'to' in the specified input string.

// replaceAll("Foo123Foo", "Foo", "Bar"); // Bar123Bar

string replaceAll( string in, string from, string to )

{

    string tmp = in;



    if ( from.empty())

    {

    return in;

    }



    size_t start_pos = 0;



    // tmp.find() fails to match on ""

    while (( start_pos = tmp.find( from, start_pos )) != std::string::npos )

    {

    tmp.replace( start_pos, from.length(), to );

        start_pos += to.length(); // In case 'to' contains 'from', like replacing 'x' with 'yx'

    }



    return tmp;

}



int main(int argc, char* argv)

{

    string stringWithNull = { '', '1', '', '2' };

    printf("size=[%d] data=[%s]n", stringWithNull.size(), stringWithNull.c_str());



    // This doesn't work in the special case of a null character and I don't know why

    string replaced = replaceAll(stringWithNull, "", "");

    printf("size=[%d] data=[%s]n", replaced.size(), replaced.c_str());

}

Output:

size=[4] data=

size=[4] data=

The reason why it doesn't work in your case is that std::string constructor from const char* without size is going to read all elements up to, but not including nul-terminating char. As a result,

 replaceAll(stringWithNull, "", "");

Calls replaceAll with from set to empty string (replaceAll( string in, string from, string to )), which returns in unmodified.

To solve the problem, use a constructor which takes size, or initialize with list initialization, the same way you do it for your original string, for example:

replaceAll(stringWithNull, {''}, "");

When you do

replaceAll(stringWithNull, "", "");

"" is the same as "" since std::string's constructor stops at the null character when being constructed from a c-string. That means you are searching for nothing and replacing it with nothing. What you need is

string replaced = replaceAll(stringWithNull, {''}, "");

to actually get from populated with a null character.