How to reversely strtok a C++ string from tail to head?

Question

I think I need a reverse version of strtok, like:

char* p = rstrtok(str, delimeters);

For example, sequentially get the position of '-', '_' and '+' in the string "hello+stack_over-flow" using a delimeter set of "+_-"

I only care about the delimeters, and their position, (not the content between), so I guess the boost::split_iterator is not appropriate here.

Is there any existing utility function I can leverage? or any solution to deal with this kind of situation?
Furthermore, since I am doing C++, is there any convenient approach to avoid this old fashion C?

(I searched "reverse strtok" but merely get "stack over flow" to "flow over stack" stuff...)

Answer 1

You could roll your own using strrchr.

If you use C++ style std::string you can leverage string::find_last_of.

Answer 2

You could do this with strpbrk:

char string[] = "hello+stack_over-flow";

char *pos = string;
while (*pos != '\0' && (pos = strpbrk(pos, "+-_")) != NULL)
{
    /* Do something with `pos` */

    pos++;  /* To skip over the found character */
}